To evaluate the diagnostic value of acoustic radiation force impulse (ARFI) to test the elasticity of renal parenchyma by measuring the shear wave velocity (SWV) which might be used to detect chronic kidney disease (CKD).327 healthy volunteers and 64 CKD patients were enrolled in the study. The potential influencing factors and measurement reproducibility were evaluated in the healthy volunteers. Correlations between SWV and laboratory tests were analyzed in CKD patients.?Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of ARFI.The SWV of healthy volunteers correlated significantly to age  and differed significantly between men and women . However, it did not correlate significantly to height, weight, body mass index, waistline, kidney dimension and the depth for SWV measurement (n = 30). Inter- and intraobserver agreement expressed as intraclass coefficient correlation were 0.64  and 0.6  (n = 40). The mean SWV in healthy volunteers was 2.15±0.51 m/s, while was 1.81±0.43 m/s, 1.79±0.29 m/s, 1.81±0.44 m/s, 1.64±0.55 m/s, and 1.36±0.17 m/s for stage 1, 2, 3, 4 and 5 in CKD patients respectively. The SWV was significantly higher for healthy volunteers compared with each stage in CKD patients. ARFI could not predict the different stages of CKD except stage 5. In CKD patients, SWV correlated to e-GFR , to urea nitrogen , and to creatinine . ROC analyses indicated that the area under the ROC curve was 0.752 (95% CI: 0.704 to 0.797) (P<0.001). The cut-off value for predicting CKD was 1.88 m/s (sensitivity 71.87% and specificity 69.69%).ARFI may be a potentially useful tool in detecting CKD. Chronic kidney disease (CKD) is a major public health problem in developed countries Regardless of etiology, all patients with CKD show a progressive decline in renal function with time. The process is largely irreversible, inevitably leading to ESRD, a condition that requires life-long dialysis or renal transplantation. Histologically, CKD manifests itself as progressive glomerulosclerosis, vascular sclerosis, and tubulointerstitial injury, which encompasses tubular atrophy and interstitial fibrosis. If these histological changes associate with elasticity of renal parenchyma, there may be a new way to detect CKD through assessing the parenchyma elasticity.Acoustic radiation force impulse (ARFI) is a newly developed, noninvasive, inexpensive, safe and convenient technique to assess the tissue elasticity. It is integrated in a conventional ultrasound (US) machine and is able to quantify the parenchyma elasticity by measuring the shear wave velocity (SWV). ARFI uses acoustic radiation force to transiently deform soft tissues in the region of interest (ROI), and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue’s mechanical properties et al. ARFI has also been used to detect renal transplant’s elasticity. Chronic allograft nephropathy is a major cause of renal transplant failure, which is characterized by interstitial fibrosis and tubular atrophy Between March 2012 and August 2012, 327 healthy volunteers  for health examinations were assessed with ARFI. None of them had abnormal renal function test  and abnormal imaging findings by conventional US such as cysts, stones, masses, nephrarctia or hydronephrosis.We evaluated the influence of age and gender to ARFI measurement of the renal parenchyma in all 327 healthy volunteers, and chose 30 volunteers  randomly from the 327 healthy volunteers to evaluate other possible influencing factors including waistline, height, weight, body mass index (BMI), kidney dimension, and the depth for SWV measurements.To test the inter- and intra-observer agreement, another 40 volunteers  were chosen from the 327 healthy volunteers randomly. When investigating the interobserver agreement, they were examined on the same day by observer 1 and observer 2, both of whom had previous training in performing ARFI and were blinded to the clinical and laboratory data. When investigating the intraobserver agreement, each volunteer was examined by observer1 twice with one day interval under the same conditions.s  were assessed with ARFI. Serum cystatin C, urea nitrogen, creatinine, uric acid, cholesterol, triglycerides, low-density lipoprotein, high-density lipoprotein, calcium, phosphate, hemoglobin, albumin and urinary albumin were measured after an overnight fast of at least 10 h in CKD patients.In addition, 64 CKD patient2), and was classified into stages as shown in Estimated glomerular filtration rate (eGFR) was calculated with an equation developed by adaptation of the Modification of Diet in Renal Disease equation:The study was approved by the Ethical Committee of the Tenth People’s Hospital of Tongji University. According to the local legislation, oral informed consent was obtained from all healthy volunteers and CKD patients older than 18 years old, whereas for the healthy volunteers or CKD patients under the age of 18, oral informed consent was obtained from the next of kin, caretakers, or guardians on the behalf of the minors participants. The committee approved the consent procedures because the technique used in this study was incorporated in a commercially available US machine and its safety has been well documented. The study would not do harm and invasiveness to the healthy volunteers and CKD patients. The consent process was documented in a separate file after the oral informed consent was obtained.All US examinations were performed using an Acuson S2000 ultrasound system , equipped with the ARFI function. The convex probes  and mechanical index of 1.7 were applied. Tissue harmonic imaging was used to optimize the US images. ARFI was performed with the identification of target ROI  on a conventional US. To quantify the wave propagation speed, the quantitative implementation of ARFI, known as virtual touch tissue quantification was used.All cases underwent ARFI in prone position . by obseIn the event of a non valid measurement (expressed as X.XX m/s), a repeated measurement was carried out. All measurements were performed during breath holding.t-test was used to analyze the differences in SWV between two different groups. The differences in SWV in different groups  were evaluated by a one-way analysis of variance (ANOVA) test. When differences among them were found to be statistically significant (P<0.05), each group was compared with every other group using least significant difference (LSD) test. Correlation between SWV and variables  were analyzed with Pearson’s correlation coefficients in the 64 CKD patients. The diagnostic performance of ARFI in determining CKD was assessed using receiver operating characteristic (ROC) curves. The P<0.05 was defined as statistically significant.The SPSS version 17.0 software package for Windows  was used for statistical analysis. The continuous data were expressed as mean± SD (range). Influencing factors were analyzed with Pearson’s correlation coefficients. Inter- and intraobserver reproducibility were analyzed with intraclass correlation coefficient (ICC). Agreement was classified as poor (ICC = 0.00 to 0.20), fair to good (ICC = 0.40 to 0.75) or excellent (ICC = 0.75). A Bland-Altman plot was used to analyze observer-related variations. Unpaired P = 0.011). Interobserver variability was given as a Bland-Altman plot in P = 0.001).The interobserver agreement, expressed as ICC, was 0.64  and in the 64 CKD patients . The linear regression equation was y = 2.399–0.005x in the healthy volunteers, where x and y represented years and the SWV velocity respectively (P = 0.018) and in the 64 CKD patients . The Pearson’s correlation coefficients analysis showed that SWV did not correlate significantly with height, weight, BMI, waistline, kidney dimension and the depth for SWV measurements . Furthermore, we stratified our study population into two groups according to influencing factors cutoffs, however, there were no significant differences between them  (P<0.001), the sensitivity and specificity was 71.87% and 69.69% respectively  . The meaectively ..P<0.001). Multiple comparisons analyzed with the LSD showed that the SWV was significantly higher for healthy volunteers compared with different stages in CKD patients , and it was significantly lower for stage 5 compared with stage 1, 2, 3 and stage 4 in CKD patients . However, there were no significantly differences among stage 1, 2, 3 and stage 4. The mean SWV was 1.81±0.43 m/s (range: 1.19–2.62 m/s), 1.79±0.29 m/s (range: 1.32–2.21 m/s), 1.81±0.44 m/s (range: 0.97–2.57 m/s), 1.64±0.55 m/s (range: 0.85–2.68 m/s), and 1.36±0.17 m/s (range: 1.14–1.71 m/s) for stage 1, 2, 3, 4 and stage 5, respectively, in CKD patients , serum urea nitrogen  and creatinine  (The laboratory data of the CKD patients were shown in = 0.001) .. But SWIncreasing evidences, accrued in the past decades, indicate that the adverse outcomes of CKD, such as kidney failure, cardiovascular disease, and premature death, can be prevented or delayed. Treatment of earlier stages of CKD, irrespective of cause, is effective in slowing the progression toward kidney failure However, traditional markers of CKD, such as serum creatinine, urea nitrogen and proteinuria are insensitive and reliance on these may result in extensive time lapse when successful interventions could be tested and applied Besides serum or urine test, imaging techniques may help to diagnose CKD et al.et al.’s evaluation that the cut-off SWV was 1.34 m/s for the diagnosis of significant fibrosis, 1.55 m/s for the diagnosis of severe fibrosis and 1.80 m/s for the diagnosis of liver cirrhosis, respectively ARFI shows a good positive correlation in evaluation of the grade of hepatic fibrosis and cirrhosis, Kircheis Furthermore, significant association was observed between SWV and e-GFR, serum urea nitrogen and creatinine. These results support our hypothesis that the change in renal parenchyma stiffness is a useful sign for detecting CKD. However, ARFI could not predict the different stages of CKD except for stage 5, due to overlaps among CKD stage 1, 2, 3 and 4. Studies with larger sample size are mandatory to evaluate whether ARFI is able to make differentiation among them.et al.et al. P = 0.53 and P = 0.11 for comparison of fibrosis grade 0 vs. grade 1 and fibrosis grade 0 vs. grade 2/3 respectively), the mean SWV was 2.8 m/s, 2.6 m/s, 2.5 m/s, and 1.8 m/s for grade 0, 1, 2 and grade 3 fibrosis respectively. For observer 1, the SWV was significantly lower for fibrosis grade 2/3 compared with fibrosis grade 0 (P = 0.02), whereas no such significant difference was found for observer 2 The tubulointerstitium comprises 80% of the volume of the kidney. Histological ESRD manifests itself as glomerulosclerosis, vascular sclerosis, and tubulointerstitial fibrosis, with tubulointerstitial fibrosis having consistently been shown to be the best histological predictor of progression et al.The age related decline in GFR in adults is accompanied by pathological findings of glomerulosclerosis and cortical atrophy As a new technique, several shortcomings should be mentioned. Due to the fixed box dimension (1 cm in length and 0.6 cm in width) of the ROI, this technology does not apply to some CKD patients whose renal parenchyma thickness is less than 1 cm. It has been reported that SWV measurements in renal transplant are dependent on the applied transducer force There are some limitations of this study. First, in our study SWV had high standard deviation in the healthy volunteers and CKD patients. In another study SWV showed highest standard deviation in the kidneys than those in the livers, pancreas, and thyroids Although advances in proteomics technologies, sample conditioning, and analysis methods have greatly improved productivity and efficiency in biomarker discovery, biomarker verification and validation remains a significant, costly, and high-risk undertaking in the commercial development and deployment of novel biomarkers for CKD


Ambulatory blood pressure monitoring (ABPM) shows a better correlation to target organ damage and cardiovascular morbidity-mortality than office blood pressure. A loss of arterial elasticity and an increase in carotid artery intima-media thickness (IMT) has been associated with increased cardiovascular morbidity-mortality. Tools have been developed that allow estimation of the retinal arteriovenous index but not all studies coincide and there are contradictory results in relation to the evolution of the arteriosclerotic lesions and the caliber of the retinal vessels. The purpose of this study is to analyze the relationship between peripheral and central arterial pressure (clinic and ambulatory) and vascular structure and function as evaluated by the carotid artery intima-media thickness, retina arteriovenous index, pulse wave velocity (PWV) and ankle-brachial index in patients with and without type 2 diabetes. In turn, software is developed and validated for measuring retinal vessel thickness and automatically estimating the arteriovenous index.A cross-sectional study involving a control group will be made, with a posterior 4-year follow-up period in primary care. The study patients will be type 2 diabetics, with a control group of non-diabetic individuals. Consecutive sampling will be used to include 300 patients between 34-75 years of age and no previous cardiovascular disease, one-half being assigned to each group. Main measurements: age, gender, height, weight and abdominal circumference. Lipids, creatinine, microalbuminuria, blood glucose, HbA1c, blood insulin, high sensitivity C-reactive protein and endothelial dysfunction markers. Clinic and ambulatory blood pressure monitoring. Carotid ultrasound to evaluate IMT, and retinography to evaluate the arteriovenous index. ECG to assess left ventricle hypertrophy, ankle-brachial index, and pulse wave analysis (PWA) and pulse wave velocity (PWV) with the Sphigmocor System.We hope to obtain information on the correlation of different ABPM-derived parameters and PWA to organ target damage - particularly vascular structure and function evaluated from the IMT and PWV - and endothelial dysfunction in patients with and without type 2 diabetes. We also hope to demonstrate the usefulness of the instrument developed for the automated evaluation of retinal vascularization in the early detection of alterations in vascular structure and function and in the prognosis of middle-term cardiovascular morbidity.NCT01325064Clinical Trials.gov Identifier:  Blood pressure measurement at the clinic remains the standard of reference, but there are increasing evidence that the values obtained after home blood pressure measurement by the patient and particularly 24-hour ambulatory blood pressure monitoring (ABPM)  shows a A loss of arterial elasticity, or arterial stiffness, has been associated with increased cardiovascular morbidity-mortality. At present the gold standard for evaluating arterial stiffness is carotid-femoral pulse wave velocity . This paThe classical Keith Wagener classification applied to the analysis of retinal vascular lesions has some limitations, particularly in correctly evaluating the initial phases of the vascular lesions. Tools have been developed that allow estimation of the retinal arteriovenous index ,20-23, aIn a phase prior to this project we developed a tool that determines retinal artery and vein thickness and estimates the retina arteriovenous index based on a semiautomated method, with the purpose of obtaining an automatic tool for this study. Associated cardiovascular disorders are the main cause of mortality in diabetic patients . PatientThe present project was therefore designed to analyze the relationship between arterial pressure (clinic and ambulatory), the arterial pressure circadian profile and other parameters generated by ABPM and central arterial pressure, and vascular structure and function as evaluated by the carotid IMT, retina arteriovenous index, PWV and ankle-brachial index (ABI) in patients with and without type 2 diabetes.An evaluation also will be made of the prognostic usefulness of the retina arteriovenous index in relation to the presence of vascular damage and cardiovascular disease, and to biological markers of endothelial dysfunction. To this effect an automated tool will be developed for estimating retinal artery and vein calibers, and for calculating the retina arteriovenous index.The first phase will comprise a cross-sectional observational study with a control group, while the second phase will consist of a prospective observational study with annual follow-up during four years. The study will be carried out in the urban primary care setting.The study population will be composed of type 2 diabetics, and an age- and gender-matched control group without diabetes will also be included. Based on consecutive sampling of all patients referred to the research unit for cardiovascular risk assessment, we will invite those who meet the inclusion criteria and show no reasons for exclusion to participate in the study, until the estimated sample sizes of both groups have been reached.Inclusion criteria: Patients aged 34 years or older and less than 75 years, with and without type 2 diabetes. Exclusion criteria: patients unable to comply with the protocol requirements , patients with ischemic heart disease, cerebrovascular disease or other atherosclerotic disease, patients participating or who will participate in a clinical trial during the study, and patients with serious comorbidities representing a threat to life over the subsequent 12 months.The sample size was estimated to detect differences between the subjects with and without diabetes in reference to PWV, as this represents the most unfavorable situation. Accepting an alpha risk of 0.05 and a beta risk of 0.20 in two-sided contrasts, 149 subjects are required in the first group and 149 in the second, in order to detect a difference of ≥ 1 unit. The common standard deviation (SD) is taken to be 3 , with a Age and gender. Family history of cardiovascular disease. Associated cardiovascular diseases, arterial hypertension, dyslipidemia, diabetes mellitus. History of smoking, alcohol consumption and physical activity. Arterial pressure and heart rate in clinic and with ABPM. Height, weight, and abdominal (waist) circumference. Blood sampling will be carried out under fasting conditions, and first morning urine will be collected. A blood sample and the urine will be sent to the core laboratory, and another blood sample will be centrifuged and frozen for posterior analysis. Initial determination will be made of blood glucose, HbA1c, insulinemia, microalbuminuria, blood and urine creatinine, lipids and high sensitivity C-reactive protein. Posteriorly, biological markers of endothelial dysfunction will be determined .The office blood pressure and heart rate measurement will be obtained by performing three measurements of systolic blood pressure (SBP) and diastolic blood pressure (DBP), with a validated sphygmomanometer, OMRON M7 model , following the recommendations of the European Society of Hypertension -diastolic blood pressure [DBP])/(first peak SBP-DBP)×100(%). Using the SphygmoCor System (Vx Pulse Wave Velocity), and with the patient in the supine position, the pulse wave of the carotid and femoral arteries will be analyzed, estimating the delay with respect to the ECG wave and calculating the PWV. Distance measurements will be taken with a measuring tape from the sternal notch to the carotid and femoral arteries at the sensor location.Carotid ultrasonography to assess IMT will be performed by two investigators trained for this before starting the study. The reliability of which was evaluated before the study began using the intraclass correlation coefficient, which showed values of 0.974 (95%CI: 0.935 to 0.990) for intra-observer agreement on repeated measurements in 20 subjects, and 0.897 (95%CI:0.740 to 0.959) for inter-observer agreement, and according to the Bland-Altman analysis, the limit of inter-observer agreement was 0.022 (-0.053 to 0.098) and the limit of intra-observer agreement was 0.012 -0.034 to 0.059). A Sonosite Micromax ultrasound device paired with a 5-10 Mhz multifrequency high-resolution linear transducer with Sonocal software will be used for performing automatic measurements of IMT in order to optimize reproducibility. Measurements will be made of the common carotid after the examination of a longitudinal section of 10 mm at a distance of 1 cm from the bifurcation, performing measurements in the anterior or proximal wall, and in the posterior or distal wall in the lateral, anterior and posterior projections, following an axis perpendicular to the artery to discriminate two lines, one for the intima-blood interface and the other to the media-adventitious interface. A total of 6 measurements will be obtained of the right carotid and other 6 of the left carotid, using average values (average IMT) and maximum values (maximum IMT) calculated by the software automatically. The measurements will be obtained with the subject lying down, with the head extended and slightly turned opposite to the carotid examined, following the recommendations of the Manheim Carotid Intima-Media Thickness Consensus [ to 0.059This will be evaluated using the ankle-brachial index (ABI), performed in the morning without having consumed coffee or tobacco for at least 8 hours prior to measuring and an ambient temperature of 22-24°C. With the feet uncovered, in a supine decubitus position after 20 minutes of rest, the pressure in the lower extremities and blood pressure in both arms will be measured using a portable WatchBP Office ABI (Microlife AG Swiss Corporation).The ABI will be calculated automatically for each foot by dividing the higher of the two systolic pressures in the ankle by the highest measurement of the two systolic pressures in the arm .The electrocardiographic examination will be performed with a General Electric MAC 3.500 ECG System , that measures automatically the voltage and duration of waves and estimates the criteria of the Cornell voltage-duration product (Cornell VDP) to assess the LVH by the following equation: Men ((RaVL + SV3) * QRS) and women ((RaVL + SV3) * QRS + 6). LVH is defined as the voltage-duration product > 2,440 mm/ms . We willThe kidney damage will be assessed by measuring creatinine plasma concentration, the glomerular filtration rate will be estimated by CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration)  and the Retinography will be performed with a Topcon TRC NW 200 non-mydriatic retinal camera (Topcon Europe B.C. Capelle a/d IJssel The Netherlands), obtaining images centered on the papilla, nasal and temporal. Once the images will be captured, two independent observers classified them according to the Keith-Wagener and Wong classification for hypertensive retinopathy ,42, and As part of the project we include development of the second phase of software designed to semiautomatically measure the arterial  and venous caliber  of the retinal vascular tree and to automatically estimate the retina arteriovenous index, based on a method similar to that of the Atherosclerosis Risk in Communities (ARIC) study in the United States , making For validation of the retina software in its semiautomated and automated versions, the following steps will be followed after prior training of the examiners who will evaluate the images obtained: 1.- Intraobserver variability: in order to assess the repeatability of the measurement, an operator must measure the same photograph in the same individual at least twice. To this effect, an operator will evaluate 200 images of a random sub-sample of 100 patients, with a difference of one week between the two evaluations. In this case the operator and the images analyzed will be the same on both days, and the operator will have no information on the previously performed evaluation. 2.- Interobserver variability: in order to assess the reproducibility of the measurement system, an operator different from that in phase 1 will evaluate the same 200 images previously analyzed. This operator will be blinded to the results already obtained in the previous phase. The two operators will have the same experience in the subject and in the use of the software, and both will receive the same prior training. 3.- Ocular variability: one month later, new photographs will be obtained of the same group of patients. These results will be evaluated by the operator of phase 1, and in this case the origin of the image, the patient characteristics and the results obtained in the previous evaluation will not be known. 4.- Furthermore, the retina software in its automated version (phase 2) generates the results relating to the retina arteriovenous index, CRAE and CRVE. In the semiautomated version the user participates and decides the interpretations made by the computer, and can change them if considered necessary. The automatic and semiautomatic evaluation of 200 images will be used to assess the degree of concordance between the two methodologies. In this way we will be able to show that the automatic method not only affords the same results but moreover also improves daily practice, affording greater objectivity and speed in producing the results. 5.- The validity of the measurement will be analyzed comparing the results with the carotid IMT as measure of vascular structure and with PWV as measure of vascular function and gold standard of arterial stiffness of the 300 patients included in the study. 6.- An analysis also will be made of the association of the estimated retina arteriovenous index and the evolution or appearance of new target organ damage and cardiovascular events during follow-up of the patients over the four years of the second phase of this project.Post hoc contrasts will be made with the least significant difference (LSD) technique, with an alpha < 0.05. The relationship between quantitative variables will be analyzed using Pearson's correlation coefficient. Estimation of the slope of the straight line needed to calculate the ambulatory arterial stiffness index (AASI) will be made based on a linear regression model. Lastly, multiple linear regression and logistic regression analysis will be made to analyze the most significant variables conditioning the alterations in arterial pressure and vascular damage with the different methodologies used in the two groups. Hypothesis contrasting will establish an alpha risk factor of 0.05 as the limit of statistical significance.The data will be presented with the mean and 95% confidence interval (95%CI) in the case of quantitative variables, and as frequency distributions for qualitative variables. The Pearson chi-squared test will be used to analyze associations between qualitative variables. Student's t test for independent samples will be used to compare the means of two groups, and analysis of variance (ANOVA) will be performed in the case of a larger number of groups. Validation of the retina software: For evaluating the measurements of the retina arteriovenous index, CRAE and CRVE obtained in the three validation phases, calculation will be made of the intraclass correlation coefficient as comparison method, together with the Bland-Altman technique, which allows graphical evaluation of the concordance or agreement between the two measurement systems. The results obtained with the two types of measurements that can be made with the software (automated or semiautomated) will be analyzed with the intraclass correlation coefficient and Kappa concordance coefficient on categorizing the variable. This coefficient will allow us to evaluate the degree of concordance between the two types of results. The SPSS/PC+ version 18.0 statistical package will be used.The sample is composed of diabetics and non-diabetics, many of them with arterial hypertension referred by their primary care physician to the research unit for ABPM and the evaluation of cardiovascular risk. As a result, consecutive non-randomized sampling is involved. However, the large size of the sample partially offsets this limitation, and the real clinical practice conditions can bring us closer to the real-life situation than if more restrictive criteria were used for including the patients in the study. We will have diabetic, hypertensive and control subjects without these disorders for analysis and comparison of the results.In order to ensure data quality, the nursing professionals in charge of data collection will receive specific training. Periodic external monitoring will be performed to verify adequate application of the methodology, both in performing the different examinations and in collecting the information.In order to guarantee data confidentiality, all the electronic and paper copies of the protocol, signed informed consent documents and results of the tests made in each of the patients will be kept locked in a safe place, and only the study investigators will have access to the data on the subjects who agree to participate in the study. The study has been approved  by the research ethics committee from University Hospital of Salamanca, Spain and complies with Spanish data protection law 15/1999 and its recently developed specifications  1720/2007). Knowledge and agreement to cooperate has been established with the implicated services, signed by the legal representative of the centre. Written informed consent to participation in the study will be obtained in all cases.The measurement of arterial pressure, both in the clinic and on an ambulatory basis, is very widespread in clinical practice, and its direct correlation to mortality and morbidity has been extensively studied -46. HoweWe also hope to demonstrate the usefulness of the instrument developed for the automatic evaluation of retinal vascularization in the early detection of alterations in vascular structure and function and in the prognosis of middle-term cardiovascular morbidity. This tool could help improve the information derived from retinal photographs and make their use more efficient thanks to automatization of the procedures, in both diabetics and in individuals without diabetes. Lastly, we hope to clarify the prognostic role of the biological markers of endothelial dysfunction such as osteoprotegerin and endoglin, and to standardize their use in clinical practice.AASI: Ambulatory arterial stiffness index; ABI: Ankle-brachial index; ABPM: Ambulatory blood pressure monitoring; AIx: Augmentation Index; ARIC: Atherosclerosis Risk in Communities study; ASCOT: Anglo-Scandinavian Cardiac Outcomes Trial; CAFE: Conduit Artery Function Evaluation; CKD-EPI: Chronic Kidney Disease Epidemiology Collaboration; CRAE: central retinal artery equivalent; CRVE: central retinal vein equivalent; DPB: Diastolic blood pressure; ESH: European Society of Hypertension; IMT: Intima-media thickness; MDRD-IDMS: Modification of Diet in Renal Disease-Isotopic Dilution Mass Spectrometry; OPG: Osteoprotegerina; PP: Pulse pressure; PWA: Pulse Wave Analysis; PWV: Pulse Wave Velocity; SBP: Systolic blood pressure.The authors declare that they have no competing interests.Conception of the idea for the study: LGO, ERD and MAGM. Development of the protocol, organization and funding: LGO, ERD, JIRR, CAC, CMS, MCPA, ERS and MAGM. Writing of the manuscript: LGO and MAGM. All the authors have read the draft critically, to make contributions, and have approved the final text. The project will be developed by Vaso risk group.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2458/11/266/prepub


BMC Medicine by Huang et al. clearly indicates that pre-hypertension (120 to 140/80 to 90 mmHg) is a significant marker of increased cardiovascular risk. This raises the question as to whether we now need to lower the threshold of ‘hypertension’ (as opposed to ‘pre-hypertension’) to >120/80 mmHg, redefining a significant proportion of currently healthy people as ‘patients’ with an established disease. These data need to be interpreted with some caution. It is controversial whether pre-hypertension is an independent risk factor or just a risk marker and even more controversial whether treatment of pre-hypertension will lower cardiovascular risk.Hypertension is one of the most important and common cardiovascular risk factors. Defining the level at which blood pressure starts causing end-organ damage is challenging, and is not easily answered. The threshold of blood pressure defining hypertension has progressively been reduced over time, from systolic >160 mmHg to >150 mmHg, then to >140 mmHg; and now even blood pressures above 130 to 120 mmHg are labeled as ‘pre-hypertension’ by some expert committees. Are interest groups creating another ‘pseudodisease’ or is this trend scientifically justified? A recent meta-analysis published in http://www.biomedcentral.com/1741-7015/11/177.Please see related research:  What exAs illustrated by these variable definitions from different committees, it is difficult to come up with a clear cut-off value to define ‘good’ and ‘bad’. While clinicians understandably prefer clear binary disease definitions, there is a continuous association between blood pressure and cardiovascular risk .BMC Medicine, Huang et al. challenge current guidelines which label blood pressures >140/>90 mmHg as being ‘normal’ by concluding that pre-hypertension (even at lower levels of 120 to 129/80 to 84 mmHg) is a significant cardiovascular risk factor.In a recent study published in et al. have performed a systematic review on the clinical relevance of pre-hypertension [Huang rtension . They peet al., the Framingham study further showed an increased risk even for those with blood pressure values of 120 to 129/80 to 84 mmHg compared with those with ‘optimal’ blood pressure (<120/<80 mmHg). Another very important study in this context is the Women's Health Initiative, involving over 60,785 women in their postmenopausal phase. Pre-hypertensive women showed a 76% increased risk for cardiovascular death, a 93% increased risk for myocardial infarction and 36% increased risk for stroke [et al.Let us now have a closer look at some individual studies included in this meta-analysis. The Framingham Heart Study  showed a 2.5-fold increased risk for cardiovascular events at 10 years for women and a 1.6-fold increase for men with blood pressures between 130 to 139/85 to 89 mmHg [per se. We know that pre-hypertensive individuals are much more likely to progress to hypertension. In the Framingham cohort, patients with ‘higher range pre-hypertension’ (130 to 139/85 to 89 mmHg) developed hypertension in 37% of cases, those with ‘lower range pre-hypertension’ developed hypertension in 18% of cases and those with ‘optimal blood pressure’ only in 5% of cases, over a 4-year period in patients >65 years [The question arises based on these data, whether we should now reclassify ‘pre-hypertension’ as ‘hypertension’, even at the low blood pressure (BP) range, which would apply to a significant proportion of the population as newly labeled hypertensive patients? It is estimated that about 37% of people in the US, that is, more than 100 million fall within this pre-hypertension category. Whether these patients would benefit from pharmacologic therapy and if so, what the exact cost/benefit relation would be remains uncertain. Pre-hypertension is clearly associated with cardiovascular risk, but it is questionable whether a blood pressure level in this pre-hypertension range is a causal risk factor for cardiovascular events The question still remains whether active treatment of pre-hypertension will prevent progression to more advanced hypertension and future cardiovascular events. Experimental data indicate that it may actually be possible to change the natural history of pre-hypertension. In a hypertensive rat model, if antihypertensive therapy is given within the first 2 to 6 weeks of life it can prevent the development of hypertension [In the clinical setting, these findings could not be fully confirmed. The ‘TRial of Preventing Hypertension’ (TROPHY) study was a 4-year trial of 806 patients with pre-hypertension who were randomly assigned to 2 years of therapy with either candesartan or placebo (16 mg/day) . After 2While temporary treatment of pre-hypertension does not seem to prevent progression to hypertension, the question remains as to whether it reduces CV risk? Data on this question are conflicting. A recent meta-analysis pooling the results of trials of antihypertensive treatment in patients with cardiovascular disease but without hypertension showed a benefit. It was based on 25 randomized trials and 64,162 participants and found a 23% reduction in the risk of stroke, a 20% reduced risk of myocardial infarction, a 15% reduced risk of heart failure and a 13% reduced mortality risk . Whetheret al., in patients who had renal denervation on ABPM. There was a significant reduction of 8 to 10 mm Hg systolic and 4 to 7 mm Hg diastolic, but clearly less impressive that the reduction of the office blood pressure in the same population (21 to 27 mm Hg (systolic)) and (9 to 12 mm (diastolic)) [ABPM has become a useful tool to evaluate the true blood pressure burden and it has been shown to be a better predictor of cardiovascular events than are office blood pressure measurements. In a recent study of almost 5,000 patients from the Spanish ABPM Registry 60% of patients with office pressure of 130 to 139/85 to 89 mmHg, 42% with office pressure of 140 to 159/90 to 99 mmHg and 53% with office blood pressures of above 160/100 mmHg were actually normotensive according to the 24-h ABPM measuring criteria, that is, their mean ABPM was below 130/80 mmHg) [stolic)) .et al. clearly indicate that a blood pressure level currently defined as pre-hypertension is a significant marker of increased cardiovascular risk. However, we lack evidence that pre-hypertensive blood pressure itself is harmful and that an earlier intervention to reduce the blood pressure is beneficial in the absence of cardiovascular disease. Since pre-hypertensive individuals are at a high risk to progress to sustained hypertension, we advise periodic screening.The data of Huang ad hoc consultant for the following organizations: Novartis, Daiichi Sankyo, Pfizer, Takeda, Abbott, Servier, Medtronic, Ipca Laboratories Ltd.FHM: PM drafted the first version, FHM, AB and AJL revised it critically for its intellectual content. All authors contributed substantially to this editorial and approved the final manuscript.http://www.drpascalmeier.com). He is editor-in-chief of the journal Open Heart and associate editor of the Cochrane Heart group (http://heart.cochrane.org/). Franz H Messerli is an expert in hypertension. He is Professor of Clinical Medicine at Columbia University College of Physicians and Surgeons, New York. Andreas Baumbach is a cardiologist at the Bristol Heart Institute. He has an interest in novel treatment options for hypertension, such as renal artery denervation. He is a co-director of the EuroPCR course, one of the major international cardiology conferences. Alexandra Lansky is a cardiologist and associate professor at Yale University School of Medicine and a renowned expert in clinical cardiovascular research. She is heading the Yale-UCL Cardiovascular Research collaborative .Pascal Meier is a cardiologist at University College London, UK, and Yale Medical School, CT, USA (The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1741-7015/11/211/prepub


Mean systolic blood pressure was 136±18 mmHg and mean diastolic blood pressure was 80±11 mmHg. Only 18% of patients had a mean blood pressure <130/80 mmHg during the study period. Multivariate analysis revealed several independent factors of poor blood pressure control: body mass index ≥23 kg/m2, the presence of stable angina pectoris (SAP), family history of diabetes, and use of calcium channel blockers (CCB). Further analysis showed that non-dihydropyridine calcium antagonist was significantly correlated with low BP control rate. Some of these may be amenable to modification. The results of our study suggest that overweight, the presence of SAP and family history of diabetes are important factors for tight BP control in primary care. In addition, non-dihydropyridine calcium channel blockers appear less effective than other therapies in control of blood pressure and should not be the first choice among hypertensive patients with CHD. Further identification of patients at risk of poor BP control can lead to targeted interventions to improve management.Blood pressure (BP) remains poorly controlled among hypertensive patients with coronary heart disease (CHD) in China. Improvement of its management will require an understanding of the patient characteristics and treatment factors associated with uncontrolled hypertension. A cross-sectional survey of 3,279 patients from 52 centers in China was performed to examine potential barriers to adequate blood pressure control of hypertensive patients with CHD. Uncontrolled hypertension was defined as blood pressure ≥130/or 80 mmHg. Multivariable logistic regression was used to identify factors associated with poor blood pressure control. Mean age of the patients was 65 years, 40% were women, and mean BMI was 25 kg/m Hypertension is an important risk factor for cardiovascular disease and has become a major global burden on public health Generally, most guidelines stipulated a blood pressure treatment goal of 140/90 mmHg. However, recent clinical trials showed further benefit could be achieved by more aggressive blood pressure lowering to well below 130/80 mmHg in hypertensive populations, including those patients with CHD Previous trials did not measure blood pressure control rates among hypertensive patients with CHD. It will therefore be important to identify factors that could affect blood pressure control in hypertensive patients with CHD in a large, nationally representative sample population. The purpose of this study was to use data from a previously reported China Cholesterol Education Program (CCEP) 2 was recommended to use to define overweight The China Cholesterol Education Program (CCEP) was a cross-sectional, large multicenter investigation, which involved 52 centers in 6 cities  in China CHD was diagnosed physicians, and supported by at least one of the following objective findings; abnormal stress tests  indicating significant myocardial ischemia, a coronary angiogram revealing >50% stenosis of the lumen of any major coronary artery, a history of confirmed myocardial infarction (MI) or evidence of prior MI on electrocardiogram, or a history of a prior coronary revascularization procedure (percutaneous coronary intervention or coronary artery bypass graft). The CHD diagnosis was classified as stable angina pectoris (SAP), previous MI, or acute coronary syndromes (ACS), which included unstable angina pectoris, ST-segment elevation MI and non-ST-segment elevation MI Hypertension was defined as systolic blood pressure ≥140 mmHg, and/or diastolic blood pressure ≥90 mmHg, and/or current antihypertensive medication 2 test. Stepwise logistic regression models were used to estimate the odds ratios (ORs) and associated 95% CI of blood pressure control, and the probability for variable entry into models was 0.05 and for variable removal was 0.10. The variables that were significant (P<0.1) in the bivariate analysis were included in a multivariate logistic regression model. Full model included BMI≥23 kg/m2, stable angina pectoris (SAP), family history of diabetes, and CCB.All case record form data were entered into dual Epidata 3.02 databases. The databases were compared and necessary corrections were made. All analyses were performed with the Statistics Package for Social Science, version 13.0 . Continuous variables are expressed as mean ± SD, and discrete variables as percentages. The differences in continuous variables between groups were examined by t-test. The differences in discrete variables between groups were calculated by the Pearson χ2 . This was a multicenter observational study conducted in the Chinese society of cardiology. Demographic and clinical characteristics of hypertensive patients with CHD are listed in The results of bivariate analysis of factors affecting BP control are shown in The study represents the first analysis of factors that may be associated with blood pressure control in hypertensive patients with CHD. We observed that nearly 95% of individuals were receiving antihypertensive medication, but only 16.7% subjects  and 19.1%  had adequate BP control (<130/80 mmHg). Previous meta-regression analysis demonstrated that the benefit of antihypertensive drug treatment was largely attributable to BP reduction In our present study, we found a significant association of uncontrolled BP with the presence of obesity, SAP and family history of DM, which were consistent with other previous publications Uncontrolled high blood pressure can lead to a variety of changes in the myocardial structure, coronary vasculature, and conduction system of the heart. These changes in turn can lead to the development of left ventricular hypertrophy, coronary artery disease, and systolic and diastolic dysfunction of the myocardium, complications that manifest clinically as angina Multivariate logistic regression analysis showed poor control of blood pressure was also associated with use of calcium channel blockers (CCB). Although several studies have shown improvements in the outcomes of patients with CHD using the dihydropyridine calcium channel blocker The present analysis has several potential limitations. First, the analysis is cross-sectional, and we cannot determine temporal direction or causality. Second, because the present analysis is performed from an aspect differing from the original purpose of observation, a bias in the selection of patients cannot be excluded. Another limitation is potential measurement error from the medication use data. We do not have information on actual adherence to the treatment regimen. In addition, because the dosages of CCB including non-dihydropyridine calcium channel blockers and their continuation states are not investigated, the effective dosages of CCB could not be clarified. Further studies are necessary to clarify these points. However, these data have relevant clinical implications, suggesting that physicians pay close attention toward the rational use of CCB. The current analysis also extends our understanding of cross-sectional covariates associated with hypertensive patients with CHD.Our data suggest that the presence of obesity, SAP and family history of diabetes are important factors for tight BP control in adults with CHD. In addition, non-dihydropyridine calcium channel blockers may be less effective than other therapies in control of blood pressure and should not be the first choice among hypertensive patients with CHD.


Carbon monoxide (CO) poisoning can be a life threatening condition. Systemic hyperbaric oxygen (HBO) therapy is used to induce CO detoxification. However, little is known about the hemodynamic response to HBO in severely intoxicated patients.We retrospectively analyzed the medical records of 6 CO-poisoned patients treated with propofol, rocuronium bromide, and HBO. The HBO protocol comprised 3 HBO treatments (HBOT1 to HBOT3) within 24 hours. During all HBO sessions heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse blood pressure (ΔBP) were measured every five minutes. Non-parametric tests were used to compare data between HBO sessions.p < 0.05). In addition, while no significant change was found for DBP, both SBP and ΔBP showed a transient and significant increase during HBOT2, compared to HBOT1, that did not return to basal values during HBOT3.HR increased significantly as the number of HBOT increased, from 68 beats per minute (bpm) during HBOT1 to 77 and 86 bpm during HBOT2 and HBOT3, respectively (Based on previous studies that have established the respective effects of rocuronium bromide, propofol, HBO, and CO alone on HR, SBP, and ΔBP, it is concluded that the hemodynamic responses observed in the present study are likely to be due to CO. If such, given that neither HR nor SBP and ΔBP returned to basal values by the end of HBOT3, it is suggested that more than 3 HBOT sessions could be necessary to provide full hemodynamic recovery in CO-poisoned patients. Carbon monoxide (CO) poisoning can be a life threatening condition that is associated with a long-term increased risk of mortality in severely intoxicated patients ,2. BecauThis retrospective study is based on the review of the medical records of patients admitted for CO poisoning between 2008 and 2011 at the CSSS Alphonse-Desjardins Hôtel-Dieu de Lévis hospital , and was approved by the CSSS Alphonse-Desjardins ethic committee with number # CER 1112–030.et al., [Among the 11 patients diagnosed for critical CO-poisoning based on their carboxyhemoglobin level upon arrival at the emergency department of CSSS Alphonse-Desjardins Hospital, 6 patients ≥ 18 years were included in the present study as they completed the entire drug treatment and HBO protocol described below. All patients were administered rocuronium bromide  to allow proper intubation before being placed in the pressure chamber, propofol  to provide sedation, and then were treated with HBO according to a protocol adapted from that of Weaver Based on clinical assessment, additional pharmacological treatments were given during the 24-h HBO/ICU period: Patient #3 was administered a single injection of 0.05 mg fentanyl before HBOT1 in addition of propofol; Patient #1 and Patient #5 were given ventolin®; Patient #1, Patient #3, and Patient #4 were given water-soluble vitamin B1 (thiamin). Also, Patient #3 and Patient #4 were given one additional HBOT. No catecholamine was given.One investigator reviewed and abstracted the data from the medical records. Demographic information, CO-poisoning history, comorbidities, blood gas measurements, and sedation protocol were extracted. The patients’ hemodynamic profile comprising heart rate (HR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were also reviewed. Values measured from one of the patients’ arm using an Oscill Mate 1630 automated device  were recorded every five minutes and averaged to obtain mean value during HBOT1, HBOT2, and HBOT3. Also, pulse blood pressure (ΔBP) was further assessed by calculating the difference between SBP and DBP.F value, post hoc comparisons were made using the Wilcoxon t-test (two-tailed). The statistical significance was set at α = 5%.Data are expressed as the median value and the 25th and 75th percentiles, and analyzed using non-parametric methods with the SAS 9.2 software . Within-group comparisons between HBOT were performed using the Friedman analysis of variance; following a significant Patients were 4 males and 2 females of 36 to 63 years of age. Four CO-poisonings were intentional and two were declared accidental. Three cases were related to fire smoke inhalation. Individual detailed demographic information, CO-poisoning history, and comorbidities are given in Table p < 0.05). This resulted in a trend toward increase in HR between HBOT1 and HBOT2  that reached statistical significance between HBOT1 and HBOT3 . SBP showed significant changes across treatments from 102 mmHg during HBOT1 to 130 and 112 mmHg during HBOT2 and HBOT3, respectively . This led to a significant difference in SBP between HBOT1 and HBOT2  but not between HBOT1 and HBOT3 (T = 1.153). In addition, ΔBP also showed significant changes across treatments from 44 mmHg during HBOT1 to 58 and 49 mmHg during HBOT2 and HBOT3, respectively . This resulted in a significant difference in ΔBP between HBOT1 and HBOT2 , but not between HBOT1 and HBOT3 (T = 1.577). In contrast with HR, DBP and ΔBP, no significant change was found for DBP (F = 0.882). Individual data of HR, SBP, DBP, and ΔBP are shown in Table We examined the effects of HBOT on the hemodynamic parameters of these CO-poisoned patients. We found that HR increased significantly as the number of HBOT increased from 68 beats per minute (bpm) during HBOT1 to 77 and 86 bpm during HBOT2 and HBOT3, respectively  still exhibited borderline hemodynamic responses -27, withAs the vast majority of the retrospective case-series studies, the present report should be interpreted carefully because of its inherited limitations. This includes the small sample of patients, the lack of information on the duration of the exposure to CO, the uncontrolled delay between the end of the exposure to CO and the first HBOT session, the uncontrolled administration of medication, and the absence of actual post-treatment evaluations that could have indicated that HR, SBP, and ΔBP had finally returned to basal values. However, despite these limitations, we believe that the present study is of actual interest since it is the first one, to the best of our knowledge, to report the hemodynamic effects of HBO in critically ill CO-poisoned patients.Given the respective effects of rocuronium bromide, propofol, HBO, and CO on the hemodynamic parameters, we conclude as discussed in details above that the increase in HR, SBP and ΔBP observed in the present study is likely to be due to CO, and that more than 3 HBO sessions would be necessary to provide full hemodynamic recovery in CO-poisoned patients. If such, it is likely that HR, SBP, and ΔBP could be used as physiological markers to assess CO detoxification. Monitoring these hemodynamic parameters together with patient outcomes in future prospective clinical studies could document this possibility. With no doubt, further studies are needed to confirm our hypothesis, and lead clinicians to use hemodynamic parameters as a clinical biomarker for CO-poisoning and HBO detoxification.Written informed consent was obtained from the representant of the participant for the publication of this report.The authors declare that they have no competing interests.JP conceived the study and actively participated in the data collection. MLCD and JHA designed the study, analyzed the data and drafted the manuscript. All of the authors interpreted, revised and approved the final version of the manuscript for publication. MLCD takes the responsibility for this paper as a whole.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2253/13/26/prepub


Objective: Pulse wave velocity (PWV) and aortic augmentation index (AI) are indicators of arterial stiffness. Pulse wave reflection and arterial stiffness are related to cardiovascular events and sickle cell disease. However, the effect of these parameters on the heterozygous sickle cell trait (HbAS) is unknown. The aim of this study is to evaluate the arterial stiffness and wave reflection in young adult heterozygous sickle cell carriers.Materials and Methods: We enrolled 40 volunteers  aged between 18 and 40 years. AI and PWV values were measured by arteriography.Results: Aortic blood pressure, aortic AI, and brachial AI values were significantly higher in HbAS cases compared to the control group (HbAA) . A statistically significant positive correlation was found between aortic pulse wave velocity and mean arterial pressure, age, aortic AI, brachial AI, weight, and low-density lipoprotein levels  in the whole study population. Aortic AI and age were also significantly correlated (p=0.026). In addition, a positive correlation between aortic PWV and systolic blood pressure and a positive correlation between aortic AI and mean arterial pressure  were found in HbAS individuals. Our study reveals that mean arterial pressure and heart rate are independent determinants for the aortic AI. Mean arterial pressure and age are independent determinants for aortic PWV. Conclusion: Arterial stiffness measurement is an easy, cheap, and reliable method in the early diagnosis of cardiovascular disease in heterozygous sickle cell carriers. These results may depend on the amount of hemoglobin S in red blood cells. Further studies are required to investigate the blood pressure changes and its effects on arterial stiffness in order to explain the vascular aging mechanism in the HbAS trait population. Conflict of interest:None declared. Sickle cell disease (SCD) affects many systems as it is a chronic and hemolytic autosomal recessive disease. Atherosclerosis is a common finding in patients with sickle cell anemia . MoreovePatientsTwenty individuals with HbAS  and 20 healthy participants with HbAA as a control group  were included in the study. Diagnosis was made by hemoglobin electrophoresis and family screening in both groups. Atrial fibrillation and/or flutter, chronic renal failure, mild or severe valvular heart disease, and other chronic diseases were the exclusion criteria. Our local ethics committee approved the study and written informed consent was obtained from all participants. Physical ExaminationBlood pressures were measured with the aid of a mercury sphygmomanometer after subjects rested for at least 15 min and had not consumed caffeinated beverages or tobacco in the last 12 h. We recorded heart rate by counting the number of heart beats in 1 min. Circulatory and cardiac examinations were performed. Skin pallor, cold extremities, peripheral cyanosis, cardiac cachexia, cardiac murmurs, increased apex beat, and third and fourth heart sounds were noted as pathological findings on physical examination. Laboratory Examination A 12-lead electrocardiogram was recorded on admission. Fasting venous blood samples were taken after 12 h of fasting. Complete blood count, thyroid function tests, fasting blood glucose, blood urea, creatinine, sodium, potassium, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and hemoglobin electrophoresis were checked for all participants. Echocardiographic ExaminationAll echocardiographic measurements were obtained from the patients at rest. Standard echocardiographic examination and pulsed-wave Doppler and tissue Doppler imaging were performed on an ACUSON SequoiaTM ultrasound machine  with a 2.5- or 3.5-MHz phased-array transducer. The mean of all recordings from 3 consecutive cycles was used for measurements. M-mode measurements of left ventricular end-diastolic and end-systolic dimensions and volumes, ventricular septal and posterior wall thicknesses, and left atrial end diastolic dimensions were calculated in accordance with the recommendations of the American Society of Echocardiography [9]. Left ventricular mass was calculated by use of the Penn formula (1.04 × [(SVd + IVSd + ADd)³ – (SVd)³] – 13.6). Left ventricular ejection fraction was calculated by use of the modified Simpson technique. Left ventricular diastolic function was evaluated in the apical 4-chamber view by means of pulsed-wave and tissue Doppler imaging. The pulsed-wave Doppler imaging was performed in order to measure transmitral flow values, including the peak early diastolic filling velocity (E), the peak late diastolic filling velocity (A), the early diastolic/late diastolic filling velocity (E/A) ratio, the E-wave deceleration time, and the isovolumic relaxation time. The tissue Doppler imaging was performed in order to measure systolic myocardial velocity (Sm), peak early diastolic myocardial velocity (Em), and peak late diastolic myocardial velocity (Am). The Em/Am ratio was calculated at the end of expiration. Pulse Waveform AnalysisAssessment of arterial stiffness was performed noninvasively with the commercially available Arteriograph  [10]. We measured the participants’ oscillometric pulse waves and the distance between the jugulum and symphysis (which is the same as by the invasive method for the distance between the aortic root and the aortic bifurcation), and the PWV was calculated. Pulse waves were recorded at suprasystolic pressure. The oscillation signs were identified from a cuff inflated to at least >35 mmHg above the systolic blood pressure. In this state there is complete brachial artery occlusion and it functions as a membrane before the cuff. Pulse waves hit the membrane and oscillometric waves were measured by the device, and we could see the waveforms on the monitor. The augmentation index (AI) was defined as the ratio of the difference between the second  and first systolic peaks  to pulse pressure (PP), and it was expressed as a percentage of the ratio (AI = [P2 – P1] / PP × 100). SBP, DBP, PP, central aortic pressure (AP), heart rate, and other hemodynamic parameters were expressed as return time , and diastolic reflection area (DRA), systolic area index (SAI %), and diastolic area index (DAI %) were measured noninvasively with the TensioMed Arteriograph. DRA reflects the quality of the coronary arterial diastolic filling, while SAI and DAI are the areas of the systolic and diastolic portions under the pulse wave curve of a complete cardiac cycle, respectively. Hence, coronary perfusion is better when DAI and DRA values are higher. Furthermore, RT is the PWV time from the aortic root until the bifurcation and return, and so this value gets smaller as the aortic wall gets stiffer. Statistical AnalysisStatistical analysis was performed using SPSS 13.0. Categorical measures were summarized as number and percentage; numerical measures were summarized as mean and standard deviation . The chi-square test was used to compare categorical measurements between the groups. The quantitative measurements of independent groups were compared by either t-test or Mann–Whitney U test for parametric and non-parametric data, respectively. Univariate analysis was used to determine the correlations between PWV and AI, SBP, heart rate, weight, height, fasting plasma glucose, serum urea, creatinine, LDL-C, total cholesterol, and Hb. Stepwise multiple regression analysis was used to determine whether HbAS, age, weight, mean arterial pressure (MAP), heart rate, Hb, and the value of total cholesterol were independent predictors of PWV and AI. The mutual relationship of PWV and AI with blood pressure and heart rate was determined by covariance analysis. In correlation analysis, p≤0.01 was considered significant. In other analyses, we treated p≤0.05 as significant. Positive correlations were found between PWV and AI and SBP, MAP, age, and weight in HbAS individuals . PWV incAfter performing multiple stepwise regression analysis, we established that PWV and aortic AI were both independently positively associated with MAP . At the same time, PWV was also positively associated with age (p=0.029). The aortic AI was independently negatively associated with heart rate (p=0.041). Multiple stepwise regression analysis results are shown in Cardiovascular effects of pulse reflection and arterial stiffness have been demonstrated. The effect of vascular aging on prognosis has been proven in publications about many diseases. Major determinants of these detrimental results were pulse pressure , AI 12]12], and Rees et al.  measuredThe influence of age-dependent vascular damage and the effect of arterial stiffness are well established . There wPannier et al. [27] examined the simultaneous PWV measurements of the aorta, brachial, and femoral arteries in 305 patients and unequivocally proved that only the PWV measurements of the aorta had a predictive value. We measured PWV only from the aorta.Noninvasive measurement of arterial stiffness is a valuable method. Arteriography results have a considerably tight relationship with cardiac catheterization measurements [10]. Nevertheless, a study comparing other devices that can measure PWV showed that similar PWV values were obtained using the SphygmoCor (8.1±1.1 m/s) or the Arteriograph (8.6±1.3 m/s). However, for the Complior method, values were significantly different (10.1±1.7 m/s) because the recorded travel distance for PWV was higher than the others [28].Our study revealed that MAP and heart rate were independent determinants for the aortic AI. MAP and age were also independent determinants for aortic pulse wave velocity. The most important independent predictors of arterial stiffness were MAP and age. Sickle cell disease (HbSS) is associated with shortened life expectancy, although the sickle cell trait (HbAS) is a benign carrier condition and is not associated with shortened life expectancy in ordinary people. HbAS patients have a better life quality with fewer complaints than HbSS patients, but still at levels lower than among the normal healthy population. Unpredictable cardiovascular collapse and death may occur in the HbAS population during or after vigorous exercise. Therefore, measurement of arterial stiffness might help achieve a better understanding of complications associated with sickle cell carriers. Arterial stiffness measurement is an easy, cheap, and reliable method in the early diagnosis of cardiovascular disease in heterozygous sickle cell carriers. These results may depend on the amount of S hemoglobin in red blood cells. Further studies are required to investigate blood pressure changes and their effects on arterial stiffness in order to explain the vascular aging mechanism in patients with sickle cell disorder.The authors of this paper have no conflicts of interest, including specific financial interests, relationships, and/ or affiliations relevant to the subject matter or materials included.


To investigate the association between plasma concentrations of N-terminal pro-B-type natriuretic peptide (NT-proBNP) and formation of esophageal varices.Thirty-five patients with alcoholic cirrhosis were divided into three groups according to the Child-Pugh classification: grade A , B , and C . System hemodynamic parameters were measured using sphygmomanometry, electrocardiography, and echocardiography. NT-proBNP was analyzed by using an electrochemiluminiscence sandwich immunoassay.P < 0.001).The presence of esophageal varices was associated with a higher serum NT-proBNP level, with a cut-off value of >101 pg/mL (sensitivity, 87.60% and specificity, 72.73%; NT-proBNP was found to be a marker of the presence of esophageal varices, but not a marker of progression of liver cirrhosis. In cirrhotic patients, NT-proBNP value >101 pg/mL was shown to be a valuable noninvasive parameter in predicting the presence of varices. Cirrhotic patients are characterized by hyperdynamic circulation with increased cardiac output, heart rate and plasma volume, normal or low arterial blood pressure, and decreased systemic vascular resistance -3. The pPro-B-type natriuretic peptide proBNP1-108) is a 108-amino acid prohormone secreted from the cardiomyocytes secondary to cardiac wall distension and stretching, and neurohumoral activation in response to ventricular volume and pressure overload 8 is a 10,12. PatiThe aim of this study is to investigate the association between plasma concentrations of NT-proBNP and formation of esophageal varices. Additionally, we investigated the association between plasma concentrations of NT-proBNP and severity of liver disease (Child-Pugh score), presence of ascites, as well as hemodynamic and neurohumoral parameters involved in modified circulatory homeostasis in patients with alcoholic liver cirrhosis.The study included 35 adult male and female patients diagnosed with alcoholic liver cirrhosis from urban and suburban parts of Zadarska County in Croatia treated in the General Hospital Zadar. Age range of eligible patients was 32-83 years. The diagnosis of liver cirrhosis included a complex set of typical clinical findings including relevant medical history, presenting symptoms, decreased prothrombin time, hypoalbuminemia with albumin-globulin inversion, hypergammaglobulinemia, advanced diffuse chronic hepatic lesion on abdominal ultrasound examination, or liver biopsy (9 patients).Patients with liver cirrhosis of other etiology than alcohol and patients with suspected malignant comorbidity, advanced multiorgan disorders or infections, acute gastrointestinal bleeding, cardiac arrhythmias, ischemic or valvular heart disease, renal failure, along with those treated with pharmacological agents that potentially affect systemic circulation, such as beta-adrenergic blockers or nitrates were not included in the study. Patients treated with diuretics were included.All patients signed an informed consent prior to the inclusion according to the approval of the ethics committee of General Hospital Zadar and following good clinical practice criteria.The patients were asked to fast overnight and then lie down for approximately two hours prior to having blood samples taken and system hemodynamic parameters measured. The blood samples were used to measure liver function tests, plasma renin activity, and NT-proBNP concentrations. System hemodynamic parameters were measured by using a sphygmomanometer, electrocardiography, and echocardiography. System circulation assessment included heart and great vessels within the mediastinum and was done by the Philips ATL Ultramark 7  ultrasound device by combining pulse Doppler and two-dimensional echocardiography of the left ventricle in lying supine patients.We measured the serum levels of NT-proBNP, noradrenalin (NRA), and plasma rennin activity (PRA), and cardiac index (CI), systemic vascular resistance (SVR), stroke volume (SV), cardiac output (CO), and mean arterial blood pressure (MAP). Arterial blood pressure was measured with a sphygmomanometer. Mean arterial blood pressure was calculated as the sum of one-third of the systolic plus 2-fold diastolic values (MAP = 1 (systolic)/3 + 2 (diastolic)/3). The ratio of cardiac output to body surface represented the cardiac index (CI = CO/body surface). Systemic vascular resistance index (SVRI) was calculated by multiplication of MAP and 80, divided by cardiac index (SVRI = MAP × 80/CI).2π. Stroke volume was calculated by multiplying valve surface area with the integral of valve flow velocity. Cardiac minute output volume represented multiplication of stroke volume with pulse rate recorded through synchronized electrocardiography.Sample volume values were measured just above the aortal valve with pulsating Doppler. Aortal valve diameter values were obtained from parasternal longitudinal position and aortic valve surface area was calculated by the formula rPropeptide of the brain natriuretic peptide was analyzed in plasma by using an electrochemiluminiscence sandwich immunoassay  . Plasma t test, ANOVA, and Pearson correlation. Receiver operating characteristic (ROC) curve analysis was used to define cut-off value of proBNP regarding varices. P values less than 0.05 were considered significant. IBM SPSS, version 19.0.0.1  and MedCalc for Windows, version 11.5  were used.According to Smirnov-Kolmogorov test, appropriate parametric tests were used in the analyses: independent This study included 35 patients with an age range from 32 to 83 years . Patients were divided into three groups according to the Child-Pugh classification: grade A , B , and C . Esophageal varices were found in 24 (69%) patients, whereas ascites was found in 21 (60%) patients.2, of SVR 2187.6 ± 625.9 dyn · s/cm5, of SV 85.3 ± 19.6 mL, of CO 7.1 ± 2.0 L/min, and of MAP 92.1 ± 8.1 mm Hg.Mean value ± standard deviation of CI was 3.6 ± 1.0 L/min/mP = 0.053) in the group A (P = 0.006). In the group B, there was a negative association between NRA and MAP (P = 0.071). Patients without esophageal varices had a significant association between NRA and SV (P = 0.006), and between NT-proBNP and MAP (P = 0.021).There was no significant association of NT-proBNP, NRA, and PRA with CI, SVR, and SV in neither of the groups. A significant association was found between NRA and SV and between NRA and CO (P = 0.014) than patients without esophageal varices. Additional analysis showed the serum level of NT-proBNP>101 pg/mL as a cut-off value for the presence of esophageal varices in patients with liver cirrhosis (P < 0.001), with a sensitivity of 87.60% and specificity of 72.73%  had a significantly higher serum NT-proBNP level . There were no significant differences in NRA, PRA, CI, SVR, SV, and CO values between the groups of patients with and without esophageal varices. Patients with ascites  had significantly lower MAP values   (= 0.010) .Our study showed an association between NT-proBNP and cardiac dysfunction, but the association with the progression of the disease was not established. With increasing disease stage, plasma NT-proBNP levels were greater and SV was lower. This correlates with the hyperdinamic circulation theory based on a central hypovolemia  and systPatients with cirrhosis and ascites present with lower blood pressure, lower peripheral vascular resistance, and increased stroke volume . The assIt has been demonstrated that patients without esophageal varices have a lower cardiac index and systolic volume, higher values of peripheral vascular resistance, and mean arterial blood pressure . In cirr


Blood pressure is considered to be a leading example of a valid surrogate endpoint. The aims of this study were to (i) formally evaluate systolic and diastolic blood pressure reduction as a surrogate endpoint for stroke prevention and (ii) determine what blood pressure reduction would predict a stroke benefit.We identified randomised trials of at least six months duration comparing any pharmacologic anti-hypertensive treatment to placebo or no treatment, and reporting baseline blood pressure, on-trial blood pressure, and fatal and non-fatal stroke. Trials with fewer than five strokes in at least one arm were excluded. Errors-in-variables weighted least squares regression modelled the reduction in stroke as a function of systolic blood pressure reduction and diastolic blood pressure reduction respectively. The lower 95% prediction band was used to determine the minimum systolic blood pressure and diastolic blood pressure difference, the surrogate threshold effect (STE), below which there would be no predicted stroke benefit. The STE was used to generate the surrogate threshold effect proportion (STEP), a surrogacy metric, which with the R-squared trial-level association was used to evaluate blood pressure as a surrogate endpoint for stroke using the Biomarker-Surrogacy Evaluation Schema (BSES3).In 18 qualifying trials representing all pharmacologic drug classes of antihypertensives, assuming a reliability coefficient of 0.9, the surrogate threshold effect for a stroke benefit was 7.1 mmHg for systolic blood pressure and 2.4 mmHg for diastolic blood pressure. The trial-level association was 0.41 and 0.64 and the STEP was 66% and 78% for systolic and diastolic blood pressure respectively. The STE and STEP were more robust to measurement error in the independent variable than R-squared trial-level associations. Using the BSES3, assuming a reliability coefficient of 0.9, systolic blood pressure was a B + grade and diastolic blood pressure was an A grade surrogate endpoint for stroke prevention. In comparison, using the same stroke data sets, no STEs could be estimated for cardiovascular (CV) mortality or all-cause mortality reduction, although the STE for CV mortality approached 25 mmHg for systolic blood pressure.In this report we provide the first surrogate threshold effect (STE) values for systolic and diastolic blood pressure. We suggest the STEs have face and content validity, evidenced by the inclusivity of trial populations, subject populations and pharmacologic intervention populations in their calculation. We propose that the STE and STEP metrics offer another method of evaluating the evidence supporting surrogate endpoints. We demonstrate how surrogacy evaluations are strengthened if formally evaluated within specific-context evaluation frameworks using the Biomarker- Surrogate Evaluation Schema (BSES3), and we discuss the implications of our evaluation of blood pressure on other biomarkers and patient-reported instruments in relation to surrogacy metrics and trial design. Substantive discussions of surrogate endpoint validation began in the late 1980s and early 1990s partly driven by the need to find valid biomarkers for Acquired Immunodeficiency Syndrome (AIDS) randomised controlled trials. A systematic review of the literature of statistical methods, conceptual frameworks and schema , found texcellent rank statistical evidence specified in the BSES requires high trial-level association of treatment effects, high individual-level associations and high surrogate threshold effect proportion (STEP) between the surrogate endpoint and the true clinical endpoint. Using mixed model methods, Buyse, Molenberghs [2trial) and of the patient-level association between both endpoints . These statistics provide qualitative and different evaluations of the surrogate endpoint. They are reported as a relative measure and can take any value from 0 to 1. The surrogate threshold effect proportion (STEP), proposed by Lassere [absolute measure, the surrogate threshold effect (STE). The STE, developed from work undertaken by Daniel and Hughes [The enberghs  and theienberghs  proposedd Hughes , and indd Hughes  and Johnd Hughes ,11, provd Hughes ,7. Here,d Hughes   controlled trials that randomised patients that (i) were at least six months duration of pharmacologic treatment for primary or secondary prevention, (ii) used any anti-hypertensive regimen, (iii) reported baseline and on-trial blood pressure for treated and for control patients, and (iv) reported number of events for fatal and non-fatal stroke for treated and for control patients. A negatively controlled trial was a trial with no mandatory anti-hypertensive treatment requirement for patients in the control arm. However, discretionary treatment, for example, rescue medication, was permitted. Exclusion criteria were (i) trials that only recruited patients with chronic heart failure, diabetes or chronic renal failure, (ii) trials in patients with acute stroke or acute myocardial infarct, (iii) trials designed to assess blood pressure in responders rather than all randomised patients, (iv) trials using a second on-trial randomisation that re-assigned some active arm patients to placebo treatment, (v) trials that simultaneously evaluated multiple interventions targeting vascular risk (e.g. hypertension and hyperlipidaemia) and (vi) trials with fewer than five cerebrovascular (CVA) events per treatment arm . We did Our first search strategy was a search of Medline (1950 to February 2009) for randomised trials of blood pressure using exp Hypertension/ OR exp Blood Pressure/ OR (blood pressure or hyperten* or systolic or diastolic).mp.  that identified 528,263 citations. These were limited to  yielding 50,780 unique citations, a random selection of which identified most as unsuitable for our objective and a systematic evaluation of all was not feasible. Therefore, an alternative strategy to identify trials that met our inclusion criteria was applied.Our second strategy was a rapid review process to identify original trial reports that met our trial inclusion criteria by sourcing secondary data identified in meta-analyses of randomised trials of hypertension. We searched Medline (1950 to May 2009) using the search terms  OR exp Blood Pressure/ OR (blood pressure or hyperten* or systolic or diastolic).mp. ; limited to humans AND adults AND to meta-analysis OR reviews OR systematic reviews. This yielded 1199 citations. A search of the Cochrane Database identified 8 reviews that already had been identified in the Medline search. The abstracts of these 1199 citations were evaluated and 38 meta-analyses or systematic reviews reported trials that satisfied our inclusion criteria  independently extracted the data from trial reports and uncertainty was further adjudicated (ML). Intention-to-treat extractions were applied throughout. We extracted the following for treated and control patients: treatments at trial entry; initial, on-trial and final diastolic and systolic blood pressure; fatal and non-fatal stroke events (CVAs), and any other interventions used. We also extracted all cardiovascular fatal events and all-cause fatal events if the trial reported fatal and non-fatal stroke events. Trials enrolling both primary and secondary prevention patients were coded as combined primary and secondary prevention. We also extracted, if reported, information on trial: demographics , additional risk factors , trial year, trial size, trial duration, trial blinding, and the proportion of subjects that were blood pressure treatment naïve, had past treatment or were on current treatment at trial entry. We also recorded whether add-on treatment was permitted in either arm if protocol defined blood pressure targets were not met and the proportion that required that add-on treatment. No publication included individual level data for analysis.The surrogate endpoint independent variables were two, diastolic blood pressure and systolic blood pressure. Each was a difference between arms of the differences over the trial for each arm. For diastolic blood pressure (DBP) the difference over the trial was defined as the mean baseline DBP in the treated patients minus the mean on-trial DBP  in the treated patients, and similarly for the control patients. The DBP independent variable was then the mean DBP difference in treated patients minus the mean DBP difference in control patients. The systolic blood pressure independent variable was defined similarly. Systolic and diastolic blood pressure differences were analysed separately. The dependent variable was the relative risk reduction (RRR) of fatal and non-fatal stroke, i.e., the stroke rate in the control arm minus the stroke rate in the test arm, divided by the stroke rate in the control arm. RRR was selected as the most intuitively understandable outcome metric for clinicians. All trial data are from intention-to-treat analysis. If a trial report pre-specified a comparison combining treatment arms, these were used. Otherwise, the comparison used from multiple arm trials was the comparison with the largest difference in BP changes. We used the BSES3 for the multidimensional quantitative evaluation of blood pressure reduction as a surrogate endpoint for stroke events.2trial-level) of the weighted errors-in-variables regression model as well as the coefficient (slope) of the blood pressure reduction difference. No publication included individual level data therefore, we were unable to determine the patient-level association between both endpoints .The independent variable mean blood pressure difference is an estimated variable; therefore, its true value is not known with certainty in regression analysis. When both the independent variable as well as the dependent variable are measured with error, then the effect of the independent variable is biased, usually towards the null (underestimated) ,20. TherGiven that reduction of blood pressure with antihypertensive drugs has a greater effect on stroke prevention than on reduction of cardiovascular mortality or on all-cause mortality ,25, we eThe search of the 38 meta-analyses yielded 197 individual trials that were greater than 6 months duration and were of any anti-hypertensive pharmacologic treatment. Hand-searching of the citations from these trial reports did not identify any trials missed by the 38 meta-analyses. All 197 trials including all secondary reports and publications were reviewed and data extracted. Of these 63 were for at least six months of pharmacologic treatment for primary or secondary prevention and were not excluded based on exclusion criteria (i) to (v). Of these 48 reported pre- and on-trial blood pressure and cerebrovascular events. Of these, 39 had at least 5 cerebrovascular events in each arm. Of these, 18 were negatively controlled -43  inhibitor in 4 trials and an angiotensin II receptor antagonists in 2 trials. Only one trial, PATS , limitedp < 0.01) and the R2 was 0.37.The by-trial scatterplot of stroke relative risk and systolic blood pressure difference labelled by trial name is shown in upper graph of Figure p < 0.001) and the R2 is 0.58.The results for diastolic blood pressure are in Figure Baseline blood pressure was not a significant coefficient. Table In contrast to stroke, no STE could predict a cardiovascular mortality benefit. Assuming a reliability coefficient of 1.0 (i.e. no measurement error in the surrogate) for systolic blood pressure, the slope of the mean regression line is 0.009 and is non-significant, the R-square is 0.15, the STE approaches the x axis at 25 mmHg, but it does not cross the axis; therefore, there is no STE and no STEP. In diastolic blood pressure the slope is 0.012 and is also non-significant, the R-squared is only 0.05 and the STE approaches no value of diastolic blood pressure reduction within the model data-points. These results are displayed in Figure Similarly, no STE predicts an all-cause mortality benefit. Assuming a reliability coefficient of 1.0 (i.e. no measurement error in the surrogate) for systolic blood pressure, the slope is 0.005 and is non-significant, the R-squared is 0.06, the STE approaches infinity. In diastolic blood pressure the slope is 0.005 and is also non-significant, the R-squared is only 0.02 and there is no STE. These results are displayed in Figure 2individual specific to our dataset, therefore we assumed that the R2individual was as least as large as the R2trial. Under assumptions of minimal uncertainty (reliability coefficient 0.9) systolic blood pressure reduction is a B + surrogate endpoint for stroke prevention as there is good statistical evidence from multiple (n = 17) randomised controlled trials, of irreversible morbidity (stroke), across different drug class mechanisms (at least 5) and clinical risk populations . Under assumptions of uncertainty (reliability coefficient 0.9) diastolic blood pressure is an A grade surrogate endpoint for stroke prevention, because it scored the highest rank on all domains including the statistical domain . However, under the assumption of no uncertainty, (reliability coefficient 1.0), both systolic and diastolic blood pressure performed less well because they dropped rank on the statistical domain. The BSES3 requires a valid surrogate endpoint to have a combined score of at least 9 (one domain of rank 3 and the remainder at least of rank 2) and a minimum threshold rank of at least 2 across all domains  estimating trial-level systolic and diastolic blood pressure reduction, the STE for systolic blood pressure is 7.1 mmHg and the STE for diastolic blood pressure is 2.4 mmHg. Furthermore, assuming having patient-level data would not influence the results on the BSES3, systolic blood pressure is a Grade B + surrogate endpoint for stroke protection and diastolic blood pressure is a Grade A surrogate endpoint for stroke protection. A discussion of the assumptions that underpin these results, supporting evidence, and caveats are fundamental to the debate on surrogate endpoint evaluation specific to blood pressure as well as to other biomarkers and patient-reported instruments.These STEs for systolic and diastolic blood pressure assume that the new trial measuring only the surrogate endpoint is otherwise similar to past trials used in the predictive model regarding intervention, population, trial design and pharmacologic therapy. These STEs were derived from negatively controlled antihypertensive randomised controlled trials of varying design, clinical populations and pharmacologic classes. Therefore, these STEs may not be applicable to trials that require subjects in all arms to be randomised to an anti-hypertensive drug, or to trials of homogeneous populations, for example, trials of only heart or renal failure patients. As our data-set of trials spans four decades, secular changes in standard of care of hypertension is to be expected and is reflected in changes in trial design and in relation to inclusion and exclusion criteria of risk populations. At one extreme, severe hypertension rapidly became incompatible with trials with no treatment controls. Another secular change is the large number of different pharmacologic classes of agents used singly and in combination. As the evidence for the benefits of blood pressure reduction accrued, equipoise for negatively controlled trials diminished, and as more pharmacologic classes of anti-hypertensive agents appeared, polypharmacy became the rule. Few patients were treatment-naïve, and trials increasingly used designs with provisions for add-on to established "background" regimens. Trial entry criteria changed as did the cut-off for mandatory discontinuation in the event of the on-trial development of severe, uncontrolled hypertension. Older patients and those with lower entry BP and improved risk profiles generally were increasingly enrolled in more recent trials. In seven trials, a proportion of enrolled patients  were already on antihypertensive drugs either for hypertension or other indications. We did not exclude these trials because they met our inclusion criteria. Also, to capture drug effects that may occur with BP lowering from a baseline high-normal range, we did not require elevated BP at baseline. Cross-over also occurred in some trials, although generally it was less than 15% and occurred from active to control arm as well as in the other direction. Only four trials recruited treatment-naïve patients exclusively, where one might expect greater BP and outcome responses compared to trials with treatment-experienced patients. Fourteen trials had varying proportions of treatment-naïve versus treatment-experienced patients which also might dilute or delay the effect on stroke reduction. These changes are likely to attenuate the relationship between blood pressure and stroke, impede the compilation of new data supporting surrogacy, and increase the size of the STE. It is likely that the STEs estimated from active-control randomised trials would be larger because subjects in all arms are randomised to hypertensive drugs. Furthermore, trials clinically of homogeneous populations, such as heart or renal failure populations may also have different STEs. These hypotheses, if substantiated, imply that the initial evaluation of all existing and new biomarkers should be in negatively controlled heterogeneous randomised trials; otherwise, the surrogacy potential of these biomarkers may be underestimated.Ordinary linear regression has several assumptions, one being that all variation is in the dependent variable and that as long as these measurement errors are uncorrelated and unbiased the results are not influenced. However, the independent variable must be measured without error. In the presence of random measurement error in the independent variable coefficients are biased towards the null. In our analysis both stroke relative risk reduction and mean blood pressure reduction are trial-level estimations. Therefore, a priori, they are measured with error. Unfortunately, trials did not report the within arm standard deviation of blood pressure reduction. Individual blood pressure readings are highly variable, because of position, rest, etc, and measurement errors due to the instrument and observer ,45. SystSurrogacy is a complex construct and requires several qualitatively different statistical (and substantive) metrics for its evaluation. We were limited to the STE, the STEP and trial-level linear regression to statistically evaluate blood pressure's surrogacy status. We did not have access to any patient-level data, therefore, were unable to evaluate surrogacy status on an individual-level. Other approaches have been proposed, including a mixed models analysis  that comOur trial-level association for systolic blood pressure may be considered low (R-squared 0.37 assuming no uncertainty). The results for diastolic blood pressure were somewhat better (R-squared 0.58 assuming no uncertainty). Trial-level associations of reported surrogate endpoints that are considerably higher (> 0.8) are those that evaluate progression-free survival, disease-free survival and event-free survival as a surrogate endpoint for overall survival, where survival is included in the surrogate . AnalyseOthers have found similar relationships using different regression methods relating BP differences and expected outcome differences, but none calculated prediction bands to estimate an STE. Staessen et al  was the Others have also found that the relationship for stroke reduction is stronger than that for cardiovascular mortality or all-cause mortality reduction . We therAre there any caveats that may bias the STE and our conclusions towards non-conservative results? We propose that the STE, STEP and trial-level associations we have reported are conservative. As we only had access to trial level data we could not undertake a full hierarchical mixed model regression. Our model could also be vulnerable to ecological bias. Our preliminary unpublished simulation work in SAS on comparing ordinary least squares (OLS) regression with a joint hierarchical linear mixed model has indicated that OLS regression STE is almost always larger therefore conservative compared to the STE obtained from the linear mixed model. In fact, the exceptional simulation scenarios seem to be clinically highly implausible ones; for example, models with very few (5) trials, very small (50 patients) trials, or very small between-trial outcome variance compared to the patient-level outcome variance. Furthermore, these scenarios presented computational problems when fitting a linear mixed model, while the by-trial model is computationally straightforward. In fact, because of its ability to incorporate both trial and patient-level variances, the mixed model may be expected to produce narrower prediction bands.Our simulation work also suggests that the OLS STE is not influenced by individual-level correlation between surrogate and true endpoints. Therefore, the STE may be less subject to ecological bias. Individual-level correlation is usually first explored in observation cohort studies, as was the case in blood pressure, and is often the basis for subsequent evaluation in randomised controlled trials.Other potential methodological weaknesses that may bias the STE towards a non-conservative value deserve mention. Even though some individual patient analyses suggest the hazard ratio for stroke varies over time , we assuIt is important that the concepts that define surrogate validity are developed in a properly conceived context. Formal statistical, rather than anecdotal, evaluation of rigorously defined populations and other context-determined heterogeneity is needed to systematically explore and compare surrogacy status of biomarkers and patient-reported instruments. Our results support that diastolic blood pressure reduction is a very good surrogate for stroke prevention. Systolic blood pressure performs less well. Our analysis of mortality endpoints indicates that the surrogacy of blood pressure is more context specific than generally appreciated. The context could be drug-class specific, clinical endpoint specific and clinical population specific . How much is the effect on cardiovascular mortality mediated by blood pressure reduction, and how much by other drug class effects? Once the clinical endpoint is broadened to all-cause mortality, the effect of blood pressure is further diluted by other drug class effects, including drug class toxicity. Recently it has been shown that different drug classes mediate a heterogeneous effect on stroke through variable effects of blood pressure visit-to-visit variability  and visiUsing the BSES the surrogacy status of different biomarkers and patient-reported instruments can be compared within these specified contexts. The STE, a trial-level metric, is a useful measure because it provides information on the surrogate endpoint in the units of the surrogate and therefore could be used to inform drug registration and drug reimbursement decisions that are based on surrogate endpoints. Moreover, the STE is needed to determine the STEP, which we have shown is a robust relative metric of surrogacy. We should emphasise that we have not analysed data nor do we report a metric that provide decisions regarding individual patients, for example, how much to decrease an individual patient DBP or what is the optimal final DBP target to use. For those claims to be data-driven would require, for example, an RCT to demonstrate that lowering DBP to, say, 80 mmHg is superior (fewer strokes) than lowering the DBP to 85 mmHg. Undertaking such 'target' trials is feasible but difficult as evidenced by the experience of the Hypertension Optimal Treatment (HOT) Study ,68. The Formal evaluation of surrogacy status using a standardised framework, such as the BSES3, can be used to begin discussions on a surrogate biomarkers qualification process . HoweverIn this report we provide the first surrogate threshold effect (STE) values for systolic and diastolic blood pressure. The STEs appear to have face and content validity as evidenced by the inclusivity of trial populations, subject populations and pharmacologic intervention populations in their calculation. The STE and STEP metrics offer another method of evaluating the evidence supporting surrogate endpoints. We have demonstrated how surrogacy evaluations are strengthened if formally evaluated within specific-context evaluation frameworks using the Biomarker- Surrogate Evaluation Schema (BSES3), and we note the implications of our evaluation of blood pressure on other biomarkers and patient-reported instruments in relation to surrogacy metrics and trial design.STE: Surrogate threshold effect; BP: Blood pressure; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; RRR: Relative risk reduction; RCT: Randomised controlled trial; CVA: Cerebrovascular accident; ACE: Angiotensin converting enzyme; ARB: Angiotensin II receptor blocker.The authors declare that they have no competing interests.ML contributed to the conception, design and co-ordination of the study, carried out duplicate data extraction for some randomised controlled trial articles and items, compiled the results, performed the statistical analysis and co-drafted the manuscript. KJ contributed to the conception and design, carried out data extraction for all meta-analysis and randomised controlled trial articles and items, compiled the results, and co-drafted the manuscript. MS performed the Medline searches, carried out duplicate data extraction for some randomised controlled trial articles and data items, and commented on the manuscript. DR contributed to the design, and commented on the manuscript. All authors read and approved the final manuscript.The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2288/12/27/prepubAppendix 1. Scenarios illustrating the application of the Biomarker-Surrogate (BioSurrogate) Evaluation Schema (BSES3).Click here for fileReference list of 38 meta-analyses or systematic reviews reporting trials that satisfied our inclusion criteria.Click here for file