contrastinduced nephropathy ( cin ) is the third most common cause of hospitalacquired kidney injury , which contributes to decreased mobility and motility , prolonged hospitalization , and increased healthcare costs . identifying patients at risk of cin easily and accurately would allow the administration of prophylactic interventions to those at high risk . several riskscore models reflecting the cumulative risk of several periprocedural predictors , such as the mehran cin score and bmc2 cin score , have been established and have proven useful for both bedside clinical decisionmaking and risk assessment . however , although these score models include a multitude of qualitative risk factors , they lack quantitative biomarkers that are associated with multiple organ function and might serve as predictors in riskscore models . thus , there is a need for a more objective identification tool , readily available at hospital admission , before patients are subjected to contrast exposure during coronary angiography or percutaneous coronary intervention ( pci ) . nterminal probrain natriuretic peptide ( ntprobnp ) , an easily available biomarker , is associated with advanced age , kidney dysfunction , anemia , heart failure , and diabetes , which are risk factors for cin . recent data suggest that measurement of serum bnp at hospital admission may help identify patients with stsegment elevation myocardial infarction who are at risk for developing cin after primary pci . in the present study , our objective was to investigate the predictive value of objective preprocedural ntprobnp for cin in patients undergoing selective coronary angiography . we conducted a prospective observational study at the guangdong cardiovascular institute of guangdong general hospital , guangdong academy of medical sciences , between october 2008 and december 2012 . all consecutive patients aged > 18 years who underwent coronary angiography or pci were eligible for enrollment . the exclusion criteria included pregnancy , lactation , intravascular administration of a contrast medium within the previous 7 days or 3 days postoperation ( n=83 ) , cardiovascular surgery or endovascular repair ( n=382 ) , endstage renal disease or renal replacement ( n=7 ) , missing preoperative or postoperative creatinine ( n=61 ) , and malignancy ( n=3 ) . patients undergoing emergent coronary intervention ( n=406 ) and others who had no preprocedural evaluation of ntprobnp ( n=691 ) were also excluded . the study was approved by an institutional review committee and the subjects gave informed consent . once the patients had been admitted to the hospital , preprocedural ntprobnp was measured using electrochemiluminescence immunoassay ( roche diagnostics , germany ) . serum creatinine concentration was assessed in all patients , as a part of standard clinical care , at the time of hospital admission and daily for 3 days after contrast administration , as well as upon hospital discharge . estimated glomerular filtration rate ( egfr ) was evaluated using the levelmodified modification of diet in renal disease equation : 186.3serum creatinine(age in years)1.212 ( if patient was black)0.742 ( if patient was female ) . the contrast type and dose were left to the discretion of the interventional cardiologist , according to the patient 's need . the use of adrenergic blocking agents , angiotensinconverting enzyme inhibitors , diuretics , intraaortic balloon pump support , or inotropic drugs was left to the discretion of the interventional cardiologist and the physicians responsible for the patients . patients received intravenous normal ( 0.9% ) saline at a rate of 1 ml / kg per hour , 2 to 12 hours before and 6 to 24 hours after the administration of contrast medium . in patients with a left ventricular ejection fraction ( lvef ) < 40% or overt heart failure , the hydration rate was reduced to 0.5 ml / kg per hour . the primary end point of the study was the development of cin , defined as an increase in serum creatinine of > 0.5 mg / dl over the baseline value within 48 to 72 hours after the administration of contrast medium . additional end points recorded during the study included major adverse clinical events and cin requiring renal replacement therapy . major adverse clinical events included death , renal replacement therapy , target vessel revascularization , rehospitalization , and stroke . demographics and traditional risk factors were compared between patients who developed cin and those who did not , and the clinical outcomes and incidence of cin were compared among ntprobnp quartiles . comparisons between normally distributed continuous variables , expressed as meansd , were performed using 1way analysis of variance ; nonnormally distributed continuous variables , presented as median and interquartile range , were analyzed using kruskal the pearson  or fisher exact tests were used , as appropriate , for categorical data , expressed as percentages . analyses of receiver operating characteristic curves were conducted and the youden index was used to determine the cutoff value of ntprobnp for predicting cin . the area under receiver operating characteristic curves of ntprobnp and mehran cin score for predicting cin were compared using the nonparametric approach of delong et al . higher ntprobnp group , congestive heart failure , age > 75 years , egfr < 60 ml / min per 1.73 m , diabetes mellitus , and contrast dose > 200 ml were included in the multivariable logistic regression analysis for cin . univariate analyses of mortality were performed using a logrank test for patients categorized by ntprobnp . all data analyses were performed using sas version 9.3 ( sas institute , cary , nc ) . we conducted a prospective observational study at the guangdong cardiovascular institute of guangdong general hospital , guangdong academy of medical sciences , between october 2008 and december 2012 . all consecutive patients aged > 18 years who underwent coronary angiography or pci were eligible for enrollment . the exclusion criteria included pregnancy , lactation , intravascular administration of a contrast medium within the previous 7 days or 3 days postoperation ( n=83 ) , cardiovascular surgery or endovascular repair ( n=382 ) , endstage renal disease or renal replacement ( n=7 ) , missing preoperative or postoperative creatinine ( n=61 ) , and malignancy ( n=3 ) . patients undergoing emergent coronary intervention ( n=406 ) and others who had no preprocedural evaluation of ntprobnp ( n=691 ) were also excluded . the study was approved by an institutional review committee and the subjects gave informed consent . once the patients had been admitted to the hospital , preprocedural ntprobnp was measured using electrochemiluminescence immunoassay ( roche diagnostics , germany ) . serum creatinine concentration was assessed in all patients , as a part of standard clinical care , at the time of hospital admission and daily for 3 days after contrast administration , as well as upon hospital discharge . estimated glomerular filtration rate ( egfr ) was evaluated using the levelmodified modification of diet in renal disease equation : 186.3serum creatinine(age in years)1.212 ( if patient was black)0.742 ( if patient was female ) . coronary angiography or pci the contrast type and dose were left to the discretion of the interventional cardiologist , according to the patient 's need . the use of adrenergic blocking agents , angiotensinconverting enzyme inhibitors , diuretics , intraaortic balloon pump support , or inotropic drugs was left to the discretion of the interventional cardiologist and the physicians responsible for the patients . patients received intravenous normal ( 0.9% ) saline at a rate of 1 ml / kg per hour , 2 to 12 hours before and 6 to 24 hours after the administration of contrast medium . in patients with a left ventricular ejection fraction ( lvef ) < 40% or overt heart failure , the hydration rate was reduced to 0.5 ml / kg per hour . the primary end point of the study was the development of cin , defined as an increase in serum creatinine of > 0.5 mg / dl over the baseline value within 48 to 72 hours after the administration of contrast medium . additional end points recorded during the study included major adverse clinical events and cin requiring renal replacement therapy . major adverse clinical events included death , renal replacement therapy , target vessel revascularization , rehospitalization , and stroke . demographics and traditional risk factors were compared between patients who developed cin and those who did not , and the clinical outcomes and incidence of cin were compared among ntprobnp quartiles . comparisons between normally distributed continuous variables , expressed as meansd , were performed using 1way analysis of variance ; nonnormally distributed continuous variables , presented as median and interquartile range , were analyzed using kruskal the pearson  or fisher exact tests were used , as appropriate , for categorical data , expressed as percentages . analyses of receiver operating characteristic curves were conducted and the youden index was used to determine the cutoff value of ntprobnp for predicting cin . the area under receiver operating characteristic curves of ntprobnp and mehran cin score for predicting cin were compared using the nonparametric approach of delong et al . higher ntprobnp group , congestive heart failure , age > 75 years , egfr < 60 ml / min per 1.73 m , diabetes mellitus , and contrast dose > 200 ml were included in the multivariable logistic regression analysis for cin . univariate analyses of mortality were performed using a logrank test for patients categorized by ntprobnp . all data analyses were performed using sas version 9.3 ( sas institute , cary , nc ) . mol / l , and mean egfr was 82.225.2 ml / min per 1.73 m. of the total patient population , 565 ( 25.2% ) had diabetes , and 324 ( 14.6% ) had congestive heart failure . tables 1 and 2 show the univariate analysis of the baseline and procedural characteristics , including the traditional risk factors for cin between the patients with and without cin . patients who developed cin were more likely to be older , hypotensive , and smokers , as well as have anemia , congestive heart failure , lower lvef and hemoglobin values , and higher levels of serum creatinine , uric acid , lowdensity lipoprotein cholesterol , and highsensitivity creactive protein values . they presented with longer procedure durations or more multivessel disease , and they were more frequently treated with diuretics . furthermore , these patients were more likely to have a higher mehran risk score ( 9.535.14 versus 4.753.76 ) and higher ntprobnp levels ( 53207423 versus 10782548 pg / ml ) . quartiles of ntprobnp for the present study population were q1 ( < 65 pg / ml ) , q2 ( 65 to 247.5 pg / ml ) , q3 ( 247.5 to 976 pg / ml ) , and q4 ( 976 pg / ml ) . baseline characteristics for patients with and without cin values are meansd or n ( % ) . alb indicates albumin ; cabg , coronary artery bypass grafting ; cho , cholesterol ; cin , contrastinduced nephropathy ; crcl , creatinine clearance ; dbp , diastolic blood pressure ; egfr , estimated glomerular filtration rate ; hba1c , hemoglobin a1c ; hgb , hemoglobin ; ldlc , lowdensity lipoprotein cholesterol ; lvef , left ventricular ejection fraction ; mi , myocardial infarction ; ntprobnp , nterminal probrain natriuretic peptide ; sbp , systolic blood pressure ; tg , triglyceride ; uri , uric acid . procedural characteristics for patients with and without cin values are meansd or n ( % ) . acei indicates angiotensinconverting enzyme inhibitor ; arb , angiotensin receptor blocker ; ccb , calcium channel blocker ; cin , contrastinduced nephropathy ; hvwratio , hydration volumetoweight ; iabp , intraaortic balloon pump ; vcrclratio , volume of contrast agenttocreatinine clearance rate . individuals with high preprocedural ntprobnp concentrations were more likely to develop cin ( q1 , q2 , q3 , q4 : 0.5% , 1.2% , 1.2% , 5.9% ; p<0.001 ) . the differences were consistent with a different definition of cin , including an absolute increase of > 0.3 mg / dl and/or a relative increase of > 50% in serum creatinine from baseline within 72 hours after contrast administration ( table 3 ) . the patients with elevated ntprobnp levels were more likely to have major adverse clinical events , including overall death ( 0.2% , 0% , 0.2% , 1.8% ; p<0.001 ) and a need for renal replacement therapy ( q1 , q2 , q3 , q4 : 0.0% , 0.4% , 0.2% , 1.2% , p=0.023 ) . cin incidence and clinical outcomes according to ntprobnp quartiles cin indicates contrastinduced nephropathy ; ntprobnp , nterminal probrain natriuretic peptide ; rrt , renal replacement therapy ; scr , serum creatinine . receiver operating characteristic curve analysis indicated that a cutoff value of 682 pg / dl for ntprobnp could predict cin with a sensitivity of 78% and a specificity of 70% ( area under the curve=0.766 , p<0.001 ) ( figure 1 ) . ntprobnp was not significantly different from the mehran cin score with respect to predicting cin ( c=0.7657 versus c=0.7729 , p=0.8431 ) . receiver operating characteristic curve analysis for nterminal probrain natriuretic peptide ( ntprobnp ) and mehran scores in the prediction of contrastinduced nephropathy ( c=0.7657 vs c=0.7729 ; p=0.8431 ) . when analyzing all of the patients , we observed a significant positive correlation between ntprobnp and the patients ' age and mehran cin score . a significant negative correlation was demonstrated between ntprobnp and the values of lvef and hemoglobin ( figure 2 ) . correlation between nterminal probrain natriuretic peptide ( bnp ) and age ( a ) , creatinine clearance ( crcl ) ( b ) , left ventricular ejection fraction ( lvef ) ( c ) , and mehran contrastinduced nephropathy score ( d ) . pg / dl was significantly associated with cin ( odds ratio : 8.16 ; 95% ci : 4.15 to 16.02 , p<0.001 ) . pg / dl was an independent predictor of cin ( odds ratio : 4.007 ; 95% ci : 1.950 to 8.234 ; p<0.001 ) , even after adjustment for other established risk factors , including congestive heart failure , age > 75 years , egfr < 60 ml / min per 1.73 m , diabetes mellitus , and dose > 200 ml ( table 4 ) . univariate and multivariable logistic regression analysis egfr indicates estimated glomerular filtration rate ; ntprobnp , nterminal probrain natriuretic peptide ; or , odds ratio . we assessed the predictive value of different ntprobnp cutoffs ( 682 pg / dl ) . after adjusting for baseline clinical and other procedural variables , a higher ntprobnp group remained an independent predictor of longterm clinical outcomes ( figures 3 and 4 ) ; the adjusted mortality was higher for patients with ntprobnp > 682 pg / dl ( hazard ratio : 2.53 ; 95% ci : 1.49 to 4.30 ; p=0.0006 ) . cumulative mortality for patients according to the cutoff value for nterminal probrain natriuretic peptide ( bnp ) ( 682 ng / ml ) . hazard ratios for patients ' 2year death according to the cutoff value for bnp ( 682 ng / ml ) . bnp indicates nterminal probrain natriuretic peptide ; chf , congestive heart failure ; ckd , chronic kidney disease ; dm , diabetes mellitus ; hr , hazard ratio ; iabp , intraaortic balloon pump . mol / l , and mean egfr was 82.225.2 ml / min per 1.73 m. of the total patient population , 565 ( 25.2% ) had diabetes , and 324 ( 14.6% ) had congestive heart failure . tables 1 and 2 show the univariate analysis of the baseline and procedural characteristics , including the traditional risk factors for cin between the patients with and without cin . patients who developed cin were more likely to be older , hypotensive , and smokers , as well as have anemia , congestive heart failure , lower lvef and hemoglobin values , and higher levels of serum creatinine , uric acid , lowdensity lipoprotein cholesterol , and highsensitivity creactive protein values . they presented with longer procedure durations or more multivessel disease , and they were more frequently treated with diuretics . furthermore , these patients were more likely to have a higher mehran risk score ( 9.535.14 versus 4.753.76 ) and higher ntprobnp levels ( 53207423 versus 10782548 pg / ml ) . quartiles of ntprobnp for the present study population were q1 ( < 65 pg / ml ) , q2 ( 65 to 247.5 pg / ml ) , q3 ( 247.5 to 976 pg / ml ) , and q4 ( 976 pg / ml ) . baseline characteristics for patients with and without cin values are meansd or n ( % ) . alb indicates albumin ; cabg , coronary artery bypass grafting ; cho , cholesterol ; cin , contrastinduced nephropathy ; crcl , creatinine clearance ; dbp , diastolic blood pressure ; egfr , estimated glomerular filtration rate ; hba1c , hemoglobin a1c ; hgb , hemoglobin ; ldlc , lowdensity lipoprotein cholesterol ; lvef , left ventricular ejection fraction ; mi , myocardial infarction ; ntprobnp , nterminal probrain natriuretic peptide ; sbp , systolic blood pressure ; tg , triglyceride ; uri , uric acid . procedural characteristics for patients with and without cin values are meansd or n ( % ) . acei indicates angiotensinconverting enzyme inhibitor ; arb , angiotensin receptor blocker ; ccb , calcium channel blocker ; cin , contrastinduced nephropathy ; hvwratio , hydration volumetoweight ; iabp , intraaortic balloon pump ; vcrclratio , volume of contrast agenttocreatinine clearance rate . individuals with high preprocedural ntprobnp concentrations were more likely to develop cin ( q1 , q2 , q3 , q4 : 0.5% , 1.2% , 1.2% , 5.9% ; p<0.001 ) . the differences were consistent with a different definition of cin , including an absolute increase of > 0.3 mg / dl and/or a relative increase of > 50% in serum creatinine from baseline within 72 hours after contrast administration ( table 3 ) . the patients with elevated ntprobnp levels were more likely to have major adverse clinical events , including overall death ( 0.2% , 0% , 0.2% , 1.8% ; p<0.001 ) and a need for renal replacement therapy ( q1 , q2 , q3 , q4 : 0.0% , 0.4% , 0.2% , 1.2% , p=0.023 ) . cin incidence and clinical outcomes according to ntprobnp quartiles cin indicates contrastinduced nephropathy ; ntprobnp , nterminal probrain natriuretic peptide ; rrt , renal replacement therapy ; scr , serum creatinine . receiver operating characteristic curve analysis indicated that a cutoff value of 682 pg / dl for ntprobnp could predict cin with a sensitivity of 78% and a specificity of 70% ( area under the curve=0.766 , p<0.001 ) ( figure 1 ) . ntprobnp was not significantly different from the mehran cin score with respect to predicting cin ( c=0.7657 versus c=0.7729 , p=0.8431 ) . receiver operating characteristic curve analysis for nterminal probrain natriuretic peptide ( ntprobnp ) and mehran scores in the prediction of contrastinduced nephropathy ( c=0.7657 vs c=0.7729 ; p=0.8431 ) . when analyzing all of the patients , we observed a significant positive correlation between ntprobnp and the patients ' age and mehran cin score . a significant negative correlation was demonstrated between ntprobnp and the values of lvef and hemoglobin ( figure 2 ) . correlation between nterminal probrain natriuretic peptide ( bnp ) and age ( a ) , creatinine clearance ( crcl ) ( b ) , left ventricular ejection fraction ( lvef ) ( c ) , and mehran contrastinduced nephropathy score ( d ) . univariate logistic regression found that ntprobnp > 682 pg / dl was significantly associated with cin ( odds ratio : 8.16 ; 95% ci : 4.15 to 16.02 , p<0.001 ) . multivariable logistic regression analysis showed that bnp > 682 pg / dl was an independent predictor of cin ( odds ratio : 4.007 ; 95% ci : 1.950 to 8.234 ; p<0.001 ) , even after adjustment for other established risk factors , including congestive heart failure , age > 75 years , egfr < 60 ml / min per 1.73 m , diabetes mellitus , and dose > 200 ml ( table 4 ) . univariate and multivariable logistic regression analysis egfr indicates estimated glomerular filtration rate ; ntprobnp , nterminal probrain natriuretic peptide ; or , odds ratio . we assessed the predictive value of different ntprobnp cutoffs ( 682 pg / dl ) . after adjusting for baseline clinical and other procedural variables , a higher ntprobnp group remained an independent predictor of longterm clinical outcomes ( figures 3 and 4 ) ; the adjusted mortality was higher for patients with ntprobnp > 682 pg / dl ( hazard ratio : 2.53 ; 95% ci : 1.49 to 4.30 ; p=0.0006 ) . cumulative mortality for patients according to the cutoff value for nterminal probrain natriuretic peptide ( bnp ) ( 682 ng / ml ) . hazard ratios for patients ' 2year death according to the cutoff value for bnp ( 682 ng / ml ) . bnp indicates nterminal probrain natriuretic peptide ; chf , congestive heart failure ; ckd , chronic kidney disease ; dm , diabetes mellitus ; the present study showed that elevation of preprocedural ntprobnp , an easily available biomarker , was significantly associated with an increased risk of cin . after adjustment for other traditional confounders , including congestive heart failure , a level of preprocedural ntprobnp > 682 pg / ml , the best cutoff point , was a strong and independent predictor of cin and longterm death ; thus , besides the mehran cin score , preprocedural ntprobnp could become another objective and rapidly available tool for risk stratification and/or a modifiable target for prevention in patients undergoing coronary angiography . ntprobnp may be a promising and timely tool for predicting the risk of cin and adverse events in patients undergoing coronary angiography . the predictive value of the preprocedural ntprobnp level was not significantly different from that of the mehran cin score ( p=0.8431 ) , including 8 periprocedural risk factors , some of which were related to the patients ' medical histories and were often unavailable to the cardiologists before the procedure . ntprobnp , a qualitative and more objective risk stratification tool compared with the mehran score system , may potentially help cardiologists to identify highrisk patients ( with high ntprobnp ) , who may then receive timely preventive measures . at our institute , 80% patients who were undergoing elective coronary angiography and who were suspected to be at risk of heart failure also underwent ntprobnp testing ; this ntprobnp test is routinely performed at our facility . in addition , most of the risk factors included in the mehran score were associated with elevated ntprobnp levels in our study . therefore , this simple and readily available test may be a better tool for predicting cin than the existing mehran cin score system . cin is highly prevalent in patients with congestive heart failure and chronic kidney disease ( ckd ) undergoing coronary interventions . one study showed that lvef < 40% was significantly associated with cin ( odds ratio : 4.52 ; 95% ci : 1.30 to 15.71 ; p=0.02 ) in patients without congestive heart failure . another study conducted in denmark showed that using a heart failure diagnosis requiring elevated ntprobnp reduces the prevalence of heart failure with preserved ejection fraction and results in a survival rate similar to that of heart failure with reduced ejection fraction ; the finding supported the use of ntprobnp for the selection of highrisk patients having heart failure with preserved ejection fraction in future interventional clinical trials . in 1 recent study , ntprobnp also had strong associations with left ventricular systolic dysfunction , even in patients without clinical heart failure ; the study evaluated the crosssectional associations of ntprobnp with cardiac structural and functional abnormalities in patients with ckd ( n=3232 ) . ntprobnp significantly reclassified participants ' likelihood of having left ventricular systolic dysfunction ( net reclassification improvement 0.28 , 95% ci : 0.27 to 0.30 ; p<0.001 ) . in addition , pointofcare tests are available in which bnp concentrations are available within 20 minutes , making it a potentially useful candidate for early prognostication . therefore , preprocedural ntprobnp may be a more objective and rapidly available tool for the estimation of the risk of worsening renal function after coronary angiography . measurement of ntprobnp on admission has been a routine procedure for patients with suspected coronary heart disease who are to undergo coronary angiography . natriuretic peptides are a family of hormones synthesized in myocytes and secreted increasingly in response to the elevation of any chamber wall stress . consequently , as the inactive metabolite of bnp , ntprobnp has diagnostic and prognostic capabilities across a variety of conditions involving heart dysfunction . elevated ntprobnp levels have been shown to be a powerful predictor of shortterm and longterm outcomes . in the general population , elevated ntprobnp levels predict poor outcomes in both asymptomatic and dyspneic subjects , irrespective of renal function . ckd itself also amplifies the cardiovascular risk . even medical care supported by heart failure treatment that is guided by bnp therefore , recent clinical practice guidelines recommended ntprobnp for guiding heart failure management . in the present study , the data suggested that elevation of preprocedural ntprobnp was also an independent risk factor for cin in patients undergoing selected cardiac catheterization . one recent study , a substudy of the horizonsami trial , focused on the correlation between bnp and the risk of cin in patients with acute stsegment elevation myocardial infarction ( odds ratio : 1.29 , 95% ci : 1.10 to 1.51 ; p<0.001 ) ; however , bnp and serial creatinine levels suitable for complete measurement were only available in 979 of the 3602 patients enrolled ( 27.2% ) and were not sufficient to determine an optimal bnp cutoff concentration for the prediction of cin . another study indicated that preoperative bnp level is associated with postoperative acute kidney injury in highrisk patients undergoing cardiac surgery . bnp was linearly associated with the risk of at least mild acute kidney injury , whereas for evaluating severe acute kidney injury , a risk threshold was observed above the intermediate levels of bnp . our results are in accordance with the observations of a recent study , showing that patients with acute heart failure who develop acute kidney injury within 48 hours after admission have significantly higher initial bnp concentrations . according to our findings , an ntprobnp level > 682 pg / ml was a strong and independent predictor of ckd patients presenting with acute onset or worsening of symptoms ; in contrast , the optimal cutoff value of ntprobnp for diagnosing heart failure in unselected patients is 300 pg / ml . because all the subjects presented with renal dysfunction , the cutoff value of ntprobnp for predicting cin was strikingly higher than that for diagnosing heart failure . the reasons for the strong association between elevated preprocedural ntprobnp levels and a higher risk of cin were not clear ; however , the potential mechanisms by which high bnp concentrations are associated with cin may include the following . first , elevated bnp concentrations are also related to other risk factors , which are themselves directly associated with the development of cin , such as worse heart and renal dysfunction , advanced age , and diabetes mellitus . higher levels of ntprobnp were significantly associated with a higher risk of developing endstage renal disease in diabetic patients with ckd after adjustment for other risk factors . second , the elevated ntprobnp in patients with ckd may be due to decreased renal clearance , or decreased renal responsiveness to bnp . since previous studies found that plasma concentrations of ntprobnp increase as gfr declines in patients with or without apparent cardiac dysfunction , the decreased clearance ability of ntprobnp due to impaired renal function may play an important role . elevated ntprobnp concentrations may reflect cardiac involvement in patients with ckd , especially those undergoing catheterization . third , bnp , the source of ntprobnp , reduces the effects of catecholamines , and potentiates the generation of nitric oxide , which in turn is a known inhibitor of myocardial contractility , thereby possibly resulting in systemic vasodilation and renal hypoperfusion . cin is regarded as a specific subtype of cardiorenal syndrome type 1 , which is defined as worsening renal function attributed to acute heart dysfunction that may exacerbate the condition of both cardiac and renal impairment . it is associated with increased cardiovascular mortality and morbidity , increased stroke risk , longer hospitalization , and a higher readmission rate . although there is growing recognition of the frequency of cardiorenal syndrome , its underlying pathophysiology is not yet well understood . vascular factors such as nitric oxide , prostaglandin , natriuretic peptides , and endothelin may modulate renal perfusion independently of cardiac hemodynamics . recently , researchers have focused on the role of inflammatory markers as links between cardiovascular and kidney disease . the natriuretic peptides are established biomarkers in heart failure and , since elevated natriuretic peptide levels can be caused by renal dysfunction as well as congestive heart failure , they probably also reflect renal injury . thus , natriuretic peptides are emerging as pleiotropic biomarkers that are useful in the settings of both cardiac and renal dysfunction and have the potential to serve as a valuable diagnostic tool in the diagnosis of type 1 cardiorenal syndrome . moreover , bnp has been shown to cause natriuresis and diuresis in animals , healthy men , and patients with congestive heart failure . recombinant human bnp significantly reduced the incidence of cin , reduced serum creatinine , and improved egfr in a population of patients with congestive heart failure and stelevation myocardial infarction . the hormone may be especially beneficial in patients with acute myocardial infarction complicated by congestive heart failure , because of its inhibitory effect on the neuroendocrine system and its diuretic and natriuretic action . the cutoff value of ntprobnp , 682 pg / ml in the present study , may provide guidance for carrying out fluid management , as do the 35% or 40% limits for lvef . it may be reasonable to limit the hydration speed and volume , or even to consider the use of diuretics , in patients with ntprobnp > 682 pg / ml who are undergoing cardiac catheterization . patients with very high levels of ntprobnp may become optimal target subjects for receiving therapeutic measures to prevent cin in future randomized trials . it was a singlecenter , observational study without longterm followup for the systematic measurement of creatinine concentrations , such as at 3 months or 1 year . patients undergoing primary pci were excluded because they lacked preprocedural ntprobnp measurements ; this might have caused selection bias . variations in the measurement times may have led to missed peak levels of creatinine after the procedure . failure to perform systematic measurements at optimal times for determining peak creatinine concentrations may have led to an underestimation of the true incidence of cin . it was a singlecenter , observational study without longterm followup for the systematic measurement of creatinine concentrations , such as at 3 months or 1 year . patients undergoing primary pci were excluded because they lacked preprocedural ntprobnp measurements ; this might have caused selection bias . variations in the measurement times may have led to missed peak levels of creatinine after the procedure . failure to perform systematic measurements at optimal times for determining peak creatinine concentrations may have led to an underestimation of the true incidence of cin . besides the mehran cin score , measurement of serum ntprobnp at hospital admission may also help identify patients who are at high risk for developing cin after cardiac catheterization . the data may provide a modifiable target for therapeutic measures to prevent cin in future randomized trials , where patients with ntprobnp > 682 pg / ml may be the optimal target subjects .