New England Journal of Medicine,It is said that the concept of the Swan–Ganz catheter came up in Dr Swan's mind in the 1960s after watching the sailboats in Santa Monica Bay being drifted by streams and winds: he assumed that a balloon‐ended catheter would be driven into the pulmonary artery by the blood flowing out of the pulmonary outflow tract, allowing a catheterization of the pulmonary artery without the aid of fluoroscopy. Following the presentation of the balloon flotation catheter, its use and its potential benefits in the Inserted from a central vein to a pulmonary artery, PAC allows measurements of right heart, pulmonary capillary wedge pressure (PCWP), and cardiac outflow. Beyond the absolute values of the recorded pressure, valuable data can be provided by the morphology of the curves. A proper analysis of those curves thus allows diagnosis of mitral regurgitation or pericardial constriction, for instance. Moreover, it offers possibility of stepped blood sampling, for measurement of central oxygenation or quantification of intra‐cardiac shunt. Last, if retained, PAC allows bedside continuous monitoring and also an individually tailored management, such as the evaluation of the haemodynamic responsiveness to a fluid challenge or an inotrope/vasopressor infusion. This opportunity of a dynamic evaluation made the PAC a theoretical perfect tool for management of critically ill patients, especially in the case of cardiogenic shock (CS). Various devices have been proposed to provide more sophisticated approaches but without further evidences for efficacy.However, PAC has three obvious major limitations.First is the safety concern: as an invasive tool, PAC provides potential significant complications. Besides vascular complications because of central venous catheterization Second, PAC use requires specific skills: because the haemodynamic situation is often complex, multifaceted, and time varying, the interpretation and analysis of the recorded values and curves can be challenging. Thus, any misinterpretation of the recorded haemodynamic data can lead to inappropriate therapy.Last but not least is the lack of proven benefit: to date, no randomized trial has shown any improvement of the mortality outcome with a routine PAC.ESC Heart Failure, Vallabhajosyula et al. present 15 years' nationwide data about 364,001 admissions with CS in the setting of an acute myocardial infarction.With this background, strong data about the use of PAC in large cohorts, during a long study period, are more than expected. In this issue of n = 29 centres; 87%) and level 2 ICU with on‐site interventional cardiology . Fifty per cent reported never using the Swan–Ganz catheter in daily practice. The main causes of non‐use of PAC monitoring were as follows: preference for echocardiographic assessment  or iterative invasive haemodynamic evaluation by serial right‐heart catheterization (RHC) when considered useful , absence of evidence for benefit , and/or worries about PAC‐associated complications . Moreover, invasive assessment is poorly used in general, because 13 centres (41%) reported never having performed intermittent or iterative RHC, whereas left ventricular end‐diastolic pressure (LVEDP) in patients with myocardial infarction is never recorded in 14 centres (44%), even in the case of low cardiac output, elevated filling pressures, or mechanical complication suspicion. Unsurprisingly, PAC monitoring is mainly adopted in patients with CS, mixed shock, and right heart failure and in patients under mechanical cardiac support (MCS), whereas iterative RHC is more frequently used in the case of heart transplantation or MCS discussion, pulmonary hypertension, or pericardial constriction suspicion. Last, the Swan–Ganz is mainly used in level 3 ICU, whereas level 2 ICU rather rely on iterative RHC.Consistently, we conducted in 2020 January a survey about PAC and invasive assessment usage patterns in order to better understand the dramatic decrease of use of PAC. This survey was conducted in 32 French intensive care units (ICUs), mostly university centres  and, on the other hand, severe and complex situations, all the more as the haemodynamic appraisal of critically ill patients is often highly variable. Thus, a multi‐parametric modality assessment including invasive haemodynamic parameters seems important for complex haemodynamic impairments such as in a patient with a ventilator‐acquired pneumonia and extra‐corporal life support, or a severe hypotension in a patient with deep vasoplegia and severely depressed ejection fraction in the setting of a post‐cardiac arrest syndrome.Last, this decrease of PAC use was conducted with a modification of CS definition itself, because the initial PAC‐recorded haemodynamic criteria (low cardiac index and high PCWP) have been abandoned in the last ESC definition. Because we strongly believe that the haemodynamic assessment of critically ill patients requires a multi‐parametric modality assessment, we recently proposed a new integrative definition for CS. This so‐called Frenshock definition (NCT02703038) considers all the available modalities—encompassing clinical, biological, radiological, echographic, and haemodynamic data—for assessment of the three necessary parts  of the CS.et al. report expected decrease of PAC use in ischemic CS in the USA,In conclusion, Vallabhajosyula None declared.


To evaluate the clinical value of foetal intelligent navigation echocardiography (5D Heart) for the display of key diagnostic elements in basic sections.3D volume datasets of 182 normal singleton foetuses were acquired with a four chamber view by using a volume probe. After processing the datasets by using 5D Heart, eight cardiac diagnostic planes were demonstrated, and the image qualities of the key diagnostic elements were graded by 3 doctors with different experiences in performing foetal echocardiography.A total of 231 volume datasets acquired from the 182 normal foetuses were used for 5D Heart analysis and display. The success rate of 8 standard diagnostic views was 88.2%, and the success rate of each diagnostic view was 55.8–99.2% and 70.7–99.0% for the random four chamber view as the initial section and for the apical four chamber view as the initial section, respectively. The success rate of each diagnostic element in the 8 diagnostic sections obtained by 5D Heart was 58.9%~ 100%. Excellent agreement was found between experienced sonographers and less-experienced sonographers (kappa> 0.769). Inter- and intra-observer agreement were substantial to near-perfect, kappa values ranging from 0.612 to 1.000 (Cohen’s kappa).5D Heart can significantly improve the image quality of key diagnostic elements in foetal echocardiography with low operator dependency and good reproducibility. Congenital heart diseases (CHDs) are the leading cause of organ-specific birth defects, with a prevalence of 3–8 per 1000 live births, and they are also the leading cause of infant mortality due to congenital malformations . Indeed,STIC is a new approach for the clinical assessment of the foetal heart , 12, 19.As conventional 2D echocardiography visualizes only the length and width of the heart, 3D images were based on a series of 2D images, showing a visual heart through three orthogonal planes. 4D techniques use the added dimension of time to present a real-time 3D image. 5D Heart uses intelligent 4D images. 5D Heart is the latest STIC technology based on foetal intelligent navigation echocardiography (FINE) technology –23. It cA total of 209 foetuses were randomly selected from patients with singleton pregnancies in the second and third trimesters who had sonographic examinations in our outpatient clinic  from January 2017 to March 2017. Among them, satisfactory volume datasets could not be obtained from 27 foetuses due to maternal obesity, foetal motion and other factors. Therefore, the number of selected cases was 182, and the number of effective volume datasets was 231. The gestational ages ranged from 17 to 38 weeks , and the pregnant women’s ages were between 16 and 41 years old . In this study, all pregnant women had an accurate menstrual history, or the sonographic age was consistent with the gestational age calculated by the menstrual history (less than 2 weeks). Biparietal diameter and femoral diaphysis length were used to estimate the gestational age. If there was a difference of more than 1 week, the sonographic age was used , 25. NonThe 3D volume datasets of the foetal hearts were obtained by an expert  via sonography and foetal echocardiography using a curved array transducer . First, routine screening with 2D ultrasound of the foetal heart was performed to exclude foetal cardiac structural abnormalities, and the cardiac rate and regular rhythm were confirmed. Second, an attempt was made to obtain clear 2D images via foetal echocardiography. The frame rate was maximized by decreasing the depth, narrowing the sector width, and placing a single focal zone at the level of the foetal heart. The normal rate ranged from 120 to 160 beats per minute. 3D volume datasets of the foetal heart were acquired from a transverse apical four chamber view of the foetal chest. Images were magnified until the heart filled at least one-third to one-half of the displayed screen. Finally, participants were asked to momentarily hold their breath during 5D Heart acquisition, and volume datasets were acquired by automatic scanning. Acquisition times ranged from 7 to 10 s depending on the size of the foetal heart and its distance from the probe, while the angle of acquisition ranged between 35° and 45° depending on the gestational age. The imaging volume was set to include the spine, a complete four chamber view, the abdominal aorta, the upper mediastinum and the gastric bubble but to exclude other unnecessary foetal or maternal body parts , 23. If After marking seven anatomical structures of the foetal heart using the feature Anatomic Box® Fig. , nine stWith reference to the guidelines of the International Society of Ultrasound in Obstetrics and Gynecology, the 8 diagnostic sections and 29 diagnostic elements were studied , 8, 26. The diagnostic value was divided into 3 grades  accordinWe evaluated the success rate of each diagnostic plane obtained by the inexperienced physician (Observer A). The mean scores of each diagnostic element of 8 diagnostic sections were assessed, and the success rate of each diagnostic element was calculated. Inter- and intra-observer agreement on obtaining 8 diagnostic planes with 5D Heart were evaluated using Cohen’s kappa statistic. Values from 0.61 to 0.80 are considered substantial agreement; 0.81–1.00, near-perfect agreement. 95% confidence intervals (CI) of all statistics were calculated. All statistical analyses described above were performed with IBM SPSS package 21.0 .A total of 262 volume datasets were obtained in 209 normal foetuses, and 231 volume diagnostic sections were successfully obtained with the 5D Heart technique. Finally, 88.2% of the 262 volume datasets could be annotated. Observer A scored all diagnostic elements in each plane. Only when average scores of all diagnostic elements in each diagnostic section  were more than or equal to 2 points was this plane considered to be successful in 5D Heart analysis. The results of 8 diagnostic sections were analysed, and the success rate of each diagnostic section is shown in Table We further explored the success rate of each diagnostic element in the 8 diagnostic sections obtained with 5D Heart. The results are shown in Table Observer A and Observer B were both less-experienced doctors but had been engaged in ultrasound diagnosis for more than 5 years and had at least 6 months of systematic training for foetal echocardiography. Observer C was an expert in foetal echocardiography. The agreement of Observer A and Observer B with Observer C was assessed by Cohen’s kappa. Values of kappa ranged from 0.769 to 1.000, indicating substantial agreement to near-perfect agreement. The data are presented in Table Inter-observer reliability was evaluated by agreement of Observer A and Observer B. The inter-observer reliability was high and the results are shown in Table The prenatal diagnosis of CHDs remains a challenge. The difficulties of prenatal diagnosis are generally attributed to the complex anatomy of the heart as well as its motion and small size , 26. AdeTo further confirm 5D Heart’s clinical value in routine screening, our study investigated 29 diagnostic elements obtained by 5D Heart in 8 standard foetal echocardiography views and the display rate of each section with random foetal heart position according to the guidelines of the International Society of Ultrasound in Obstetrics and Gynecology , 26. An n = 27) of STIC volumes demonstrated more than six echocardiography views. Recent studies have demonstrated that four chamber views can detect 30% of CHDs [Additionally, the number of foetal echocardiography views successfully obtained through 5D Heart was calculated in 50 randomly selected data volumes  for the detection of CHDs –52.8% fo, 26. ThiThe inter-observer and intra-observer variability of 5D Heart was assessed by agreement of two physicians with relatively poor experience and the agreement of the same physician at different times . The kappa values ranged from 0.612 to 1.000, suggesting that 5D Heart has good reproducibility. The results are shown in Tables However, 5D Heart has some disadvantages. First, it has relatively poorer 3D imaging spatial and temporal resolution compared to 2D imaging; additionally, it lacks interactions for avoiding acoustic shadowing during a fixed volume acquisition compared to a real-time 2D scan; and finally, the imaging quality will be degraded by motion artefacts, even with the use of STIC.In addition, this study has several limitations. First, all volume datasets in this study were acquired by an expert, and differences between physicians in terms of obtaining datasets need further study. In addition, in the volume dataset acquisition, the factors that affect the quality of 2D echocardiography images can also affect 5D Heart, such as the shadowing of the spine and ribs, foetal movement and so on. Second, we did not evaluate the cardiac rate, rhythm disturbances or Doppler velocimetry of foetal heart in this study. Additionally, this study also does not include any abnormalities. Therefore, the ability of this method to be used generally merits further investigation. In addition, this study provides information limited to 20–40 weeks of gestation. Further studies need to include foetuses with a lower gestation age.In summary, our study is the first to demonstrate that 5D Heart based on FINE can easily display the main diagnostic factors in 8 basic foetal echocardiography sections. 5D Heart improves diagnostic elements with ease of operation, efficiency, examiner independency and good repeatability. Furthermore, once the datasets are obtained and stored, they are convenient and useful for teaching, remote consultation and research. However, applying this technology clinical use requires further study and more practice. In conclusion, 5D Heart is a feasible, accurate and operator-independent method for foetal heart examination during the second and third trimesters.


Cardiovascular disease (CVD) is the leading non-malignant cause of death in childhood cancer survivors. Heightened risk of CVD is often attributable to treatment with anthracycline chemotherapy. Anthracycline-mediated cardiac injury may lie latent for years following cessation of treatment and is therefore often not detected until disease is advanced and aggressive therapy is required. Symptomatic CVD may be preceded by subclinical cardiac and vascular dysfunction. This study aimed to determine whether such dysfunction could be detected in healthy, anthracycline-treated survivors of childhood leukaemia.Cardiac magnetic resonance imaging (cMRI) with late gadolinium enhancement and endothelial function were used to characterise pre-clinical stages of CVD. Twenty-two long-term  childhood leukaemia survivors were assessed. All survivors were asymptomatic and had normal resting echocardiography. To exclude potential confounding effects of radiotherapy, no survivors had received this treatment. Twenty-two similarly aged (25 ± 3 years) gender-matched controls were recruited for comparison.p = 0.010). Further, five survivors (23%) had clinically reduced (<50%) left ventricular ejection fraction. Normalised left ventricular end systolic volume was augmented in survivors . Cardiac MRI did not show any late gadolinium enhancement. High resolution, ultrasound-derived flow mediated dilation was impaired in survivors .Left ventricular ejection fraction was lower in the survivors (55.0 ± 4.6%) compared to the controls (59.4 ± 6.2%; We detected subclinical changes in cardiovascular structure and function indicative of early disease in anthracycline-treated childhood leukaemia survivors with normal echocardiography. Early detection and characterisation of underlying disease allows for timely intervention and improved outcomes in this at-risk population. The current five-year survival rate for childhood cancer in developed countries is approaching 85% –3. UnforCardiac magnetic resonance imaging (cMRI) has high spatial resolution and superb contrast resolution; it also has very low inter and intra observer variability and is the gold-standard for assessment of cardiac morphology –14. ContEndothelial dysfunction has been independently established as an early event in the progression of CVD , 25. MorEarly characterisation of subclinical disease is important for maximising the time available to test interventions commonly used for other types of heart disease, until an appropriate course of treatment is identified. In the present study, we used cMRI with late gadolinium enhancement to assess cardiac structure, function and tissue composition in a cohort of adolescent and young adult (AYA) survivors of childhood acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML) who were treated with anthracyclines but no radiotherapy. Secondary to this, we also performed an assessment of endothelial function. These results will allow us to make a novel analysis of cardiovascular health that will potentially allow for improved outcomes due to earlier characterisation and more timely and targeted intervention.The Princess Margaret Hospital for Children  oncology database was searched in order to identify long-term (≥5 years) AYA (15–30 years) survivors of childhood ALL and AML. Those who had received radiotherapy as part of their treatment protocol were excluded, as were survivors with any abnormalities of cardiac structure or function  in their most recent echocardiograms . Survivors with a history of acute and/or early-onset cardiac toxicity were not excluded if current echocardiograms were deemed normal by a cardiologist. Eligible survivors were either approached by study clinicians during long-term follow-up clinics or were called by study clinicians if appointments had not been attended or were not scheduled within the recruitment time-frame. If survivors consented to receive further information about the study, the primary researcher emailed them official information sheets and then performed a phone call to discuss the study, answer any questions and, if necessary, arrange written consent. Of 132 eligible survivors, 22  consented to participation and completed all necessary assessments. The primary reasons for non-participation were loss to follow-up and a lack of time  and the University of Western Australia Human Research Ethics Committee . All participants (or parents/guardians for those under 18 years) were required to provide informed, written consent prior to participation.Participants were asked to fast for a minimum of 4 h and to avoid exercise for 24 h prior to their initial testing session. During this session, measurement of anthropometry, resting heart rate (HR) and resting blood pressure (BP) occurred, followed by evaluation of endothelial function using the flow mediated dilation (FMD) technique. Cardiac MRI’s were performed after the survivors were cleared for gadolinium infusion via assessment of renal function. Control participants did not receive gadolinium.Height, body mass, waist circumference and hip circumference were assessed according to protocols detailed by The American College of Sports Medicine . Height Participants lay supine for 20 min before having their resting HR and BP assessed using an automated sphygmomanometer . Endothelial function was then assessed using the FMD technique described by Thijssen et al. . RecordiLeft and right ventricular  morphology were assessed using cMRI . Participants were scanned in a supine position, with the examination taking approximately 30 min. To improve image quality and spatial resolution over the standard body coil, a posterior phased array spinal coil and an anterior flexible phased array body surface coil were used whilst imaging. Standard cardiac imaging planes were obtained using multi-plane breath hold True FISP localisers. Breath hold times ranged between 5 and 20 s, depending on the participants resting HR. In order to assess functional parameters, breath hold True FISP, electrocardiogram-gated cine images consisting of 10–15 individual slices  were acquired. Cine images of the LV and RV were acquired in the short axis plane, perpendicular to the ventricular septum. Long axis cine images were acquired in the axial plane  to better visualise the RV free wall. Four chamber cine views and LV outflow tract cine images  were also taken to assess valve function, myocardial wall motion and blood flow through the heart.Late gadolinium enhancement imaging was acquired in the leukaemia survivor group to detect the possible presence of treatment-induced myocardial tissue pathologies. Gadoteric acid  was administered via an intravenous cubital fossa injection. After a 5 min delay, a short axis mid-ventricular inversion time Scout (TrueFISP sequence) was acquired to determine the inversion time for the nulling of normal myocardial signal. Within the next 5–10 min, the late gadolinium enhancement images were obtained using both standard inversion recovery and Phase Sensitive Inversion Recovery sequences . A slice thickness of 8 mm was used in the short axis, 2-chamber view , 3-chamber view (LV outflow tract) and 4-chamber view .Cardiac MRI’s were analysed by the primary researcher (TML) using Siemens specialised cardiac analysis software (syngo.via VB20A_HF04). In the initial phase of analysis, the primary researcher was unable to be blinded to participant status as scans were taken clinically and had been saved under each participant’s name. However, an experienced radiographer (PW) who was blinded to participant status repeated all analysis to reduce bias and ensure consistency of figures. Additionally, a blinded cardiologist (LGD) confirmed the final data set.Reported measures were automatically calculated by the analysis software following segmentation of appropriate anatomical regions and structures. Systemic and pulmonary outflow tracts were auto-segmented in individual slices on cine images and then manually adjusted where necessary using a nudging tool. Short axis cines were visually inspected to identify end diastolic and end systolic frames for ventricular analysis. The end diastolic frame was selected as the one with the largest ventricular cavity/greatest blood pool , while the end systolic frame had the smallest ventricular cavity/lowest blood pool. An accompanying cine volume graph confirmed selection of end diastolic and end systolic frames. Marking of the mitral valve on two and four chamber cine images for the LV was automated but manually adjustable if tracking was inconsistent over frames. Manual placement was required for markers of the tricuspid valve annular plane in RV analysis. The basal frame was taken as the first complete slice below the level of the mitral and tricuspid valves. Endocardial and epicardial borders of the LV were automatically contoured on each individual frame and then manually adjusted using nudging and drawing tools. The RV endocardium was manually traced on each short axis frame. Papillary muscles were included in the blood pool in both systole and diastole. Data was internally validated by confirming that aortic flow, pulmonary flow, LV stroke volume and RV stroke volume were all within 5% of each other. Any deviations resulted in re-analysis and, if required, review by a cardiologist.All gadolinium scans were visually inspected by a cardiologist (LGD) who determined whether any myocardial morphological abnormalities or intra-cardiac shunts were present.p ≤ 0.05.Statistical analysis was performed using IBM SPSS version 20.0 . Differences between cancer survivors and controls were identified using independent samples t-tests, with significance set at n = 11) had no history of cardiac toxicity, while the other half had a history of acute and/or early-onset cardiac toxicity that recovered in the years following treatment. Additional treatment and diagnostic information is presented in Table Twenty-two  leukaemia survivors participated in the study and completed all assessments. The average age of the leukaemia survivors was 21 ± 3 years (range 15–25 years). Mean age at diagnosis was 6 ± 4 years, resulting in an average time since diagnosis of 14 ± 4 years. The average time since final treatment was 13 ± 4 years. All survivors entered the study with completely normal echocardiograms. Half of the survivors  and a comparable mean arterial pressure of 82 ± 7 mmHg (p = 0.249). However, the survivors had a higher resting HR than the controls .The controls had a mean systolic BP of 118 ± 11 mmHg, a diastolic BP of 65 ± 9 mmHg, a mean arterial pressure of 85 ± 9 mmHg and a resting HR of 63 ± 9 bpm. The leukaemia survivors had similar mean systolic and diastolic BPs , body mass  and BMI  were not significantly different in the control group. With regards to circumferences, the survivors and the controls had similar waist  and hip measurements . Similarly, waist-to-hip ratio was not different between groups .The leukaemia survivors had an average height of 173.0 ± 7.7 cm, a body mass of 76.15 ± 19.05 kg and a BMI of 25.2 ± 5.1. Height , as can be seen in Fig. p = 0.030). Despite this, there were no differences between survivor and control groups for baseline diameter , peak diameter , or time to peak .The survivors had a lower FMD than the controls . Five survivors  had clinically reduced LVEF (defined as <50% )g et al. , who repg et al.  study haA reduction in LVEF can be attributable to a decrease in end diastolic volume or an increase in end systolic volume . In the In the anthracycline-exposed individual, increased ventricular volumes and cardiac dysfunction typically result from underlying myocardial injury caused by cancer treatment – for example, myocardial fibrosis, myofibrillar lysis, infiltrative disorder and myocellular dysfunction –36. HoweAnthracycline chemotherapy induces oxidative stress that is toxic to the vascular endothelium , 38. EndThere is currently no consensus on the best management or treatment options for cardiovascular complications relating to anthracycline chemotherapy –44. UnfoIt may be considered that a limitation of this study is the small sample size. However, when using cMRI the sample size needed to detect a 3% change in EF, a 10 mL change in end diastolic volume and end systolic volue, and a 10 g change in myocardial mass is 81–97% smaller than the sample size that is needed to detect the same differences when using standard echocardiography (range: 9–15 patients using cMRI vs. 53–273 patients using echocardiography) . FurtherThe present study has demonstrated that cMRI is successful in unmasking early subclinical changes in cardiac structure and function indicative of future disease in asymptomatic childhood leukaemia survivors exposed solely to anthracycline chemotherapy. While gadolinium enhancement did not appear to add any additional value to scans in this stage of survival, cMRI alone allowed for nearly one-quarter of the survivors to be referred for cardiology review, possibly saving future costs of having to treat advanced diseases and allowing for better outcomes due to prompt initiation of treatment. In addition to this, the current study has demonstrated the importance of also assessing endothelial health in this cohort as a means of investigating risk of exacerbated and/or concomitant CVD.


Fragmented QRS (fQRS) complex on routine 12‐lead electrocardiogram (ECG) predicts adverse outcomes in patients with cardiovascular diseases. In addition, it has been found to be associated with subclinical myocardial dysfunction in chronic diseases. We sought to investigate the relationship between the presence of fQRS with the myocardial functions in individuals free from known systemic cardiovascular diseases.In a case‐control study, we evaluated normal individuals from March 2017 to February 2018. All participants underwent a 2‐dimensional transthoracic echocardiographic examination using tissue Doppler imaging (TDI) and speckle‐tracking echocardiography. In addition, all participants were examined using a 12‐lead surface ECG, and patients with fQRS and a group of age‐ and sex‐matched controls without fQRS were enrolled in our study.P = .110). Patients with fQRS had significantly lower values of apical left ventricular global longitudinal strain (LV GLS) in 2‐chamber , 4‐chamber , LAX views , and averaged LV GLS  values compared to patients without fQRS. In a multivariate analysis, averaged LV GLS and smoking history were independent predictors for positive fQRS.The patients' mean age was 40.3 ± 10.7 and 35.4 ± 11.2 years in fQRS‐positive and fQRS‐negative groups, respectively (The presence of fQRS on 12‐lead ECG in healthy population was associated with lower values of LV GLS compared to normal individuals without fQRS. The presence of fragmented QRS complex on standard 12‐lead electrocardiogram in healthy individuals is associated with lower values of left ventricular global longitudinal strains compared to individuals without fragmented QRS complex, indicating a subclinical myocardial dysfunction. All participants underwent a comprehensive 2D‐TTE examination using TDI and STE modalities to evaluate the structural and functional features of their heart. The study was approved by the institutional review board in Seyyed‐al‐Shohada Heart Center and the local ethics committee of Urmia University of Medical Sciences, Urmia, West Azerbaijan province, Iran. In addition, informed consent was obtained from all participants at baseline.Twenty‐six consecutive patients who visited our outpatient clinic with positive fQRS were recruited into this study. In addition, 28 age‐ and sex‐matched individuals who had negative fQRS in baseline ECG were also enrolled. Inclusion criteria included healthy individuals who were referred to be evaluated for probable cardiac diseases before military service entrance, employment in governmental organizations, a requirement for insurance validity, and participation in sport events. In addition, some people who visited our outpatient clinic for palpitation and atypical chest pain with a low probability of coronary artery diseases whose stress tests and/or cardiac scans had been negative for any ischemic heart diseases. Exclusion criteria included patients with known history of coronary artery diseases, any signs of ischemic heart diseases in stress tests and cardiac scan, heart failure, diabetes mellitus, hypertension, hypercholesterolemia, LVEF lower than 55%, any significant valvular diseases , any congenital heart diseases, atrioventricular conduction abnormalities, QRS duration longer than 120 milliseconds, pulmonary arterial hypertension, chronic obstructive pulmonary diseases, consumption of any medications for chronic diseases, and bundle branch block in ECG trace.2.2All participants were examined by a 12‐lead surface ECG at rest . ECGs were analyzed by two clinicians who were blinded to the impression of cases. In case of disagreement, the mutual agreement was used to reach a final diagnosis. The fQRS was defined as the detection of RSRʹ pattern, which can be observed as follows: (i) an additional R wave; (ii) a notching in nadir of the S wave; (iii) a notching of the R wave; (iv) Rʹ wave >1 millimeter; and (v) the presence of fragmentation, more than one Rʹ wave, in two contiguous ECG leads.2.3All echocardiographic measurements were performed based on the recommendations of the American Society of Echocardiography and the European Association of Cardiovascular Imaging,A standard M‐mode, 2D, and color‐coded TDI images were obtained during breath hold, as an average of three consecutive beats. The TDI was provided from the annular and septal mitral valve area. The harmonic image recordings of apical and short‐axis views at mitral valve and papillary muscle levels (30‐90 frames/second) were provided and stored to be analyzed offline using AFI  software. The left ventricular GLS (LV GLS) was calculated by averaging apical 4‐chamber, 2‐chamber, and LAX views. Based on a meta‐analysis,2.4t test was used to compare continuous variables between groups. Chi‐squared tests or Fisher's exact test was implemented for comparing categorical variables as appropriate. A multivariate regression analysis was conducted to evaluate the relationship between fQRS and LV GLS values. The model was also adjusted for age, gender, smoking history, QRS duration, QT interval corrected for heart rate, body mass index, and total cholesterol level. Adjusted odds ratios (ORs) and corresponding confidence intervals (CIs) were reported. A two‐tailed P < .05 was considered statistically significant. All statistical analyses were performed using the IBM SPSS software version 22.0 .All variables are presented as mean ± standard deviation, and 3P = .110). The number of smokers was significantly higher in positive fQRS compared to negative fQRS group . The half of patients with fQRS  had fQRS in less than three leads and others had fQRS in three or more than three leads. Fifteen patients (57.7% of fQRS patients) had fQRS in inferior leads, five patients (19.3% of fQRS patients) in precordial leads, and others (23% of fQRS patients) in a combination of precordial and limb leads. The QRS duration was comparable between individuals with or without fQRS . All laboratory data and other parameters of ECG were comparable between groups . However, based on 2D‐STE, patients with fQRS had significantly lower values of apical LV GLS in 2‐chamber , 4‐chamber , LAX views , and averaged LV GLS  values compared to individuals without fQRS . In addition, there was no significant difference between groups regarding the number of individuals with mild LV diastolic dysfunction . Other echocardiographic values are summarized in Table When comparing echocardiographic parameters, the LVEF was comparable between groups . When compared individuals with fQRS in less than three leads and those with fQRS in more than three leads, the LV GLS value was comparable between both groups (data not reported).P = .003) and smoking history  were independent predictors for positive fQRS. Other data are summarized in Table In multivariate analysis, averaged LV GLS . In addition, when compared to healthy controls, metabolic syndrome patients with fQRS had a higher E/e' and lower e' velocity, indicators of diastolic dysfunction, as well as lower isovolumic acceleration, indicating subclinical LV systolic dysfunction. In addition, E/e' and isovolumic acceleration were independent predictors of fQRS in patients with metabolic syndrome. Yan et alThe fQRS has also been found to be associated with subtle myocardial dysfunction in several reports. Oner et alBased on a population‐based study in Finland,P < .001 per 1% decrease in GLS levels). Moreover, on multivariate analysis, this association remained significant even after adjustment for other factors; however, gender modified this association, so that GLS did not predict outcomes in women rather than men. The present study was a case‐control study and participants were matched by sex and age, so we could not find any effect of sex on our findings. Given previous studies and our study, we believe that it can be postulated that among apparently healthy population, the presence of fQRS might be considered as a surrogate of subclinical myocardial dysfunction, which can be evaluated by 2D‐STE. The impact of this association on the outcomes of apparently healthy population warrants further large‐scale studies to assess whether concomitant fQRS and decreased LV GLS in a healthy population are associated with worse outcomes at long‐term follow‐up or not.In our study, the majority of participants were young and all individuals were healthy without cardiovascular diseases on routine screening; however, there was significant subclinical myocardial dysfunction in the echocardiographic examination. Similar to Yaman et al 4.1This study suffers from some shortcomings needed to be addressed in future studies. Firstly, it was a case‐control study with small sample size. Secondly, all participants with atypical chest pain were categorized as low‐risk group and they did not undergo coronary angiography, so we could not definitely say that all patients were free of coronary artery disease. Thirdly, we performed neither noninvasive imaging for the evaluation of myocardial scar/fibrosis nor a pathologic evaluation of myocardial tissue to show that which pathogenesis might contribute to such a phenomenon in our population, fQRS and lower LV GLS. Finally, we did not follow‐up individuals to pursue the prognostic value of concomitant fQRS and decreased LV GLS in the healthy population. Given these limitations in this study, it seems that future studies should focus on these issues.5The presence of fQRS on standard 12‐lead ECG in the apparently healthy population is significantly associated with lower values of LV GLS compared to individuals without fQRS, indicating a subclinical myocardial dysfunction.The authors declare no conflict of interests for this article.


Lipomatous metaplasia is an infrequently discussed condition characterized by adipose tissue replacing scar tissue from ischemic events. Lipomatous metaplasia specifically of the myocardium is an adverse physiological result of myocardial infarction. In the past, several different imaging and diagnostic techniques were utilized to recognize lipomatous metaplasia of the myocardium. The aim of this study is to discuss an individual case with this condition to highlight several key aspects that are under-discussed in current literature, such as determining the most suitable modality for the recognition of lipomatous metaplasia. The clinical significance of lipomatous metaplasia remained unclear for a long time owing to the relatively little amount of literature about the topic in the past. More recently, however, there have been a few studies in the literature highlighting the association between lipomatous metaplasia and significant adverse cardiac conditions such as ventricular arrhythmia, infarct size, and heart failure . HoweverWe present a case of left ventricular (LV) lipomatous metaplasia after myocardial infarction evaluated with cardiac magnetic resonance imaging. A 56-year-old male with anterior myocardial infarction eight years ago presented with a transient ischemic attack. The patient underwent a transthoracic echocardiogram as part of the diagnostic evaluation, which suggested possible LV thrombus. He was referred to cardiac MRI to assess for possible LV thrombus and to quantify the LV function.Original cardiac MRI showed moderately impaired LV systolic function with hypokinesis of the mid to apical anteroseptal wall. There was a linear high signal lesion with surrounding low signal chemical shift artifact in balanced steady-state free precession (SSFP) cine sequences in the mid anteroseptum, mid anterior, and apical septal segments Figures , 1D. T1-Following a myocardial infarction, myofibroblasts lay connective tissue that serves as a protective agent against future myocardial rupture and prevents dilation of the infarcted area . HoweverThe bright signal in T1-weighted images without fat suppression and high signal lesion with chemical shift artifact in balanced SSFP sequences show lipomatous metaplasia without intravenous contrast media. Therefore, cardiac MRI, with its high contrast resolution capabilities and lack of ionizing radiation, is the most suitable modality to identify lipomatous metaplasia of the myocardium.


Candida prosthetic endocarditis is associated with high mortality rates and valve replacement surgery, together with antifungal treatment, play a major role in eradicating the fungal infection.Valve reoperations in these scenarios may be relatively common due to the high infection relapse rates and, in some cases, heart transplantation may be an imposing therapy for infection resolution and for the heart failure related to the myocardial reoperation injury. Among the many postoperative complications related to heart transplantation, chylopericardium is a rare but challenging example.Candida parapsilosis infective endocarditis. Transthoracic echocardiogram showed a markedly reduced left ventricular systolic function and normofunctioning bioprosthetic valves. An inotropic dependency condition led to heart transplantation surgery. In the early postoperative period, a persistent chylous fluid started to drain from the pericardial tube, compatible with the diagnosis of chylopericardium. The lack of clinical response to total parenteral nutrition and intravenous infusion of octreotide imposed the need of interventional radiology with diagnostic lymphography through cisterna chyli puncture and thoracic duct catheterization, confirming the presence of a lymphatic fistula. A successful treatment outcome was achieved with percutaneous thoracic duct embolization using coils and n-butyl-cyanoacrilate glue, possibiliting hospital discharge.We report the case of a 55-year-old man who was admitted to our hospital with a 1-month history of progressive dyspnea and fatigue. His past medical history included four open-heart surgeries for aortic and mitral valve replacement due to recurrent Fungal endocarditis requires combined treatment  for eradication. Valve replacement, while necessary, may lead to severe ventricular deterioration and heart transplantation may be the only viable therapeutic solution. Among the several postoperative complications of heart transplantation, chylopericardium is an uncommon and defiant example. Advances in interventional radiology like the percutaneous embolization allow a less invasive and highly efficient approach for this complication. Some patients, like a Greek epic legend, face true medical challenges in real life. Candida prosthetic endocarditis represents a major defiance in clinical practice due to its devastating potential, requiring surgical intervention and prolonged antimicrobial therapy. Although rare, corresponding to less than 1% of all infective endocarditis, this condition determines high mortality and relapse rates . Among tWe present a clinical report of a 55-year-old male patient with a past medical history of four open-heart surgeries for aortic and mitral valve replacement. His first cardiac surgery was performed in 2009 and consisted in mitral valve replacement using a bioprosthesis due to symptomatic severe mitral regurgitation related to an anterior leaflet prolapse . Due to Candida parapsilosis and transesophageal echocardiography showed multiple vegetations attached to the mitral prosthesis and native aortic valve. Given the diagnosis of fungal infective endocarditis, another cardiac surgical approach was necessary, consisting of combined mitral and aortic valve replacement using biological prostheses [Candida parapsilosis was isolated from blood cultures and intravenous antifungal treatment with liposomal amphotericin-B was started. Candida endocarditis relapse was confirmed by transesophageal echocardiography, revealing mitral and aortic prosthesis with leaflet thickening and large vegetations with extension into the left atrium  . After 3Lymphangiography and thoracic duct embolization were performed in a dedicated interventional radiology suit, according to the following steps: (1) inguinal lymph nodes guided puncture followed by microbubble contrast infusion for regional lymphatic ducts anatomic evaluation; (2) lymphangiography with lipiodol infusion ; 3) the lack of contrast impregnation into the upper abdomen and cisterna chyli led to a retrograde access approach; (4) left upper limb phlebography allowed the thoracic duct ostium identification and its retrograde catheterization; (5) thoracic duct lymphangiography showed a lymphopericardial fistula with lipiodol leakage into the pericardical sac; (6) thoracic duct embolization using micro coils and n-butyl-cyanoacrilate glue was performed . However, in the subsequent days, there was a progressive increase in the daily drainage volume. A new approach was then performed by transhepatic percutaneous direct puncture of the cisterna chyli, using 50 ml of lipiodol contrast. Another thoracic duct embolization with liquid agent n-butyl-2-cyanoacrylate was achieved, taking 3 h of procedure , as described in some case series, could prevent this relapse [Our patient experienced the dramatic natural history of candida prosthetic endocarditis, characterized by high morbidity mainly related to elevated recurrence rate around 36%) despite combined treatment  . Candida6% despited agent . Despite relapse .After 4 open-heart cardiac surgeries, an inexorable complication arose for our patient: severe systolic left ventricular dysfunction. In a retrospective study, Ataka et al. found that up to 2/3 of patients with second/third valvar reoperation had a significant loss of ventricular function (around 25%), possibly related to ischemic/reperfusion injury in the previous operations [Taylor et al. found that about 4% of patients undergoing heart transplantation had their cardiomyopathy related to a valvular pathology, representing a small proportion when compared to other etiologies such as ischemic or dilated cardiomyopathy . The reaAfter successful orthotopic heart transplantation, our patient was diagnosed with chylopericardium in the early postoperative period. Chylopericardium is a rare condition with variable clinical presentation, involving the development of a lymphatic fistula to the pericardium . The mosRegarding the patient’s perspective, it is worth highlighting the strength that has always motivated him during the many intercurrences experienced. Despite some disappointments and moments of uncertainty, he has never lost confidence in the medical team. His willingness and cooperation were crucial for the positive outcomes achieved.From an educational point of view, this case report brings some relevant conclusions: (1) fungal endocarditis requires a strict clinical follow-up after hospital discharge with special care in implementing and maintaining antifungal suppression therapy to avoid recurrence; (2) cardiac reoperations, even when necessary, can lead to permanent ventricular dysfunction; (3) heart transplantation remains a method for definitive clinical recovery in refractory heart failure; (4) integrated multidisciplinary work in the form of heart team is essential to ensure favorable clinical outcomes in such challenging scenarios.Additional file 1. Thoracic duct lymphangiography video confirming the lymphopericardial fistula after infusion of the lipiodol contrast.Additional file 2. Slide set containing details of the case presentation.


Mapping techniques using cardiac magnetic resonance imaging have significantly improved the diagnostic accuracy for myocarditis with focal myocardial injuries. The aim of our study was to determine whether T1 and T2 mapping techniques could identify diffuse myocardial injuries in “normal-appearing” myocardium in pediatric patients with clinically suspected myocarditis and to evaluate the associations between diffuse myocardial injuries and cardiac function parameters.Forty-six subjects were included in this study: 20 acute myocarditis patients, 11 subacute/chronic myocarditis patients and 15 control children. T2 values, native T1 values and the extracellular volume (ECV) of “normal-appearing” myocardium were compared among the three groups of patients. Associations between diffuse myocardial injuries and cardiac function parameters were also evaluated.P =0.004). No significant differences in T1 and T2 values between the acute myocarditis and control groups were found. In the subacute/chronic myocarditis group, a significant association between ECV and left ventricle ejection fraction was found (P=0.03).The ECV of “normal-appearing” myocardium was significantly higher in the subacute/chronic myocarditis group than in the control group (30.1 ± 0.9 vs 27.0 ± 0.6, Diffuse myocardial injuries are likely to occur in subacute/chronic myocarditis patients with prolonged inflammatory responses. Mapping techniques have great value for the diagnosis and monitoring of myocarditis. Myocarditis is a myocardial inflammatory disease associated with various injuries, clinical manifestations and outcomes . MyocardCardiac magnetic resonance (CMR) has been an established noninvasive tool for the diagnosis and evaluation of myocarditis . ConventCurrently, T1 and T2 mapping techniques are applied to determine the diagnosis and prognosis of myocarditis. Mapping techniques offer a quantitative assessment of the myocardium by using standardized, reproducible T1 and T2 values and have the potential to identify both focal and diffuse myocardial injuries from myocarditis . ExtraceIn our study, we focused on the “normal-appearing” myocardium—myocardium without focal myocardial edema or necrosis/fibrosis visible on conventional CMR—in pediatric patients with clinically suspected myocarditis. We attempted to determine whether T1 and T2 mapping techniques could identify diffuse myocardial injuries in pediatric myocarditis patients, and we then evaluated whether there were associations between diffuse myocardial injuries and cardiac function in these patients.In this prospective study, pediatric patients with clinically suspected myocarditis from Feb 2016 to Jan 2018 in our hospital were included. All patients were diagnosed by an experienced pediatrician according to the myocardial diagnostic criteria proposed by the European Society of Cardiology Working Group on Myocardial and Pericardial Diseases . AccordiCMR imaging was performed using a MAGNETOM Skyra 3T MR scanner  with an 18-channel body matrix coil. All data acquired was retrospectively gated based on the ECG results. Respiratory gating was applied in pediatric patients who could cooperate for a breath-hold during the CMR examinations , and CMR images were acquired at the end-expiratory point. Patients who could not hold their breath  were sedated with 10% chloral hydrate solution and examined under free-breathing conditions.2, and voxel size =1.3 × 1.3 × 6 mm3). LGE imaging was performed using phase-sensitive inversion recovery (PSIR) sequences in the HLA and SA orientations 7–10 min after intravenous administration of 0.2 mmol/kg Gd-DTPA . The parameters were as follows: TR/TE=448∕2.0 ms, FOV = 300 ×350 mm2, matrix = 256 ×192, and voxel size = 1.4 × 1.4 × 6 mm3. The inversion time (TI) of LGE imaging was determined by using the TI scout. Steady-state free precession (SSFP) cine images were acquired in the HLA and sequential SA orientations from ventricular base to apex with the following imaging parameters: TR/TE =39.2∕1.4, FA = 80°, FOV = 300 × 225 mm2, and voxel size = 1. 6 × 1. 6 × 6.0 mm3).The CMR imaging protocols included T2-weighted imaging, LGE imaging, cine imaging and quantitative image mapping. T2-weighted turbo inversion recovery magnitude (TIRM) sequences were performed in the short-axis (SA) and horizontal long-axis (HLA) orientations (repetition time (TR)/echo time (TE) = 800/44 ms, flip angle (FA) = 180° , field of view (FOV)= 300 × 225 mm2, acquisition matrix = 256 ×192 mm2, and voxel size = 1.4 ×  1.4 ×  8.0 mm3. T2 mapping was acquired using a SSFP sequence with three different T2 preparation times in the HLA and three SA orientations . The parameters were as follows: TE = 0 ms, 25 ms, 55 ms; TR = 3 × RR; FA = 50° ; FOV = 300 ×  225 mm2; acquisition matrix = 256 × 384 mm2; and voxel size = 0.9 ×  0.9 × 8.0 mm3.T1 mapping was performed with 3(3)5 modified Look-Locker inversion recovery (MOLLI) sequences in the HLA and three SA orientations   before aAll the original image data were processed on the workstation . Two experienced CMR radiologists (C.Y.W and H.P.W), who were blinded to patient information, independently analyzed all CMR images.Left ventricular (LV) cardiac function parameters were evaluated in the cine images. LV endocardial and epicardial contours were drawn manually for each diastolic and systolic frame in the sequential SA cine images, and LV cardiac function parameters, including end-diastolic volume (EDV), end-systolic volume (ESV), left ventricle ejection fraction (LVEF), LV mass and stroke volume (SV), were automatically acquired on the workstation. LV cardiac function parameters were standardized as follows :Standardized LV cardiac function parameters = LV cardiac function parameters/ body surface area (BSA).The papillary muscles and trabeculations were included as part of ventricular cavity .Myocardial edema and necrosis/fibrosis were defined by visual assessment in the T2-weighted images and LGE images. The presence and location of myocardial edema or fibrosis were independently evaluated by two CMR radiologists according to the 17-segment model proposed by the American Heart Association (AHA) . For theT1 and T2 values of “normal-appearing” myocardium in the HLA and SA orientations were measured directly in their T1 and T2 maps. Endocardial and epicardial borders were carefully contoured to exclude artifacts, epicardial fat and blood pools. Then, the T2 values, native T1 values, and postcontrast T1 values of “normal-appearing” myocardium in the HLA and three SA orientations were acquired . T1 and The native and postcontrast T1 values of the blood pools were also measured directly in the LV cavity, avoiding the papillary muscle. Myocardium with higher T1 and T2 values and ECV was identified as abnormal myocardium with diffuse myocardial injuries.http://www.empowerstats.com) software. Categorical data were reported as percentages (%), and continuous data were reported as the mean ±standard deviation (SD) or median (range). The Shapiro–Wilk test was used to assess the normality of the variables using SPSS. Clinical characteristics in the AM, CM and NC groups were compared using chi-square tests for categorical variables, one-way analysis of variance (ANOVA) for normally distributed continuous variables, and the Kruskal–Wallis test for nonnormally distributed continuous variables. The interaction test and covariate screening were performed to adjust for patient-specific factors using Empower Stats. Linear regression analyses were used to compare T2 values, native T1 values and the ECV of “normal-appearing” myocardium in the HLA and SA orientations among the AM, CM and NC groups. The influence of focal myocardial injuries on T1 and T2 values and the ECV of “normal-appearing” myocardium in myocarditis patients were also evaluated using linear regression analyses. Associations between ECV and LV cardiac function parameters in the AM and CM groups were evaluated using multiple linear regression analyses with adjustment for confounding variables, and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.All analyses were performed using the Statistical Package for the Social Sciences  and Empower Stats , 11 patients with subacute/chronic myocarditis  and 15 control children  were included in the study.The clinical characteristics of all pediatric patients are shown in The standard LV cardiac function parameters and myocardial tissue characterizations in the AM, CM and NC groups are shown in P = 0.004). No significant differences in T1 and T2 values were found between the AM and NC groups.The T1 and T2 values and ECV of “normal-appearing” myocardium in the AM, CM and NC groups are shown in To study whether focal myocardial injuries would influence the T1 and T2 values and ECV of “normal-appearing” myocardium, we divided myocarditis patients into another two groups: myocarditis patients with focal myocardial injuries (35.5%) and without focal myocardial injuries (64.5%). No significant differences in T1 or T2 values or ECV between the two groups were found. The T1 and T2 values and ECV of “normal-appearing” myocardium in myocarditis patients with and without focal myocardial injuries are shown in P = 0.03) after adjusting for age, sex, heart rate or HCT. The associations between ECV and LV cardiac function parameters in the CM group are shown in In the CM group, we found negative associations between ECV and LVEF (OR, −0.4; 95% CI, −0.7, −0.1; In our study, we evaluated the tissue-related changes of “normal-appearing” myocardium in pediatric patients with clinically suspected myocarditis using mapping techniques. We found that ECV could detect diffuse myocardial injuries in “normal-appearing” myocardium in pediatric CM patients, and ECV was associated with LVEF. Therefore, mapping techniques could increase the sensitivity of CMR for monitoring diffuse myocardial injuries in patients with clinically suspected myocarditis.Mapping technologies could be influenced by numerous factors, including the MR scanner, magnetic field strength, exact sequence used, image acquisition plane, contrast agent dose and patient’s physiological differences . In our LGE has been an established noninvasive tool to evaluate focal myocardial necrosis/fibrosis and has shown excellent correlation with pathology . In acutIn our study, we found that the ECV of “normal-appearing” myocardium was significantly higher in pediatric CM patients than in NC patients, which indicated diffuse myocardial injuries. Myocarditis has been identified as an underlying cause of DCM, and up to 40% of DCM cases are caused by myocarditis . The avaIn our study, native T1 values of the “normal-appearing” myocardium were not significantly higher in AM and CM patients than in NC patients, which was inconsistent with recent data by In our study, T2 values in the “normal-appearing” myocardium of AM patients was not significantly higher than those in the NC group, which was in agreement with the findings of In our study, we found associations between ECV and LVEF in CM patients, which have also been reported in patients with diabetic cardiomyopathy, myocardial infarction, hypertrophic cardiomyopathy and heart failure . The patThis study has several potential limitations. First, the myocarditis patients involved in our study were diagnosed according to the diagnostic criteria for clinically suspected myocarditis proposed by the ESC Working Group on Myocardial and Pericardial Diseases . EndomyoIn conclusion, diffuse myocardial injuries are likely to occur in CM patients with prolonged inflammatory responses. Mapping techniques have great value for the diagnosis and monitoring of myocarditis.10.7717/peerj.10252/supp-1Supplemental Information 1The cardiac magnetic resonance of normal control, acute myocarditis and subacute/chronic myocarditis in pediatric patients.Baseline characteristics, cardiac function parameters, T1 and T2 mapping values in three groups. Group 1: normal control; Group 2: subacute/chronic myocarditis; Group 3: acute myocarditis.Click here for additional data file.10.7717/peerj.10252/supp-2Supplemental Information 2Click here for additional data file.


Since the first studies on bowhead whale singing behaviour, song variations have been consistently reported. However, there has been little discussion regarding variability in bowhead whale singing display and its ecological significance. Unlike the better studied humpback whales, bowhead whales do not appear to share songs at population level, but several studies have reported song sharing within clusters of animals. Over the winter season 2013–2014, in an unstudied wintering ground off Northeast Greenland, 13 song groups sharing similar hierarchical structure and units were identified. Unit types were assessed through multidimensional maps, showing well separated clusters corresponding to manually labelled units, and revealing the presence of unit subtypes. Units presented contrasting levels of variability over their acoustic parameters, suggesting that bowhead whales keep consistency in some units while using a continuum in values of frequency, duration and modulation parameters for other unit types. Those findings emphasise the need to account for variability in song analysis to better understand the behavioural ecology of this endangered species. Additionally, shifting from song toward units or phrase-based analysis, as it has been suggested for humpback whales, offers the opportunity to identify and track similarities in songs over temporal and geographical scales relevant to population monitoring. Balaena mysticetus) are highly vocal animals and during the coldest and darkest Arctic winter months they exhibit an elaborated acoustic display that rivals the complexity of the better known humpback whale songs1. Although the sex of the singers and the song function in bowhead whales are still unknown, it has been hypothesised that singing behaviour plays a major role in mediating sexual interactions5 in a way similar to humpback whales and songbirds7.Bowhead whales . For example, song variations in humpback whales have been used to investigate the function of song components in the context of inter- and intrasexual selection10, to examine population connectivity or group dynamics (e.g.13), and to investigate mechanisms underpinning gradual song evolution and cultural revolution (e.g.16).Bowhead whale songs have been described following the same hierarchical framework established to study humpback whales, with sequences of repeated units composing phrases, phrases composing themes, and themes composing a song17. Unfortunately, there are currently no clear criteria establishing the acceptable level of variability within a unit type and the classification procedure remains highly subjective. Manual or automated categorisation into unit types can be furthermore complicated by the graded nature of the bowhead whale repertoire. For example, Johnson et al.8 described ‘subnotes’ (subtypes of units) along a graded unit sequence , where both unit duration and frequency parameters evolved along the song. The authors eventually assigned the last units of the sequence to a different type, based on “trend of frequency”, a criterion that has not been reported in other song studies. At the song level, one of the most variable components appears to be the number of repetition of units per phrase. All studies describing song acoustic and structural parameters report on a high level of variation, with repetition rates ranging from one to tens of times, and some units being sometimes entirely omitted or rarely present in the song8. Directly linked to unit repetition, variability across renditions of the same song have been previously reported including variability in song duration along a song bout2 and the occurrence of ‘primitive versions’ during the initial development of a song as well as song variants based on unit or phrase repetition, order or absence8. Similar variants have been recently identified as “song fragments” in humpback whales songs20. Collectively, the bowhead whale acoustic studies indicate that variability at multiples levels is an important part of the bowhead whale singing behaviour. Although this variability has been consistently reported either as a qualitative descriptor of songs21 or with a statistical measure of dispersion in previous publications17, the study of variability itself has never been the central subject of bowhead whale acoustic research.In bowhead whales, variability is similarly present at different levels of the hierarchical song structure. At the unit level, the unit contour shape can change through splitting, missing components, frequency shifts, or modification in the number of inflection and modulation points22. At first glance, counting songs might seem straightforward, but defining at which point a song is different enough to be considered new represents a delicate problem when the signals to be categorised display high variability. Furthermore, integrating variability in the definition of what is new or different is essential to delve into the potential functions of a song and advances our understanding of singing behaviour in bowhead whales.Research challenges related to the bowhead whale Arctic distribution have constrained the advances of acoustic studies and although the first reports of bowhead whale songs date back to the early 1980s there have only been a handful of publications since then describing their songs. Many of those studies have focused on song diversity using the number of different songs as a single metricHere we used a one-year dataset that sampled bowhead whales from the critically endangered Spitsbergen population in a previously undescribed overwintering area in Northeast Greenland coastal waters to examine song variability. We selected songs shared by multiple individuals as a basis to focus on inter and intra individual aspects of variability. The shared songs, displaying comparable song structure and unit acoustic characteristics, were used to identify patterns of variations using semi-automated methods. We explored the potential ecological and behavioural significance of this song variability within the bowhead whale mating context.23.Acoustic data were collected in coastal waters of Northeast Greenland (78°30′N and 10°0′W) on the continental shelf about 170 km offshore, close to the Northeast Water (NEW) polynya  framework and software package24.The recording equipment was deployed during the Oden Artic Technology Research Cruise 2013 on the 23th of August 2013 and retrieved on the 17th of September 2014. The hydrophone, an AGUAtech Low-Power Scientific Measurement Hydrophone (sensitivity -160 dB re 1 V/μPa), was directly connected to the acoustic recorder, an RTSys EA SDA14 . The system was suspended a few tens of metres above the sea floor using a subsurface float, in a water depth of 227 m. The recording was set on a duty cycle of 2 min on and 30 min off, at a sampling frequency of 39,062 Hz in 24 bits. The data was hosted in the LIDO (The dataset was first subsampled to 25% (one out of four 2-min files) and then explored to detect the occurrence of shared songs. Files were aurally and visually analysed by an expert in Adobe Audition . Each 2-min file was displayed as a spectrogram . The songs shared by multiple animals were identified based on two criteria: the songs overlapped in time and contained similar unit types temporally arranged in similar phrases. Figure M unit type) and a short whistle-like unit usually containing one inflection (S unit type). M and S units were temporally associated in a phrase, that was usually repeated multiple times. Subsequently, the analysis was focused only on the songs containing M and S units. All the song occurrences containing the M and S units were identified from the subsampled dataset. Songs were manually classified into song groups. Song groups were defined as songs presenting a high level of similarity on the following aspects of the song characteristics and structure: overall similarity of the frequency contours of the units M and S, presence of others unit types, order of units, and biphonation characteristics if present (overview given in Table MSG11 refer to the units M from the song group SG11).Two unit types were consistently present in most of the detected shared songs: a long whistle-like unit displaying multiple inflections . Some of the measured units displayed biphonation, a nonlinear phenomenon consisting of the simultaneous production of two independent frequencies26. Due to degraded signal to noise ratio in the lower frequencies, biphonated components were not measured in Raven, but an estimation of their frequency bandwidth and duration were noted to allow comparison and define biphonation types. The unit measurements consisted of frequency, modulation and duration parameters that are commonly used in literature describing or classifying animal vocalisations. These parameters included minimum frequency (1), maximum frequency (2), frequency bandwidth (3), frequency bandwidth 90% (4), and duration (5). Unit contours were extracted using the Frequency Contour Measurements tool in Raven. The extracted contours were imported in Matlab v.R2017a  and a custom-made smoothing function (moving average) was applied to remove noise. Additional parameters (frequency start (6) and frequency end (7), number of inflections (8), median frequency (9)) were automatically extracted in Matlab from the smoothed contours. To describe the distribution of the parameters in each unit, the mean, standard deviation (sd) and coefficient of quartile variation (cqv) were used. The cqv was preferred over the coefficient of variation to take into account that some distributions were leptokurtic27.In order to reduce subjectivity inherent to human observer categorisation, we investigated unit classification and variability using a semi-automated procedure based on unit frequency, modulation and duration measurements. For each song group, all units occurring in a song were assessed for inclusion in further analysis. A unit was selected if it was complete without overlap with other signals. Spectrogram measurements of units comprising the songs were performed in Raven . Multidimensional scaling maps (MDS), based on pairwise similarities, were produced to examine the pattern of acoustic variation in units. MDS was used to provide an automatic way of investigating visually the grouping of units into clusters and to determine whether unit types fell into distinct subtypes without stipulating a priori categories. MDS analysis allows to view the clustering tendency of the data in a few dimensions, without forcing a certain number of clusters as is needed for many clustering algorithms. Unit clusters from the manual analysis were plotted against the MDS map to explore further the acoustic similarity/dissimilarity patterns. Kruskall stress and R-squared values were used to assess the quality of the MDS model30. Higher R-squared values indicate that the distances between points in the high dimensional feature space correlate well with the distances between the same points in the MDS projection. Similarly, a stress value inferior to 0.05 suggest that the goodness of fit of the MDS distance model can be considered as good29. Correlation between the selected features and the MDS dimensions was used to provide an interpretation of the MDS dimension.After a normalisation process , the nine parameters described above were used as features . The hierarchical clustering algorithm was run on each dataset. Cluster solutions from the semi-automated (MDS map) and fully automated method  were assessed for performance using a cluster validity measurement, the Silhouette index. This index is an indication of clustering quality and takes values between -1 and 1. The higher the silhouette value is, the better is the quality of clustering, i.e. the intra-cluster dissimilarities are small compared to the inter-cluster dissimilarities32.In order to compare the results to a fully automated clustering method, a hierarchical clustering  was performed on the dataset. To take into account the higher variability regarding the 33 could actually extend some 170 km further east towards the coast of Greenland. The manual analysis of the songs resulted in the identification of 13 song groups that comprised songs sharing similar acoustic characteristics  were detected in 6 song groups, the higher frequency sLFconst2 replacing sLFconst in half of them. Other units, such a s Vhigh and rumble-like units were present in different song groups, with the exception of sup occurring only in SG4.A total of 804 units were measured and manually classified into 9 unit types using visual and audio properties of the units as well as the temporal arrangement of units in a song. An overview of the units and their main characteristics is provided in Table 2 = 0.99) and goodness of fit (stress = 0.066). Close relationships (R2 > 0.7) were found between the first MDS axis and the variables median frequency, high frequency, low frequency, contour start and frequency bandwidth, suggesting that this dimension was strongly related to the global positioning of the unit in the frequency domain. The second MDS axis was less correlated to the acoustic variables, although correlations with inflections and duration were noticeable (R2 = 0.3–0.4)  were closely positioned along the first dimension, i.e. they separated along a frequency gradient, respectively from lower to higher frequency .Units defined by the manual procedure appeared to be well separated on the MDS map. Short units  was consistently observed. The MDS projection suggested that M units formed five distinct subtypes  containing 68% of the M units from 9 song groups overlapping each other, and 4 smaller separated clusters, each one containing M units from a specific song group. MSG11 was characterised by a very high number of inflection points and a reduced bandwidth  and MSG11 cluster .Unlike the densely grouped pes Fig. b online.ges Fig. b online,M unit acoustic parameters were higher than for the other unit types, and still superior to S type values when considering only the Mo cluster  values for the er Table a. Short an Table b.Figure M units and the Except-M units were higher than the values obtained for the hierarchical clustering for the same number of clusters (respectively 0.40 and 0.28) . A similar biphonation pattern was present on S unit from SG1 (Sbi2). M from SG4 showed a distinct type of biphonation, a short constant tonal around 130 Hz with 3 harmonics, present at the end of the unit. Altogether, biphonation patterns resulting from the combination of biphonation types on M and S units were unique for almost half of the song groups.All the analysed song groups presented a biphonation on one or two unit types. Biphonation presented strong similarities between some song groups, and could be divided into 3 and 4 major types for 34 to the remarkably high song diversity described for the Spitzbergen population22. Although previous studies provided song or unit descriptions, there has been little discussion about variability and consistency in bowhead whale singing display and its impact on our understanding of bowhead whale acoustic ecology in a mating context.Bowhead whales singing behaviour has been studied for more than 3 decades and an increasing diversity in their song repertoire has been described from the simple patterned moan sequences reported by Ljungblad et al.22, also described intense singing activity of bowhead whales in winter months, suggesting that this location was a mating ground for the Spitsbergen population33. Our data, recorded approximately 170 km from the Fram Strait, provides compelling acoustic evidence that the spatial range of the mating ground of this critically endangered population would likely extend from the western Fram Strait to the Northeast Greenland coastal area, hundreds of kilometres more west than previously reported.Bowhead whale songs were almost continuously present from November 2013 to March 2014, with a peak of vocal activity between December 2013 to February 2014. Previous studies in the Fram Strait8. Elaborating on this finding, Johnson et al.8 estimated that during the migration of whales from the Bering-Chukchi-Beaufort population, a song type could be shared by up to nine animals. Temporal overlapping of songs in our data revealed that at least three animals were sharing the same song  and in a similar way, sexual selection might be one of the mechanisms underlying innovation in humpback whale song38.Variations in a given unit type have been described in previous acoustic studies of bowhead whale songs. Evolution of unit structure  or frequency (e.g. shifting) has been reported from all the populations that have been acoustically studied so far17. In this context, a possible advantage of displaying calls with longer duration could be linked to an increase in stamina with age or as an honest advertisement of physical fitness as it has been described in bearded seals, Erignathus barbatus39. Variability in inflection points could similarly be associated to fitness since highly modulated sounds require higher motor control of the vocal apparatus. Interestingly, for most of the unit types, variability was contained inside a unique cluster corresponding to a single unit type (i.e. unit types were separable in the feature space as they had little to no overlap). However, combined variability on both frequency and modulation/duration parameters led to a gradual split of M units into subtypes, some of them matching the song groups labels. The M unit type, possessing characteristic of long duration, numerous inflections points and variable bandwidth could be identified as the unit that best represents abilities of the animal to produce physically challenging sounds. This would be similar to trilled songs in songbirds where production of trills, expressing vocal performance, defines a constraint on the song, represented by a trade-off between trill rate and frequency bandwidth42  and the frequency range they can span , although the exact nature of the bowhead whale mating system is still unclear to researchersh42 Fig. . The upppan Fig. . Song grnce Fig. . If song4 and that the use of biphonated signals can be quite common in bowhead whale songs8. All the song groups studied here showed biphonation on one or two unit types, with the occurrence of different biphonation types including continuous whistle-like sounds, short impulsive broadband sounds and harmonics signals. Functions of biphonated signals remain unclear and they have been suggested to encode information on size44, individuality47 or localisation of the signal emitter49. Mastering the production of biphonated signals, which require high vocal control of the laryngeal apparatus (Musculus diverticuli laryngei)50, could function as another honest signal of mate quality in a context of reproductive display4. If one structure is the source of two simultaneous sounds, then producing two very different sounds i.e. decoupling mechanisms of air movements in the larynx, would require strong vocal skills. Broadband discrete impulsive signals coupled with continuous M units could be more difficult to produce than whistle-like types. As such, the presence of type Mbi2 could indicate older or more experienced singers and, interestingly, this biphonation type occurred concurrently with M units than can be associated with higher vocal performance (SG11). Similarly, recent studies on bowhead whales’ closest relatives, the North Atlantic right whales, have linked age with increasing structure in non-linear phenomena, from disorder (deterministic chaos) to increased control (biphonation and subharmonics)51.An additional source of unit-level variability described here comes from the presence of biphonated signals. Recent acoustic studies confirmed that bowhead whales use biphonationM and S were present in every song group, phrases containing the short alternating units  were only present in half the song groups. The duty cycle used in this study  could have resulted in recording only partially the variability of each song group. The average song duration of a bowhead whale song is considered to be approximately one minute21 but songs lasting almost two minutes have been reported. Therefore, in our study, most of the time, only one entire song was present in the file, and variability at the song bout level  could not be assessed. Nevertheless, the aforementioned phrases containing the short alternating units were present in half of the studied song groups, and can be considered as common and part of the song structure. In humpback whales, the only other cetacean species to produce such complex songs, omission or insertion of entire themes is considered part of the natural evolution of song types and themes present in 50% or more of the songs were included in song sequence study14. Similarly, temporal evolution of a song type over a period of a few months has been previously described in bowhead whales. Delarue et al.3 reported the observations of primitive versions occurring during the initial development of the song until the final, stable version emerged. The overall song variability suggested a low level of constraint in the song structure . In humpback whale songs, phrase structure is reported to be much more flexible than in bird songs and can even be progressively modified within individual songs52. While there are inherent recording limitations when conducting acoustic studies in the high Arctic, longer duty cycles are required to quantitatively describe song structure variability and evolution over a season.On the upper level of the song hierarchy (phrases), temporal arrangement of units in phrases showed regular patterns of association between units in stable phrases. However, while phrases containing M unit type. Units were positioned along a continuum on the MDS axes, following a gradation in the frequency, modulation and duration parameters of this unit type, which complicated the classification into subtypes. Graded vocal repertoire has been described for many mammalian taxa such as primates53, elephants54, sirenians55, odontocetes58, and mysticetes including humpback59 and right whales61. Graded repertoires are challenging for classification tasks since there is no clear boundary where a grouping begins or ends. Manual (human) classification of animal vocalisations usually leads to accurate results62, but with a strong subjective component, whereas automatic methods can add objectivity and standardisation. It appears that a combined method such as the one we described here can greatly help the classification process at the unit level. The next step forward towards standardisation of bowhead whale song studies would be applying automated methods that have been validated on other species. For example, the Levenshtein distance, a similarity analysis that compares vocal sequences, has been successfully applied to humpback whale songs to objectively quantify differences among groups of songs65.To describe and quantify variability at unit level and to allow the description of song structure, we have used a semi-automated method combining multidimensional scaling maps and human expertise. MDS maps showed unit clusters corresponding well to human classification into nine distinct unit types. Based on this agreement, MDS was used to investigate subclustering in the -Beaufort (BCB) population on their migration route3 and for the Eastern Canada-Western Greenland (EC-WG) population in Disko Bay in spring5. It is likely that these studies only sampled a small part of the song repertoire, neither locations being wintering grounds where most of the singing is thought to occur in relation to reproduction66. A recent study from the Spitsbergen population analysed data from a probable mating area in the Fram Strait during four successive winter seasons. As predicted, researchers recorded and described a much higher diversity of songs. Again, the results highlighted the lack of recurrence of song types from year to year, indicating that bowhead whales completely renew their singing repertoire each year22.Earlier studies suggested that bowhead whales, unlike all other singing whale species, entirely change their song repertoire from year to year. This feature has been reported for the Bering-Chukchi22 study revealed that identical units forming highly similar songs were present at the two locations (170 km apart), during the same time period (December 2013–January 2014) and moreover, were present at the same location in the Fram Strait during two consecutive years , some unit types and patterns of association between unit types may be maintained over time. Acknowledging this inherent variability could help to track patterns in units and song presence at different temporal and geographical scales. For example, close examination of songs from the Spitzbergen population from our dataset and from the Stafford et al.ape Fig. .Figure 723. Whether the individuals recorded from the Greenland Sea are remnant of the nearly extirpated Spitzbergen population or immigrants from other populations (BCB or EC-WG) is not known. Drastic sea ice loss in the high Arctic has already made contact possible between once ice-separated bowhead populations and the continuous increase of this phenomena is likely to open new areas for bowhead whale migration67. Tracking acoustic similarities at the unit or phrase level will help to gather acoustic evidence revealing these movements.These findings are highly relevant in the context of population exchanges questions that arose from recent studies of the Spitzbergen population19 to investigate song similarities in the context of song sharing, song evolution and cultural transmission, (iii) conducting collaborative studies to track acoustic patterns at larger temporal and geographic scales.Bowhead whales are undoubtedly amongst the most prolific singers, and the high diversity of the singing repertoire has just begun to unveil. In order to build up our understanding of bowhead whale acoustic ecology, we propose that future acoustic studies should consider (i) further developing automated methods using objective categorisation to facilitate inter study comparisons, (ii) shifting the framework of acoustic studies from a song-based to a unit or phrase-based approach as it has been suggested for humpback whalesSupplementary Information.