Self-supervised contrastive learning of echocardiogram videos enables label-efficient cardiac disease diagnosis

Advances in self-supervised learning (SSL) have shown that self-supervised pretraining on medical imaging data can provide a strong initialization for downstream supervised classification and segmentation. Given the difficulty of obtaining expert labels for medical image recognition tasks, such an "in-domain" SSL initialization is often desirable due to its improved label efficiency over standard transfer learning. However, most efforts toward SSL of medical imaging data are not adapted to video-based medical imaging modalities. With this progress in mind, we developed a self-supervised contrastive learning approach, EchoCLR, catered to echocardiogram videos with the goal of learning strong representations for efficient fine-tuning on downstream cardiac disease diagnosis. EchoCLR leverages (i) distinct videos of the same patient as positive pairs for contrastive learning and (ii) a frame re-ordering pretext task to enforce temporal coherence. When fine-tuned on small portions of labeled data (as few as 51 exams), EchoCLR pretraining significantly improved classification performance for left ventricular hypertrophy (LVH) and aortic stenosis (AS) over other transfer learning and SSL approaches across internal and external test sets. For example, when fine-tuning on 10% of available training data (519 studies), an EchoCLR-pretrained model achieved 0.72 AUROC (95% CI: [0.69, 0.75]) on LVH classification, compared to 0.61 AUROC (95% CI: [0.57, 0.64]) with a standard transfer learning approach. Similarly, using 1% of available training data (53 studies), EchoCLR pretraining achieved 0.82 AUROC (95% CI: [0.79, 0.84]) on severe AS classification, compared to 0.61 AUROC (95% CI: [0.58, 0.65]) with transfer learning. EchoCLR is unique in its ability to learn representations of medical videos and demonstrates that SSL can enable label-efficient disease classification from small, labeled datasets

Cooperatively breeding banded mongooses do not avoid inbreeding through familiarity-based kin recognition

In species that live in family groups, such as cooperative breeders, inbreeding is usually avoided through the recognition of familiar kin. For example, individuals may avoid mating with conspecifics encountered regularly in infancy, as these likely include parents, siblings, and closely related alloparents. Other mechanisms have also been reported, albeit rarely; for example, individuals may compare their own phenotype to that of others, with close matches representing likely relatives (“phenotype matching”). However, determinants of the primary inbreeding avoidance mechanisms used by a given species remain poorly understood. We use 24 years of life history and genetic data to investigate inbreeding avoidance in wild cooperatively breeding banded mongooses (Mungos mungo). We find that inbreeding avoidance occurs within social groups but is far from maximised (mean pedigree relatedness between 351 breeding pairs = 0.144). Unusually for a group-living vertebrate, we find no evidence that females avoid breeding with males with which they are familiar in early life. This is probably explained by communal breeding; females give birth in tight synchrony and pups are cared for communally, thus reducing the reliability of familiarity-based proxies of relatedness. We also found little evidence that inbreeding is avoided by preferentially breeding with males of specific age classes. Instead, females may exploit as-yet unknown proxies of relatedness, for example, through phenotype matching, or may employ postcopulatory inbreeding avoidance mechanisms. Investigation of species with unusual breeding systems helps to identify constraints against inbreeding avoidance and contributes to our understanding of the distribution of inbreeding across species. Significance statement: Choosing the right mate is never easy, but it may be particularly difficult for banded mongooses. In most social animals, individuals avoid mating with those that were familiar to them as infants, as these are likely to be relatives. However, we show that this rule does not work in banded mongooses. Here, the offspring of several mothers are raised in large communal litters by their social group, and parents seem unable to identify or direct care towards their own pups. This may make it difficult to recognise relatives based on their level of familiarity and is likely to explain why banded mongooses frequently inbreed. Nevertheless, inbreeding is lower than expected if mates are chosen at random, suggesting that alternative pre- or post-copulatory inbreeding avoidance mechanisms are used

Clinical Fellowships in Surgical Training: Analysis of a National Pan-specialty Workforce Survey

BACKGROUND: Fellowship posts are increasingly common and offer targeted opportunities for training and personal development. Despite international demand, there is little objective information quantifying this effect or the motivations behind undertaking such a post. The present study investigated surgical trainees’ fellowship aims and intentions. METHODS: An electronic, 38-item, self-administered questionnaire survey was distributed in the United Kingdom via national and regional surgical mailing lists and websites via the Association of Surgeons in Training, Royal Surgical Colleges, and Specialty Associations. RESULTS: In all, 1,581 fully completed surveys were received, and 1,365 were included in the analysis. These represented trainees in core or higher training programs or research from all specialties and training regions: 66 % were male; the mean age was 32 years; 77.6 % intended to or had already completed a fellowship. Plastic surgery (95.2 %) and cardiothoracic (88.6 %) trainees were most likely to undertake a fellowship, with pediatrics (51.2 %), and urology (54.3 %) the least likely. Fellowship uptake increased with seniority (p < 0.01) and was positively correlated (p = 0.016, r = 0.767) with increasing belief that fellowships are necessary to the attainment of clinical competence, agreed by 73.1 %. Fellowship aims were ranked in descending order of importance as attaining competence, increasing confidence, and attaining subspecialist skills. CONCLUSIONS: Over three-quarters of trainees have or will undertake a clinical fellowship, varying with gender, specialty, and seniority. Competence, confidence, and subspecialty skills development are the main aims. The findings will influence workforce planning, and perceptions that current training does not deliver sufficient levels of competence and confidence merit further investigation

Long-range potential fluctuations and 1/f noise in hydrogenated amorphous silicon

We present a microscopic theory of the low-frequency voltage noise (known as "1/f" noise) in micrometer-thick films of hydrogenated amorphous silicon. This theory traces the noise back to the long-range fluctuations of the Coulomb potential produced by deep defects, thereby predicting the absolute noise intensity as a function of the distribution of defect activation energies. The predictions of this theory are in very good agreement with our own experiments in terms of both the absolute intensity and the temperature dependence of the noise spectra.Comment: 8 pages, 3 figures, several new parts and one new figure are added, but no conceptual revision

Variation in Hospital-use and Outcomes Associated with Pulmonary Artery Catheterization in Heart Failure in the United States

Background There has been an increase in the use of pulmonary artery (PA) catheters in heart failure (HF) in the United States in recent years. However, patterns of hospital-use and trends in patient outcomes are not known. Methods and Results In the National Inpatient Sample 2001–2012, using ICD-9 codes we identified 11,888,525 adult (≥18 years) HF hospitalizations nationally, of which an estimated 75,209 (SE 0.6%) received a PA catheter. In 2001, the number of hospitals with ≥1 PA catheterization was 1753, decreasing to 1183 in 2011. The mean PA catheter use per hospital trended from 4.9/year in 2001 (limits 1–133) to 3.8/year in 2007 (limits 1–46), but increased to 5.5/year in 2011 (limits 1–70). During 2001–2006, PA catheterization declined across hospitals; however, in 2007–2012 there has been a disproportionate increase at hospitals with large bedsize, teaching programs, and advanced HF capabilities. The overall in-hospital mortality with PA catheter use was higher than without PA catheter use (13.1% vs. 3.4%, P<0.0001), however, in propensity-matched analysis, differences in mortality between these groups have attenuated over time – risk-adjusted odds ratio for mortality for PA-catheterization, 1.66 (95% CI 1.60–1.74) in 2001–2003 down to 1.04 (95% CI 0.97– 1.12) in 2010–2012. Conclusions There is substantial hospital-level variability in PA catheterization in HF along with increasing volume at fewer hospitals overrepresented by large, academic hospitals with advanced HF capabilities. This is accompanied by a decline in excess mortality associated with PA catheterization

TCT-100 Real-World Experience and Outcomes of Protected Versus Unprotected Left Main Percutaneous Coronary Intervention: Insights From the VA CART Program

Background: Outcomes of protected left main (PLM) and unprotected left main (ULM) percutaneous coronary intervention (PCI) are not well defined in contemporary U.S. practice. Previous studies of real-world data have shown worse in-hospital outcomes of ULM PCI compared with randomized trial data. We used a large national registry to characterize real-world practice and outcomes of left main PCI. Methods: Data were collected from the Veteran Affairs (VA) Clinical Assessment Reporting and Tracking (CART) Program for patients undergoing left main PCI between 2009 and 2019. PLM PCI was defined by the presence of at least 1 functioning bypass graft, and ULM PCI was defined as patients with no bypass grafting. Temporal trends, patient and procedure characteristics, anatomic complexity, and clinical complexity were assessed. A 1-to-1 propensity-matched analysis was performed using common comorbidities and clinical variables. One-year outcome analyses were conducted for major adverse cardiovascular events (MACE), all-cause mortality, rehospitalization for myocardial infarction (MI) and revascularization. Results: Of 4,351 patients undergoing left main PCI, 2,800 were PLM PCI and 1,551 were ULM PCI, of which 1,335 PLM and ULM PCI were included in the propensity matched cohort. Patients undergoing ULM PCI were older, more likely to present with acute coronary syndrome (ACS) and had a higher clinical complexity. In the propensity-matched cohort, there was no difference in age, rate of ACS presentation, burden of comorbidities, or left ventricular ejection fraction. There were no differences in in-hospital adverse events between the 2 groups. At 12 months, MACE occurred more frequently with ULM PCI compared with PLM PCI (25% [334] vs 20% [270]; P = 0.004), and all-cause mortality was also higher (18% [239] vs 14% [185]; P = 0.005). There was no difference in rehospitalization for MI, stroke, or revascularization at 12 months. Conclusion: In the VA Healthcare System, patients undergoing ULM PCI were older and more clinically complex than those undergoing PLM PCI. In the propensity-matched cohort, patients undergoing PLM PCI had better 12 outcomes than those undergoing ULM PCI, but there was a high rate of mortality and MACE at 1 year in both groups, despite a relatively low rate of MI or revascularization