Computer Vision Self-supervised Learning Methods on Time Series

Self-supervised learning (SSL) has had great success in both computer vision and natural language processing. These approaches often rely on cleverly crafted loss functions and training setups to avoid feature collapse. In this study, the effectiveness of mainstream SSL frameworks from computer vision and some SSL frameworks for time series are evaluated on the UCR, UEA and PTB-XL datasets, and we show that computer vision SSL frameworks can be effective for time series. In addition, we propose a new method that improves on the recently proposed VICReg method. Our method improves on a \textit{covariance} term proposed in VICReg, and in addition we augment the head of the architecture by an IterNorm layer that accelerates the convergence of the model

Acute myocardial infarction - consequences of new treatment modalities and smoking status : Observations from two prospective cohort studies

This thesis is based upon a comparison of two cohorts of consecutive patients admitted with chest pain suspected to be acute coronary syndrome (ACS) in 2003 (n = 755) and 2006 (n = 934). In 2003 the predominant reperfusion strategy for patients with ST-segment elevation myocardial infarction (STEMI) was prehospital fibrinolysis. Patients with non-ST-segment elevation myocardial infarction (NSTEMI) and unstable angina pectoris (UAP) were managed with an ischemia-driven approach for invasive procedures. In September 2005, following the introduction of new European guidelines on invasive treatment, an early invasive strategy was implemented. Patients with STEMI were transported 100 km to Rikshospitalet University Hospital in Oslo for primary percutaneous coronary intervention. Those with NSTEMI or UAP were routinely transported for invasive management within 48-72 hours in the absence of contraindicating factors. In 2003, 48% of patients qualified for a diagnosis of ACS as compared with 39% in 2006 (p<0.001). In both cohorts NSTEMI patients were older and had greater co-morbidity than patients with STEMI. From 2003 to 2006 the incidence rate for STEMI decreased from 100 to 77 cases per 100,000 personyears, whereas for NSTEMI this decrease was 147 to 143 cases per 100,000 person-years. The oneyear all-cause mortality for NSTEMI decreased from 32% in 2003 to 19% (p = 0.002) in 2006. The corresponding figures for STEMI were 20% and 11% (p = 0.086). After adjustment for age, sex, previous acute myocardial infarction (AMI), previous stroke, diabetes, smoking status, previous left ventricular dysfunction and serum creatinine on admission, patients with AMI in the 2006 cohort had a significantly lower risk for one-year mortality than those managed for AMI in 2003 (hazard ratio 0.54, 95% confidence interval 0.38-0.78, p = 0.001). In a post-hoc analysis, smokers with NSTEMI seemed to be a subset of patients with a particular survival benefit of early invasive management, but smoking on admission was still an independent predictor of death. In a systematic literature search on studies addressing the occurrence of the “smoker’s paradox” in ACS (i.e. that smokers have lower adjusted case fatality than non-smokers), we found that studies supporting the existence of the paradox were from the pre-thrombolytic and thrombolytic era. No studies of patients with contemporary management found support for the paradox. The “smoker’s paradox” most probably represents a historical phenomenon without relevance for today’s practice. In conclusion, the implementation of routine early invasive management for unselected patients with AMI was followed by a 41% reduction in one-year total mortality. For NSTEMI this survival benefit was especially pronounced for smokers, but smoking was still an independent predictor of one-year mortality

VNIbCReg: VICReg with Neighboring-Invariance and better-Covariance Evaluated on Non-stationary Seismic Signal Time Series

One of the latest self-supervised learning (SSL) methods, VICReg, showed a great performance both in the linear evaluation and the fine-tuning evaluation. However, VICReg is proposed in computer vision and it learns by pulling representations of random crops of an image while maintaining the representation space by the variance and covariance loss. However, VICReg would be ineffective on non-stationary time series where different parts/crops of input should be differently encoded to consider the non-stationarity. Another recent SSL proposal, Temporal Neighborhood Coding (TNC) is effective for encoding non-stationary time series. This study shows that a combination of a VICReg-style method and TNC is very effective for SSL on non-stationary time series, where a non-stationary seismic signal time series is used as an evaluation dataset

The effect of tobacco smoking and treatment strategy on the one-year mortality of patients with acute non-ST-segment elevation myocardial infarction

<p>Abstract</p> <p>Background</p> <p>The aim of the present study was to investigate whether a previously shown survival benefit resulting from routine early invasive management of unselected patients with acute non-ST-segment elevation myocardial infarction (NSTEMI) may differ according to smoking status and age.</p> <p>Methods</p> <p>Post-hoc analysis of a prospective observational cohort study of consecutive patients admitted for NSTEMI in 2003 (conservative strategy cohort [CS]; n = 185) and 2006 (invasive strategy cohort [IS]; n = 200). A strategy for transfer to a high-volume invasive center and routine early invasive management was implemented in 2005. Patients were subdivided into current smokers and non-smokers (including ex-smokers) on admission.</p> <p>Results</p> <p>The one-year mortality rate of smokers was reduced from 37% in the CS to 6% in the IS (p < 0.001), and from 30% to 23% for non-smokers (p = 0.18). Non-smokers were considerably older than smokers (median age 80 vs. 63 years, p < 0.001). The percentage of smokers who underwent revascularization (angioplasty or coronary artery bypass grafting) within 7 days increased from 9% in the CS to 53% in the IS (p < 0.001). The corresponding numbers for non-smokers were 5% and 27% (p < 0.001). There was no interaction between strategy and age (p = 0.25), as opposed to a significant interaction between strategy and smoking status (p = 0.024). Current smoking was an independent predictor of one-year mortality (hazard ratio 2.61, 95% confidence interval 1.43-4.79, p = 0.002).</p> <p>Conclusions</p> <p>The treatment effect of an early invasive strategy in unselected patients with NSTEMI was more pronounced among smokers than non-smokers. The benefit for smokers was not entirely explained by differences in baseline confounders, such as their younger age.</p

The limited usefulness of real-time 3-dimensional echocardiography in obtaining normal reference ranges for right ventricular volumes

<p>Abstract</p> <p>Background</p> <p>To obtain normal reference ranges and intraobserver variability for right ventricular (RV) volume indexes (VI) and ejection fraction (EF) from apical recordings with real-time 3-dimensional echocardiography (RT3DE), and similarly for RV area indexes (AI) and area fraction (AF) with 2-dimensional echocardiography (2DE).</p> <p>Methods</p> <p>166 participants; 79 males and 87 females aged between 29–79 years and considered free from clinical and subclinical cardiovascular disease. Normal ranges are defined as 95% reference values and reproducibility as coefficients of variation (CV) for repeated measurements.</p> <p>Results</p> <p>None of the apical recordings with RT3DE and 2DE included the RV outflow tract. Upper reference values were 62 ml/m²for RV end-diastolic (ED) VI and 24 ml/m²for RV end-systolic (ES) VI. Lower normal reference value for RVEF was 41%. The respective reference ranges were 17 cm²/m²for RVEDAI, 11 cm²/m²for RVESAI and 27% for RVAF. Males had higher upper normal values for RVEDVI, RVESVI and RVEDAI, and a lower limit than females for RVEF and RVAF. Weak but significant negative correlations between age and RV dimensions were found with RT3DE, but not with 2DE. CVs for repeated measurements ranged between 10% and 14% with RT3DE and from 5% to 14% with 2DE.</p> <p>Conclusion</p> <p>Although the normal ranges for RVVIs and RVAIs presented in this study reflect RV inflow tract dimensions only, the data presented may still be regarded as a useful tool in clinical practice, especially for RVEF and RVAF.</p

The "smoker's paradox" in patients with acute coronary syndrome: a systematic review

<p>Abstract</p> <p>Background</p> <p>Smokers have been shown to have lower mortality after acute coronary syndrome than non-smokers. This has been attributed to the younger age, lower co-morbidity, more aggressive treatment and lower risk profile of the smoker. Some studies, however, have used multivariate analyses to show a residual survival benefit for smokers; that is, the "smoker's paradox". The aim of this study was, therefore, to perform a systematic review of the literature and evidence surrounding the existence of the "smoker's paradox".</p> <p>Methods</p> <p>Relevant studies published by September 2010 were identified through literature searches using EMBASE (from 1980), MEDLINE (from 1963) and the Cochrane Central Register of Controlled Trials, with a combination of text words and subject headings used. English-language original articles were included if they presented data on hospitalised patients with defined acute coronary syndrome, reported at least in-hospital mortality, had a clear definition of smoking status (including ex-smokers), presented crude and adjusted mortality data with effect estimates, and had a study sample of > 100 smokers and > 100 non-smokers. Two investigators independently reviewed all titles and abstracts in order to identify potentially relevant articles, with any discrepancies resolved by repeated review and discussion.</p> <p>Results</p> <p>A total of 978 citations were identified, with 18 citations from 17 studies included thereafter. Six studies (one observational study, three registries and two randomised controlled trials on thrombolytic treatment) observed a "smoker's paradox". Between the 1980s and 1990s these studies enrolled patients with acute myocardial infarction (AMI) according to criteria similar to the World Health Organisation criteria from 1979. Among the remaining 11 studies not supporting the existence of the paradox, five studies represented patients undergoing contemporary management.</p> <p>Conclusion</p> <p>The "smoker's paradox" was observed in some studies of AMI patients in the pre-thrombolytic and thrombolytic era, whereas no studies of a contemporary population with acute coronary syndrome have found evidence for such a paradox.</p