Selection of endurance capabilities and the trade-off between pressure and volume in the evolution of the human heart.

Chimpanzees and gorillas, when not inactive, engage primarily in short bursts of resistance physical activity (RPA), such as climbing and fighting, that creates pressure stress on the cardiovascular system. In contrast, to initially hunt and gather and later to farm, it is thought that preindustrial human survival was dependent on lifelong moderate-intensity endurance physical activity (EPA), which creates a cardiovascular volume stress. Although derived musculoskeletal and thermoregulatory adaptations for EPA in humans have been documented, it is unknown if selection acted similarly on the heart. To test this hypothesis, we compared left ventricular (LV) structure and function across semiwild sanctuary chimpanzees, gorillas, and a sample of humans exposed to markedly different physical activity patterns. We show the human LV possesses derived features that help augment cardiac output (CO) thereby enabling EPA. However, the human LV also demonstrates phenotypic plasticity and, hence, variability, across a wide range of habitual physical activity. We show that the human LV's propensity to remodel differentially in response to chronic pressure or volume stimuli associated with intense RPA and EPA as well as physical inactivity represents an evolutionary trade-off with potential implications for contemporary cardiovascular health. Specifically, the human LV trades off pressure adaptations for volume capabilities and converges on a chimpanzee-like phenotype in response to physical inactivity or sustained pressure loading. Consequently, the derived LV and lifelong low blood pressure (BP) appear to be partly sustained by regular moderate-intensity EPA whose decline in postindustrial societies likely contributes to the modern epidemic of hypertensive heart disease.

Personalized treatment for coronary artery disease patients: a machine learning approach.

Current clinical practice guidelines for managing Coronary Artery Disease (CAD) account for general cardiovascular risk factors. However, they do not present a framework that considers personalized patient-specific characteristics. Using the electronic health records of 21,460 patients, we created data-driven models for personalized CAD management that significantly improve health outcomes relative to the standard of care. We develop binary classifiers to detect whether a patient will experience an adverse event due to CAD within a 10-year time frame. Combining the patients' medical history and clinical examination results, we achieve 81.5% AUC. For each treatment, we also create a series of regression models that are based on different supervised machine learning algorithms. We are able to estimate with average R2 = 0.801 the outcome of interest; the time from diagnosis to a potential adverse event (TAE). Leveraging combinations of these models, we present ML4CAD, a novel personalized prescriptive algorithm. Considering the recommendations of multiple predictive models at once, the goal of ML4CAD is to identify for every patient the therapy with the best expected TAE using a voting mechanism. We evaluate its performance by measuring the prescription effectiveness and robustness under alternative ground truths. We show that our methodology improves the expected TAE upon the current baseline by 24.11%, increasing it from 4.56 to 5.66 years. The algorithm performs particularly well for the male (24.3% improvement) and Hispanic (58.41% improvement) subpopulations. Finally, we create an interactive interface, providing physicians with an intuitive, accurate, readily implementable, and effective tool.

Catecholamine response to exercise in patients with non-obstructive hypertrophic cardiomyopathy.

KEY POINTS: Intense physical activity, a potent stimulus for sympathetic nervous system activation, is thought to increase the risk of malignant ventricular arrhythmias among patients with hypertrophic cardiomyopathy (HCM). As a result, the majority of patients with HCM deliberately reduce their habitual physical activity after diagnosis and this lifestyle change puts them at risk for sequelae of a sedentary lifestyle: weight gain, hypertension, hyperlipidaemia, insulin resistance, coronary artery disease, and increased morbidity and mortality. We show that plasma catecholamine levels remain stably low at exercise intensities below the ventilatory threshold, a parameter that can be defined during cardiopulmonary exercise testing, but rise rapidly at higher intensities of exercise. These findings suggest that cardiopulmonary exercise testing may be a useful tool to provide an individualized moderate-intensity exercise prescription for patients with HCM. ABSTRACT: Intense physical activity, a potent stimulus for sympathetic nervous system activation, is thought to increase the risk of malignant ventricular arrhythmias among patients with hypertrophic cardiomyopathy (HCM). However, the impact of exercise intensity on plasma catecholamine levels among HCM patients has not been rigorously defined. We conducted a prospective observational case-control study of men with non-obstructive HCM and age-matched controls. Laboratory-based cardiopulmonary exercise testing coupled with serial phlebotomy was used to define the relationship between exercise intensity and plasma catecholamine levels. Compared to controls (C, n = 5), HCM participants (H, n = 9) demonstrated higher left ventricular mass index (115 ± 20 vs. 90 ± 16 g/m2 , P = 0.03) and maximal left ventricular wall thickness (16 ± 1 vs. 8 ± 1 mm, P < 0.001) but similar body mass index, resting heart rate, peak oxygen consumption (H = 40 ± 13 vs. C = 42 ± 7 ml/kg/min, P = 0.81) and heart rate at the ventilatory threshold (H = 78 ± 6 vs. C = 78 ± 4% peak heart rate, P = 0.92). During incremental effort exercise in both groups, concentrations of adrenaline and noradrenaline were unchanged through low- and moderate-exercise intensity until reaching a catecholamine threshold (H = 82 ± 4 vs. C = 85 ± 3% peak heart rate, P = 0.86) after which levels of both molecules rose rapidly. In patients with mild non-obstructive HCM, plasma catecholamine levels remain stably low at exercise intensities below the ventilatory threshold but rise rapidly at higher intensities of exercise. Routine cardiopulmonary exercise testing may be a useful tool to provide an individualized moderate-intensity exercise prescription for patients with HCM.

Utilization of stress testing for low-risk patients with chest discomfort in the emergency department.

BACKGROUND: The management of patients presenting to an emergency department with chest discomfort at low-risk for acute coronary syndrome represents a common clinical challenge. Such patients are often triaged to chest pain units for monitoring and cardiac stress testing for further risk stratification. METHODS: We conducted a retrospective study of 292 low-risk patients who presented to an emergency department with chest discomfort. We performed physician-adjudicated chart reviews of all patients with positive stress tests to assess downstream testing, subsequent coronary revascularization, and outcomes. RESULTS: Of the 292 patients, 33 (11.3%) had stress tests positive for ischemia, and 12 (4.1%) underwent diagnostic cardiac catheterization. Of the 292 patients, 4 (1.4%) underwent coronary revascularization that may have resulted in a mortality benefit. CONCLUSION: These data suggest a very low yield of detecting clinically significant coronary disease with stress testing low-risk patients with chest discomfort in emergency department chest pain units.

The application of appropriate use criteria for transthoracic echocardiography in a cardiac intensive care unit.

BACKGROUND: Appropriate use criteria (AUC) represent an important mechanism by which to promote the rational utilization of healthcare resources. No study to date has been conducted assessing the applicability of current AUC to transthoracic echocardiograms (TTEs) performed in a cardiac intensive care unit (CICU). We analyzed 2 years of consecutive TTEs performed in a CICU at a quaternary-care academic medical center, hypothesizing that current AUC may not adequately describe the role of TTE in a modern CICU. METHODS: Indications for TTEs were independently classified by two investigators in accordance with 2011 AUC. If investigators were unable to assign an AUC classification to a given study, it was deemed to be unclassifiable. Disagreements between investigators were resolved by consensus. Cases in which consensus could not be reached underwent definitive adjudication by a third investigator. RESULTS: Of the 826 TTEs, 619 TTEs were classified as appropriate (74.9%, CI 71.8%-77.9%), 12 as uncertain (1.5%, CI 0.75%-2.5%), 21 as rarely appropriate (2.5%, CI 1.6%-3.9%), and 174 were unable to be classified (21.1%, CI 18.3%-24.0%). The most common unclassifiable indication was "initial evaluation of cardiac structure or function after cardiac arrest of unknown etiology" (n = 101). CONCLUSION: Current AUC for TTEs may not adequately address the complexity of clinical cases encountered in the CICU. In our study of 826 consecutive TTEs, 21.1% were unable to be classified, reflecting the difficulty in applying AUC to this unique clinical environment. Further studies are therefore needed to better delineate the appropriateness of TTEs performed in the CICU.

Cardiovascular Toxicity of Illicit Anabolic-Androgenic Steroid Use.

BACKGROUND: Millions of individuals have used illicit anabolic-androgenic steroids (AAS), but the long-term cardiovascular associations of these drugs remain incompletely understood. METHODS: Using a cross-sectional cohort design, we recruited 140 experienced male weightlifters 34 to 54 years of age, comprising 86 men reporting ≥2 years of cumulative lifetime AAS use and 54 nonusing men. Using transthoracic echocardiography and coronary computed tomography angiography, we assessed 3 primary outcome measures: left ventricular (LV) systolic function (left ventricular ejection fraction), LV diastolic function (early relaxation velocity), and coronary atherosclerosis (coronary artery plaque volume). RESULTS: Compared with nonusers, AAS users demonstrated relatively reduced LV systolic function (mean±SD left ventricular ejection fraction = 52±11% versus 63±8%; P<0.001) and diastolic function (early relaxation velocity = 9.3±2.4 cm/second versus 11.1±2.0 cm/second; P<0.001). Users currently taking AAS at the time of evaluation (N=58) showed significantly reduced LV systolic (left ventricular ejection fraction = 49±10% versus 58±10%; P<0.001) and diastolic function (early relaxation velocity = 8.9±2.4 cm/second versus 10.1±2.4 cm/second; P=0.035) compared with users currently off-drug (N=28). In addition, AAS users demonstrated higher coronary artery plaque volume than nonusers (median [interquartile range] 3 [0, 174] mL3 versus 0 [0, 69] mL3; P=0.012). Lifetime AAS dose was strongly associated with coronary atherosclerotic burden (increase [95% confidence interval] in rank of plaque volume for each 10-year increase in cumulative duration of AAS use: 0.60 SD units [0.16-1.03 SD units]; P=0.008). CONCLUSIONS: Long-term AAS use appears to be associated with myocardial dysfunction and accelerated coronary atherosclerosis. These forms of AAS-associated adverse cardiovascular phenotypes may represent a previously underrecognized public-health problem.

Application of the Pediatric Appropriate Use Criteria for Chest Pain.

OBJECTIVES: To characterize the subgroup of outpatient pediatric patients presenting with chest pain and to determine the effectiveness of published pediatric appropriate use criteria (PAUC) to detect pathology. STUDY DESIGN: The Pediatric Appropriate Use of Echocardiography study evaluated the use and yield of transthoracic echocardiography (TTE) before and after PAUC release. Data were reviewed on patients ?18 years of age who underwent TTE for chest pain. Indications were classified as appropriate (A), may be appropriate (M), and rarely appropriate (R) based on PAUC ratings, and findings were normal, incidental, or abnormal. RESULTS: Chest pain was the primary indication in 772 of 4562 outpatient TTE studies (17%) (median age 14 years, IQR 10-16) ordered during the study period: 458 of 772 before (59%) and 314 of 772 after (41 %) the release of PAUC with no change in appropriateness. In A indications (n?=?654), 642 (98%) were normal, 5 (1%) had incidental findings, and 7 (1%) were abnormal. A and M detected 100% of all abnormal findings (A: n?=?7; M: n?=?6; R: n?=?0), with an association between ratings and findings (P?<.001). There was no association between R rating and any pathology. CONCLUSIONS: There was no change in ordering patterns with publication of the PAUC. Despite the high rate of TTEs ordered for indications rated A, most studies were normal. Studies that detected pathology were performed for indications rated A or M, but not R. This study supports PAUC as a useful tool in pediatric chest pain evaluation that may subsequently improve the use of TTE.

Left ventricular twist mechanics in the context of normal physiology and cardiovascular disease: a review of studies using speckle tracking echocardiography.

The anatomy of the adult human left ventricle (LV) is the result of its complex interaction with its environment. From the fetal to the neonatal to the adult form, the human LV undergoes an anatomical transformation that finally results in the most complex of the four cardiac chambers. In its adult form, the human LV consists of two muscular helixes that surround the midventricular circumferential layer of muscle fibers. Contraction of these endocardial and epicardial helixes results in a twisting motion that is thought to minimize the transmural stress of the LV muscle. In the healthy myocardium, the LV twist response to stimuli that alter preload, afterload, or contractility has been described and is deemed relatively consistent and predictable. Conversely, the LV twist response in patient populations appears to be a little more variable and less predictable, yet it has revealed important insight into the effect of cardiovascular disease on LV mechanical function. This review discusses important methodological aspects of assessing LV twist and evaluates the LV twist responses to the main physiological and pathophysiological states. It is concluded that correct assessment of LV twist mechanics holds significant potential to advance our understanding of LV function in human health and cardiovascular disease.