The influence of heart rate on echocardiographic assessment of aerobic training

Low birth weight and reduced postnatal nutrition lead to cardiac dysfunction in piglets

Heart disease is the leading cause of death in humans and evidence suggests early life growth-restriction increases heart disease risk in adulthood. Therefore, this study sought to investigate the effects of low birth weight (LBW) and postnatal restricted nutrition (RN) on cardiac function in neonatal pigs. We hypothesized that LBW and RN would reduce cardiac function in pigs but this effect would be reversed with refeeding. To investigate this hypothesis, pigs born weighing <1.5 kg were assigned LBW, and pigs born >1.5 kg were assigned normal birth weight (NBW). Half the LBW and NBW pigs underwent ~25% total nutrient restriction via intermittent suckling (assigned RN) for the first 4 wk post-farrowing. The other half of piglets were allowed unrestricted suckling access to the sow (assigned NN). At 28 d of age (weaning), pigs were weaned and provided ad libitum access to a standard diet. Echocardiographic, vascular ultrasound, and blood pressure (BP) measurements were performed on day 28 and again on day 56 to assess cardiovascular structure and function. A full factorial three-way ANOVA (NN vs. RN, LBW vs. NBW, male vs. female) was performed. Key findings include reduced diastolic BP (P = 0.0401) and passive ventricular filling (P = 0.0062) in RN pigs at 28 d but this was reversed after refeeding. LBW piglets have reduced cardiac output index (P = 0.0037) and diastolic and systolic wall thickness (P = 0.0293 and P = 0.0472) at 56 d. Therefore, cardiac dysfunction from RN is recovered with adequate refeeding while LBW programs irreversible cardiac dysfunction despite proper refeeding in neonatal pigs.

Physiologic hypertrophy: effects on left ventricular systolic mechanics in athletes

Physiologic hypertrophy resulting from intense athletic participation has been reported to result in normal, reduced and augmented overall left ventricular performance. Rather than representing true differences in left ventricular contractility, these data may reflect the variable degree of ventricular dilation and increased wall thickness that occur with different types of exercise. As such, the resultant altered loading conditions may diminish the ability of the usual indexes of left ventricular function to accurately assess the left ventricular contractile state. Therefore, three groups of elite athletes with distinct patterns of myocardial hypertrophy were investigated utilizing recently developed load-independent contractility indexes. Age-matched control subjects (n = 33) were compared with 11 swimmers, 11 long-distance runners and 11 power lifters. Rest echocardiogram, phonocardiogram and calibrated carotid pulse tracing were used to calculate left ventricular dimensions, wall thickness, mass, fractional shortening, velocity of shortening and mean, peak and end-systolic wall stresses and the stress-time and minute stress-time integrals. Compared with control subjects, all athletes had increased left ventricular mass, even when values were normalized for body surface area. Runners had a dilated left ventricular and normal wall thickness, swimmers had a mildly dilated ventricle with increased wall thickness and power lifters had normal cavity size with markedly increased wall thickness. Peak systolic wall stress was normal in runners and swimmers and reduced in power lifters, whereas end-systolic stress was low in swimmers and power lifters and normal in runners. The minute stress-time integral, a measure of myocardial oxygen consumption, was normal in runners and swimmers but was significantly reduced in lifters.(ABSTRACT TRUNCATED AT 250 WORDS)