Shiino, Kenji

High-intensity endurance exercise elicits acute cardiac imbalances that may be an important stimulus for adaptive cardiac remodeling. This study highlights that following a bout of high-intensity exercise that is typical of routine day-to-day cycling training, exercise-induced autonomic, biochemical, and functional cardiac imbalances are attenuated in middle-aged relative to young well-trained cyclists. These findings suggest that aging may alter exercise-induced stress stimulus response that initiates cardiac remodeling in Athlete’s Heart.

ABSTRACT Introduction Regional heterogeneity of the human heart plays an important role in left ventricular (LV) and right ventricular (RV) function and may contribute to enhanced myocardial efficiency in the athlete’s heart. Purpose This study comprehensively characterized regional and transmural myocardial tissue deformation (strain) in recreationally active (RA) and endurance-trained (ET) men to determine if regional nonuniformity evolves alongside morphological adaptations associated with endurance training. Methods Echocardiography was used to measure LV and RV global, regional (apical, mid, basal) and transmural (endocardial, epicardial) longitudinal strain in 30 endurance-trained (ET) (age, 31 ± 2 yr; body mass index, 23.1 ± 0.5 kg·m −2 ; V˙O 2peak , 60.2 ± 6.5 mL·kg −1 ·min −1 ) and 30 RA (age: 29 ± 2 yr; body mass index, 23.4 ± 0.4 kg·m −2 ; V˙O 2peak : 42.6 ± 4.6 mL·kg −1 ·min −1 ). Nonuniformity was characterized using apex-to-base and transmural (endocardial-to-epicardial) strain gradients. Results Global longitudinal strain was similar in ET and RA in the left (−17.4% ± 0.4% vs −17.8% ± 0.5%, P = 0.662) and right ventricle (−25.8% ± 0.8% vs 26.4% ± 1.0%, P = 0.717). The apex-to-base strain gradient was greater in ET than RA in the left (−6.5% ± 0.7% vs −2.7% ± 0.8%, P = 0.001) and right ventricle (−9.6% ± 1.8% vs −3.0% ± 1.6%, P = 0.010). The LV transmural strain gradient was greater than RV in both groups, but similar in ET and RA (−4.7% ± 0.2% vs −4.7% ± 0.2%, P = 0.850), whereas RV transmural strain gradient was greater in ET than RA (−3.4% ± 0.3% vs −1.6% ± 0.4%, P = 0.003). RV apex-to-base and transmural strain gradients correlated with RV end-diastolic area ( R = 0.536 & 0.555, respectively, P < 0.01) and V˙O 2peak ( R = 0.415 & 0.677, respectively, P < 0.01). Conclusions Transmural nonuniformity is more pronounced in the left ventricle than the RV free wall; however, RV functional nonuniformity develops markedly after endurance training. Differences in myocardial architecture and exercise-induced wall stress in the left and right ventricles are possible explanations for the marked functional nonuniformity throughout the myocardium and in response to endurance exercise training.

Heart failure (HF) patients are susceptible to heat strain during exercise, secondary to blunted skin blood flow (SkBF) responses, which may be explained by impaired nitric oxide (NO)-dependent vasodilation. Folic acid improves vascular endothelial function and SkBF through NO-dependent mechanisms in healthy older individuals and patients with cardiovascular disease. We examined the effect of folic acid supplementation (5 mg/day for 6 wk) on vascular function [brachial artery flow-mediated dilation (FMD)] and SkBF responses [cutaneous vascular conductance (CVC)] during 60 min of exercise at a fixed metabolic heat production (300 ẆHprod) in a 30°C environment in 10 patients with HF (New York Heart Association Class I–II) and 10 healthy controls (CON). Serum folic acid concentration increased in HF [preintervention (pre): 1.4 ± 0.2; postintervention (post): 8.9 ± 6.7 ng/ml, P = 0.01] and CON (pre: 1.3 ± 0.6; post: 5.2 ± 4.9 ng/ml, P = 0.03). FMD improved by 2.1 ± 1.3% in HF ( P < 0.01), but no change was observed in CON postintervention ( P = 0.20). During exercise, the external workload performed on the cycle ergometer to attain the fixed level of heat production for exercise was similar between groups (HF: 60 ± 13; CON: 65 ± 20 external workload, P = 0.52). Increases in CVC during exercise were similar in HF (pre: 0.89 ± 0.43; post: 0.83 ± 0.45 au/mmHg, P = 0.80) and CON (pre: 2.01 ± 0.79; post: 2.03 ± 0.72 au/mmHg, P = 0.73), although the values were consistently lower in HF for both pre- and postintervention measurement intervals ( P < 0.05). These findings demonstrate that folic acid improves vascular endothelial function in patients with HF but does not enhance SkBF during exercise at a fixed metabolic heat production in a warm environment.