ATHLETIC HEART - A METABOLIC, ANATOMICAL, AND FUNCTIONAL-STUDY

Previous studies have suggested a reduced glucose uptake by the athlet e's heart at rest. To examine whether there is a compensatory increase in the myocardial fatty acid utilization, we studied nine male endura nce-trained athletes (age 26 +/- 2 yr, VO2max 60 +/- 1 ml . kg(-1). mi n(-1), mean +/- SEM) and eight sedentary subjects (age 26 +/- 1 yr, VO 2max 38 +/- 2 ml . kg(-1). min(-1)) by single photon emission tomograp hy using I-123-heptadecanoic acid (HDA) and mathematical modeling. Mag netic resonance imaging (MRI) and echocardiography were performed for the measurments of cardiac dimensions and left ventricular (LV) mass. No significant differences were found in the myocardial HDA beta-oxida tion index (5.2 +/- 2.0 vs 7.4 +/- 1.6 mu mol . min(-1). 100 g(-1), P = NS) between endurance-trained and sedentary subjects. Fractional amo unts of HDA beta-oxidation, backdiffusion, and esterification were als o similar. In MRI study, LV mass was greater in the trained subjects ( 213 +/- 9 vs 179 +/- 10 g, P < 0.01) and in particular, LV long-axis d iameter measured from the mitral valve level to the apex was increased (102 +/- 2 vs 88 +/- 2 mm, P < 0.001, trained vs sedentary subjects). VO2max correlated with LV long-axis diameter (r = 0.77, P < 0.001). I n contrast to our hypothesis, myocardial HDA utilization was not enhan ced in endurance-trained athletes at rest. Increases in LV mass and es pecially in LV long-axis diameter were observed in the athletes, indic ating LV longitudinal remodeling.