Background: Increases in coronary artery size and dilating capacity have been observed in some animals after endurance training, and at autopsy, active men appear to have enlarged epicardial coronary arteries. This cross-sectional study was designed to test the hypothesis that highly trained endurance runners have larger epicardial coronary arteries and greater dilating capacity than inactive men.
Methods and results: The subjects, ages 39-66 years, included 11 male volunteers who had participated in ultradistance running during the past 2 years and 11 physically inactive men who had been referred for arteriography but had no visible coronary artery disease. The internal diameter of the proximal segments of each major epicardial coronary artery was measured before and after nitroglycerin administration using a computer-based quantitative arteriographic analysis system. Measurements also included maximal oxygen uptake, plasma lipoprotein concentrations, body composition, and cardiac mass by echocardiography. Before nitroglycerin, the sum of the cross-sectional areas for the proximal right, left anterior descending, and circumflex arteries was not different for the runners and the inactive men: 22.7 +/- 4.79 versus 21.0 +/- 7.97 mm2 (p = 0.57), respectively. However, the increase in the sum of the cross-sectional area for the proximal right, left anterior descending, and circumflex arteries in response to nitroglycerin was greater for the runners (13.20 +/- 4.76 versus 6.00 +/- 3.02 mm2; p = 0.002). Left ventricular mass index (152 +/- 21 versus 116 +/- 41 g/m2; p < 0.05) but not left ventricular mass (284 +/- 40 versus 246 +/- 91 g; p = 0.22) was significantly greater for the runners. Among the runners, dilating capacity was positively correlated with aerobic capacity and negatively related to adiposity, resting heart rate, and plasma lipoprotein concentrations.
Conclusions: Highly trained, middle-aged endurance runners demonstrated a significantly greater dilating capacity of their epicardial coronary arteries in response to nitroglycerin compared with inactive men. The causes of this greater dilating capacity and its clinical significance need to be determined.