Altered cardiac function and minimal cardiac damage during: Prolonged exercise

SHAVE, R., E. DAWSON, G. WHYTE, K. GEORGE, D. GAZE, and P. COLLINSON. Altered Cardiac Function and Minimal Cardiac Damage during Prolonged Exercise. Med. Sci. Sports Exerc., Vol. 36, No. 7, pp. 1098-1103, 2004. Purpose: The purpose of the present study was to examine markers of cardiac function and cardiac damage during a simulated half-ironman triathlon in highly trained athletes. Methods: Nine highly trained male triathletes volunteered for the study (mean +/- SD; age: 33 +/- 3 yr; height: 1.8 +/- 0.1 m; body mass: 77.7 +/- 3.2 kg). The subjects completed a half-ironman triathlon; 1.9-km swim in an indoor 20-m pool, followed by a laboratory-based 90-km cycle and 21.1-km run. Venous blood samples were drawn and echocardiographic assessment completed before the start of exercise, immediately after each stage, and 24 h postexercise. Serum was analyzed for total creatine kinase activity (CK), creatine kinase isoenzyme MBmass (CK-MBmass), and cardiac troponin T (cTnT). Left ventricular systolic (stroke volume, and systolic blood pressure/end systolic volume ratio (SBP/ESV)) and diastolic (ratio of early [E] to late [A], ventricular filling E:A) measurements were derived from echocardiographic assessment. Results: The mean completion time of the half-ironman triathlon was 301 +/- 28 min. Left ventricular contractility (SBP/ESV) was significantly reduced after the half-ironman triathlon (P < 0.05). A significant reduction in E:A was observed after the run phase of the half-ironman triathlon (P < 0.05). Significant increases in CK and CK-MBmass, were observed during and after the half-ironman triathlon (P < 0.05), and cTnT was elevated in four subjects over the course of the half-ironman triathlon. Conclusions: The physiologic stress imposed by the half-ironman triathlon resulted in a reduced left ventricular contractility and altered diastolic filling, coupled with minimal cardiac damage in a number of highly trained male triathletes. The mechanisms behind such altered cardiac function and cardiac damage after prolonged exercise are yet to be elucidated.