Echocardiograph-determined Left Ventricular Function Immediately After Prolonged Exercise

Abstract

Exercise-induced acute cardiac fatigue (EACF) is characterised by a reduction in left ventricular function immediately following prolonged athletic events. Individual studies on EACF have involved small sample sizes (n<20) and have differed in the selected exercise duration and the training status of study participants. PURPOSE: To quantify, using meta-analytic procedures, the immediate impact of endurance exercise on left ventricular function, as determined by echocardiography, and explore possible moderating factors and mechanisms of EACF. METHODS: The results of 23 studies, involving a total of 413 participants, were collated. Using the inverse variance approach, a random-effects meta-analysis of the weighted mean acute changes in ejection fraction (EF), systolic blood pressure/end systolic volume ratio (SBP/ESV) and early to late diastolic filling ratio (E:A) was conducted. Mean exercise-induced changes in heart rate (HR), systolic blood pressure (SBP) and the internal diameter of the left ventricle during diastole (LVD) were also analysed. Ninety-five percent confidence limits (CL) of each mean change were calculated from the reported between-subjects standard deviations. The presence of study heterogeneity was followed-up with sub-group analyses using the moderator variables of training status ('trained' and 'untrained') and exercise duration; 'moderate' (60–151 min), 'long' (166–430 min) and 'ultra-long' (640–1440 min). RESULTS: The pooled CL for the immediate post-exercise reductions in EF, SBP/ESV and E:A were 1.03 to 2.88%, 0.63 to 0.97, and 0.39 to 0.51, respectively (p<0.05). The reduction in EF was most marked for untrained participants performing moderate exercise (CL = 3.08 to 7.85%). For the trained participants, exercise duration did not influence the generally smaller reductions in EF and E:A. Post-exercise changes in E:A were not related to those in LVD (r=0.25, p=0.451), HR (r= −0.35, p=0.198) or SBP (r= 0.16, p=0.585). CONCLUSIONS: Exercise-induced acute cardiac fatigue is most marked in untrained individuals after 1–3 hrs of physical activity. Well-trained athletes demonstrate smaller reductions in left ventricular function even immediately after ultra-endurance events. The acute decrease in ejection fraction and SBP/ESV indicates a transitory reduction in systolic function, which probably represents a reversible change in cardiac loading conditions. The decrease in diastolic filling that was found to be unrelated to changes in loading or heart rate may suggest a sub-clinical and transient impairment of left ventricular relaxation after prolonged exercise.