The relationship between resting echocardiographic measures of cardiac function and exercise capacity is weak. The details of ventricular augmentation may provide insight into determinants of cardiac efficiency for optimal exercise performance. The aims of this study were to establish how much of the variability in exercise performance could be explained by myocardial recruitment and which parameters describing cardiac function were most closely related to exercise performance.
Untrained volunteers were recruited before training for the London Marathon. All performed a cardiopulmonary exercise test combined with stress echocardiography. Systolic and diastolic longitudinal velocities (S′ and E′), left ventricular ejection fraction (LVEF), stroke volume (SV), and strain (GLS) were obtained throughout exercise.
A variety of parameters including S′, E′, GLS, and SV showed a correlation with V̇o2 throughout exercise (ρ = 0.83, P < 0.0001). At the prespecified sample point (respiratory exchange ratio > 1.0) only SV and S′ were predictive of V̇o2peak. LVEF and E′ as well as both global longitudinal and circumferential strain showed no correlation with V̇o2peak. The systolic efficiency slope (SES) that we developed by determining the individual regression lines for V̇o2 and S′ showed a relationship between with V̇o2 peak for both septal S′, r = 0.57, P < 0.001, and lateral S′, r = 0.53, P < 0.001.
A detailed description of myocardial function is described, linear for S′ and E′ and a plateau for EF and GLS. S′ during exercise is a better predictor of exercise performance than LVEF, SV, or GLS. The SES slope predicted V̇o2peak, suggesting the process driving systolic velocity and its augmentation is a key determinant of exercise ability.