Myocardial recruitment and the systolic efficiency slope; how do they relate to exercise performance in healthy young adults?

Aims The extent to which augmentation of heart function mirrors the increased metabolic demands of the peripheral musculature is not well characterised. The details of ventricular augmentation may provide insight into determinants of cardiac efficiency for optimal exercise performance. The aims were to establish how much of the variability in exercise performance could be explained by myocardial recruitment, and which parameter of systolic function was most closely related to exercise performance. Methods and results Untrained volunteers were recruited prior to training for the London Marathon. All performed a cardiopulmonary exercise test combined with stress echocardiography. Systolic and diastolic longitudinal velocities (S’ and E’), ejection fraction (LVEF), stroke volume (SV) and strain were obtained throughout exercise. Continuous S’ showed a strong correlation with absolute VO2 (rho=0.83;p<0.0001). Only SV and S’ were predictive of VO2peak. LVEF and E’ as well as both global longitudinal and circumferential strain showed no correlation. The systolic efficiency slope (SES) was calculated by determining the individual regression lines for VO2 and S’. A moderate relationship between the SES and VO2peak was observed for both septal S’; r=0.57;p<0.001 and lateral S’, r=0.53;p<0.001). Conclusion 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 was able to predict VO2peak suggesting the process driving systolic velocity and its augmentation is a key determinant of exercise ability.