Relationships between biventricular myocardial function and oxygen uptake during exercise in healthy adolescent male athletes

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): UK Research and Innovation Medical Research Council Doctoral Training Programme Grant Work supported as part of a research partnership between the University of Bristol and Canon Medical Systems UK that determines the independence of the research from either parties. Background Biventricular cardiac function improves with increasing work-rate during exercise in healthy elite athletes, but how it relates to concomitantly measured oxygen uptake (VO2) is not well known. Assessing cardiac determinants of cardiorespiratory fitness through multimodal evaluations may lead to improvements in clinical stress testing protocols and better understanding of exercise physiology. Purpose The aim of this study was to investigate whether left and right ventricular (LV and RV) systolic function measured by speckle tracking echocardiography (STE) at submaximal exercise (moderate and high intensity domains) is associated with concomitantly measured VO2 in healthy adolescent male athletes. Methods Elite male football players <16 years-old underwent cardiopulmonary exercise testing with concomitant STE at 50 W steps. Exercise intensity domains were defined based on the gas exchange threshold (GET). LV and RV free wall (FW) peak systolic longitudinal strain (Sl), strain rate (SRl) and LV average (12 mid and basal segments) circumferential strain (Sc) and strain rate (SRc) were measured. Cardiac function relation to peak VO2 was evaluated using linear regression, and its relationships to VO2 within each exercise intensity domain using repeated measures mixed linear models, before and after adjusting for heart rate (HR). Results A total of n=94 athletes were included (mean age 14.7 ± 1 years). Mean peak VO2 and work-rate were 43 ± 7 mL·min-1·kg-1 and 215 ± 40 W, respectively. Relationships between cardiac function and VO2, by exercise intensity domain are shown in Figure 1 with all regression coefficients shown in Table 1. Only LV Sl at high intensity was correlated to peak VO2 (p = 0.04). Within exercise intensity domains higher LV Sl (Figure 1A) and SRl (Figure 1B) were associated with higher concomitantly measured VO2 at both moderate and high intensity. Higher SRc (Figure 1C) and RV FW SRl (Figure 1F) were associated with higher VO2 only at moderate intensity. LV Sc (Figure 1C) and RV FW Sl (Figure 1E) were not associated with concomitant VO2 during exercise at moderate or high intensity. Only LV Sl and SRl at moderate and high intensity remained significantly associated to concomitantly measured VO2 after further adjusting by HR (Table 1). Conclusions In healthy adolescent athletes, only LV longitudinal strain and strain rate measured at moderate and high intensity were associated with VO2 independent of HR response. There were differences in myocardial response to exercise both between the two ventricles, and between the longitudinal and circumferential components of LV function. These require further research, both in healthy and disease groups, especially in RV pathology, where components of myocardial function could play different roles in limiting exercise capacity.

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