Noninvasive biventricular myocardial work analysis by pressure-strain-volume loops for assessing supernormal systolic function in athletes at rest

Intense exercise imposes an increased hemodynamic load on the heart, inducing structural and functional adaptations that optimize cardiovascular performance in athletes. While morphological remodeling is well-characterized, assessing exercise-induced functional changes - such as enhanced ventricular contractility - remains challenging. Conventional resting echocardiographic metrics often fail to accurately capture the intrinsic contractile state of the athlete’s heart, necessitating more advanced assessment techniques. We aimed to introduce a novel 3D echocardiography (3DE)-derived method for noninvasive quantification of biventricular systolic function, less dependent on preload and afterload in a large cohort of elite athletes. Additionally, we aimed to explore the relationship between these novel metrics and peak exercise capacity. We enrolled 266 elite athletes and 26 healthy, age- and sex-matched sedentary volunteers. Athletes underwent cardiopulmonary exercise testing (CPET) to determine peak oxygen uptake (VO2/kg). Under resting conditions, all subjects underwent 3DE to measure left (LV) and right ventricular (RV) volumes and ejection fractions (EF). LV and RV 3DE-derived global longitudinal strain (GLS) tracings and non-invasively estimated LV and RV pressure curves were concatenated, respectively, to calculate LV and RV global myocardial work indices. Then, this pressure-strain relationship was further adjusted to instantaneous LV and RV volumes to create pressure-strain-volume loops and derive volume-adjusted myocardial work indices (LV GWIV and RV GWIV, respectively). Athletes had lower LV EF (athletes vs. controls; 56.5±4.3 vs. 60.4±4.8%; p<0.01) and RV EF (55.0±4.7 vs. 60.0±4.7%; p<0.05), as well as LV GLS (-19.1±2.2 vs. -21.0±2.4%, p<0.05) and RV GLS (-21.7±3.4 vs. -23.2±4.0%, p<0.05). However, athletes had significantly higher values of volume-adjusted LV GWIV (9494±2912 vs. 6264±1792 mmHg%·mL, p<0.05) and RV GWIV (3433±1365 vs. 2374±812 mmHg%·mL, p<0.05). Among systolic functional metrics, LV EF (r=-0.19, p<0.05) and LV GLS (r=-0.25, p<0.001) correlated inversely, whereas LV GWIV correlated directly (r=0.19, p<0.05) with CPET-derived VO2/kg. In the RV, interestingly, RV GWIV showed a better correlation with VO2/kg (r=0.28, p<0.001) compared to RV EF (r=-0.22, p<0.001), whereas RV GLS did not correlate. Using multivariable linear regression analysis, RV GWIV was found to be an independent predictor of CPET-derived VO2/kg. By the analysis of the pressure-strain-volume relationship, our noninvasive myocardial work metrics were able to reflect the enhanced LV and RV systolic functions in athletes, even during resting conditions. Moreover, increased RV volume-adjusted myocardial work was independently associated with better CPET-derived peak exercise capacity.