Exercise Induced Left Ventricular Remodeling Among Competitive Athletes: A Phasic Phenomenon

 Background: Contemporary understanding of exercise-induced cardiac remodeling (EICR) is based on cross-sectional data and relatively short duration longitudinal studies. Temporal progression of EICR remains incompletely understood. Methods and Results: A longitudinal repeated measures study design using 2-dimensional and speckle-tracking echocardiography was used to examine “acute augmentation” phase (AAP; 90 days) and more extended “chronic maintenance” phase (CMP; 39 months) left ventricular (LV) structural and functional adaptations to endurance exercise training among competitive male rowers (n=12, age 18.6±0.5 years). LV mass was within normal limits at baseline (93±9 g/m2), increased after AAP (1057 g/m2; p=0.001), and further increased after CMP (11310 g/m2, p<0.001 for comparison to post-AAP). AAP LV hypertrophy was driven by LV dilation (ΔLVEDV = 93 mL/m2, p=0.004) with stable LV wall thickness (Δwall thickness = 0.30.1 mm, p=0.63). In contrast, CMP LV hypertrophy was attributable to LV wall thickening (Δ wall thickness = 1.10.4 mm, p=0.004) with stable LV chamber volumes (ΔLVEDV = 11 mL/m2, p=0.48). Early diastolic peak tissue velocity increased during AAP (-11.7±1.9 vs. -13.6±1.3 cm/s, p<0.001) and remained similarly increased after CMP. Conclusions: In a small sample of competitive endurance athletes, EICR follows a phasic response with increases in LV chamber size, early diastolic function, and systolic twist in an acute augmentation phase of exercise training. This is followed by a chronic phase of adaptation characterized by increasing wall thickness and regression in LV twist. Training duration is a determinant of EICR and has implications for the assessment of myocardial structure and function in athletes.