Comparison of different aerobic exercise modalities on echocardiographic variables in early cardiac rehabilitation

Abstract Background Exercise-based cardiac rehabilitation (CR) is known to induce central (cardiac) and peripheral (vascular and skeletal muscle) adaptations, improving prognosis and functional capacity in patients with coronary artery disease (CAD) (Anderson et al., 2016). High-intensity interval training (HIIT) has shown larger gains in cardiorespiratory fitness than moderate-intensity continuous training (MICT) (Weston et al., 2014). However, the differential impact of these aerobic training modalities on echocardiographic parameters—cardiac structure and remodelling—has not been compared during early CR. Purpose To compare the 6-week effects of short-HIIT, long-HIIT and MICT on left- and right-heart structure and function in patients with CAD enrolled in phase II CR. Methods 24 patients with stable CAD were randomised to short-HIIT (n = 9), long-HIIT (n = 7) or MICT (n = 8). Echocardiography was performed at baseline and after 6 weeks. Mixed ANOVA models assessed time and time×group effects on echocardiographic variables: left ventricular end-diastolic (LVEDV) and end-systolic volume (LVESV), left and right ventricular end-diastolic diameter (LVEDD, RVEDD), left atrial volume indexed (LAVi), mitral annular tissue Doppler velocity (e’), E/e’ ratio, tricuspid annular plane systolic excursion (TAPSE), LV ejection fraction (LVEF), and systolic pulmonary artery pressure (sPAP). Results LVEDV showed a significant time effect (p=.038) and a time×group interaction (p=.039), with post-hoc increases in short-HIIT. LVESVi increased selectively in short-HIIT. LVEDD increased only in MICT (interaction p=.012). There were no differences in LVEF. LAVi tended to decrease (η²=0.223), while e’ medial decreased (p=.029) and E/e’ showed a marginal increase (p=.059). RVEDD showed a trend towards enlargement (p=.053), consistent with physiological RV adaptation. TAPSE increased (p=.030) and sPAP decreased markedly (p=.001), indicating improved RV systolic performance and reduced pulmonary pressures. Conclusion Six weeks of CR elicited modality-dependent cardiac adaptations. Short-HIIT produced the most pronounced LV volumetric remodelling, whereas MICT selectively increased LVEDD. Diastolic function parameters showed conflicting results (reduction of LAVi but worsening of e’ and E/e’). RV size increased and systolic function improved consistently. These findings support the notion that CR drives rapid structural cardiac changes and align with prior evidence that interval-based training provides a strong central stimulus.