BACKGROUND AND AIM: Myocardial infarction (MI) triggers adverse structural and functional cardiac remodeling. While moderate-intensity exercise-based cardiac rehabilitation (CR) improves recovery, emerging evidence suggests higher-intensity regimens may yield greater benefits. Although high-intensity interval training has demonstrated safety and efficacy in cardiac populations, the impact of high-intensity continuous aerobic training (HICT) on left atrial (LA) mechanics post-primary percutaneous coronary intervention (PCI) for anterior wall ST-segment elevation MI (STEMI) remains underexplored. This study aims to investigate the impact of HICT versus moderate-intensity continuous training (MICT) on LA mechanics in patients post-primary PCI for anterior STEMI. MATERIALS AND METHODS: In a single-center randomized controlled trial at Aim Shams University Hospital, 60 adults 1-month post-primary PCI for anterior STEMI were randomized to 6 weeks of CR involving either high-intensity continuous training (HICT; 80 to 90% peak heart rate (HR)) or (MICT; 50 to 70% peak HR). Participants completed 18 treadmill sessions (3/week). Diastolic function and LA mechanics (reservoir, conduit, contractile strains) were assessed via two-dimensional speckle-tracking echocardiography pre- and post-intervention. RESULTS: This study examined patients with a mean age of 51.82 years, predominantly male (91.7%). Both the HICT group and the comparator group exhibited improvements in LA mechanics and diastolic function, though intergroup differences were statistically non-significant. HICT group demonstrated numerically greater gains in LA reservoir strain (5.67 +/- 4.39% versus 3.80 +/- 3.32%, p = 0.115) and LA contractile strain (-2.93 +/- 4.27% versus -1.33 +/- 3.74%, p = 0.110). Similarly, reductions in diastolic indices were comparable between groups: E/A (0.14 +/- 0.12 versus -0.14 +/- 0.14, p = 0.927) and E/E' (-0.25 +/- 0.16 versus -0.30 +/- 0.34, p = 0.568). While trends favored HICT, no outcome reached statistical significance, suggesting comparable efficacy between interventions. CONCLUSIONS: HICT and MICT show comparable safety and efficacy in enhancing cardiac function, suggesting exercise intensity may be tailored to patient preference or tolerance.

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