Early Post-STEMI Cardiac Rehabilitation in the CSC-Infarct Program: Real-World Safety and Effectiveness of Individualized Training Protocols

<b>Background/Objectives</b>: Cardiac remodeling post-myocardial infarction is a critical process determining patient prognosis. Poland's Coordinated Specialist Care program enables early cardiac rehabilitation (CSC-Infarct) during peak remodeling period. This study evaluated the safety and effectiveness of very early cardiac rehabilitation initiated during peak remodeling (mean 16.8 ± 3.4 days post- ST-elevation myocardial infarction [STEMI]) within the CSC-Infarct program. We examined outcomes following two training modalities-interval and continuous-applied according to clinical guidelines based on baseline exercise capacity. <b>Methods</b>: We enrolled 288 patients (135 women, 153 men, age 59.7 ± 9.8 years) after first STEMI into a 24-day rehabilitation program (5 sessions/week) within CSC-Infarct. Patients received either interval training (n = 127) or continuous training (n = 161) according to National Health Fund protocols. Hemodynamic, metabolic (metabolic equivalents [MET], maximal oxygen uptake [VO2max]), and functional parameters (6-minute walk test [6MWT]) were assessed pre- and post-rehabilitation. <b>Results</b>: Both groups showed significant improvement in most parameters. The continuous training group achieved higher final MET values (8.9 ± 2.5 vs. 6.5 ± 1.9; <i>p</i> < 0.001), VO₂max (31.0 ± 8.8 vs. 22.9 ± 6.5 mL/kg/min; <i>p</i> < 0.001), and 6MWT distance (530.9 ± 108.9 vs. 455.6 ± 104.3 m; <i>p</i> < 0.001). Significant improvement in heart rate recovery (HRR), indicating autonomic balance, was observed only in the continuous training group (<i>p</i> = 0.026), not in the interval group (<i>p</i> = 0.290). <b>Conclusions</b>: Early rehabilitation within CSC-Infarct (mean 16.8 days post-infarction) during intensive remodeling is safe and effective. Both training modalities produced clinically significant improvements when appropriately matched to patient baseline capacity. Continuous training showed additional benefit in autonomic balance (HRR improvement), while interval training achieved substantial relative gains (+11.8% in 6MWT) in lower-capacity patients. The CSC-Infarct program provides optimal timing for rehabilitation implementation during the critical cardiac remodeling period.