Outpatient cardiac rehabilitation dose after acute coronary syndrome in a nationwide cohort

Objective Cardiac rehabilitation (CR) is effective in patients with acute coronary syndrome (ACS); however, CR programmes have not been fully implemented. This study aimed to reveal the current practice of outpatient CR and the dose-effect relationship of CR in real-world settings. Methods We performed a nationwide retrospective cohort study using the National Database of Health Insurance Claims and Specific Health Checkups of Japan. Patients with ACS who underwent percutaneous coronary intervention between April 2014 and March 2018 were included. We analysed the implementation rate and dose of outpatient CR and the association between dose and outcomes. Results Out of 202 320 patients who underwent percutaneous coronary intervention for ACS, a total of 20 444 (10%) underwent outpatient CR. The median (IQR) number of total CR sessions was 9 (3-17), and the median (IQR) duration for each session was 60 (42-60) min. Patients were divided into four groups according to the total number of sessions (<= 9 times or >= 10 times) and the duration per session (<50 min or >= 50 min). Compared with the low-number/short-duration group, the adjusted HR for all-cause mortality was 1.00 (95% CI 0.80 to 1.24, p=0.97) in the low-number/long-duration group, 0.63 (95% CI 0.46 to 0.87, p=0.005) in the high-number/short-duration group and 0.74 (95% CI 0.60 to 0.92, p=0.008) in the high-number/long-duration group, respectively. Conclusion We found that the participation rate for outpatient CR after ACS was low and the doses of sessions vary in real-world settings. A higher number of total sessions of outpatient CR is associated with a better prognosis irrespective of the session's duration.