Abstract Funding Acknowledgements Type of funding sources: None. Introduction Together with the aging population, the part of older frail patients after cardiac surgery is increasing in cardiac rehabilitation (CR) settings. Frailty detection is crucial for choosing appropriate training programs, but according to the literature, there is not enough evidence on what tools should be used to detect frailty and evaluate its dynamics during CR. Purpose To evaluate the effectiveness of CR for older frail patients after open heart surgery using the Edmonton frail scale. Methods A prospective, randomized controlled clinical trial. Inclusion criteria: all patients were admitted to CR after open heart surgery, ≥ 65 years old, within 6-minute walking distance (6-MWD) ≥150 m, Edmonton frailt scale (EFS) score ≥ 4, patient’s agreement to participate in the study. Patients (N=100, 73,3±5,1 years, 17,1±7,4 days post-surgery, 62,0% male)) were randomly allocated for gender assigned (1:1 ration) to intervention or control groups (IG n=50, CG n=50). Both groups participated in exercise training during inpatient-CR. After completing the 20-day rehabilitation program, the intervention group (IG) participated in home-based exercise training that lasted 12 weeks. The home-based exercise training program included four different types of exercise: aerobic endurance training (5/week, 20–60 min) including walking, stair climbing, and cycling of moderate to high intensity; sensomotoric training (3/week, 15 min) including exercises on postural control, dynamic balance, and coordination of moderate to high intensity; resistance training (3/week, 20–25 min) including 4 – 8 exercises at moderate intensity, involving main muscle groups of the legs; flexibility training (3/week, 10–15 min) including isolated type flexibility exercises at low to moderate intensity. Participants of IG were monitored by phone calls every two weeks and the CG were assigned to usual care. Patients were assessed before (T1) and after 20-days inpatient CR (T2) and 12 weeks after completion of CR (T3). Patients' frailty was evaluated between groups and over time by the Edmonton frail scale (frail ≥ 6, prefrail 4-5, robust 0-3). SPSS 22 was used for statistical analysis. The Mann-Whitney U and chi-squared tests were applied to compute p-values for the differences between the groups and periods. Results There were no significant differences in patient characteristics between the groups except that in CG there were more women (p=0,013). As a result of inpatient-CR and home-based exercise training program prevalence of frailty decreased in both groups, but no statistical significance between the groups was observed. (Table 1). Conclusions EFS is a suitable tool to detect frailty and evaluate its dynamic during short-term CR (after 20 days) and medium-term (after 12 weeks) home-based CR programs. The results are encouraging, but probably because of the small sample size and short monitoring time, no significant differences were found between the groups.