Abstract Aim This retrospective observational study aims to compare patients diagnosed with antibody-mediated or cell-mediated rejection with patients without episodes of rejection and study any predictors of rejection at follow-up with particular attention to PIRCHE-II scores. Materials and Methods We performed a retrospective evaluation of prospectively collected data of heart transplant patients from January 2022 to August 2023, at a single hospital. Preoperative, intraoperative and postoperative parameters are collected anonymously in our institutional database used for internal quality control. The primary endpoint was the incidence of rejection in one of three control endomyocardial biopsies. As pre-operative data, age, sex, BSA, blood group mismatch, risk such as dyslipidemia, hypertension, diabetes, peripheral vascular disease, COPD, previous cardiac surgery, PRA, ischemia time and post-operative infections. We evaluated patients at a mean follow-up of 106 (78 – 180) days. In patients who tested positive for cell-mediated or antibody-mediated rejection, the PIRCHE-II score was calculated. Results There were 45 patients with no diagnosis of rejection and they were aged 61 [50-65]; 22.2% were women, with a mean BSA of 1.87 ± 0.19. 22.2% had a blood type mismatch. They had a mean PIRCHE-II of 111.88 ± 43.6. There were 15 patients diagnosed with rejection and they were 63 years old [52 – 66]; 20.0% were women, with a mean BSA of 1.84 ± 0.23. 13.3% had a blood type mismatch. They had a mean PIRCHE-II of 113.70 ± 33.90. In multivariable analysis, the main predictors of rejection were plasma transfusions [OR 0.053, 95% CI, p=0.02], post-operative infections [OR 0.076, 95% CI, p=<0, 02] and the PIRCHE – II [OR 3.284, 95% CI, p=0.04]. The mean PIRCHE-II of patients who presented antibody-mediated or cell-mediated rejection was 113.70 ± 33.90 and that of patients who did not present any rejection was 111.88 ± 33.90; Conclusion According to the results obtained, the PIRCHE-II algorithm could be a tool in immunological risk stratification in patients undergoing cardiac transplantation. It is necessary, however, to apply PIRCHE-II to a larger number of patients and should also be considered in light of other factors such as the immunological status of the recipients, the immediate post-operative course (infections, CMV reactivation, blood component transfusions), which could constitute an immunological trigger and patient compliance in immunosuppressive therapy.Patients' featuresResuts