Long-Term Sirolimus for Primary Immunosuppression in Heart Transplant Recipients

Background: Small studies have reported superiority of sirolimus (SRL) over calcineurin inhibitor (CNI) in mitigating cardiac allograft vasculopathy (CAV) after heart transplantation (HT). However, data on the long-term effect on CAV progression and clinical outcomes are lacking.

Objectives: The aim of this study was to test the long-term safety and efficacy of conversion from CNI to SRL as maintenance therapy on CAV progression and outcomes after HT.

Methods: A cohort of 402 patients who underwent HT and were either treated with CNI alone (n = 134) or converted from CNI to SRL (n = 268) as primary immunosuppression was analyzed. CAV progression was assessed using serial coronary intravascular ultrasound during treatment with CNI (n = 99) and after conversion to SRL (n = 235) in patients who underwent at least 2 intravascular ultrasound studies.

Results: The progression in plaque volume (2.8 ± 2.3 mm³/mm vs. 0.46 ± 1.8 mm³/mm; p < 0.0001) and plaque index (plaque volume-to-vessel volume ratio) (12.2 ± 9.6% vs. 1.1 ± 7.9%; p < 0.0001) were significantly attenuated when treated with SRL compared with CNI. Over a mean follow-up period of 8.9 years from time of HT, all-cause mortality occurred in 25.6% of the patients and was lower during treatment with SRL compared with CNI (adjusted hazard ratio: 0.47; 95% confidence interval: 0.31 to 0.70; p = 0.0002), and CAV-related events were also less frequent during treatment with SRL (adjusted hazard ratio: 0.35; 95% confidence interval: 0.21 to 0.59; p < 0.0001). Further analyses suggested more attenuation of CAV and more favorable clinical outcomes with earlier conversion to SRL (≤2 years) compared with late conversion (>2 years) after HT.

Conclusions: Early conversion to SRL is associated with attenuated CAV progression and with lower long-term mortality and fewer CAV-related events compared with continued CNI use.