O411 Aims: Calcineurin-inhibitor (CNI) related nephrotoxicity is a common problem after cardiac transplantation. We studied the impact of CNI-free immunosuppressive regimen (mycophenolate mofetil (MMF) and sirolimus (Sir)) on renal function in heart transplant recipients with posttransplant renal impairment (serum creatinine level >2mg/dl). Methods: Thirty heart transplant recipients (27men, 7 woman; 0.1 to 14.2 years after transplantation) with CNI-based immunosuppression (plus MMF) and a serum creatinine level >2.0 mg/dl were included in the study. Serum creatinine level and cystatine were monitored to detect renal function. Mean patient age was 52±14 years (range 19-68years). Sir was started with 6mg, continued with 2mg and adjusted according fasting target trough levels. Target trough levels for Sir were of 10-14 ng/mL. Subsequently, the CNIs were tapered down and finally stopped. Clinical follow up (1 month after conversion and every three month thereafter) included endomyocardial biopsies, echocardiography, EKG and laboratory studies. Results: No acute rejection episode occurred during the study period. Renal function improved significantly after a mean follow up of 22.5±8months after conversion: Creatinine pre vs post conversion: 3.10±0.88mg/dl vs 2.12±0.71mg/dl, p=0.001. Cystatin pre vs post conversion: 2.9±0.6mg/dl vs 2.2±0.6mg/dl, p=0.04. Three patients were on hemodialysis prior conversion and recovered after conversion from CI treatment so that hemodialysis therapy could be stopped completely. Graft function remained stabile: Fractional shortening pre vs post conversion: 36.8±6% vs 35.9±8%. Serious adverse events did not occur. One patient had to be excluded due to noncompliance. Conclusions: Conversion from CI based immunosuppression to MMF and Sir in heart transplant recipients with chronic renal failure is safe, preserves graft function and improves renal function.