Alnsasra H, Asleh R, Oh JK, et al. - Given the significant contribution of myocardial fibrosis in development of diastolic dysfunction, researchers here examined how sirolimus, as primary immunosuppression, affects diastolic dysfunction and fibrosis progression among heart transplantation recipients. They assessed diastolic function parameters in 100 heart transplantation recipients, who were either managed with a calcineurin inhibitor (CNI) (n = 51) or converted from CNI to sirolimus (n = 49), using serial echocardiograms and right heart catheterizations. The sirolimus group exhibited a trend for increased percentage of fibrosis as compared with marginally significant progression in the CNI group. Outcomes revealed improvement in diastolic dysfunction and filling pressures in correlation with early conversion to sirolimus as compared with CNI therapy. Further investigation is required to determine if this could be attributed to attenuation of myocardial fibrosis progression with sirolimus treatment.