Index of microvascular resistance after early conversion from calcineurin inhibitor to everolimus in heart transplantation: A sub-study to a 1-year randomized trial

BACKGROUND: Microvascular function in transplanted hearts can be evaluated by methods used in routine left heart catheterization follow-up after heart transplantation (HTx). This sub-study of a randomized study compared the effects of everolimus (EVR) and calcineurin inhibitor (CNI) treatment on microvascular function as expressed by the index of microvascular resistance (IMR) at 1 year after HTx. A secondary objective was to compare the change in IMR from 7-11 weeks to 1 year after HTx between randomized groups. METHODS: There were 70 HTx recipients included and randomly assigned to combination therapy (EVR and CNI with early CM withdrawal) vs conventional CM treatment. Coronary physiologic assessment was performed 7-11 weeks and 1 year after HTx. A linear mixed model was used to assess the group difference at 1 year and the difference in IMR change between 7-11 weeks and 1 year after HTx. RESULTS: At 1 year, there was no significant difference in IMR between the EVR group (17.5 mm Hg.sec +/- 8.9) (mean +/- SD) and the CNI group (14.9 mm Hg.sec 6.6, p = 0.17). The difference in IMR change between the 2 treatment arms was 1.6 mm Hg.sec (95% confidence interval, -2.8 to 5.9; p = 0.49). Spearman's rank correlation coefficient at 1 year after HTx between IMR and maximal intimal thickness as assessed with intravascular ultrasound in the left anterior descending artery was -0.13 (p = 0.28). CONCLUSIONS: In this prospective, open, randomized study comparing early CNI withdrawal with mammalian target of rapamycin inhibitors immunosuppression during the first year after HTx, early transition from CM-based immunosuppression to EVR-based treatment did not result in differences in microvascular function as assessed by the IMR. (C) 2016 International Society for Heart and Lung Transplantation. All rights reserved.