Abstract 11935: The Index of Microcirculatory Resistance to Predict Subsequent Acute Cellular Rejection and Cardiac Events After Heart Transplantation

Abstract

Introduction: Single center data suggest that the index of microcirculatory resistance (IMR) measured early after heart transplantation predicts subsequent acute cellular rejection. Hypothesis: To validate whether IMR measured early after transplantation can predict subsequent acute cellular rejection and long-term outcome in a large multicenter cohort. Methods: From 5 international heart transplantation cohorts, 237 patients who underwent IMR measurement early after transplantation were enrolled. The primary outcome was biopsy-proven acute cellular rejection of grade 2 or 3 within 1 year after transplantation. A key secondary outcome was major adverse cardiac events (MACE, the composite of death, re-transplantation, myocardial infarction, stroke, graft dysfunction, and readmission due to a cardiac cause) at 10 years. Results: IMR was measured at a median of 7 weeks (interquartile range: 3 to 10 weeks) post-transplantation. Patients with acute cellular rejection grade 2 or 3 at the time of IMR assessment were excluded. At 1 year, the incidence of acute cellular rejection was 14.0%. IMR was associated proportionally with the risk of acute cellular rejection (per increase of 1-unit IMR; adjusted hazard ratio [aHR], 1.04; 95% confidence interval [CI], 1.01-1.06; P=0.002). The incidence of acute cellular rejection in patients with IMR ≥ 18 was 23.8%, while the incidence of acute cellular rejection in those with IMR < 18 was 5.5% (aHR, 4.09; 95% CI, 1.67-10.0; P=0.002). At 10 years, MACE occurred in 86 (36.3%) patients. IMR was significantly associated with the risk of MACE (per increase of 1-unit IMR; aHR, 1.03; 95% CI, 1.01-1.05; P=0.002). Conclusions: IMR measured early after heart transplantation is associated with subsequent acute cellular rejection at 1 year and clinical events at 10 years. Early IMR measurement after transplantation identifies patients at higher risk and may guide personalized post-transplantation management.