Microcirculatory resistance predicts allograft rejection, cardiac events after heart transplant

Measuring the index of microcirculatory resistance (IMR) early after heart transplantation can predict subsequent acute allograft rejection (AAR) at 1 year and clinical events at 10 years, suggests a study. In addition, early IMR measurement identifies patients at greater risk and may guide personalized post-transplantation management.

A team of investigators sought to validate whether IMR measured early following transplantation could predict subsequent acute rejection and long-term outcome in 237 patients from five international cohorts. AAR within 1 year after transplantation was the primary outcome, while major adverse cardiac events (MACE; composite of death, retransplantation, myocardial infarction, stroke, graft dysfunction, and readmission) at 10 years were secondary ones.

IMR was measured at a median of 7 weeks (interquartile range, 3–10) after heart transplantation. The incidence of AAR at 1 year was 14.4 percent. IMR correlated proportionally with the risk of AAR (per increase of 1-U IMR: adjusted hazard ratio [aHR], 1.04, 95 percent confidence interval [CI], 1.02–1.06; p<0.001). AAR incidence was 23.8 percent in patients with an IMR ≥18, while that in those with an IMR <18 was 6.3 percent (aHR, 3.93, 95 percent CI, 1.77–8.73; p=0.001).

MACE occurred in 86 patients (36.3 percent) at 10 years. IMR also significantly correlated with the risk of MACE (per increase of 1-U IMR: aHR, 1.02, 95 percent CI, 1.01–1.04; p=0.005).

“Single-centre data suggest that IMR measured early after heart transplantation predicts subsequent acute rejection,” the investigators said.