Abnormal myocardial blood flow reserve predicts death in heart transplant recipients

Heart transplant recipients appear to be at an increased risk of mortality or retransplantation if they have abnormal myocardial blood flow reserve (MBFR), even in the absence of epicardial cardiac allograft vasculopathy (CAV), according to a study.

In addition, “[m]easures of myocardial blood flow provide prognostic information in addition to traditional CAV assessment,” the investigators said.

The study included 181 heart transplant recipients who underwent positron emission tomography (PET) to assess for CAV, with a median follow-up of 4.7 years. The investigators grouped patients according to the total MBFR: >2.0 and ≤2.0. Microvascular CAV was characterized as no epicardial CAV seen by PET or coronary angiography, but with an MBFR ≤2.0 by PET.

Of the recipients, 71 (39 percent) had an MBFR ≤2.0. These patients were at higher risk for all outcomes: sevenfold increase in death or retransplantation (hazard ratio [HR], 7.05, 95 percent confidence interval [CI], 3.2‒15.6; p<0.0001), 12-fold increase in cardiovascular death (HR, 12.0, 95 percent CI, 2.64‒54.12; p=0.001), and 10-fold increase in cardiovascular hospitalization (HR, 10.1, 95 percent CI: 3.43‒29.9; p<0.0001).

The 5-year mean survival of recipients with an MBFR ≤2.0 was 302 days fewer than those with an MBFR >2.0 (95 percent CI, 260.2‒345.4; p<0.0001). Moreover, microvascular CAV independently correlated with an elevated risk of death or retransplantation (HR, 3.86, 95 percent CI, 1.58‒9.40; p=0.003).

“CAV causes impaired blood flow in both epicardial coronary arteries and the microvasculature,” the investigators said. “A leading cause of post-transplant mortality, CAV affects 50 percent of heart transplant recipients within 10 years of heart transplant.”