Coronary microvascular dysfunction by positron emission tomography and outcomes in patients after cardiac transplantation without epicardial allograft vasculopathy.

Abstract

Background: Cardiac allograft vasculopathy (CAV) affects both epicardial and microvascular coronary arteries, however few studies have characterized microvascular dysfunction in this population. Several prior studies have shown positron emission tomography/computed tomography (PET/CT) can be used to screen for epicardial CAV, however the clinical implications of abnormal blood flow in the absence of epicardial CAV is unknown.

Objective: Our study sought to assess the prognostic implications of microvascular dysfunction and its sub-types, endogen/functional and classical/structural, using PET/CT in cardiac transplant patients without epicardial CAV.

Methods: Transplant patients with no prior history of CAV and normal myocardial perfusion imaging were included. Patients were then classified by the presence of microvascular dysfunction (CMD) (MFR <2.0); patients with CMD were further subcategorized into endogen/functional (stress myocardial blood flow ≥1.7 mL/min/g) and classical/structural (stress myocardial blood flow <1.7 mL/min/g). The primary outcomes were all-cause mortality and a composite of all-cause mortality, heart failure hospitalization, acute coronary syndrome, revascularization, and re-transplantation.

Results: 356 patients met the inclusion criteria. CMD was present in 141 (39.6%) patients, of which 112 (31.4%) had endogen/functional CMD and 29 (8.1%) had classical/structural CMD. After multivariable adjustment, endogen/functional CMD was associated with a higher rate of the composite outcome (HR 2.39, 95%CI 1.32-4.29, p = 0.004) and all-cause mortality (HR 2.98, 95%CI 1.34-6.64, p = 0.008). Classical/structural CMD was not associated with the primary composite outcome (HR 0.92, 95%CI 0.27-3.17, p = 0.893) or all-cause mortality (HR 1.22, 95%CI 0.263-5.69, p = 0.797).

Conclusions: In cardiac transplant patients with no history of CAV and normal myocardial perfusion, an endogen/functional pattern of CMD is associated with higher rate of adverse events and death. This association was not present in patients with a classical/structural CMD pattern. Incorporating endogen/microvascular dysfunction assessment in PET/CT reporting may identify a higher risk group hereto now considered low risk.