Can the grading of mild cardiac allograft vasculopathy be further refined? An angiographic and physiologic assessment of heart transplant recipients with ISHLT CAV 1.

Background: Cardiac allograft vasculopathy (CAV) results in impaired blood flow in both epicardial vessels and the microvasculature and is a leading cause of poor outcomes in heart transplant (HT) recipients. Most patients have mild (International Society for Heart and Lung Transplantation [ISHLT] CAV 1) disease. This study examined outcomes among those with ISHLT CAV 1 and investigated the value of physiologic assessment via cardiac positron emission tomography/computed tomography (PET/CT) for added risk stratification.

Methods: CAV was graded using ISHLT criteria. Those with CAV 1 were further subgrouped into CAV 1a (maximal lesion <30% stenosis) or CAV 1b (maximal lesion ≥30% stenosis).

Results: 299 HT recipients underwent invasive coronary angiography for CAV assessment with a median follow-up of 4.7 years. ISHLT CAV 1 was associated with a 2.9-fold risk of death/retransplantation compared to ISHLT CAV 0 (95% confidence interval [CI] 1.7-5.3, p < 0.001). Of those with ISHLT CAV 1, 12% had ISHLT CAV 1b, which was associated with a 2.8 times greater risk of death/retransplantation compared to CAV 1a (95% CI 1.4-5.9, p = 0.003). In a subgroup of 158 patients with contemporary cardiac PET/CT, among those with CAV 1a, a myocardial blood flow reserve (MBFR) ≤2 was associated with a 4.6-fold risk of death/retransplantation compared to a normal MBFR (95% CI 1.7-12.6, p = 0.001).

Conclusion: Patients with CAV 1b had worse outcomes than those with CAV 1a. Among those with CAV 1a, the poorer outcomes than ISHLT CAV 0 observed were predominantly associated with reduced MBFR. These data suggest additional anatomic classification and physiologic assessment can further risk stratify those with ISHLT CAV 1.