Angio-IMR identifies microvascular cardiac allograft vasculopathy in heart transplant recipients

Abstract Background/Introduction Microvascular cardiac allograft vasculopathy (mCAV) is a prognostic factor for long-term survival after heart transplantation, which can be assessed by endomyocardial biopsies (EMBs). (1) Routine diagnostic follow-up consists of coronary angiography and an EMB in selected patients. Non-biopsy methods for diagnosing microvascular dysfunction (MVD) have increasingly been proven valuable in these patients and avoid the inherent risk of repeated EMB. (2) Recently, an angiography-derived index of microcirculatory resistance (angio-IMR) has been reported as a novel, post-processing pressure-wire-free tool to assess coronary microvascular dysfunction in coronary angiograms. (3) Its usefulness in heart transplant recipients remains unknown. Purpose This analysis aimed to compare the assessment of mCAV with angio-IMR and EMB findings. Methods We retrospectively evaluated coronary angiograms of 27 asymptomatic heart transplant recipients (11% female, mean age 46.6 years ± 12.3 years) who underwent simultaneous coronary angiography and right ventricular biopsy within post-transplant aftercare at our institution. We derived angio-IMR from the left anterior descending coronary artery (LAD) using two views with at least a 30° angle to each other and invasively measured mean aortic pressure (MAP). Histopathologic mCAV was routinely evaluated by light microscopy (x200) and defined as no mCAV, obstructive or non-obstructive mCAV. The correlation between time after heart transplantation and angio-IMR was using Pearson's Correlation Coefficient and angio-IMR was compared between mCAV groups using Kruskal–Wallis test, assuming statistical significance at p<0.05. (1) Results Three patients (11%) showed obstructive, 13 (48%) non-obstructive, and 11 (41%) showed no mCAV. The mean time after heart transplantation was 1683 days ± 1140 days. The mean angio-IMR was 38.6 mmHg*s ± 10.2 mmHg*s, with a positive correlation between angio-IMR and time since heart transplantation (r[25] = 0.695, p < 0.001, figure A [green = no; yellow = non-obstructive and red = obstructive mCav]). Compared to patients without mCAV (29.7 mmHg*s ± 5.3 mmHg*s), angio-IMR was increased in patients with non-obstructive (42.4 mmHg*s ± 6.9 mmHg*s, p = 0.002) and obstructive mCAV (54.6 mmHg*s ± 8.5 mmhg*s, p = 0.002, figure B). Conclusion Angio-IMR correlates with histological mCAV and time since transplantation in heart transplant recipients. This value could potentially help in the clinical routine management of these patients and avoid the inherent risk of repeated EMB.Figure AFigure B