The role of invasive assessment of coronary physiology in detection of microcirculatory dysfunction in patients after heart transplantation

Introduction Coronary vasculopathy is one of the most serious distant complications after heart transplantation (Htx). It involves not only the epicardial vessels, but also the coronary microcirculation. Aim The aim of this study was to assess the utility and safety of the invasive assessment of coronary physiology, to investigate the prevalence of coronary microcirculatory dysfunction (CMD) and its association with clinical characteristic of graft recipient and donor. Methods Coronary microcirculation was assessed invasively during routine coronary angiography by using the index of microcirculatory resistance (IMR) and coronary flow reserve (CFR). Values of IMR ≥25 and/or CFR <2.0 confirmed CMD. Subsequent examinations performed prospectively between 01/12/2020 and 24/07/2023 were analyzed. Results 33 patients aged 49±14 years were measured, of whom 21 (64%) were men. Abnormal IMR and/or CFR were found in 8 (24%) patients. The median for IMR and CFR was, respectively: 13 [10-20] and 3.6 [2.2-4.9]. CMD was more common in younger patients 40±16 vs. 51±13 years (P=0.045), with lower BMI value: 22±4 vs 26±4 [kg/m2], (P=0.016). The patients with CMD were more likely to require pacemaker implantation 3 (12%) vs. 1 (4%) in the post-transplant period (P=0.012). The median time since Htx was 2 [2-10], and it was higher in the group with CMD 9.5 [6-16] vs 2 (1-8), (P = 0.042). In laboratory tests triglyceride levels were lower in those with CMD:76 [65-96] vs 114 [77-158] mg/dL (P=0.048). There were no significant difference in atherosclerotic changes in the epicardial arteries between groups. Moreover, no significant differences were observed in other characteristic of graft recipient and donor. Conclusions The invasive assessment of coronary physiology is safe and effective method which enabled CMD identification in nearly one-fourth of Htx patients. CMD is related to age, time since transplantation and other complications, such as chronotropic dysfunction of the transplanted heart.