The role of the angiography-derived index of microcirculatory resistance in the prognosis of patients with dilated cardiomyopathy.

Background: The coronary angiography-derived index of microcirculatory resistance (caIMR) is a novel noninvasive method to assess coronary microvascular dysfunction (CMD). However, the association between caIMR and the prognosis of patients with dilated cardiomyopathy (DCM) is unclear. We aimed to explore the role of the caIMR in evaluating the outcome of patients with DCM. Methods: We consecutively and retrospectively enrolled patients with DCM in the Department of Cardiology, the First Affiliated Hospital of Nanjing Medical University, Nanjing, China, from January 2013 to January 2018. The caIMR was calculated for eligible patients. The primary end point in this study was composite events, including rehospitalization related to heart failure (HF), device implantation, heart transplantation, or cardiac death. Patients were categorized into groups based on whether they had composite events (the events and no-events groups), and differences in the baseline and end points between these two groups were analyzed. Results: A total of 95 eligible patients with DCM were enrolled in the study, 36 of whom had end point events. The best cutoff values of the caIMR for the left anterior descending (LAD) artery, left circumflex (LCX) artery, and right coronary artery (RCA) were >29.8 with an area under the curve (AUC) of 0.828, >25.5 with an AUC of 0.720, and >29.7 with an AUC of 0.717, respectively (all P values <0.001). Patients were then classified into the higher caIMR group and the lower caIMR group based on the cutoff value. Kaplan-Meier analyses showed that patients with a higher caIMR had increased cumulative risks of end point events regardless of the cutoff values for the LAD, LCX, and RCA (all log-rank P values <0.001). After adjustment for confounders, Cox regression analyses indicated that LAD-caIMR was an independent risk factor for end point events in patients with DCM [hazard ratio (HR) =1.11; 95% CI: 1.06-1.16]. Conclusions: A higher caIMR was significantly associated with the poor prognosis of patients with DCM.