Coronary slow flow and angiography-derived index of microcirculatory resistance as prognostic predictors in patients with angina and normal coronary arteries: a retrospective cohort study

Abstract

Background This study aims to investigate prognostic implications of coronary slow flow (CSF) and angiography-derived index of microcirculatory resistance (caIMR) in patients with angina and normal coronary arteries. Methods A total of 582 patients were enrolled with angiographically normal coronary arteries. caIMR was calculated using a commercial software. Patients were followed up for a median of 45 months. The primary endpoint was defined as major adverse cardiovascular events (MACEs) comprising death, myocardial infarction and readmission for angina or heart failure. Results CSF was diagnosed when TIMI grade 2 flow presented in at least one coronary artery. Multivariate analysis indicated TIMI-flow-based determination of CSF was not significantly associated with MACEs [hazard ratio (HR): 2.14; 95% confidence interval (CI): 0.87–5.31; p = 0.099), while caIMR >42 (HR: 2.53; 95% CI: 1.02–6.32; p = 0.047) were independent predictors of MACEs. Incorporation of caIMR improved the area under the curve from 0.587 to 0.642. Conclusions caIMR was an independent prognostic factor of long-term cardiovascular events in patients with CSF. Evaluation of caIMR improved the risk stratification of patients with angiographically-normal coronary arteries.