Coronary flow capacity map for classification and prognostication in patients with coronary microvascular diseases

Background: Coronary flow reserve (CFR) has been an indicator used to evaluate coronary microvascular diseases (CMVD), despite its regional heterogeneity and diagnostic inaccuracies. The coronary flow capacity (CFC) map assesses regional size, severity of resting flow, hyperaemic flow, and CFR simultaneously, which may more likely illuminate CMVD. The objective of this study is to clarify the diagnostic, typing, and prognostic value of CFC for CMVD. Methods: Patients with a high suspicion of CMVD who underwent rest and adenosine-stress 13 N-ammonia myocardial perfusion imaging (MPI) were included and further classified into three types: type 1, CMVD without obstructive coronary artery disease (CAD) and myocardial diseases; type 2, CMVD in the presence of myocardial diseases; type 3, CMVD co-existing with obstructive CAD. The associations of CMVD types with clinical variables, myocardial blood flow (MBF), CFR, and CFC map were evaluated. Factors predictive of therapy response and prevention of major adverse cardiovascular events (MACE) were also analyzed. Results: A total of 83 patients were diagnosed with CMVD, and there were 40, 16, and 27 patients in types 1, 2, and 3, respectively. Type 2 patients showed the lowest values of MBF and CFR, and the largest CFC areas of dysfunction. The cutoff value of stress MBF between types 1 and 2 was 1.70 mL·min −1 ·g −1 . Severe CFC dysfunction area and CMVD classification were prognostic factors for therapy response, as well as independent predictors of MACE. A severe CFC value of 19.00% was the best cutoff value for therapeutic responses, and patients with higher severe CFC values tended to have a higher incidence of MACE. Conclusion: CFC mapping helps to classify CMVD, and has prognostic value for therapeutic response and MACE.