Impact of Isolated Coronary Microvascular Disease Diagnosed Using Various Measurement Modalities on Prognosis: An Updated Systematic Review and Meta-Analysis

INTRODUCTION: The main aim of this study was to investigate the impact of isolated coronary microvascular disease (CMD) as diagnosed via various modalities on prognosis. METHODS: A systematic literature review of PubMed, Embase, and Cochrane Library databases was conducted to identify relevant studies published up to March 2023. Included studies were required to measure coronary microvascular function and report outcomes in patients without obstructive coronary artery disease (CAD) or any other cardiac pathological characteristics. The primary endpoint was all-cause mortality, and the secondary endpoint was a major adverse cardiac event (MACE). Pooled effects were calculated using random effects models. RESULTS: A total of 27 studies comprising 18,204 subjects were included in the meta-analysis. Indices of coronary microvascular function measurement included coronary angiography-derived index of microcirculatory resistance (caIMR), hyperemic microcirculatory resistance (HMR), coronary flow reserve (CFR), and so on. Patients with isolated CMD exhibited a significantly higher risk of mortality (OR: 2.97, 95% CI, 1.91-4.60, p < 0.0001; HR: 3.38, 95% CI, 1.77-6.47, p = 0.0002) and MACE (OR: 5.82, 95% CI, 3.65-9.29, p < 0.00001; HR: 4.01, 95% CI, 2.59-6.20, p < 0.00001) compared to those without CMD. Subgroup analysis by measurement modality demonstrated consistent and robust pooled effect estimates in various subgroups. CONCLUSION: CMD is significantly associated with an elevated risk of mortality and MACE in patients without obstructive CAD or any other identifiable cardiac pathologies. The utilization of various measurement techniques may have potential advantages in the management of isolated CMD.