Long-term outcomes of patients with ischemia and no obstructive coronary artery disease (INOCA) - a systematic review and meta-analysis

Background Myocardial ischemia with no obstructive coronary artery disease (INOCA) is an increasingly recognized syndrome that encompasses coronary vasomotor disorders such as coronary microvascular dysfunction (CMD) and coronary vasospasm. However, the prognosis of patients with INOCA is not well defined. Purpose To perform a systematic review and meta-analysis of previous studies evaluating the long-term prognosis of patients with INOCA stratified by the underlying vasomotor disorder. Methods We searched Medline, Embase, Web of Science, and Cochrane databases combining terms for INOCA and outcomes to identify observational studies evaluating the prognosis of patients with INOCA published between 1984 and 2021. The primary outcomes were composite of all-cause death and MI, and major adverse cardiovascular events (MACE) at annual intervals for up to 5-year follow-up. Meta-analytic averages with 95% confidence intervals (CI) of the incidence of primary outcomes for INOCA, each INOCA endotype, and by method used to determine the diagnosis were calculated using the random effect models. Results We identified a total of 52 studies (19765 patients) meeting eligibility criteria. Of those, 22 included patients with vasospastic angina and 34 with microvascular angina. The rate of all-cause death and MI in the vasospastic angina group was 0.7 (95% CI 0.4-1.0)/100 patient-years [Figure 1] and the rate of MACE was 1.1 (95% CI 0.6-1.9)/100 patient-years [Figure 2]. For patients with microvascular angina the rate of all cause death and MI was 1.2 (95% CI 0.7-1.7)/100 patient-years [Figure 1] and the rate of MACE was 2.8 (95% CI 1.8-4.0)/100 patient-years [Figure 2]. Patients with evidence of microvascular dysfunction by non-invasive (CFR) or invasive (CFR, IMR, TIMI frame count) criteria had 2.7 times higher all-cause death and MI rates than patients whose diagnosis was established solely based on an abnormal exercise or imaging stress test (2.6 (95% CI, 0.8-5.1) vs. 0.7(95% CI, 0.4-1.2)/100 patient-years, p=0.034). Conclusions Overall, patients with INOCA have a low rate of MACE events or death, although there is heterogeneity based on the underlying phenotype. Patients with vasospastic angina have a relatively benign long-term prognosis, whereas patients with microvascular angina have a significantly higher rate of MACE at long-term follow-up. Among patients with microvascular angina, those with objective evidence of abnormal microvascular function (such as reduced CFR) had 2.7 times higher rates of all-cause death and MI.