Coronary Flow Reserve and Intermediate Stenosis
What are the implications of coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR) in patients with intermediate stenosis and high fractional flow reserve (FFR)?
The investigators studied 313 patients (663 vessels) who underwent FFR, CFR, and IMR. Patients with high FFR (>0.80) were grouped according to CFR (≤2) and IMR (≥23 U) levels: group A, high CFR with low IMR; group B, high CFR with high IMR; group C, low CFR with low IMR; and group D, low CFR with high IMR. The outcome was a major adverse cardiac event (MACE) defined as a composite of any death, myocardial infarction, and revascularization. The median follow-up was 658 days.
There were 141 patients (61%) in group A, 42 (18%) in group B, 31 (16% in group C), and 16 (7%) in group D. The cumulative incidence of the composite endpoint was 10%, 0%, 7%, and 28%, respectively, and patients with high IMR with low CFR had the worst outcome (p = 0.002). There were no significant differences in clinical and angiographic characteristics among groups. Inclusion of low CFR and high IMR significantly improved model fit for predicting the likelihood of the composite MACE.
A low CFR and high IMR is associated with poor prognosis in patients with a high FFR.
The results of this small study add to prior data demonstrating that those with abnormal CFR in the absence of flow-limiting epicardial stenosis have worse long-term outcome (van de Hoef TP, et al. JACC Cardiovasc Interv 2015;8:1681-91). Currently, there is no specific therapy for this population beyond aggressive risk factor control, and further studies are needed to define the best strategy for the care of these patients.
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