Minimal microvascular resistance is associated with the extent of epicardial stenosis severity and is significantly associated with the presence of reversible myocardial ischemia

Background: Although myocardial ischemia is a consequence of both epicardial and microvascular abnormalities, clinical decision-making by fractional flow reserve is based on the extent of epicardial disease only. We sought to determine the association between epicardial stenosis severity and minimal microvascular resistance, and its pertinence for the occurrence of myocardial ischemia in patients with stable coronary artery disease of intermediate severity. Methods: We studied 232 patients, including 299 intermediate coronary lesions that were evaluated by intracoronary pressure and flow measurements. From these data, we calculated the fractional flow reserve (FFR) and hyperemic microvascular resistance (HMR). Myocardial perfusion imaging was performed prior to angiography in all patients. Logistic regression analysis was performed to evaluate the association between FFR, HMR, and ischemia. Moreover, the effect of a high HMR on myocardial ischemia in the presence of a significant stenosis by FFR was evaluated. High microvascular resistance was defined as HMR >2.0 mmHg/cm/s. Results: In bivariate analysis, FFR and HMR were both associated with myocardial ischemia on MPS (Odds ratio 0.001 95% confidence interval 0.000 – 0.009; P<0.001 for FFR, and odds ratio 1.62 95% confidence interval: 1.21 – 2.16; P=0.001 for HMR, respectively). In the presence of a significant coronary stenosis by FFR ≤0.80, the presence of a high HMR was associated with a significantly higher frequency of reversible ischemia on MPS (Figure). ![Figure][1] Conclusion: Minimal microvascular resistance is of significant added pertinence to epicardial stenosis severity for the occurrence of myocardial ischemia in coronary lesions of intermediate severity. [1]: pending:yes