Influence of microvascular resistance on fractional flow reserve after successful percutaneous coronary intervention

Abstract

Background: There have been concerns that microvascular dysfunction could limit the maximal and constant microvascular vasodilation, which are the requisites of fractional flow reserve (FFR) measurement. Increased microvascular resistance may impair hyperemic coronary flow, resulting in an underestimation of the translesional pressure gradient with an increased FFR values compared with that without microvascular dysfunction. Aim: We assessed the hypothesis that increased microvascular resistance represented by an index of microcirculatory resistance (IMR) may lead to an increased FFR in patients with successful percutaneous coronary intervention (PCI). Methods and results: A total of 104 coronary arteries from 98 patients treated with successful stenting (less than 20% residual stenosis with TIMI 3 flow grade) underwent FFR and IMR measurements during maximal hyperemia induced after PCI by intravenous administration of adenosine triphosphate. FFR values were compared according to the quartiles of the IMR values. Coronary flow was assessed using the hyperemic mean transit time (Tmn). The median IMR values for the interquartile ranges of 8.5–11.3, 13.9–16.3, 20.9–24.5, and 34.2–61.6 were 10.2, 15.1, 22.8, and 38.2, respectively. Both FFR and Tmn values differed significantly across the IMR quartiles (p<0.001). The angiographic and intravascular ultrasound findings and post-PCI cardiac troponin levels showed no significant difference across the IMR quartiles. Multivariate logistic regression analysis revealed that the left anterior descending artery lesion location (odds ratio [OR] 0.17, 95% confidence interval [CI] 0.06–0.49, p=0.001), IMR (OR 1.05, 95% CI 1.01–1.09, p=0.012), and minimal cross-sectional lumen area (OR 1.49, 95% CI 1.03–2.17, p=0.036) were independent predictors of increased FFR values. Conclusions: IMR values after successful PCI were widely distributed, and increased IMR was not uncommon. Increased microvascular resistance may reduce coronary flow and increase FFR after successful elective PCI.