Objectives and background: Increased microvascular resistance may impair hyperemic coronary flow by limiting the maximal and constant vasodilation, resulting in increased fractional flow reserve (FFR) due to the underestimation of the translesional pressure gradient. We examined whether microvascular resistance affects FFR after successful percutaneous coronary intervention (PCI).
Methods and results: We measured FFR and the index of microcirculatory resistance (IMR) in 104 coronary arteries of 98 patients after successful elective stenting. FFR values were compared according to the quartiles of the IMR values. Coronary flow was assessed using the hyperemic mean transit time (Tmn ). The 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.
Conclusions: Increased microvascular resistance may reduce coronary flow and increase FFR after successful elective PCI.
Keywords: coronary flow; coronary physiology; fractional flow reserve; microcirculation; percutaneous coronary intervention.
© 2014 Wiley Periodicals, Inc.