Preprocedural fractional flow reserve and microvascular resistance predict increased hyperaemic coronary flow after elective percutaneous coronary intervention

Background Epicardial focal coronary artery stenosis, diffuse coronary disease, and microvascular resistance (MR) may limit coronary flow. The purpose of percutaneous coronary intervention (PCI) is to increase coronary flow by targeting epicardial lesions. After PCI, MR might change and affect coronary flow. We investigated whether PCI influences MR using the index of microcirculatory resistance (IMR) and if pre‐PCI fractional flow reserve (FFR) or MR predicts the post‐PCI change in hyperaemic coronary flow. Methods and Results This prospective study included 245 vessels from 229 patients with stable angina pectoris undergoing elective PCI. FFR and IMR were measured before and after PCI. Post‐PCI increase in hyperaemic coronary flow was assessed using the change in thermodilution‐derived transit time (pre‐PCI T mn – post‐PCI T mn ). IMR significantly decreased after PCI (median 1.9; interquartile range, −4.9 to 10.1) and was significantly associated with pre‐PCI IMR ( r = 0.70, P < 0.001). Increased coronary flow was significantly correlated with pre‐PCI IMR ( r = 0.62, P < 0.001) and pre‐PCI FFR ( r = 0.51, P < 0.001). In multivariate analysis, factors significantly associated with decreased post‐PCI IMR were pre‐PCI IMR (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.08–1.19; P < 0.001) and angiographic reference diameter (OR, 2.44; 95% CI; 1.09–5.48; P = 0.03). Factors significantly associated with increased coronary flow post‐PCI were pre‐PCI IMR (OR, 1.15; 95% CI, 1.08–1.23; P < 0.001) and pre‐PCI FFR (OR, <0.001; 95% CI, 0.000–0.003; P < 0.001). Conclusion PCI affected MR. Pre‐PCI FFR and MR were independent predictors of post‐PCI changes in hyperaemic coronary flow.