Microvascular functional assessment using microvascular resistance reserve in patients undergoing elective fractional flow reserve-guided percutaneous coronary intervention

Abstract Background Microvascular resistance reserve (MRR) has been proposed as an index for coronary microvascular function. However, the determinants of MRR and the prevalence of coexistent coronary microvascular dysfunction (CMD) in patients with obstructive coronary disease remains elusive. We sought to assess the prevalence of CMD and determinants for MRR. Methods We retrospectively investigated 703 physiologically significant (FFR≤0.80) chronic lesions in our institutional physiological registry. All patients underwent pre-PCI physiological assessment including FFR, CFR and MRR. CMD was defined with MRR<2.1. The characteristics and physiological findings were compared between CMD and non-CMD. The predicting factors for CMD were investigated. Results In a total cohort, FFR, CFR and MRR were 0.70(0.6-0.75), 1.82 (1.27-2.80) and 3.20 (2.22-4.30), respectively. CMD was observed in 142 (20.2%) vessels. Older age (71[65-77] vs 69[62-75], p=0.007), female patients (24.6% vs 14.4%, p=0.005) and non-LAD culprit lesions (42.3% vs 32.4%, p=0.014) were significantly more frequent in CMD. Furthermore, CMD group was significantly associated with the history of hemodialysis and heart failure (10.6% vs 3.6%, p=0.001, 38.0% vs 31.0%, p=0.015 respectively). FFR and CFR were lower in CMD than non-CMD (0.67[0.60-0.73] vs 0.70[0.61-0.76], p<0.001, 1.03[0.82-1.21] vs 2.16[1.56-3.00], p<0.001, respectively). In multiple linear regression analysis, low FFR, non-LAD lesion, older age, female and history of hemodialysis were significant predictors for the presence of CMD. Conclusion The prevalence of coexistent CMD in patients undergoing PCI was 20.2%, when defined as MRR≤2.1. Non-LAD lesion location, older age, women, history of hemodialysis, and FFR were significantly associated with the presence of CMD.