A Vessel-Specific Analysis of Deferred Lesions Using the Instantaneous Wave-Free Ratio and Fractional Flow Reserve

Abstract

Background: Physiologically guided revascularization improves clinical outcomes. The cutoff values for deferral with fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) are the same across all coronary arteries, despite differences in coronary flow patterns. The objective was to compare deferral rates using either FFR or iFR in the right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCx), and compare clinical outcomes in deferred lesions in the RCA, LAD, and LCx.

Methods: Right coronary artery, LAD, and LCx lesions in the Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry that were evaluated using either FFR or iFR were included. The composite of major adverse cardiac events (MACE) within 5 years and the individual components of cardiovascular death, noncardiovascular death, myocardial infarction, target segment revascularization, and target vessel revascularization were analyzed.

Results: In total, 33,241 lesions were included in the final analysis (RCA, 17.8%; LAD, 62.3%; and LCx, 19.9%). The median follow-up time was 3.4 years. The median age was 69 years, and 73.5% of patients were men. The deferral rates with iFR were 10.6% higher (P < .001) in all coronary arteries combined, 18.7% higher (P < .001) in the RCA, 9.5% higher in the LAD (P < .001), and 5.3% higher in the LCx (P = .007). No significant differences were observed in the MACE rate or its individual components at 5 years between the deferred FFR and iFR groups in any of the investigated vessels.

Conclusions: Instantaneous wave-free ratio demonstrated a higher deferral rate across all coronary arteries than those examined with FFR, which was especially pronounced in the RCA, without any associated increased risk of MACE.

Keywords: coronary blood flow; left coronary artery; right coronary artery.

Figure 1

Flowchart of the study design. The flowchart illustrates the lesions included and excluded from the study, with numbers representing the lesions remaining at each step. The last 2 steps were stratified according to the vessel investigated and the method of coronary physiology. CABG, coronary artery bypass grafting; FFR, fractional flow reserve; iFR, instantaneous wave-free ratio; IMCA, intermediate coronary artery; LAD, left anterior descending artery; LCx, left circumflex artery; LMCA, left main coronary artery; n, number; RCA, right coronary artery.

Central Illustration

A summary of the study method and outcomes. FFR, fractional flow reserve; iFR, instantaneous wave-free ratio; LAD, left anterior descending artery; LCx, left circumflex artery; MACE, major adverse cardiac event; n, number; RCA, right coronary artery; SWEDEHEART, the Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies.

Figure 2

Histograms of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) values. Illustration of the distribution of FFR and iFR values before deferral or revascularization in each vessel. LAD, left anterior descending artery; LCx, left circumflex artery; RCA, right coronary artery.

Figure 3

Deferral rate across all coronary arteries. The figure illustrates revascularization and deferral rates across all coronary arteries. The increased deferral rates with instantaneous wave-free ratio (iFR) across all arteries are presented as percent higher deferral with iFR compared to fractional flow reserve (FFR). LAD, left anterior descending artery; LCx, left circumflex artery; RCA, right coronary artery.

Figure 4

Kaplan-Meier graphs for the primary outcome. Kaplan-Meier graphs visualizing the cumulative risk of the primary outcome of major adverse cardiac events over 5 years for the (A) right coronary, (B) left anterior descending, and (C) left circumflex arteries. FFR, fractional flow reserve; HR, hazard ratio; iFR, instantaneous wave-free ratio; RR, risk ratio.