Simplifying the Assessment of Coronary Artery Stenosis by Enhancing Instantaneous Wave-Free Ratio

Background and objective The intermediate range of instantaneous wave-free ratio (iFR) measurements presents various diagnostic uncertainties. This study aimed to evaluate contrast-enhanced iFR (iFRc) to determine its correlation with fractional flow reserve (FFR). Our objective was to assess whether iFRc improves diagnostic alignment with FFR in coronary artery stenosis with intermediate iFR values (0.86-0.93). Patients and methods Thirty patients with intermediate iFR values were enrolled. The measurements included resting Pd/Pa, standard iFR, iFRc, and adenosine-mediated FFR. Detailed procedural protocols, including the type of pressure wire, guiding catheter, and contrast administration, were standardized. Results Pearson correlation between iFR and FFR was moderate (r = 0.578, p < 0.001), while iFRc showed a stronger correlation (r = 0.710, p < 0.001). The receiver operating characteristic (ROC) analysis demonstrated superior diagnostic performance for iFRc (area under the ROC curve (AUC) = 0.922, 95% confidence interval (CI): 0.799-1.0) compared with iFR (AUC = 0.856, 95% CI: 0.656-1.0). Optimal iFRc cutoff ≤0.88 yielded 88.9% sensitivity (95% CI: 51.8-99.7), 96% specificity (95% CI: 79.7-99.9), 88.9% positive predictive value (PPV) (95% CI: 51.8-99.7), and 96% negative predictive value (NPV) (95% CI: 79.7-99.9). Conclusions iFRc improves diagnostic certainty in intermediate iFR values and shows strong concordance with FFR. However, the findings are hypothesis-generating and warrant larger, multicenter validation studies.