Diagnostic accuracy of instantaneous wave free‐ratio in clinical practice

Aims To evaluate the correlation between iFR and FFR in real‐world clinical practice. Methods and Results Retrospective, single‐centre study of 229 consecutive pressure‐wire studies ( n p = 158). Real‐time iFR and FFR measurements were performed for angiographically borderline stenoses. Functionally significant stenoses were defined as iFR <0.86 or FFR ≤0.80. An iFR between 0.86 and 0.93 was considered within the grey zone (Hybrid approach). Median iFR and FFR (IQR) were 0.92 (0.87‐0.95) and 0.83 (0.76‐0.89), respectively. Pearson's correlation coefficient was 0.75 ( P < 0.001). Bland‐Altman plot showed a mean difference between iFR and FFR that remained consistent throughout the range of values. The optimal iFR cutoff was 0.91—sensitivity 80%, specificity 82% with ROC area under curve of 89%. Using the Hybrid iFR‐FFR strategy, we demonstrated high accuracy of iFR results—sensitivity 95%, specificity 96%, PPV 95%, and NPV 96%. In addition, this method would have avoided adenosine in 56% of patients. Mean follow‐up period was 17.2 (±3.4) months. All‐cause mortality was 3.2% ( n p = 5) and repeat intervention was required in six lesions (2.6%). Conclusions This study demonstrates that iFR is a valuable adjunct to FFR using the Hybrid iFR‐FFR strategy in a real‐world population. The use of adenosine may be avoided in about half the cases.