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The following is a summary of “Accuracy of Instantaneous Wave-free Ratio and Fractional Flow Reserve Derived From Single Coronary Angiographic Projections,” published in the March 2025 issue of the American Heart Journal by Onuma et al.

Angiography-derived fractional flow reserve (FFR) software has been developed to provide a non-invasive alternative to traditional pressure wire-based FFR, offering a potential improvement in clinical workflow and patient safety. However, most currently available software requires two angiographic projections separated by at least 25 degrees, which limits its applicability in routine practice. This study aimed to prospectively validate the diagnostic accuracy of a novel angiography-derived instantaneous wave-free ratio (Angio-iFR, Royal Philips, Amsterdam) in comparison with invasive pressure wire-based iFR across a multicenter registry. 

Coronary angiograms were obtained from patients presenting with coronary artery stenoses of 40–90% severity, with both iFR and FFR measurements recorded. The precise position of the pressure wire was documented during contrast injection in two distinct angiographic views, ensuring consistency between invasive and angiography-derived measurements. Independent core laboratory analysts, blinded to the physiological data, calculated Angio-iFR and FFR at the exact position of the pressure wire. The primary endpoint of this study was to assess the sensitivity and specificity of Angio-iFR relative to the corresponding invasive iFR measurements, with predefined performance thresholds set at 75% for sensitivity and 80% for specificity. A total of 441 patients were enrolled across 32 centers in Europe, Japan, and the United States. 

Of these, paired Angio-iFR and pressure wire-based iFR measurements were successfully obtained in 398 coronary vessels. The mean iFR was 0.90 (standard deviation: 0.11), with 31.9% of vessels exhibiting an iFR of ≤0.89. The Angio-iFR software demonstrated high feasibility, with a 97% success rate in obtaining valid measurements, and a median computational analysis time of 55 seconds per vessel. However, the diagnostic performance of Angio-iFR fell short of the predefined targets, yielding a sensitivity of 77% (95% [CI]: 69–84%) and a specificity of 49% (95% CI: 41–54%). These findings indicate that while Angio-iFR shows promise as a rapid and feasible tool for non-invasive physiological assessment, its current diagnostic accuracy is insufficient to replace invasive pressure wire-based iFR in clinical decision-making. The lower-than-expected specificity suggests that a significant proportion of patients may receive discordant results, potentially impacting clinical management strategies. Further refinements in software algorithms, including enhanced image processing techniques and improved lesion flow modeling, are necessary to optimize the performance of Angio-iFR. 

Additionally, future studies should explore the potential of machine learning integration to refine computational models and enhance predictive accuracy. While angiography-derived physiological assessment remains an attractive alternative to invasive wire-based techniques, its clinical adoption will depend on achieving performance metrics comparable to existing standards.

Source: sciencedirect.com/science/article/abs/pii/S0002870325000717