Interindividual Variations in the Adenosine‐Induced Hemodynamics During Fractional Flow Reserve Evaluation: Implications for the Use of Quantitative Flow Ratio in Assessing Intermediate Coronary Stenoses

BACKGROUND: Quantitative flow ratio (QFR), a novel functional angiography technique, computes fractional flow reserve (FFR) without pressure wires or adenosine. We investigated interindividual variations in the adenosine‐induced hemodynamics during FFR assessment and their influence on QFR diagnostic performance. METHODS AND RESULTS: Patients with coronary stenoses who underwent intracoronary pressure and flow assessment were analyzed. Adenosine‐induced hemodynamics during FFR measurement were determined by the percentage change in mean aortic pressure (%ΔPa) and the resistive reserve ratio (RRR). The diagnostic performance of QFR was evaluated and compared in each tertile of %ΔPa and RRR using FFR as reference. A total of 294 vessels (245 patients) were analyzed. Mean FFR was 0.80±0.11. Individuals showed a wide variation in the adenosine response in terms of %ΔPa (ranging from −75% to 43%; median, −9% [interquartile range, −3% to −17%]) and the RRR (ranging from 0.45 to 20.15; median, 3.1 [interquartile range, 2.1–4.9]). No significant differences for diagnostic efficiency of QFR were found between tertiles of %ΔPa (area under the curve for the receiver‐operating characteristic analysis, 0.950 in tertile 1, 0.929 in tertile 2, and 0.910 in tertile 3; P=0.270) or between tertiles of the RRR (area under the curve for the receiver‐operating characteristic analysis, 0.909 in tertile 1, 0.923 in tertile 2, and 0.959 in tertile 3; P=0.167). The classification agreement between QFR and FFR was not significantly modified by %ΔPa (tertile 1, 89%; tertile 2, 87%; and tertile 3, 86%; P=0.827) or by the RRR (tertile 1, 86%; tertile 2, 85%; and tertile 3, 91%; P=0.398). CONCLUSIONS: Patients undergoing FFR assessment show large interindividual variations in the magnitude of adenosine‐induced hemodynamics. However, such variations do not affect the diagnostic performance of QFR in assessing the functional relevance of observed stenoses.