BACKGROUND AND AIMS
European and American experts recommend physiology-guided myocardial revascularisation.1,2,3 Nevertheless, physiology-guided revascularisation does not exceed 10% in the best scenario, worldwide.4 The most widely used pressure wire-based methods are associated with rare but potentially threatening complication;5 therefore, a novel minimally invasive fractional flow reserve (FFR) value computation method known as quantitative flow ratio (QFR) has been developed.6,7,8 This study was aimed to investigate the agreement between QFR, FFR, and instantaneous wave-free ratio (iFR), in addition to evaluating the difference between QFR and both FFR and iFR on making a treatment decision.
MATERIALS AND METHODS
Two-hundred and thirteen patients, who had undergone a coronary angiography that revealed intermediate stenosis (lumen stenosis of 35–75%) by visual evaluation and for whom FFR or iFR measurements were performed between 1st January 2019 and 31st December 2020, were prospectively included into the study. FFR and iFR values were averaged from three independent measurements during the same procedure and FFR and iFR results were blinded online. QFR analyses were performed three times. Average QFR values were compared to average FFR or iFR values. FFR measurements were divided according to the diseased coronary artery (CA). The selected level of significance was p< 0.01.
In total, 240 lesions, including 146 left anterior descending (LAD), 25 left circumflex (LCX), and 69 right CA (RCA), were analysed. In total, 25 were iFRs. In the analyses of all lesions, a strong significant correlation coefficient between QFR and both FFR and iFR was found: r=0.782 and 0.871, respectively; p<0.001. After dividing lesions according to CA, the following results have been found: LAD: r=0.749, p<0.001; LCX: r=0.757, p<0.001; and RCA: r=0.839, p<0.001. The secondary outcome was the agreement of clinical decision-making between contrast QFR and both FFR and iFR. In the analyses of all lesions, a strong, significant correlation between QFR and FFR have been found (r=0.948; p<0.001). A weaker correlation between QFR and iFR was reported (r=0.600; p=0.002). Detailed analysis of separate CA has shown the following results: LAD: r=0.941, p<0.001; LCX: r=1.00, p<0.001; and RCA: r=0.954, p<0.001. Compared to FFR as a reference, QFR had a sensitivity of 100%, specificity of 97.63%, and accuracy of 98.14%, and when compared to iFR the values were 100%, 95%, and 88%, respectively.
The variety of methods that are currently available encourages the search for the most economical, most convenient, and most reliable method. Repeatedly proved excellent agreement between FFR and QFR supports the wider acceptance into clinical practice, while at the same time encourages further research. Excellent QFR agreement to both FFR and iFR, especially in regard to clinical decision making, makes the method more acceptable to everyday clinical practice. QFR is a safe, cheap, and convenient method, with an excellent correlation to both FFR and iFR in CA stenosis functional significance assessment and clinical decision making, with a great sensitivity, specificity, and accuracy.