Comparison of a known invasive physiological method used for the evaluation of ischemia and a newer noninvasive physiological method for the same propose

ABSTRACT

INTRODUCTION: FFR is the most validated method for evaluating the physiological significance of non-occlusive coronary stenosis. FFR is the ratio of distal pressure (Pd) and aortic pressure (Pa) determined during adenosine induced hyperemia. Nonhyperemic pressure ratios were later introduced and validated against FFR, being non-inferior on ischemia detection. New methods for non-invasive physiological evaluation of ischemia recently became available for our daily practice. The Murray law-based QFR (µQFR or µFR) is a novel computational software that enables accurate estimation of FFR based on the analysis of a single angiographic projection with the adequate quality adjusting both the reference vessel diameter and the outgoing flow through side branches according to fractal geometry. Objective: Both methods were compared and validated against FFR with non-inferiority, it´s to our understanding that both methods can be compared and have similar results. Our objective is to compare the invasive evaluation of coronary physiology with RFR with this novel non-invasive method µFR. METHODS: We revised data from 04/2022 to 04/2023 and found more than 100 RFR evaluations in patients that underwent coronary angiography and presented a non-occlusive coronary lesion. From those we selected 73 patients, based on RFR values of less than 0.95 and used the angiography of the procedure for the evaluation of ischemia with this new software. Once we calculated the µFR we compared the results(positive or negative) to the RFR results. We used Qui square test for the analysis. RESULT: From 73 patients, 50 RFR were positive for ischemia and 34 µFR were positive for ischemia. From those 50 RFR positives for ischemia, 36 underwent PCI or CABG for revascularization. The remaining patients had a value close to 0.89 or had a diffuse pattern without any focal lesion that would benefit from revascularization. The concordance was made with Qui Square Test that confirms the non concordance of both methods in the selected population. Qui square test was 23. On the 16 cases that werent treated or had negative µFR, most had a diffuse CAD pattern, and the method did not had an impact on the decision on treatment. CONCLUSION: In our comparison of RFR vs µFR in 73 patients in the last year we found that there is a non concordance between RFR and µFR as methods evaluating ischemia in this selected small group. The differences can be seen in 16 patients were diffuse pattern was observed.