Diagnostic performance of angiography-based quantitative flow ratio for the identification of myocardial ischemia as assessed by N-ammonia myocardial perfusion imaging positron emission tomography.

Background: Quantitative flow ratio (QFR) is a novel, adenosine-free method for functional lesion interrogation based on 3-dimensional quantitative coronary angiography and computational algorithms. We sought to investigate the diagnostic performance of QFR versus myocardial perfusion imaging positron emission tomography (MPI-PET), which yields the highest accuracy for detection of myocardial ischemia.

Methods: Diagnostic performance of QFR versus MPI-PET was assessed in consecutive patients undergoing both clinically indicated coronary angiography and N-ammonia MPI-PET within a six-month period.

Results: Out of 176 patients (439 coronary arteries), 19.3% were women. Percent area stenosis was 45 [32-58] %. Myocardial ischemia on N-ammonia MPI-PET was detected in 106 (24.1%) vessel territories and hemodynamic significance defined as contrast-flow vessel QFR ≤ 0.80 was observed in 83 (18.9%) vessels. Diagnostic accuracy, sensitivity, and specificity of contrast-flow vessel QFR for the prediction of myocardial ischemia on N-ammonia MPI-PET were 92.5 (95% CI 89.6-94.7) %, 73.6 (95% CI 64.1-81.7) %, and 98.5 (95% CI 96.5-99.5) %, respectively. The AUCs for contrast-flow vessel QFR, percent diameter stenosis, and percent area stenosis were 0.85 (95% CI 0.81-0.88, p < 0.001), 0.76 (95% CI 0.71-0.79, p < 0.001) and 0.75 (95% CI 0.70-0.79, p < 0.001), respectively.

Conclusions: QFR, a novel diagnostic tool for functional coronary lesion assessment, provides good diagnostic agreement with MPI-PET and superior diagnostic accuracy for the detection of myocardial ischemia as compared to anatomic indices. Future studies will have to determine the non-inferiority of QFR to fractional flow reserve with respect to clinical outcomes.