Diagnostic Accuracy of Quantitative Flow Ratio for Assessing Myocardial Ischemia in Prior Myocardial Infarction

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Background:A novel index of the functional severity of coronary stenosis, quantitative flow ratio (QFR), may not consider the amount of viable myocardium in prior myocardial infarction (MI) because QFR is calculated from 3D quantitative coronary angiography.

Methods and Results:We analyzed QFR (fixed-flow QFR [fQFR] and contrast-flow QFR [cQFR]) and fractional flow reserve (FFR) in prior-MI-related coronary arteries (n=75) and non-prior-MI-related coronary arteries (n=75). Both fQFR and cQFR directly correlated with FFR in the prior-MI-related coronary arteries (fQFR: r=0.84, P<0.001; and cQFR: r=0.88, P<0.001) and the non-prior-MI-related coronary arteries (fQFR: r=0.91, P<0.001; and cQFR: r=0.94, P<0.001). fQFR was significantly smaller than FFR in the prior-MI-related coronary arteries (0.73±0.14 vs. 0.79±0.11, P=0.002), but there was no significant difference between fQFR and FFR in the non-prior-MI-related coronary arteries. The value of cQFR minus FFR was significantly lower in the prior-MI-related coronary arteries compared with the non-prior-MI-related coronary arteries (−0.02±0.06 vs. 0.00±0.04, P=0.010). The diagnostic accuracy of fQFR ≤0.8 and cQFR ≤0.8 for predicting FFR ≤0.80 was numerically lower in the prior-MI-related coronary arteries compared with the non-prior-MI-related coronary arteries (fQFR: 77% vs. 87%; and cQFR: 87% vs. 92%).

Conclusions:When FFR is used as the gold standard, the accuracy of QFR for assessing the functional severity of coronary stenosis might be reduced in the prior-MI-related coronary arteries compared with non-prior-MI-related coronary arteries.