Abstract
Quantitative flow ratio (QFR) is a novel method to assess the relevance of coronary stenoses based only on angiographic projections. We could previously show that QFR is able to predict the hemodynamic relevance of non-culprit lesions in patients with myocardial infarction. However, it is still unclear whether QFR is also associated with the extent and severity of ischemia, which can effectively be assessed with imaging modalities such as cardiac magnetic resonance (CMR). Thus, our aim was to evaluate the associations of QFR with both extent and severity of ischemia. We retrospectively determined QFR in 182 non-culprit coronary lesions from 145 patients with previous myocardial infarction, and compared it with parameters assessing extent and severity of myocardial ischemia in staged CMR. Whereas ischemic burden in lesions with QFR > 0.80 was low (1.3 ± 5.5% in lesions with QFR ≥ 0.90; 1.8 ± 7.3% in lesions with QFR 0.81-0.89), there was a significant increase in ischemic burden in lesions with QFR ≤ 0.80 (16.6 ± 15.6%; p < 0.001 for QFR ≥ 0.90 vs. QFR ≤ 0.80). These data could be confirmed by other parameters assessing extent of ischemia. In addition, QFR was also associated with severity of ischemia, assessed by the relative signal intensity of ischemic areas. Finally, QFR predicts a clinically relevant ischemic burden ≥ 10% with good diagnostic accuracy (AUC 0.779, 95%-CI: 0.666-0.892, p < 0.001). QFR may be a feasible tool to identify not only the presence, but also extent and severity of myocardial ischemia in non-culprit lesions of patients with myocardial infarction.