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Introduction: Previously, an association between anatomic left main stem (LMS) lesion parameters, as described by intravascular ultrasound (IVUS) and fractional flow reserve (FFR), was shown. Quantitative flow ratio (QFR) is a novel, promising technique which can assess functional stenosis relevance based only on angiography. However, as little is known about the relationship between anatomic LMS parameters and QFR, it was thus investigated in this study. Methods: In 53 patients with LMS disease, we tested the association between anatomic assessment using OCT (n = 28) or IVUS (n = 25) on the one hand and functional assessment as determined by QFR on the other hand. LMS-QFR was measured using a dedicated approach, averaging QFR over left anterior descending (LAD) and circumflex (LCX) and manually limiting segment of interest to LMS. Results: The minimal luminal area of the LMS (LMS-MLA) as measured by intravascular imaging showed a consistent correlation with QFR (R = 0.61, p < 0.001). QFR could predict a LMS-MLA < 6 mm(2) with very good diagnostic accuracy (AUC 0.919) and a LMS-MLA < 4.5 mm(2) with good accuracy (AUC 0.798). Similar results were obtained for other stenosis parameters. Conclusions: QFR might be a valuable tool to assess LMS disease. Further studies focusing on patient outcomes are needed to further validate the effectiveness of this approach.

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.

Introduction: Although the relationship between the geometry of coronary stenosis and the presence of myocardial ischemia is well known, the association between stenosis geometry and severity and/or extent of ischemia is still unexplored. Thus, we investigated this relationship using optical coherence tomography (OCT) to assess stenosis parameters and cardiac magnetic resonance imaging (CMR) to determine both extent and severity of ischemia. Methods: We analyzed 55 lesions from 51 patients with stable angina. Pre-interventionally, all patients underwent OCT-analysis of stenosis morphology as well as CMR to determine both the extent and severity of myocardial ischemia. Results: Percent area stenosis (%AS) was significantly associated with ischemic burden (r = 0.416, p = 0.003). Similar results could be obtained for other stenosis parameters as well as for several other parameters assessing the extent of ischemia. Furthermore, OCT-derived stenosis parameters were associated with the product of ischemic burden and severity of ischemia (%AS: r = 0.435, p = 0.002; similar results for other parameters). A Poiseuille's-law-modelled combination of stenosis length and minimal lumen diameter yielded a good diagnostic efficiency (AUC 0.787) in predicting an ischemic burden >10%. Conclusions: Our data highlight the key role of the geometry of coronary lesions in determining myocardial ischemia.