Angiography-derived functional assessment of left main coronary stenoses.

OBJECTIVES: We aimed to evaluate the diagnostic accuracy of quantitative flow ratio (QFR) in left main (LM) coronary stenoses, using Fractional Flow Reserve (FFR) as reference. BACKGROUND: QFR has demonstrated a high accuracy in determining the functional relevance of coronary stenoses in non-LM. However, there is an important paucity of data regarding its diagnostic value in the specific anatomical subset of LM disease. METHODS: This is a retrospective, observational, multicenter, international, and blinded study including patients with LM stenoses. Cases with significant ostial LM disease were excluded. QFR was calculated from conventional angiograms at blinded fashion with respect to FFR. RESULTS: Sixty-seven patients with LM stenoses were analyzed. Overall, LM had intermediate severity, both from angiographic (diameter stenosis [%DS] 43.8 ± 11.1%) and functional perspective (FFR 0.756 ± 0.105). Mean QFR was 0.733 ± 0.159. Correlation between QFR and FFR was moderate (r = 0.590). Positive and negative predictive value, sensitivity and specificity were 85.4%, 64%, 85.4%, and 69.6% respectively. Classification agreement of QFR and FFR in terms of functional stenosis severity was 78.1%. Area under the receiver operating characteristics of QFR using FFR as reference was 0.82 [95% confidence interval [CI], 0.71-0.93], and significantly better than angiographic evaluation including %DS (area under the receiver-operating characteristic curve [AUC] 0.45 [95% CI, 0.32-0.58], p < 0.001) and minimum lumen diameter (AUC 0.60 [95% CI, 0.47-0.74], p < 0.001). CONCLUSIONS: Compared with FFR, QFR has acceptable diagnostic performance in determining the functional relevance of LM stenosis, being better than conventional angiographic assessment. Nonetheless, caution should be taken when applying functional angiography techniques for the assessment of LM stenosis given its particular anatomical characteristics.

Angiography-derived functional assessment of non-culprit coronary stenoses in primary percutaneous coronary intervention.

AIMS: Functional assessment of non-culprit lesions (NCL) in patients presenting with ST-elevation myocardial infarction (STEMI) and multivessel disease constitutes an unmet need. This study aimed to evaluate the diagnostic accuracy of quantitative flow ratio (QFR) in the functional assessment of NCL during the acute phase of STEMI. METHODS AND RESULTS: This was a retrospective, observational, multicentre study including patients with STEMI and staged fractional flow reserve (FFR) assessment of NCL. QFR in NCL was calculated from the coronary angiogram acquired during primary PCI in a blinded fashion with respect to FFR. The diagnostic value of QFR in the STEMI population was compared with a propensity score-matched population of stable angina patients. Eighty-two patients (91 NCL) were included. Target lesions were of both angiographic and functional (mean FFR 0.82±0.09) intermediate severity. The diagnostic performance of QFR was high (AUC 0.91 [95% CI: 0.85-0.97]) and similar to that observed in the matched control population (AUC 0.91 vs 0.94, p=0.5). The diagnostic accuracy of QFR was very high (>95%) in those vessels (61.5%) with QFR values out of a ROC-defined "grey zone" (0.75-0.85). A hybrid FFR/QFR approach (FFR only when QFR is in the grey zone) would adequately classify 96.7% of NCL, avoiding 58.5% of repeat diagnostic procedures. CONCLUSIONS: QFR has a good diagnostic accuracy in assessing the functional relevance of NCL during primary PCI, similar to the accuracy observed in stable patients.

Influence of Microcirculatory Dysfunction on Angiography-Based Functional Assessment of Coronary Stenoses.

OBJECTIVES: The authors sought to evaluate the influence of coronary microcirculatory dysfunction (CMD) on the diagnostic performance of the quantitative flow ratio (QFR). BACKGROUND: Functional angiographic assessment of coronary stenoses based on fluid dynamics, such as QFR, constitutes an attractive alternative to fractional flow reserve (FFR). However, it is unknown whether CMD affects the reliability of angiography-based functional indices. METHODS: FFR and the index of microcirculatory resistance (IMR) were measured in 300 vessels (248 patients) as part of a multicenter international registry. QFR was calculated at a blinded core laboratory. Vessels were classified into 2 groups according to microcirculatory status: low IMR (<23 U), and high IMR (≥23 U, CMD). The impact of CMD on the diagnostic performance of QFR, as well as on incremental value of QFR over quantitative angiography, was assessed using FFR as reference. RESULTS: Percent diameter stenosis (%DS) and FFR were similar in low- and high-IMR groups (%DS 51 ± 12% vs. 53 ± 11%; p = 0.16; FFR 0.80 ± 0.11 vs. 0.81 ± 0.11; p = 0.23, respectively). In the overall cohort, classification agreement (CA) between QFR and FFR and diagnostic efficiency of QFR (area under the receiver-operating characteristics curve [AUC]) were high (CA: 88%; AUC: 0.93 [95% confidence interval (CI): 0.90 to 0.96]). However, when assessed according to microcirculatory status, a significantly lower CA and AUC of QFR were found in the high-IMR group as compared with the low-IMR group (CA: 76% vs. 92%; p < 0.001; AUC: 0.88 [95% CI: 0.79 to 0.94] vs. 0.96 [95% CI: 0.92 to 0.98]; p < 0.05). Compared with angiographic assessment, QFR increased by 0.20 (p < 0.001) and by 0.16 (p < 0.001) the AUC of %DS in low- and high-IMR groups, respectively. Independent predictors of misclassification between QFR and FFR were high IMR and acute coronary syndrome. CONCLUSIONS: CMD decreases the diagnostic performance of QFR. However, even in the presence of CMD, QFR remains superior to angiography alone in ascertaining functional stenosis severity.