After ST-elevation myocardial infarction (STEMI), microvascular obstruction (MVO) can be assessed using semiquantitative angiographic “blush” scores subject to interoperator variability. Quantitative Blush Evaluator (QuBE) is a free computer-calculated algorithm that evaluates myocardial blush on a continuous scale with improved reproducibility. We aimed to compare QuBE with cardiovascular magnetic resonance (CMR) in detecting MVO and its severity.

Fifty-two STEMI treated with successful primary percutaneous coronary intervention were enrolled. Quantitative Blush Evaluator and electrocardiographic sum ST-segment resolution were blindly calculated. All patients underwent CMR 4 to 7 days after STEMI for assessment of infarct size (IS), myocardial salvage index, MVO (both as first-pass MVO and delayed-enhancement MVO [DE-MVO]), and presence of intramyocardial hemorrhage on T2-weighted sequences.

Quantitative Blush Evaluator values were inversely related to IS (R = −0.4, P = .008), DE-MVO (R = −0.7, P < .001), and first-pass MVO (R = −0.4, P = .002) and positively related to myocardial salvage index (R = 0.4, P = .007). Moreover, patients with intramyocardial hemorrhage had significantly lower QuBE values (3.9, 3.5-8.0 vs 12.2, 8.2-16.0, P = .001) than those without. At receiver operating characteristic curve analysis, QuBE accounted for an area under the curve of 0.88 (95% CI 0.7-0.9, P = .001) for both DE-MVO and hemorrhage detection and performed significantly better than ST resolution.

Quantitative Blush Evaluator score correlates with IS and microvascular dysfunction by CMR and can be considered as an accurate tool for the assessment of MVO in clinical practice. Quantitative Blush Evaluator is a useful quantitative angiographic technique for the assessment of myocardial reperfusion after STEMI.