Comparison of the angiographic myocardial blush grade with delayed‐enhanced cardiac magnetic resonance for the assessment of microvascular obstruction in acute myocardial infarctions

Abstract

Both myocardial blush grade (MBG) and cardiac magnetic resonance (CMR) are imaging tools that can assess myocardial reperfusion after primary percutaneous coronary intervention (PCI) for acute myocardial infarction (AMI). We studied the relation between MBG and gadolinium-enhanced CMR for the assessment of microvascular obstruction (MVO) in patients with acute ST-elevated myocardial infarction (STEMI) treated by primary PCI. MBG was assessed in 39 patients with initial TIMI 0 STEMI successfully treated by PCI, resulting in TIMI 3 flow grade and complete ST-segment resolution. These MBG values were related to MVO determined by CMR, performed between 2 and 7 days after PCI. Left ventricular (LV) volumes were determined at baseline and at 6-month follow-up. No statistical relation was found between MBG and MVO extent at CMR (P = 0.63). Regarding MBG 0 and 1 as a sign of MVO, the sensitivity and specificity of these scores were 53.8 and 75%, respectively. In this study, CMR determined MVO was the only significant LV remodeling predicting factor (beta = 31.8; P = 0.002), whatever the MBG status was. MBG underestimates MVO after an optimal revascularization in AMI compared with CMR. This study suggests the superior accuracy of delayed-enhanced magnetic resonance over MBG for the assessment of myocardial reperfusion injury that is needed in clinical trials, where the principal endpoint is the reduction of infarct size and MVO.