Impact of microvascular obstruction on left ventricular local remodeling after reperfused myocardial infarction

PURPOSE: To evaluate by cardiac magnetic resonance imaging (MRI) the impact of microvascular obstruction (MVO) on regional left ventricular (LV) wall characteristics and local remodeling after acute myocardial infarction (AMI). MATERIALS AND METHODS: In all, 114 AMI patients underwent cardiac MRI at 3T within 2-4 days (baseline) and at 6 months (follow-up) after reperfusion. Late gadolinium enhancement and cine sequences were performed. The impact of MVO (ie, presence and extent) on regional wall thickening (WT, %), end-diastolic wall thickness (EDWT, mm), and local cavity change (mm) of LV were quantitatively analyzed. Local cavity change, calculated as surface-to-surface distance from registered endocardial surface meshes of cine imaging datasets acquired initially and at follow-up, was used to assess local remodeling. RESULTS: MVO was detected in 69 patients (60.5%). WT was significantly lower when MVO was present (P < 0.05); and it was inversely related to MVO transmural extent (P < 0.0001). WT improvement was significantly worsened when MVO was present in segments with infarct transmural extent exceeding 50%. Significant wall thinning occurred at follow-up in segments with infarct transmural extent >75% with further thinning by MVO presence; and EDWT decreased with increasing MVO transmural extent (P < 0.0001). LV cavity shrank in patients without MVO, whereas it dilated in those with MVO. Local cavity changes were not significantly different by a region-to-region analysis throughout the LV within each group (P = 0.57 and 0.74, respectively). CONCLUSION: MVO has a significant adverse effect on LV wall characteristics and LV remodeling. Postinfarct remodeling seems to be globally mediated rather than locally mediated during the first 6 months. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:499-510.