The contribution of intramyocardial hemorrhage to the "no-reflow phenomenon": a study performed by cardiac magnetic resonance

Background: Percutaneous coronary intervention (PCI) in acute myocardial infarction (AMI) is sometimes complicated by microvascular damage and hemorrhage. Hemoglobin degradation products have magnetic susceptibility effects which help in detecting hemorrhagic AMI by T₂‐weighted cardiac magnetic resonance (CMR) images. Objectives: To investigate the possibility to detect intramyocardial hemorrhage after AMI and to assess its contribution to the delayed hypoenhanced core on late gadolinium enhancement (LGE) CMR, a feature traditionally referred to as microvascular obstruction. Methods: Consecutive patients with AMI who underwent PCI and CMR were investigated. Hypointense zones T₂‐weighted images were labelled as “hemorrhagic” AMI. Areas of late hypoenhancement on LGE CMR were considered as regions of persistent microvascular damage (PMD). Only transmural AMI were considered. Results: A total number of 108 transmural AMI patients were eventually enrolled and divided into two groups according to the presence of hypoenhancement on T₂ images. Thirty‐two patients showed an hypointense stria within the high signal intensity zone on T₂‐weighted images; all these patients showed midmural PMD on LGE. Among the remaining 76 patients, only 14 (18.4%) showed PMD in the subendocardial region. The angiographic outcome was worse in patients with hemorrhagic AMI, with a lower prevalence of TIMI 3 (65.6% vs. 96.1%, P = 0.017) and higher prevalence of myocardial blush grade 0 (84.4% vs. 13.2%, P < 0.001) post‐PCI. Conclusions: T₂‐weighted CMR in reperfused AMI allows identification of hemorrhage, related to PMD areas on LGE images and to a worse reperfusion profile on angiography. These features open new avenues of investigation for prognostic assessment of reperfused AMI. (Echocardiography 2010;27:1120‐1129)