Abstract 411: The Contribution of Intramyocardial Hemorrhage to the No-reflow Phenomenon: A Study Performed by Cardiac Magnetic Resonance
Background: Percutaneous coronary intervention (PCI) on acute myocardial infarction (AMI) is sometimes complicated by microvascular damage and hemorrhage. Haemoglobin degradation products have strong magnetic susceptibility effects useful to detect hemorrhagic AMI by T2-weighted cardiac magnetic resonance (MRI) images. We recently demonstrated a perfect overlap between hypointense dark areas on T2-weighted images, PMD detected on late gadolinium enhancement (LGE) and histologic evidence of hemorrhagic AMI.
Aim: To investigate the possibility to detect intramyocardial hemorrhage after AMI and to assess its contribution, in humans, to delayed hypoenhaced core traditionally referred so far only to microvascular obstruction.
Methods: 250 consecutive patients with AMI and primary PCI underwent CMR. T2-weighted black-blood turbo spin-echo sequences and LGE sequences were acquired. Hypointense zones due to paramagnetic susceptibility effect of deoxyhemoglobin on T2-weighted images were defined as “hemorrhagic AMI”. Patients with transmural infarction and hypoenhancement on T2-weighted images were selected. For each patient clinical and angiographic data (TIMI post-PCI and myocardial blush grade, MBG) were collected.
Results: the 108 patients finally enrolled were divided into two groups according to the presence of a dark area on T2 images, assumed to indicate hemorrhage. Thirty-two patients showed an hypointense stria within the high signal intensity zone on T2-weighted images; all these patients showed on LGE midmural PMD according with the extent of hypointense signal on T2-weighted sequences. Among the other patients (76) only 14 (18,4%) patients showed PMD, in the subendocardial region. Angiographic outcome was worst in patients with hypointense signal on T2-weighted and PMD, since they had less TIMI 3 (65,6% vs 96%, p=0.017) and more frequently MBG grade 0 (84,4% vs 13,1%, p<0.001) post-PCI.
Conclusion: T2-weighted CMR in reperfused AMI allows identification of an hypointense dark stria related with PMD areas on LGE and identified ex-vivo in severe microvascular damage (hemorrhage). The absence of radiological signs of hemorrhagic AMI is associated with a better angiographic reperfusion as indicated by higher MBG.