Abstract 329: T2-weighted MRI Has High Diagnostic Accuracy for Myocardial Hemorrhage in Myocardial Infarction: A Preclinical Validation Study in Swine
Background: Myocardial hemorrhage after myocardial infarction (MI) frequently goes undetected. Since the paramagnetic effects of oxidized iron may result in signal loss on T2* and T2-weighted MRI, we investigated the diagnostic accuracy of T2-weighted MRI in experimental MI.
Methods: Acute MI was created in swine (43±9.5 kg) by occluding the left anterior descending coronary artery (n=10) or circumflex (n=5) for 90 minutes followed by reperfusion for ≤3 days (n=2), 10 days (n=7) or 60 days (n=6). Cardiac MRI was performed at 1.5T using T2-prepared steady-state free-precession (T2P-SSFP) and gadolinium enhanced (CE) MRI. Left ventricular (LV) sections were visually inspected, photographed and stained for histology. Gross images and histology were scored for myocardial hemorrhage by an experienced cardiac pathologist blinded to all other data. Regions of low signal intensity on T2-weighted and CE-MRI were independently determined by 3 cardiologists blinded to the pathology results. All images were de-identified and analyzed in random order.
Results: Eighty ventricular slices of pathology were matched with MRI (n=68 for first pass CE-CMR). All pathologic sections with evidence of MI (n=63 (79%)) also exhibited hyperintense zones consistent with edema on T2-weighted, and infarct on CE-MRI. Myocardial hemorrhage occurred in 49 LV sections (61%) and corresponded with signal voids on 48 T2-weighted (98%) and 26 CE-MRI (53%). Alternatively, signal voids occurred in the absence of hemorrhage in 3 T2-weighted (90% specificity) and 5 CE-MRI (84% specificity). On first pass CE-MRI, 27/43 perfusion defects corresponded with hemorrhage (63% sensitivity) while 5/25 defects occurred in the absence of hemorrhage (80% specificity). The positive and negative predictive values for pathological evidence of hemorrhage were 94% & 96% for T2-weighted, 84% & 53% for CE-MRI, and 84% & 56% for first pass perfusion.
Conclusions: T2-weighted MRI has high diagnostic accuracy for myocardial hemorrhage. Heterogeneity of signal intensity associated with acute MI on T2-weighted MRI is partially due to intramyocardial hemorrhage.