Delayed enhancement and T2-weighted cardiovascular magnetic resonance imaging differentiate acute from chronic myocardial infarction

Background - Delayed enhancement (DE) cardiovascular magnetic resonance (CMR) detects acute and chronic myocardial infarction (MI) by visualizing contrast media accumulation in infarcted segments. T2-weighted CMR depicts infarct-related myocardial edema as a marker of acute but not chronic myocardial injury. We investigated the clinical utility of an approach combining both techniques to differentiate acute from chronic MI. Methods and Results - Seventy-three MI patients were studied in 2 groups. Group A consisted of 15 acute MI patients who were studied twice, on day 1 and 3 months after MI. In group B, 58 patients with acute or chronic MI underwent 1 CMR scan. T2-weighted and DE images of matched slices were acquired on a 1.5-T system. In group A, quantitative segmental and region of interest - based analyses were performed to observe signal changes between the acute and chronic phases. In group B, T2-weighted and DE images were examined visually by 2 blinded observers for the presence or absence of hyperintense areas in corresponding segments. For infarct localization, coronary angiography and/or ECG changes served as the reference standard. In group A, the contrast-to-noise ratio on T2-weighted images dropped in the infarcted segments from 2.7 +/- 1.1 on day 1 to 0.1 +/- 1.2 after 3 months ( P < 0.0001). There was no significant change in contrast-to-noise ratio in DE images (1.9 +/- 1.5 versus 1.3 +/- 1.0; P = NS). The qualitative assessment of T2-weighted and DE images in group B yielded a specificity of 96% to differentiate acute from chronic lesions. Conclusions - An imaging approach combining DE and T2-weighted CMR accurately differentiates acute from chronic MI.