In vivo T2-weighted magnetic resonance imaging can accurately determine the ischemic area at risk for 2-day-old nonreperfused myocardial infarction.

OBJECTIVES: To determine whether in vivo T2-weighted cardiac magnetic resonance imaging (MRI) delineates the area at risk (AAR) in 2-day-old nonreperfused myocardial infarction (MI). AAR was defined as the size of the perfusion defect on day 0. MI and the residual ischemic viable border zone comprise the AAR.
MATERIALS AND METHODS: Fourteen dogs with permanent coronary artery occlusion were imaged on day 0 and day 2. The size of the AAR as measured by first-pass magnetic resonance perfusion on day 0 was compared with retrospectively determined AAR using day 2 T2-weighted MRI. Triphenyltetrazolium chloride staining was used to measure infarct size. Microspheres were used to detect residual perfusion.
RESULTS: Hyperintense zones on day 2 T2-weighted magnetic resonance images accurately depicted the AAR as measured by first-pass perfusion on day 0 (38.9 +/- 3.0 vs. 36.3% +/- 3.3% of left ventricular, P = 0.07). Good correlation (R = 0.91) and Bland-Altman agreement was observed between the AAR measurements and the corresponding T2-weighted hyperintense regions. Both measures of AAR were larger than the infarcted zone (25.6% +/- 2.5% of left ventricular area; P < 0.001).
CONCLUSIONS: Hyperintense regions visualized with in vivo T2-weighted cardiac MRI allow determination of the AAR 2 days postinfarction in nonreperfused MI.