Acute myocardial infarction:: Evaluation with first-pass enhancement and delayed enhancement MR imaging compared with 201TI SPECT imaging

PURPOSE: To evaluate acute myocardial infarction by using first-pass enhancement (FPE) and delayed enhancement (DE) magnetic resonance (MR) imaging (20 compared with thallium 201 (Tl-201) single photon emission computed tomography (SPECT). MATERIALS AND METHODS: Contrast material-enhanced FPE MR, inversion-recovery DE MR, and rest-redistribution Tl-201 SPECT images were obtained in 60 consecutive patients (53 men, seven women; mean age [+/- SD], 56 years 13; range, 30-78 years) at 6 days +/- 3 after reperfused first myocardial infarction. Presence of microvascular obstruction was determined on FPE MR images. Infarct size was defined on DE MR images as percentage of left ventricular (LV) area and compared with uptake defect on redistribution Tl-201 SPECT images. Differences in continuous data were analyzed with Student t test. Linear regression and Bland-Altman analysis were used to compare measurements of infarct size. RESULTS: Mean infarct size was not significantly different between DE MR imaging 20.7% +/- 11.5% of LV area) and Tl-201 SPECT (19.4% +/- 14.3% of LV area; P = .26); good correlation (r = 0.73; P < .001) and agreement were found, with a mean difference of +1.3% +/- 9.8% of LV area. Tl-201 SPECT failed to depict infarct in six (20%) of 30 patients with inferior myocardial infarction (mean size, 6.4% +/- 5.7% of LV area on DE MR images), whereas DE MR images showed the infarct in all patients (P < .01). FPE MR images depicted microvascular obstruction in 23 (38%) of 60 patients; these patients had larger infarctions at DE MR imaging than did patients without microvascular obstruction (30.4% +/- 9.0% vs. 15.1% +/- 8.4% of LV area, P <.001). Tl-201 SPECT showed larger infarcts in patients with microvascular obstruction (26.7% +/- 16.2% vs 15.0% +/- 11.2% of LV area, P < .01). CONCLUSION: Good correlation and agreement with Tl-201 SPECT indicate DE MR imaging may be used to estimate infarct size 6 days after reperfused acute myocardial infarction. DE MR imaging is more sensitive for detection of inferior infarction than is Tl-201 SPECT. Patients with microvascular obstruction on FPE MR images have larger infarcts. (C) RSNA, 2004.