Reproducibility of chronic infarct size measurement by contrast-enhanced magnetic resonance imaging

Background-The reproducibility of contrast-enhanced MRI has not been established. We compared MRI reproducibility for infarct size determination with that of Tc-99m-sestamibi (MIBI) single photon emission computed tomography (SPELT). Methods and Results-Patients with chronic myocardial infarction defined by enzymes (peak creatine kinase-MB 173 +/- 119 U/L) were scanned twice by MRI (MRI I and MRI II, n=20) and twice by SPELT (SPELT I and SPELT II, n=15) on the same day. The MRI contrast agent was injected during MRI I but not MRI II to test the effect of imaging time after contrast. Resting Tc-MIBI SPELT images were acquired and infarct size was determined with commercial software. Infarct size in patients scanned by MRI and SPELT was 14 +/- 6% of left ventricular mass (%LV) by MRI (range 4%LV to 27%LV) and 14 +/- 7%LV by SPELT (range 4%LV to 26%LV). MRI I and 11 scans were performed 10 2 and 27 3 minutes after contrast, respectively. For MRI, the difference in infarct size between scans I and II (bias) was -0.1%LV, and the coefficient of repeatability was 2.4%LV. For SPELT, bias was -1.3%LV, and the coefficient of repeatability was +/-4.0%LV. Within individual patients, no systematic differences in infarct size were detected when the 2 MRI scans were compared, the 2 SPELT scans were compared, or MRI was compared to SPELT. Conclusion-The size of healed infarcts measured by contrast-enhanced MRI does not change between 10 and 30 minutes after contrast. The clinical reproducibility of contrast-enhanced MRI for infarct size determination compares favorably with that of routine clinical SPELT.