Detection and localization of recent myocardial infarction by magnetic resonance imaging.

The potential of magnetic resonance imaging (MRI) to detect and localize acute myocardial infarction (AMI) in 27 patients a mean interval of 15 days after AMI was evaluated. Eighteen asymptomatic volunteers were also studied to determine the specificity of the observations. The diagnosis of AMI was established by conventional criteria; the infarct was localized by electrocardiography in all patients, technetium pyrophosphate scintigraphy in 19 and necropsy in 1 patient. MRI detected increased myocardial signal intensity in 88%, cavitary signal in 74% and regional wall thinning in 67% of the patients. At least 1 of these 3 features was seen in the area of the infarct in each patient. The sensitivity of these MRI observations was not influenced by location of the infarct or presence of Q waves. Asymptomatic volunteers also had increased myocardial signal in 83%, cavitary signal in 94% and wall thinning in 11% of cases. Some patients had these findings in myocardial segments not suspected of being involved by recent or remote AMI. It is concluded that AMI can be detected by MRI performed an average of 15 days after infarction. However, the hearts of normal volunteers and apparently normal myocardial segments of patients with AMI may have the MRI findings previously associated with AMI. Of these findings, wall thinning was the most predictive of and specific for AMI.