Magnetic resonance imaging during acute myocardial infarction.

Experimental canine studies have demonstrated the potential of magnetic resonance imaging (MRI) for detecting and characterizing acute myocardial infarction (AMI) in humans. Accordingly, electrocardiographic-gated spin-echo MR images of the left ventricular short axis were obtained in 34 patients a mean of 11 +/- 6 days (range 3 to 30) after AMI. This imaging technique allowed division of the left ventricle into segments corresponding to the left ventricular segments on angiography. Patients were separated into 2 groups; the first 16 patients (group I) were examined using a variety of imaging techniques. Information derived from this experience resulted in a standard imaging protocol and development of criteria for the presence of AMI. The imaging protocol and interpretation criteria were used in the assessment of a subsequent group of 18 patients (group II). Of the 14 patients in group II with satisfactory image quality, all showed an increase in myocardial signal intensity consistent with an AMI. In addition, the anterior or inferior location of the abnormal MR segments corresponded to the electrocardiographic infarct location. MR segments showing increased signal intensity corresponded with severely hypokinetic or akinetic segments on the left ventriculogram in 8 patients having both procedures. In a group of volunteers who underwent imaging and whose images were interpreted in the same manner as those of the patients with AMI, 1 of 9 subjects had regional variation in myocardial signal intensity compatible with an AMI. In summary, AMI is readily detected, located and characterized by electrocardiographic-gated MRI. These findings suggest that MRI techniques may have a role in the evaluation of AMI in humans.