Magnetic resonance imaging in patients with unstable angina: Comparison with acute myocardial infarction and normals

The role of magnetic resonance imaging in characterizing normal, ischemic and infarcted segments of myocardium was examined in 8 patients with unstable angina, 11 patients with acute myocardial infarction, and 7 patients with stable angina. Eleven normal volunteers were imaged for comparison. Myocardial segments in short axis magnetic resonance images were classified as normal or abnormal on the basis of perfusion changes observed in thallium-201 images in 22 patients and according to the electrocariographic localization of infarction in 4 patients. T₂ relaxation time was measured in 57 myocardial segments with abnormal perfusion (24 with reversible and 33 with irreversible perfusion changes) and in 25 normally perfused segments. T₂ measurements in normally perfused segments of patients with acute myocardial infarction, unstable angina and stable angina were within normal range derived from T₂ measurements in 48 myocardial segments of 11 normal volunteers (42 ± 10 ms). T₂ in abnormal myocardial segments of patients with stable angina also was not significantly different from normal. T₂ of abnormal segments in patients with unstable angina (64 ± 14 in reversibly ischemic and 67 ± 21 in the irreversibly ischemic segments) was prolonged when compared to normal (p < 0.0001) and was not significantly different from T₂ in abnormal segments of patients with acute myocardial infarction (62 ± 18 for reversibly and 66 ± 11 for irreversibly ischemic segments). The data indicate that T₂ prolongation is not specific for acute myocardial infarction and may be observed in abnormally perfused segments of patients with unstable angina. Alternatively prolonged T₂ in patients with unstable angina may be a marker of subclinical myocardial necrosis and may carry prognostic importance.