Limitations in Assessment of Acute Myocardial Infarction

Two hundred-three patients had technetium 99m (stannous) pyrophosphate myocardial scintigrams for the evaluation of chest pain and suspected acute myocardial infarction. In addition to routine imaging at 60-90 minutes after injection of the radiopharmaceutical, the blood pool was imaged immediately in each patient for comparison with routine anterior, left anterior oblique, and left lateral views. Further delayed studies were obtained when residual blood pool activity was identified. Seventy patients had acute myocardial infarction by clinical, electrocardiographic, and enzymatic (CK-MB) criteria. Sixty-five of these 70 patients with acute infarction had positive myocardial scintigrams, with one technically unsatisfactory study. Only four of the 70 patients had negative scintigrams when imaged 18-72 hours after infarction in this study. Technically satisfactory scintigrams were recorded in 125 patients without evidence of infarction. Ninety-six had negative scin-