Ultrasonic Detection of Myocardial Infarction by Amplitude Analysis

Myocardial infarctions were produced in dogs by occluding the left anterior descending artery; the dogs were killed at varying times, from 30 minutes to 8 days. Prior to sacrifice, Thioflavin S was injected intravenously. The excised heart was scanned by a B-scanner interfaced with a computer that permitted quantification of signal amplitude. The heart was sectioned, photographed, and studied pathologically. Infarcted myocardium showed high ultrasonic reflectivity with average amplitudes 1.4–2.6 times that of normal muscle. Perfusion-histomorphologic evidence of infarction correlated best in infarcts of 24 hours or less; older infarcts were generally underestimated. Tissue changes, sources of false-positive and false-negative findings, signal processing, and potential clinical utility are discussed.