CHANGES IN ULTRASONIC-ATTENUATION INDICATIVE OF EARLY MYOCARDIAL ISCHEMIC-INJURY

Whether quantitative alterations in ultrasonic attenuation are associated with myocardial changes occurring after acute ischemic injury was determined. From 41 dogs, 517 regions of myocardium were studied in vitro at 5 intervals after coronary occlusion: 15 min, 1 h, 6 h, 24 h, 3 days and 6 wk. Quantitative indices of ultrasonic attenuation were determined from the measured frequency dependence of the ultrasonic attenuation coefficient characterizing each myocardial region over the range 2-10 MHz. Independent definition of regions of ischemic injury was provided by creatine kinase depletion or colloidal carbon dye distribution. Ischemic myocardial regions investigated 15 min to 24 h after coronary occlusion demonstrated ultrasonic attenuation significantly decreased from nonischemic regions (P < 0.05). Ultrasonic attenuation was significantly increased in zones of ischemia or infarction investigated at 3 days and 6 wk after coronary occlusion (P < 0.05 and P < 0.01, respectively). Apparently altered attenuation of transmitted ultrasound by myocardium in vitro is an early manifestation of ischemia.