Ultrasonic Characterization of Canine Myocardium Contraction

Absfracf-Other investigators have found ultrasonic backscatter from canine myocardium to exhibit a significant variation throughout the cardiac cycle. Also, several studies have shown a change in an ultrasonic property of canine myocardium when ischemia is induced. In an attempt to gain some understanding of the physical mechanisms responsible for these variations, several ultrasonic measurements were made on canine papillary muscle in vitro during both isotonic (constant load) and isometric (constant length) contractions. Integrated backscatter was found to exhibit a significant cyclic variation (p < 0.05) during isotonic (constant load) contractions, but not during isometric (constant length) contractions. This result suggests that the variation in the physical arrangement of structures within the tissue that occurs during contraction plays an important role in determining ultrasonic backscatter. No significant cyclic variation was found in the backscattered signal envelope statistics or in acoustic attenuation during either isotonic or isometric contractions.