Ultrasound characterization of acoustic properties of acute intracardiac thrombi: studies in a new experimental model.

Echocardiographic differentiation among intracavitary thrombus, cavity noise, and adjacent myocardium can be difficult. As an initial step toward quantitative thrombus characterization with ultrasound, 11 dogs were studied with an in vivo intracardiac thrombus model to delineate the acoustic properties of acute thrombi. The apical coronary arteries were ligated, and subsequently injections of 5% sodium rescinoleate and 1000 units of thrombin at the endocardium-blood interface created left ventricular mural thrombi. Echocardiographic images were obtained in long- and short-axis views with a digital acquisition system, and a statistical analysis of echo intensities was performed in regions of interest in the thrombus, surrounding ventricular cavity and adjacent myocardium. Statistical measurements used to evaluate echo intensities in each region of interest included mean gray level, standard deviation, skewness, and kurtosis. The results showed that thrombus could be distinguished from myocardium (by mean gray level and standard deviation) only in short-axis views, where regions of interest could be placed at similar depths of field. Mean gray level, standard deviation, and skewness all distinguished thrombus from intracavitary blood regardless of the region of interest placement. The phase of the cardiac cycle at which data were acquired did not alter the results. We conclude that acute intracardiac thrombi can be distinguished from surrounding blood and myocardium with ultrasound tissue characterization techniques that may have the potential for clinical application.