Wideband High-Frequency Echocardiography to Evaluate Myocardial Infarct Size

Abstract

Objective. This study was designed to validate the feasibility of wideband high-frequency ultrasound imaging to resolve in vivo the degree, location, and morphologic changes of myocardial infarction (MI) in a rat model. Methods. The left anterior descending coronary artery was ligated in the test group (n = 41), and the sham control group did not have ligation (n = 7). The rats were examined with 10-to 22-MHz echocardiography to evaluate the MI size, location, and geometric formation. Results. The endocardial chamber shape was deformed, with enlargement of the anteroposterior dimension and fractional shortening, and was comparable with the degree of MI both in short-and long-axis sections of the left ventricle. Histologic analysis showed remodeling to different extents corresponding to different MI sizes (small, medium, and large). Conclusions. The results suggest that this technique can be used in vivo to evaluate the MI location, size, and morphologic changes corresponding to the extent of the injury. Key words: high-frequency ultrasound imaging; histologic analysis; left anterior descending coronary artery; myocardial infarction. he rat is a preferred species for studying the pathophysiologic mechanisms of myocardial infarction (MI), cardiomyopathy, and other cardiovascular diseases. 1,2 Noninvasive in vivo study of rat cardiac structure and function has attracted interest in cardiovascular research, especially those involving the left ventricle (LV). The rat infarct model has been used extensively to study LV dysfunction after MI and in the evaluation of experimental therapies for heart failure. 3,4 Two-dimensional (2D) B-mode, M-mode, and Doppler ultrasound have been used to evaluate LV structural and functional remodeling in humans for decades, particularly in patients with MI during the acute phase and for later follow-up. However, the small size and rapid heart rate (300-500 beats per minute) of the rat heart demand an imaging modality with both high temporal resolution and high spatial resolution. 5,6 Recently developed high-resolution echocardiographic systems with high frequencies (>20 MHz) are particularly well suited for the study of the heart in rodent models of MI. These systems can be used for evaluating the heart contractility, mainly LV systolic and diastolic function.

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