938-59 Ultrasound Biopsy: A Novel Technique for Nondestructive Intracardiac Tissue Characterization

Abstract

We have previously demonstrated that ultrasonic tissue characterization with transthoracic imaging can differentiate between normal and infarcted myocardium. To determine whether intracardiac echocardiography differentiates normal myocardial tissue from fibrous scar, we used a 12 MHz intravascular ultrasound catheter to study myocardial infarction in 4 Yorkshire pigs 3 months after distal left anterior descending coronary artery occlusion. All hearts were imaged with identical TGC and gain settings. Ten frames were analyzed for each heart with the use of videodensitometry. Average gray scale pixel intensity was computed off-line for normal and infarct regions of interest after digitization of the ten image frames. Normal regions adjacent to infarct were selected for comparison in the same circumferential TGC field. Mason-Trichrome stain was used to corroborate the location of infarct tissue in histologic sections for comparison with intracardiac echocardiography. In general, greater backscatter was observed from infarcts than from normal tissue. The mean pixel value (signal intensity) for infarct tissue sUbstantially exceeded that for normal myocardium (224 ± 11 * and 147 ± 5 for infarct vs. normal, respectively; p < 0.001). Similarly, the collagen content of infarct tissue (218 ± 84 mg/g LV) markedly exceeded that of normal myocardium (36.6 ± 2.5 mg/g LV). Thus, quantitative estimation of the scattering behavior of normal and pathologic myocardial tissue is feasible with intracardiac echocardiography, which holds promise for clinical delineation of infarct regions during cardiac catheterization.