Myocardial ultrasonic tissue characterization in patients with different types of left ventricular hypertrophy: A videodensitometric approach

Abstract

Although analysis of the radio frequency signal is the most accurate approach to myocardial tissue characterization, clinical diffusion has been limited because of the complex technology required. Much easier to perform, videodensitometric analysis could represent a valuable alternative. Previous works carried out on radio frequency data have shown that the absolute value of ultrasonic back scatter increases while its diastole-to-systole variation decreases in the hypertrophied myocardium. This study was aimed at clarifying whether alterations in characterization indexes of ultrasonic tissue can be detected by means of a videodensitometric approach, whether a specific type of left ventricular (LV) hypertrophy can be identified with this method, and finally what possible relationships exist between parameters of contractile function and tissue characterization indexes. Myocardial echo intensity (MEI), its cyclic variation (CV), and the dynamic relationship between myocardial signal and wall thickness variations during the cardiac cycle were assessed in 20 healthy subjects, 11 patients with essential hypertension and LV hypertrophy, 15 patients with hypertrophic cardiomyopathy, and 4 patients with primary amyloidosis. The CV was lower in the interventricular septum of patients with cardiac hypertrophy as a group, compared with that of control subjects (13.0% +/- 5.6% versus 18.8% +/- 5.5%, p < 0.001), but it was similar among patients with different types of hypertrophy. In control subjects, a significant inverse correlation was found between the progressive decrease of the myocardial signal and the parallel increase in wall thickness during systole; this correlation was lost in 60% of patients with hypertrophic cardiomyopathy and 50% of those with amyloidosis, but only in 9% of patients with essential hypertension (chi square analysis 12.68, p < 0.01). The CV was associated with systolic wall thickening (r = 0.53, p = 0.0001) and fractional shortening (r = 0.44, p = 0.0014). MEI and its CV per se cannot distinguish among different types of LV hypertrophy; however, the loss of an inverse relationship between the myocardial signal and wall thickness may suggest abnormal myocardial conditions in individual patients with the same disease or comparable wall thickness.