Changes in cardiac tissue characterization in carriers with gene mutations associated with hypertrophic cardiomyopathy

Abstract

Background Early detection in patients with hypertrophic cardiomyopathy (HCM) is very important. Integrated backscatter (IB) provides a useful noninvasive measure of the acoustic properties of the myocardium, and may detect early myocardial changes. Methods Thirty-four carriers who had gene mutations causing HCM were studied. The patients were divided into three groups as follows: (1) 21 patients with wall hypertrophy (Group A), (2) 7 patients with ECG abnormalities but without wall hypertrophy (Group B), and (3) 6 carriers with neither ECG abnormalities nor wall hypertrophy (Group C). All subjects underwent ECG, conventional echocardiography and acoustic densitometry. In addition, we studied subjects ≤20 years old from Groups B and C (Group B-2 and Group C-2, respectively), and compared them with control subjects with no cardiac disorders who were ≤20 years old. Results In Group A, cyclic variations of integrated backscatter (CV-IB) in the interventricular septum and left ventricular posterior wall were significantly smaller than in Group C. The amplitude of IB in the interventricular septum and left ventricular posterior wall in Group A was significantly higher than those in Group C. Even in Group B, CV-IB in the interventricular septum was significantly smaller than those in Group C. Among patients ≤20 years old, CV-IB in the interventricular septum was significantly smaller in Group B-2 than in control subjects, while that in Group C-2 did not differ from that in control subjects. Conclusions Changes in tissue characterization were found in the hearts of HCM gene carriers even in the absence of wall hypertrophy. These results suggest that tissue changes detectable by the acoustic densitometry methods may occur in the hearts of HCM gene carriers without wall hypertrophy, and that they may be detectable at the time of appearance of ECG abnormalities.