Background: Hypertrophic cardiomyopathy is an autosomal dominant inherited disorder. On a routine clinical basis, genetic analysis is both time consuming and impractical at present. Thus, use of tissue Doppler imaging as a surrogate for genetic screening is an attractive option.
Methods and results: Fifty-five first-degree relatives of 15 patients with hypertrophic cardiomyopathy were screened. Of them, two were found to have hypertrophic cardiomyopathy and were included in Group 1, which hence had 17 patients with overt hypertrophic cardiomyopathy. Group 2 had 53 family members who did not manifest any overt echocardiographic abnormality. Twenty healthy volunteers comprised Group 3. Doppler tissue myocardial longitudinal velocities were measured in systole and early diastole and with atrial contraction at the medial mitral annulus, lateral mitral annulus, mid lateral wall and mid interventricular septum. The tissue Doppler characteristics were analyzed for the presence of abnormalities suggestive of subclinical myocardial involvement. Myocardial velocities were highest in the normal control group and lowest in the hypertrophic cardiomyopathy group. The velocities of the relatives without overt hypertrophy were intermediate in range. Of the 53 relatives screened, nine (17%) subjects showed tissue Doppler abnormality in the systolic and early diastolic velocities at the medial and lateral mitral annulus suggestive of a possibility of pre-clinical hypertrophic cardiomyopathy and a carrier state for a hypertrophic cardiomyopathy. Twenty-two of the 53 screened members had a mean early diastolic velocity less than 13.5 cm/s, among this group 9 had an ejection fraction more than 68%. These findings suggest that at least 16.7% of the screened population may carry beta-myosin heavy chain mutation.
Conclusions: Screening for hypertrophic cardiomyopathy is feasible and tissue Doppler imaging is a sensitive and easy means to detect subclinical myocardial involvement in apparently normal family members without overt hypertrophy.