Hypertrophic cardiomyopathy with unusual locations of left ventricular hypertrophy undetectable by M-mode echocardiography. Identification by wide-angle two-dimensional echocardiography.

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Abstract
Twenty-one patients without evidence of hypertrophy by M-mode echocardiography were studied by wide-angle two-dimensional echocardiography to determine if they had a form of hypertrophic cardiomyopathy that could not be detected by conventional M-mode echocardiography. Each patient was suspected clinically of having hypertrophic cardiomyopathy because of a distinctly abnormal ECG and either a family history of hypertrophic cardiomyopathy or cardiac symptoms. Patients were 5-49 years old (mean 16 years) and 16 of the 21 had no functional limitation. The most common electrocardiographic abnormalities were deep Q waves, T-wave inversion and right ventricular hypertrophy. Using wide-angle two-dimensional echocardiography to reconstruct the geometry of the left ventricular wall, 16 of the 21 patients (76%) were shown to have prominent but unusually located regions of left ventricular wall hypertrophy. In each instance, the hypertrophy involved regions of the left ventricular wall through which the M-mode ultrasound beam does not usually pass, i.e., posterior ventricular septum (seven patients), anterior or lateral left ventricular free wall (seven patients) and ventricular septum near the apex (two patients). There was no echocardiographic or hemodynamic evidence of left ventricular outflow tract obstruction in any patient. Hence, some patients with hypertrophic cardiomyopathy may have substantial hypertrophy present in unusual locations of the left ventricular wall. Although electrocardiographic abnormalities suggested the presence of myocardial disease, conventional M-mode echocardiography (performed from standard parasternal positions) did not reliably identify such sites of hypertrophy, which were limited to regions of the left ventricle not accessible to the M-mode beam. Only wide-angle two-dimensional echocardiography permits definitive identification of these unusually located regions of cardiac hypertrophy and confirmation of the diagnosis of hypertrophic cardiomyopathy.