M mode echocardiography in hypertrophic cardiomyopathy: Diagnostic criteria and prediction of obstruction

Abstract

To assess the reliability of the classic echocardiographic features in the heart with hypertrophic cardiomyopathy as criteria that differentiate it from normal heart and as predictors of outflow tract obstruction versus nonobstruction, 70 patients with clinical and angiographic evidence of hypertrophic cardiomyopathy were studied with M mode echocardiography. The diagnostic sensitivity and specificity of the classic features were assessed: ventricular septal thickness, 83 and 94 percent (sensitivity and specificity, respectively); ventricular septal amplitude of movement, 71 and 89 percent; ventricular septal thickness to left ventricular posterior wall ratio, 79 and 94 percent; left ventricular end-systolic dimension, 54 and 86 percent; septal-mitral valve distance at the onset of systole, 29 and 100 percent; systolic anterior motion of the mitral valve, 61 and 100 percent; and mid systolic closure of the aortic valve, 61 and 100 percent. No single M mode echocardiographic feature was consistently abnormal in hypertrophic cardiomyopathy. In nonobstructive hypertrophic cardiomyopathy, ventricular septal thickness greater than or equal to 13 mm (sensitivity 68 percent and specificity 94 percent) and ventricular septal thickness to posterior wall ratio greater than or equal to 1.5 (sensitivity 82 percent and specificity 94 percent) were the individual features with the greatest diagnostic value from the norm. Patients with obstruction at rest and labile obstruction (gradient only on provocation) had echocardiographically identical features. Ventricular septal thickness greater than or equal to 13 mm plus systolic anterior motion of the mitral valve or mid systolic closure of the aortic valve were the features that in combination best differentiated obstructive (resting and labile) from nonobstructive hypertrophic cardiomyopathy (sensitivity 82 percent and specificity 68 percent) and the heart with obstructive hypertrophic cardiomyopathy from the normal heart (sensitivity 82 percent and specificity 100 percent).