ECG pattern of left ventricular hypertrophy in nonobstructive hypertrophic cardiomyopathy: the significance of the mid-precordial changes.

A review of electrocardiograms from 33 patients with nonobstructive hypertrophic cardiomyopathy was made. In 22 patients there was noted a high QRS voltage, depression of the ST segment, and inversion of the T wave, satisfying the diagnostic criteria of left ventricular hypertrophy with the abnormal changes not only extending to the midprecordial leads but showing the most striking abnormal changes in Lead V4 in 20 patients. The frontal plane electrical axis was normal (around 60 degrees), with the most remarkable changes in Lead II. In the VCG, the magnitude of the QRS loop was increased and directed anteriorly and to the left, and the T loop was deviated posteriorly and to the right opposite the QRS loop. The asymmetric septal and apical hypertrophy was noted on echocardiography and/or angiocardiography. The coronary arteries were normal without significant obstruction in selective coronary angiography. It was postulated that the asymmetric septal and apical hypertrophy was reflected in this ECG pattern. The recognition of this ECG pattern provides pertinent information in the clinical detection of nonobstructive HCM.