Determination of the hypertrophic site of the left ventricle by body surface mapping in patients with hypertension.

To estimate the hypertrophic sites of the left ventricle by body surface mapping (MAP), we performed MAP in 55 patients with hypertension and compared the MAP data with echocardiographic findings. MAP data were analyzed using the departure map technique reported by Flowers et al. The mean and standard deviation (SD) of the normal control were obtained from 40 normal volunteers. We constructed departure maps at 20, 30, 40, 50 and 60 msec from the onset of the QRS. Each map indicates the area of abnormally increased potential outside the normal range at the time. Subjects were classified into 5 groups according to the appearance time of the abnormal positive area. Septal thickness was significantly increased in groups that had an abnormal positive area at 20 msec, and left ventricular posterior wall thickness was significantly increased in the groups that had an abnormal positive area at 60 msec. We postulate that the increased electrical potential due to hypertrophy of the interventricular septum is represented by the abnormal positive area at 20 msec, and the increased potential of the left ventricular posterior wall by the abnormal positive area at 60 msec. MAP, especially the departure map technique, is a useful method to detect the abnormal electrical potential distribution in patients with left ventricular hypertrophy.