Cardiac hypertrophy in hypertrophic cardiomyopathy and hypertension evaluated by echocardiography and body surface isopotential mapping.

To elucidate the useful indices for differentiating cardiac hypertrophy due to essential hypertension (EH) from that due to hypertrophic cardiomyopathy (HCM), we examined standard 12-lead ECGs, chest radiographs and echocardiograms (Echo) in 66 EH and 46 HCM cases. Body surface isopotential mappings (MAPs) were recorded in 16 cases of EH and 18 of HCM. The thickness of the interventricular septum (IVST) and the IVST/PWT ratio (PWT = the thickness of the posterior wall) were greater and left ventricular diastolic diameter (LVDd) was smaller in the HCM group than in the EH group. The septal activation time (SAT), the time interval during which the maximum positive potential moves from the mid-sternal line or the left sternal border to the left mid-clavicular line in the QRS complex, correlated directly with the IVST (r = 0.55, p less than 0.005) and the IVST/PWT ratio (r = 0.61, p less than 0.005). When the SAT was longer than 30 msec, the IVST was over 25 mm and the IVST/PWT ratio was over 2.0, all cases belonged to the HCM category. When subjects were limited to patients with IVST less than 25 mm, the SAT of the HCM group was significantly greater than that of the EH group. These data suggest that the SAT may reflect the etiological differences between the septal hypertrophy of the EH group and that of the HCM group, and that these parameters of MAPs may be helpful to distinguish cardiac hypertrophy due to EH from that due to HCM.