[Electrovectorcardiographic diagnosis of left ventricular hypertrophy in complete left bundle-branch block]

Diagnosis of left ventricular hypertrophy (LVH) in the presence of complete left bundle-branch block (CLBB) is difficult. The value of several electro-vectorcardiographic criteria were studied in a series of 71 patients with CLBB analyzed by echocardiography. Thirty nine of the patients (55%) had anatomical LVH defined as being a left ventricular weight (LVW) above 316 g. Twenty five of the 71 patients (35%) had dilated cardiomyopathy (dCMP). Of the hypervoltage indices, only the sum of RV6 + SV2 and the QRS spatial maximum vector (MAXQRSxyz) showed a significant difference between the group with LVH and the group without LVH. The duration of QRS and the average vector of spatial area (AQRSxyz) also differed significantly between the two groups and showed a good correlation with LVW. Of the various criteria for LVH, the best balance between sensitivity and specificity belonged to the criteria of duration of QRS greater than 150 msec and AQRSxyz greater than 140 mV.msec, with a merit ratio of 0.44 and a diagnostic accuracy of 72 per cent. In the dCMP subgroup, all the voltage and duration indices were significantly different between the two groups. The criterion AQRSxyz greater than 135 mV.msec obtained the best diagnostic score, with a sensitivity of 94 per cent, specificity of 100 per cent, and accuracy of 96 per cent. This parameter gave the best overall expression of the combination of hypervoltage and delay in ventricular depolarization produced both by hypertrophy/ventricular dilation and conduction disturbances.