[Electro-vectorcardiographic behavior of right bundle branch block in endocardial cushion defects. Its probable relation to the so-called left anterior fascicular hemiblock].

We have investigated the possible ECG signs of incomplete Left Anterior Hemiblock (LAH). As an experimental model we chose the endocardial cushion defect, which is proved to have a ventricular activation correspondent to different degrees of LAH due to the particular disposition of the AV node and the His bundle. The VCG of 50 patients with endocardial cushion defect were divided into 5 groups according to the entity of the left and superior deviation of the maximum left vector. Comparison with the ECG signs shows that: a) minimal degrees of LAH occur with simple counterclockwise rotation of the frontal loop without a significant left axis deviation; b) there is no linear correlation between the importance of the left axis deviation and the signs of left ventricular activation asincronism. We conclude that, with the exception of this particular congenital heart disease, minimal LAH degrees can only be suspected on the basis of a counterclockwise VCG frontal loop, because the ECG diagnosis is possible only when the left axis deviation becomes important.