Vectocardiography in tetralogy of Fallot before and after operation (palliative and corrective surgery).

Vectorcardiograms from 55 patients with diagnosed tetralogy of Fallot were studied and divided into the following three groups: A, 35 nonoperated cases; B, 23 with systemic-pulmonary shunt (nine studied preoperatively and also in A); and C, ten after total correction. In group A, two different types of QRS loop occurred in the horizontal plane (HP); 23 clinically and hemodynamically severe cases had right anterior position with clockwise (C) rotation, and 12 less severe cases had right posterior position with counterclockwise (CC) rotation or figure-8 morphology. In the frontal plane the QRS loop was located inferiorly and to the right, with C rotation (80 percent); two cases had the left anterior hemiblock (LAHB) pattern, and another two severe cases had CC rotation and right superior position. Group B had an evident increase of left ventricular forces in the HP, compared with group A; group-B rotation was preferentially CC or figure-8 morphology. Group C had a pattern of right bundle-branch block in nine cases (classic in one and uncharacteristic in eight); four cases also had LAHB.