Isolated ventricular septal defect of the persistent common atrioventricular canal type.

TN RECENT YEARS certain electrocardiographic patterns have come to be associated with the congenital cardiac malformation called "persistent common atrioventricular canal. " 1-4 Experience has shown, however, that the electrocardiographic features are not specific for that malformation. They may be observed also in cases in which both great vessels arise from the right ventricle without pulmonary stenosis,5 in certain cases of ventricular septal defect,6 in some cases of atrial septal defect of the ostium secundum type, and in certain cases of aequired heart disease. The same features are observed in cor triloculare biventriculare (common atrium), but this malformation may be considered a variant of persistent common atrioventricular canal.8 The purpose of this study was to review those cases of anatomically proved ventricular septal defect occupying the position of the ventricular component of the defect in the complete form of persistent common atrioventricular canal. An answer was sought to the question of whether this anatomic character of the ventricular septal defect could account for the electrocardiographic findings, namely, early QRS vectors being directed to the left and the QRS vectors in the frontal plane describing a counterclockwise loop and lying mostly superior to the isoelectric point. Search of the clinical, surgical, and pathologic files of the Mayo Clinic (involving 60