The electrocardiograms and vectorcardiograms of 29 patients with single ventricle are described and analyzed. The electrocardiographic and vectorcardiographic findings of these cases in relation to the anatomic position of the great vessels and the presence or absence of pulmonary stenosis were correlated. In the 10 cases of single ventricle with transposition of the great vessels with inversion, the electrocardiogram and vectorcardiogram exhibited an abnormal initial QRS vector in the horizontal plane directed posteriorly and to the left forming abnormal Q waves in the right precordial leads. The Q wave was absent in the left precordial leads of the scalar electrocardiogram. Right axis deviation was frequently observed. These features are commonly seen in congenital corrected transposition of the great vessels and indicate the importance of the position of the great vessels regardless of the presence of one or two ventricles. Among the 12 cases of single ventricle with transposition of the great vessels with the aorta anterior and to the right of the pulmonary artery, an abnormal direction of the initial QRS vector anteriorly and to the left was commonly observed. This was represented by absence of Q waves in the precordial electrocardiographic leads V1 through V6. Left axis deviation or an axis beyond -90 ° was frequently seen. On the other hand, in cases of single ventricle and normally related great vessels the QRS axis was commonly normal or slightly to the left, and there were stereotype Rs or rS patterns across the precordial leads. Although in our series the presence of pulmonary stenosis in single ventricle had no effect on the QRS pattern, it commonly altered atrial depolarization. Cases of single ventricle and pulmonary stenosis or pulmonary hypertension showed right atrial enlargement, but cases without pulmonary stenosis and with a large left to right shunt showed left atrial enlargement. The abnormal initial QRS vector on the vectorcardiogram observed in most cases of single ventricle as well as lack of a normal transitional zone of the precordial QRS complexes on the scalar electrocardiogram are perhaps the result of an abnormal ventricular conduction pathway.
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Twenty-nine patients were studied at the University of Minnesota Hospitals. The diagnosis of single ventricle was established in each case by angiocardiography and was confirmed by necropsy in 12 instances. Levocardia was present in all cases. Cases of asplenia, tricuspid atresia, mitral atresia and car biloculare were excluded from the study. Therefore, in each case, both atrioventricular valves were present and emptied into the single ventricle. Among the cases of single ventricle diagnosed an-giocardiographically, the characteristics of atrioventricular canal were not observed. The cases in this series have been classified according to the position of the great vessels.12 If the aorta lay in a plane anterior to the pulmonary artery, transposition of the great vessels was considered present. The cases with transposition of the great vessels were further divided into two groups depending upon the relation of the great vessels. In group I, transposition of the great vessels with inversion, the aorta was located anteriorly and to the left of the pulmonary artery. Group II, transpo- sition of the great vessels without inversion, was comprised of cases with the aorta located anteriorly and to the right of the pulmonary artery. Therefore, in group I the great vessels were in the position of congenitally corrected transposition of thr great vessels, whereas in group II their relation *From the Departments of Pediatrics and Pathology, University of Minnesota, Minneapolis and the Department of Pathology, The Charles T. Miller Hospital, St. Paul, Minn. This study was supported by U. S. Public Health Service Research Grant 5 ROl HE05694 and Research Training Grant 2 Tl HE05570 from the National