An electrocardiographic and vectorcardiographic analysis of 37 cases of corrected transposition revealed that characteristic findings were uniformly present in those cases (group I) in which the cardiac apex was on the expected or correct side in relation to the atrial chambers (on the left in situs solitus; on the right in situs inversus). When dextroversion was present (group II), however, many of these features were absent. The findings typical of the 30 cases in group I were initial QRS vectors directed to the left, anteriorly and superiorly; corresponding electrocardiographic findings of Q waves in the right precordial leads (V4R and/or V1) and in lead III with absence of the Q wave in lead V6; and corresponding vectorcardiographic findings of absence of the Q loop (represented by a leftward, straight initial efferent limb of the QRS loop in the horizontal plane). Comparative vectorcardiographic analysis of 25 cases in group I (study group) and 78 control cases without corrected transposition but with comparable associated malformations and hemodynamic states, revealed that the aforementioned characteristic vectrocardiographic findings in the study group were effective in distinguishing between the two groups. Otherwise, the patterns of ventricular hypertrophy in the cases with corrected transposition were, in most cases, similar to those of the control cases. The electrocardiographic and vectorcardiographic findings in the 7 cases with dextroversion (group II) were more variable, depending, in part, on the degree of dextroversion. There were, however, such findings as absence of the normal Q loop in the vectorcardiogram in 4 cases and absence of the Q waves in the left precordial leads in 5 cases, which may represent characteristic features of corrected transposition when dextroversion is present. In the over-all approach to the diagnosis of corrected transposition with or without associated cardiac anomalies, the vectorcardiogram proved to be a valuable adjunct to the electrocardiogram in characterizing the electrical events which produce the unusual electrocardiographic features of this condition.
Bibliographical noteFunding Information:
Minn. and the Department of Pathology, The Charles T. Miller Hospital, St . Paul, Mine . This study was supported by Research Grant HE-5694, Training Grant 5 TI IIE-5570 and through Postdoctoral Fellowship (HF 13, 715) of the National Institutes of Health, U . S . Public Health Service . t Present address : Department of Pediatrics, University of California at Los
Copyright 2018 Elsevier B.V., All rights reserved.