The Electrocardiogram in Tricuspid Atresia and Pulmonary Atresia with Intact Ventricular Septum

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Abstract
Electrocardiograms were studied in 37 patients with tricuspid atresia and in 20 with pulmonary atresia and intact ventricular septum. The results were correlated with angiocardiographic findings and postmortem examinations. Differential features were as follows: 1. Biatrial hypertrophy with characteristic P "tricuspidale" was noted in 81% of the electrocardiograms in patients with tricuspid atresia, whereas this pattern was seen in only two infants with pulmonary atresia and intact ventricular septum. 2. In tricuspid atresia, left axis deviation was usually directed posteriorly; however, anmal or right axis deviation was present in seven cases, six of whom were type 2C and the seventh, type 1A. In every case the horizontal QRS axis was oriented posteriorly. By contrast, in patients with pulmonary atresia there were no instances of left axis deviation in the frontal plane. Normal frontal plane axis was present in 12 patients, all of whom were type I; right axis deviation was evident in eight patients including the three infants with type II deformity. The horizontal QRS axis was usually directed posteriorly; however, anterior orientation occurred in several patients. 3. A typical feature of the vectorcardiogram in patients with tricuspid atresia was the increased anterior magnitude of the initial forces followed by a sharp posterior shift. The initial forces in patients with pulmonary atresia were not characteristic. 4. The electrocardiographic features in patients with tricuspid atresia and normal position of the great vessels showed decreased right ventricular potentials consistent with true hypoplasia of the right ventricle, but in patients with pulmonary atresia similar lack of right ventricular potentials could be correlated with decreased right ventricular cavity, whereas the ventricular wall was actually hypertrophied.