Six cases of patent ductus arteriosus were studied by Frank system VCG, after that the operation was performed on all of them, and the following results were obtained.
QRS maximum vectors were inscribed to left inferiorly and posteriorly in most of the cases and the direction was around +30° in the frontal plane projection. Only one case was inscribed to right inferiorly and posteriorly. T maximum vectors were inscribed to left inferiorly and posteriorly and directed more vertically than the maximum QRS vectors. The direction of QRS and T loop inscription was normal in the right sagittal plane and the horizontal plane projections. However, in the frontal plane projection the direction was remarkably variable-in the counterclockwise direction in four cases, in the figure of eight pattern in one case and in the clockwise direction in one case in the QRS loop, in the counterclockwise direction in two cases and in the clockwise direction in four cases in the T loop.
Vectorcardiographically two cases showed the normal pattern, two cases left ventricular hypertrophy, one case the changing pattern to left ventricular hypertrophy and one case right ventricular hypertrophy. Maximum QRS vectors with high oxygen saturation in the right ventricle were directed around 30° in the frontal plan projection and the direction was more vertical with less than 70% oxygen saturation.
Maximum QRS vectors in the frontal plane with more than 50 mmHg of the pulmonal systolic pressure were inscribed in the vertical position.
One case of right axis deviation was changed to normal 3 months after the operation.
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