Diagnosis of ostium primum defects of the atrial septum

Atrial Septal Defect

The results of the electrocardiographic, vectorcardiographic, and hemodynamic studies of 70 patients with atrial septal defects are analyzed. Serial electrocardiograms and vectorcardiograms were obtained in 16 patients following surgery.

The incidence of the rSR' and rSr' patterns in the right precordial leads was 60 per cent.

To a limited extent, the configuration of the electrocardiogram is related to right ventricular pressure and PBF/SBF. However, no quantitative assessment could be made by determining the magnitude of R or R' in lead V 1 .

The vectorcardiogram is an important adjunct to the electrocardiogram in detecting right ventricular hypertrophy. As the right ventricular pressure increases, the QRS sÊ loop tends to shift more to the right and anteriorly.

Although it can be generally stated that the rSR' configuration in atrial septal defects is usually due to right ventricular hypertrophy, this configuration is also due to terminal conduction delay or terminal conduction delay associated with right ventricular hypertrophy in a significant number of instances.

The vectorcardiogram is useful in detecting terminal conduction delay in patients with rSR' in the right precordial leads. It was also of value in determining the presence of right ventricular hypertrophy in combination with terminal conduction delay.

The evidence of terminal conduction delay may disappear after successful repair of atrial septal defects.

Left axis deviation, superior displacement, and counterclockwise direction of inscription of the QRS sÊ loop in the frontal plane are valuable signs for differentiating ostium primum defects from ostium secundum defects. Each of the eight proved instances of ostium primum defects had these typical features.