THE P WAVE IN ATRIAL SEPTAL DEFECT

Abstract

The P waves in the electrocardiograms from 106 patients with atrial septal defect have been studied and compared with those found in normal subjects and patients with pulmonary stenosis. Of the patients, 84 had ostium secundum or sinus venosus defects, and in this group the correlation of the P wave pattern and the hemodynamic changes has been analysed. The ostium secundum group of ASD patients generally have a slightly wider PII than the normal subjects or the patients with pulmonary stenosis, and the upstroke time is prolonged. Both the width and the upstroke time show statistically significant correlation with the volume of the left-to-right shunt: the product of these two measurements has some value in predicting the size of the shunt. This type of P wave was not found in four patients with pulmonary stenosis and ASD in whom there was no L-R shunt. It is concluded that the wide PII with a slow upstroke is the electrocardiographic pattern reflecting diastolic overloading of the right atrium as contrasted with the tall, narrow PII found with pulmonary stenosis, which reflects systolic overloading of the right atrium. In patients with ASD and some pulmonary hypertension the P wave is increased in height as well as showing the above features: this is the pattern reflecting systolo-diastolic overloading. Nearly half the ASD patients (in both ostium primum and ostium secundum varieties) showed a biphasic P in V1, and many of these also had bifid P waves in V6. It is possible that this reflects some coexisting left atrial enlargement. PII was even wider and more often bifid in the ostium primum group than in the ostium secundum group, and this may be due to a greater degree of left atrial enlargement in these cases because of associated mitral regurgitation.