Atrial septal defect electrocardiogram

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Electrocardiography

The ECG findings in atrial septal defect vary with the type of defect the individual has. Individuals with atrial septal defects may have a prolonged PR interval (a first degree heart block). The prolongation of the PR interval is probably due to the enlargement of the atria that is common in ASDs and the increased distance due to the defect itself. Both of these can cause an increased distance of internodal conduction from the SA node to the AV node.

Other EKG findings include the following:

1. Incomplete and less frequently complete Right Bundle Branch Block (RBBB) is often present.
2. Right Ventricular Hypertrophy (RVH) with strain suggests onset of pulmonary hypertension or associated pulmonic stenosis.
3. 2 out of 3 patients with an ostium secundum ASD have right axis deviation.
4. Patients with ostium secundum ASDs often develop atrial fibrillation or atrial flutter, and this occurs with a higher incidence with increasing age and with pulmonary hypertension.
5. Sinus venosus ASDs are often associated with low atrial and junctional rhythms.
6. Ostium primum ASDs are associated with a marked left axis deviation.
7. Individuals with a sinus venosus ASD exhibit a left axis deviation of the P wave (not the QRS complex).

12 lead EKG shows the rSR' pattern in V1 (R' greater than S with T wave inversion which is commonly seen in volume overload in Right Ventricular Hypertrophy)