In patients with acyanotic atrial septal defect (ASD), the shunt follows the left atrium - right atrium
- right ventricle route. If the defect is not small, shunt flow results in dilatations of left atrium, right atrium
and right ventricle.
If the ASD is not small, the result is dilatation of the left atrium, right atrium and right ventricle.
Below is the list of various ECG abnormalities that are reported in various types of ASD.
These are observed with increased frequency, but not necessarily in all ASD patients.
The most frequent ECG abnormalities in ASD are right bundle branch block (RBBB) pattern or
rsR' pattern in lead C1 . Complete RBBB is observed less frequently.
In patients with large ASD, presence of tall R or R' in lead C1 suggests development of
pulmonary hypertension .
Size of defect determines the shunt flow which in turn results in most of the ECG abnormalities.
If the ASD is very small, the ECG may be normal.