Which EKG findings are typical for atrial septal defect (ASD)?

In the context of atrial septal defect (ASD), right atrial enlargement is a hallmark EKG finding. An ASD allows for the shunting of blood from the left atrium to the right atrium, leading to volume overload in the right atrium. This extra volume causes the right atrial wall to dilate, which can be visualized on an EKG as an enlargement.

Common EKG features associated with right atrial enlargement include a peaked P wave, known as P pulmonale, which signifies the increased electrical activity due to the enlarged right atrium. This EKG change occurs because the right atrium has to handle more blood volume than normal, and the associated enlargement can also lead to conduction delays in the right atrium, contributing to potential arrhythmias.

In contrast, conditions like left ventricular hypertrophy or biatrial enlargement do not primarily arise from ASD and are influenced by different hemodynamic changes. First-degree heart block is related to conduction disturbances rather than the volume overload mechanisms seen with ASDs. Hence, the presence of right atrial enlargement on EKG is the most characteristic finding in patients with an atrial septal defect.