Question

Which one of the following statements regarding secundum atrial septal defect (ASD) is true?

• A. ECG shows a left-ward axis
• B. Atrial arrhythmias are uncommon
• C. Surgical correction is advisable when the pulmonary-to-systemic flow ratio (Qp:Qs) has reached 2:1
• D. Affected persons are usually symptomatic in childhood

Hint:

Think about how much extra blood flow through the defect is needed before the right heart's volume overload becomes worth operating on.

Answer 1

The Correct Option is C

This question tests the natural history, ECG pattern, and management threshold of secundum ASD.

1. ECG shows a left-ward axis: wrong - that pattern belongs to primum ASD; secundum ASD shows right axis deviation with an rsR' in V1.
2. Atrial arrhythmias are uncommon: wrong - chronic right atrial dilation in adults with ASD actually predisposes to atrial fibrillation and flutter.
3. Surgical correction advisable at Qp:Qs of 2:1: correct - once the shunt reaches this magnitude, closure is recommended to prevent right heart dilation and pulmonary vascular disease.
4. Usually symptomatic in childhood: wrong - most patients are asymptomatic in childhood and become symptomatic only in adulthood as right heart overload accumulates.

Correct answer: Surgical correction is advisable when the pulmonary-to-systemic flow ratio has reached about 2:1.