Question:
Which one of the following statements regarding secundum atrial septal defect (ASD) is true?
Which one of the following statements regarding secundum atrial septal defect (ASD) is true?
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Think about how much extra blood flow through the defect is needed before the right heart's volume overload becomes worth operating on.
Updated On: Jul 16, 2026
- ECG shows a left-ward axis
- Atrial arrhythmias are uncommon
- Surgical correction is advisable when the pulmonary-to-systemic flow ratio (Qp:Qs) has reached 2:1
- Affected persons are usually symptomatic in childhood
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The question asks which single statement about a secundum atrial septal defect, the most common type of ASD located in the region of the fossa ovalis, is actually correct.
Step 2: Key Concept or Approach:
A secundum ASD causes chronic left-to-right shunting with right atrial and right ventricular volume overload. The degree of shunting is quantified as the pulmonary-to-systemic flow ratio (Qp:Qs); once this ratio becomes significant, generally around 1.5-2:1, the volume load is enough to justify closing the defect to prevent progressive right heart dilation and eventual pulmonary vascular disease.
Step 3: Working Through the Options:
A left-ward ECG axis is characteristic of a primum ASD, where the defect involves the endocardial cushions and disturbs the normal conduction axis; a secundum ASD instead typically shows a right-ward axis with an rsR' pattern in V1 from right ventricular volume overload, so this statement is false for the secundum type. Atrial arrhythmias such as atrial fibrillation and flutter are actually common in adults with a long-standing secundum ASD because of chronic right atrial dilation, so calling them 'uncommon' is false. Surgical or catheter closure is advised once the shunt becomes haemodynamically significant, conventionally when Qp:Qs reaches about 1.5-2:1, which matches the statement given. Most patients with secundum ASD are asymptomatic through childhood, only becoming symptomatic in the third or fourth decade as the chronic volume overload catches up with the right heart, so 'usually symptomatic in childhood' is false.
Step 4: Conclusion:
Surgical correction being advisable once the pulmonary-to-systemic flow ratio reaches about 2:1 is the true statement.
The question asks which single statement about a secundum atrial septal defect, the most common type of ASD located in the region of the fossa ovalis, is actually correct.
Step 2: Key Concept or Approach:
A secundum ASD causes chronic left-to-right shunting with right atrial and right ventricular volume overload. The degree of shunting is quantified as the pulmonary-to-systemic flow ratio (Qp:Qs); once this ratio becomes significant, generally around 1.5-2:1, the volume load is enough to justify closing the defect to prevent progressive right heart dilation and eventual pulmonary vascular disease.
Step 3: Working Through the Options:
A left-ward ECG axis is characteristic of a primum ASD, where the defect involves the endocardial cushions and disturbs the normal conduction axis; a secundum ASD instead typically shows a right-ward axis with an rsR' pattern in V1 from right ventricular volume overload, so this statement is false for the secundum type. Atrial arrhythmias such as atrial fibrillation and flutter are actually common in adults with a long-standing secundum ASD because of chronic right atrial dilation, so calling them 'uncommon' is false. Surgical or catheter closure is advised once the shunt becomes haemodynamically significant, conventionally when Qp:Qs reaches about 1.5-2:1, which matches the statement given. Most patients with secundum ASD are asymptomatic through childhood, only becoming symptomatic in the third or fourth decade as the chronic volume overload catches up with the right heart, so 'usually symptomatic in childhood' is false.
Step 4: Conclusion:
Surgical correction being advisable once the pulmonary-to-systemic flow ratio reaches about 2:1 is the true statement.
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