American Board of Internal Medicine (ABIM) Certification Practice Exam

What murmurs are typically associated with atrial septal defect?

1. Diastolic murmur over the aortic area

2. Continuous machinery murmur

3. Midsystolic pulmonary flow murmur

4. Holosystolic murmur at the apex

The correct answer is: Midsystolic pulmonary flow murmur

In the context of atrial septal defects (ASD), a midsystolic pulmonary flow murmur is typically associated due to increased blood flow across the pulmonary valve. The presence of a left-to-right shunt caused by the defect leads to enhanced circulation in the right atrium and subsequent increased volume passing through the pulmonary arteries. This elevated volume results in turbulence and a resultant midsystolic murmur that is best heard at the left upper sternal border, often described as a soft, systolic ejection type murmur. The other murmurs listed are characteristic of different cardiac conditions. For instance, a diastolic murmur over the aortic area is associated with aortic regurgitation, while a continuous machinery murmur is indicative of a patent ductus arteriosus. A holosystolic murmur at the apex is typically heard in cases of mitral regurgitation. Each of these murmurs has distinct hemodynamic changes and origins that do not align with the pathophysiology of atrial septal defects.