A fixed split S2 and a systolic murmur may indicate which condition?

A fixed split S2, which means that the second heart sound does not vary with respiration, is often associated with conditions that affect the heart's ability to accommodate changes in blood flow. This is particularly characteristic of atrial septal defects (ASDs), where the presence of a left-to-right shunt leads to increased blood flow in the right atrium and subsequently the right ventricle. As a result, the right ventricle takes longer to eject blood, causing delayed closure of the pulmonic valve, which manifests as a fixed split S2.

In conjunction with a systolic murmur, which is typically heard due to increased flow across the pulmonary valve or through the right ventricular outflow tract, this finding reinforces the suspicion of an ASD. The murmur occurs during systole as the heart is contracting and blood passes through these structures.

Understanding the implications of a fixed split S2 and a systolic murmur helps to differentiate a wide array of cardiac conditions and is critical for proper diagnosis and patient management.