What is the clinical relevance of a "fixed split S2" heart sound?

A "fixed split S2" heart sound is clinically significant and often indicates the presence of an atrial septal defect (ASD). In a healthy heart, the second heart sound (S2), which is created by the closure of the aortic and pulmonic valves, can vary with the respiratory cycle; it typically splits wider during inspiration and narrows during expiration. However, in the case of a fixed split S2, this splitting occurs consistently regardless of the patient's breath cycle.

In the presence of an ASD, there is an increase in blood flow over the right side of the heart due to the left-to-right shunting of blood. This increased volume can lead to delayed closure of the pulmonic valve compared to the aortic valve, producing the fixed split S2 sound. Detecting this phenomenon is critical in the assessment and diagnosis of atrial septal defects, which may require monitoring or intervention depending on their size and the occurrence of symptoms.

Other potential options, like aortic stenosis or pulmonary hypertension, do not typically present with a fixed split S2. Though both conditions influence heart sounds, they lead to different auscultatory findings rather than a fixed split phenomenon. Aortic stenosis may create a single S2 due to