A physical exam finding suggestive of atrial septal defect is?

A fixed split S2 is a characteristic finding on auscultation that suggests the presence of an atrial septal defect (ASD). In patients with ASD, the left-to-right shunting of blood during the cardiac cycle leads to increased blood flow across the right heart structures, which causes delayed closure of the pulmonary valve. This results in a persistent split between the aortic valve closure (A2) and pulmonary valve closure (P2) during both inspiration and expiration, hence termed a "fixed split."

The fixed nature of the split S2 in ASD is due to the unchanged hemodynamic scenario regardless of the respiratory cycle, which differs from normal physiological splitting that varies with respiration. Recognizing this auscultation finding can be critical in the evaluation of patients with suspected heart defects.

Other choices, while potentially related to cardiac abnormalities, are not specific findings for an atrial septal defect. Increased heart rate can occur in many conditions and is not exclusive to ASD. A mechanical murmur is typically associated with valve pathologies or other types of structural heart disease, but does not specifically indicate an ASD. A blood pressure difference can indicate other more serious conditions, such as coarctation of the aorta, rather than specifically pointing to