What does a fixed split S2 heart sound during inspiration and expiration typically indicate?

A fixed split S2 heart sound occurring during both inspiration and expiration is indicative of certain cardiac conditions, primarily suggesting the presence of a septal defect. In a healthy heart, the closure of the aortic and pulmonic valves (which contributes to the S2 sound) usually has a slight variation in timing with respiration, leading to a normal physiological split that increases during inspiration and decreases during expiration.

However, when a septal defect such as an atrial septal defect is present, it can lead to the right side of the heart receiving more blood flow. This causes an increased volume of blood returning to the right atrium, resulting in higher pressure and a delayed closure of the pulmonic valve. Thus, the splitting of the S2 heart sound becomes fixed because the underlying hemodynamics are altered, causing the characteristic sound to remain unchanged regardless of the respiratory cycle.

Other conditions listed do not typically cause a fixed split S2 sound. For instance, pulmonary hypertension would more likely result in varying changes in heart sounds due to the increased pressures affecting valve closure timing differently. Healthy heart function would not present with a fixed split S2 at all, as normal variations with respiration would be expected. Similarly, ventricular hypertrophy might create other heart sounds or