What results in a split S2 heart sound?

A split S2 heart sound occurs primarily due to the timing differences in closure of the aortic and pulmonary valves during the cardiac cycle. The S2 heart sound is produced when these two valves close at the end of ventricular systole. Normally, the aortic valve closes slightly before the pulmonary valve. However, a split S2 can become pronounced under certain physiological conditions, such as during deep inspiration when there is increased venous return to the right side of the heart, leading to delayed closure of the pulmonary valve.

When there is a delay in the closure of the pulmonary valve, it contributes to an audible split S2, as the aortic valve closes normally while the pulmonary valve closure is delayed. This is often seen in circumstances like increased stroke volume or right ventricular overload.

The other choices relate to different aspects of heart sounds and valve function but do not create the classic split S2 heart sound. Delay in aortic valve closure would affect the timing of S1 and the overall heart sounds rather than specifically causing inter-valvular differences reflected in a split S2. Similarly, delays in mitral valve closure or premature closure of the tricuspid valve do not specifically contribute to a split S2 sound as they are related to different valves and phases