What heart sound is indicated by a split S2?

A split S2 heart sound occurs when there is a delay in the closure of the aortic valve (A) in relation to the pulmonary valve (P). This phenomenon is considered a normal respiratory variation because it is often more pronounced during inspiration when intrathoracic pressure decreases, leading to increased venous return to the right side of the heart. This increased volume extends the duration of right ventricular systole, causing the pulmonary valve to close slightly later than the aortic valve. As a result, a split S2 is typically observed in healthy individuals during normal breathing.

Other variations such as increased left atrial pressure, decreased left ventricular function, or right heart failure can also affect heart sounds, but they do not specifically explain the healthy variant of a split S2 heard during normal respiratory phases. Therefore, identifying a split S2 as a normal finding due to respiratory variation reflects an understanding of cardiac physiology and the dynamics of heart sounds in relation to the respiratory cycle.