Splitting Second Heart Sound Lesson #634

The patient was supine during auscultation.

Description

When the aortic and pulmonic valves close, sounds are created. Normally a combined sound is heard, which is the second heart sound (S2). If these two components can be individually distinguished, the condition is called a physiological split.

Careful analysis of the splitting and intensity of the second heart sound can indicate the presence of many cardiac abnormalities.

While listening to the audio recording, observe that splitting varies between zero and eighty milliseconds depending on the respiratory cycle phase.

In physiologic splitting, the maximum separation between aortic and pulmonic components of the second heart sound occurs at peak inspiration.

In paradoxical splitting, the maximum separation occurs at peak expiration. Paradoxical splitting can occur with left bundle-branch block (LBBB) and aortic stenosis, both of which cause the aortic valve closure to be delayed until after the pulmonic valve closure, reversing the normal sequence of events.