S2 Split Heart Sounds

Front 1

Explain the physiologic cause of a split S2 heart sound.

Back 1

Usually the aortic and pulmonic valves close at the same time to produce a single S2 sound. However, upon inspiration, the increased thoracic volume decreases pressure in the lungs thereby allowing for greater venous return and for the pulmonary valve to close later. Thus there is a distinguishable A2,P2 sound.

Front 2

Explain pathological causes of a split S2 heart sound.

Back 2

Fixed Split: Occurs at all times, not just during inspiration. This is often due to an atrial septal defect. Left to right shunt across the defect that increases blood volume in the right side of the heart and causes the pulmonic valve to close later than the aortic valve during inspiration and exhalation.

Paradoxical Split (A2, P2): This occurs when upon expiration, there is an A2,P2 split. Often due to aortic stenosis, left bundle branch block, left ventricular failure, etc --> prolong left ventricular ejection time. Thus, aortic valve usually closes slower than pulmonic.