Cardiology Heart Sounds

Split S1

S1 is generated by closure of the mitral and tricuspid valves. These paired left- and right-sided valves do not close at exactly the same time, but the human ear cannot distinguish sounds that are 0.02-0.03 seconds apart as 2 separate sounds. When conditions further delay tricuspid valve closure, a split S1 can be appreciated. One of the most common causes of delayed tricuspid valve closure is a right bundle branch block.
Card Tutorial

Patient 1

This patient was admitted to the hospital for a non-cardiac reason and was noted to have a split S1. You can hear two sounds in quick succession followed by a single S2. There was no clear cause of the split S1 in this case.

Split S1

Annotated