Split first hea sound is heard in: September 2008

Ans. C: Complete right bundle branch block S1 is caused by the closure of the tricuspid and mitral values. Generally, the closure will be simultaneous so that a single S1 is heard, loudest at the apex. With a split S1 the closure of the two valves does not occur together. Splitting of the S1 is best heard in the tricuspid area and is not effected by respiration or other maneuvers which increase intrathoracic pressure. An split S1 by 10-30 ms is a normal phenomenon. Split S1 can be associated with pathological conditions, such a right bundle branch block.