First Heart Sound (Minimal Split) - Auscultation Lesson
On occasion the first heart sound can be made up of two separate sounds separated by a very small interval (20-30 milliseconds).
The Mitral component (caused by closure of the Mitral valve) comes first and is louder than the Tricuspid component (caused by closure of the Tricuspid valve).
A minimally split first heart sound is a normal variation of the first heart sound.