Lub Dub Heart Sounds

The first heart sound, or S1, occurs at the beginning of systole (the contraction phase). It is produced by the closure of the :

| | | S2 (Dub) | |--|-------------|-------------| | Phase | Systole | Diastole | | Valves | Mitral + Tricuspid | Aortic + Pulmonic | | Pulse relation | Before pulse | After pulse | | Loudest at | Apex | Base | | Split on inspiration? | No | Yes (normally) | lub dub heart sounds

While "lub-dub" is the standard, doctors often listen for subtle additions that tell a deeper story: Chapter 9 Cardiovascular Assessment - Nursing Skills - NCBI The first heart sound, or S1, occurs at