Before revision: Normal heart sounds are associated with heart valves closing: S1 The first heart sound, or S1, forms the "lub" of "lub-dub" and is composed of components M1 (mitral valve closure) and T1 (tricuspid valve closure).
After revision: Normal heart sounds are associated with heart valves closing: First heart sound The first heart sound, or S1, forms the "lub" of "lub-dub" and is composed of components M1 (mitral valve closure) and T1 (tricuspid valve closure).