what causes the lub dub sound of heart
Normal. The two major sounds heard in the normal heart sound like âlub dubâ. The â lubâ is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole. The second sound,â dubâ or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole.