((new)) - Heart Sounds Lub-dub

Auscultation of the heart reveals two primary sounds: S1 ("lub") and S2 ("dub"). These sounds mark mechanical events of the cardiac cycle. This paper reviews their physiological basis and clinical relevance.

| Sound | Nickname | Cause | Timing | |-------|----------|-------|--------| | S1 | Lub | Closure of (mitral & tricuspid) at start of ventricular systole | Just after QRS complex on ECG | | S2 | Dub | Closure of semilunar valves (aortic & pulmonary) at start of ventricular diastole | Just after T wave on ECG | heart sounds lub-dub

It is produced when the mitral and tricuspid valves (the atrioventricular or AV valves) snap shut. Auscultation of the heart reveals two primary sounds:

The human heart is the tireless engine of life, a muscular organ that beats approximately 100,000 times a day to sustain the body. To the untrained ear, the heartbeat may seem like a singular, repetitive thumping. However, upon closer listening, one discerns a distinct dual rhythm: the "lub-dub." This iconic sound is not merely a biological noise but a sophisticated acoustic phenomenon that reflects the precise mechanical choreography of the heart’s valves. Understanding the origins of these sounds offers profound insight into the physiology of circulation and the fragility of human health. | Sound | Nickname | Cause | Timing