| Feature | S1 ("Lub") | S2 ("Dub") | | :--- | :--- | :--- | | | Closure of Mitral/Tricuspid | Closure of Aortic/Pulmonic | | Timing | Beginning of Systole | End of Systole | | Pitch | Lower, duller | Higher, sharper | | Duration | Slightly longer | Shorter | | Best heard | Apex (Mitral area) | Base (Aortic/Pulmonic area) | | Relation to pulse | Occurs just before carotid upstroke | Occurs after carotid upstroke |
The , often colloquially described as the "lub" in the "lub-dub" of a heartbeat, is the first sound heard during a cardiac cycle. It marks the definitive onset of ventricular systole —the phase where the heart's lower chambers contract to pump blood to the body and lungs. What Produces the S1 Heart Sound? s1 heart sound
So the next time you place your stethoscope on a patient’s chest, listen carefully to the first syllable. It might just tell you everything you need to know before the second one arrives. | Feature | S1 ("Lub") | S2 ("Dub")
Contrary to popular belief, the heart sound is not the blood rushing through the chambers, nor is it the muscle contracting. Specifically, it is the sound generated by the sudden closure of the atrioventricular (AV) valves —the mitral (M1) and tricuspid (T1) valves. So the next time you place your stethoscope