Lub Dub Heart Sounds Jun 2026

The second heart sound, or S2, marks the end of systole and the beginning of diastole (the relaxation phase). It is produced by the closure of the :

During , intrathoracic pressure decreases. This creates a suction effect that increases venous return to the right side of the heart. Consequently, the right ventricle takes longer to empty, delaying the closure of the pulmonic valve (P2). Simultaneously, increased capacity in the pulmonary vessels decreases return to the left heart, causing the aortic valve (A2) to close slightly earlier. lub dub heart sounds

The classic "lub-dub" isn't actually the sound of your heart muscle squeezing; it’s the sound of your , much like a door slamming. These sounds, known medically as S1 (lub) and S2 (dub), mark the major mechanical transitions in your cardiac cycle. The "Lub-Dub" Breakdown Medical Term What it Signals Lub S1 Closure of Mitral and Tricuspid valves The second heart sound, or S2, marks the

: Ventricles contract to pump blood out of the heart. Dub S2 Closure of Aortic and Pulmonic valves Consequently, the right ventricle takes longer to empty,

The "dub" signifies the start of , the relaxation phase where the heart chambers refill with blood. How the Heart Works - How the Heart Beats | NHLBI, NIH

If you can’t tell which is which: