Lub Dub — Sound Heart

The cardiac cycle is divided into two primary phases: (contraction) and diastole (relaxation). Each phase is punctuated by a specific sound, known medically as S1 and S2.

The "lub-dub" is a fundamental acoustic event produced by the closing of heart valves during the cardiac cycle. S1 marks the start of ventricular contraction (AV valve closure), and S2 marks the start of ventricular relaxation (semilunar valve closure). Changes in these sounds provide crucial diagnostic information about heart valve integrity and overall cardiac health. lub dub sound heart

| Feature | S1 ("Lub") | S2 ("Dub") | |---------|------------|------------| | | Start of systole | End of systole / start of diastole | | Valves involved | Mitral & Tricuspid (AV valves) | Aortic & Pulmonary (semilunar valves) | | Pitch | Lower | Higher | | Duration | Slightly longer | Shorter | | Best heard at | Apex of heart (mitral area) | Base of heart (left sternal border) | The cardiac cycle is divided into two primary

Occurs at the end of systole / beginning of diastole (ventricular relaxation). Cause: The closure of the semilunar valves : S1 marks the start of ventricular contraction (AV

The mitral valve closes slightly before the tricuspid valve, but normally they are heard as a single sound.

The first sound, the "lub" (medically termed S1), is the deeper and longer of the two tones. It occurs at the beginning of ventricular systole, the phase where the ventricles contract to pump blood out of the heart. When the ventricles contract, the pressure inside them rises rapidly, forcing blood upward toward the atria. To prevent this blood from flowing backward into the atria, the two atrioventricular valves—the tricuspid valve on the right side and the mitral valve on the left—snap shut simultaneously. The abrupt closure of these valves creates the "lub" sound. It is the sound of the heart's "loading" phase concluding and the "firing" phase beginning, propelling blood to the lungs and the rest of the body.