What Makes The Lub Sound In The Heart [NEW]

| Condition | Effect on S1 (“Lub”) | Why? | |-----------|----------------------|------| | | Moderate intensity | Normal valve closure and pressure. | | Mitral stenosis | Louder | The mitral valve is stiff but still moves; pressure builds higher before closing. | | Tachycardia | Louder | Faster heart rate increases the force of ventricular contraction. | | First-degree heart block | Softer | Longer delay between atrial and ventricular contraction means valves float partially shut before full closure. | | Obesity or emphysema | Softer | Extra tissue or air in the lungs muffles sound transmission. |

| Feature | | Dub (S2) | |---------|--------------|--------------| | Which valves? | Mitral & Tricuspid (AV valves) | Aortic & Pulmonary (semilunar valves) | | When? | Start of ventricular contraction | End of ventricular contraction | | Cardiac phase | Systole begins | Diastole begins | what makes the lub sound in the heart