Faint first heart sound: signs, symptoms, and causes

2021-08-28 10:11 PM

The longer PR interval allows more time between atrial and ventricular contractions for the leaflets to move closer together, so when asystole occurs, the leaflets are ready to close, making less noise

Image. Faint first heart sound associated with a long PR interval (arrow)

Description

The first heart sound is softer than usual.

Cause

Prolonged PR (eg, first-degree heart block).

Open two leaves.

Severe mitral stenosis.

Decreased left ventricular elasticity.

Mechanism

Long PR interval

The longer PR interval allows more time between atrial and ventricular contractions for the leaflets to move closer together, so when asystole occurs, the leaflets are ready to close, making less noise.

Open two leaves

In mitral regurgitation, retrograde flow prevents the leaflets from closing, thus blurring T1.

Severe mitral stenosis

In severe mitral stenosis, the leaves are stiff and difficult to move to open and close.

Left ventricular less elastic

In situations where the ventricles are hypo elastic, end-diastolic pressures are high, causing the leaflets to move toward each other more rapidly. When the ventricles contract to close the valves, the leaflets are ready to close, producing a soft sound

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