Heart sound

The heart sounds are the noises a physician listens to using a stethoscope over the heart. They are the noises of the heart valves shutting.

These noises are not the same as the pulse, or the artery turbulence noises listened to when taking blood pressure.

There are normal two distinct heart sounds, often called a lub and a dub. (Though the description of these sounds varies regionally.)

The first sound is caused by the closure of the AV valves in systole to stop blood flowing back into the atria. Systole is when the heart is actually contracting.

In diastole, the heart is no longer contracting, blood tries to flow back from the aorta (left side) and pulmonary trunk (right side) into the corresponding ventricles. This causes the semilunar valves to shut, preventing this backflow, and generating the second heart sound.

Because systole and diastole happen on the left and right sides simultaneously, each noise is generated by two valves shutting at the same time.

Abnormal heart sounds

Listening to the heart sounds can pick up problems with the valves.

Stenosis (when the ability of the valve to open is impaired) will cause turbulence as blood pushes through it. This is heard as a murmur while the blood tries to get through.

Insuffiency (when the valve cannot shut properly) will cause longer periods of murmur as the blood is pushed through it.