Fourth heart sound

Fourth heart sound or S4 is a cardiac sound produced by the atria contracting forcefully in an attempt to overcome an abnormally stiff or hypertrophic ventricle. This sound is often associated with conditions that limit ventricular filling, such as hypertension, coronary artery disease, and cardiomyopathy.

Physiology

The fourth heart sound is a low-frequency sound that occurs late in diastole, just before the first heart sound. It is caused by the atria contracting forcefully in an attempt to overcome an abnormally stiff or hypertrophic ventricle. This results in a rapid deceleration of blood flow into the ventricles, which generates the S4 sound.

Clinical significance

The presence of an S4 is considered pathological in adults. It is often associated with conditions that limit ventricular filling, such as hypertension, coronary artery disease, and cardiomyopathy. However, it can also be heard in elderly patients due to age-related changes in the heart.

In children and young adults, an S4 is usually benign and can be heard during periods of increased heart rate, such as during exercise or excitement.

Diagnosis

The fourth heart sound is typically detected during a physical examination using a stethoscope. It is best heard at the apex of the heart with the patient in the left lateral decubitus position.

The S4 can be differentiated from other heart sounds by its timing and quality. It occurs late in diastole, just before the first heart sound, and is of lower frequency.

Treatment

Treatment of an S4 involves addressing the underlying condition that is causing the ventricle to become stiff or hypertrophic. This may involve medications to control blood pressure or treat heart disease, or in some cases, surgery may be required.