S4
Overview
The S4, often referred to as the "fourth heart sound" or "atrial gallop," is a specific sound in the cardiac cycle associated with the contraction of the atria and the subsequent filling of the ventricles. It is typically heard in late diastole, just before the first heart sound (S1). The S4 is considered a normal finding in children, young adults, and athletes, but in older adults, it may indicate underlying cardiac pathology such as hypertensive heart disease, ischemic heart disease, or aortic stenosis.
Physiology
The S4 heart sound is produced by the vibration of the ventricular walls and valves due to the rapid deceleration of blood flow into the ventricles during atrial contraction. This occurs when the atria contract to push the remaining blood into the ventricles just before systole. The sound is low-pitched and is best heard with the bell of the stethoscope at the apex of the heart.
Clinical Significance
In adults, the presence of an S4 heart sound may indicate a stiff or non-compliant left ventricle, often due to conditions such as hypertension, coronary artery disease, or cardiomyopathy. It can also be heard in conditions where there is an increased resistance to ventricular filling, such as aortic stenosis or hypertrophic cardiomyopathy.
Detection and Diagnosis
The S4 heart sound is typically detected during a physical examination using a stethoscope. It is a low-pitched sound and is best heard at the apex of the heart with the patient in the left lateral decubitus position. The sound is often described as a 'gallop' rhythm due to its similarity to the sounds of a galloping horse.
Treatment and Management
The treatment of an S4 heart sound is dependent on the underlying cause. If the S4 is due to hypertension, treatment may involve lifestyle changes and medication to lower blood pressure. If the S4 is due to aortic stenosis, treatment may involve surgical intervention to repair or replace the aortic valve.