The human heart produces distinct sounds with each beat, providing valuable clues about its health. While most people are familiar with the common “lub-dub” rhythm, sometimes an additional sound can be heard, known as an S3 gallop. This extra sound can indicate an underlying issue within the heart, prompting further investigation.
Understanding Normal Heart Sounds
A healthy heart produces two primary sounds, often described as “lub” and “dub,” referred to as S1 and S2. S1, the first heart sound, signifies the closure of the mitral and tricuspid valves at the beginning of ventricular contraction (systole), marking the start of the heart’s pumping phase.
Following S1, S2 occurs as the aortic and pulmonic valves close, signaling the end of systole and the beginning of diastole (the heart’s relaxation and filling phase). These two sounds are generated by the turbulence created when heart valves snap shut, ensuring blood flows in the correct direction through the heart’s chambers.
What an S3 Gallop Is
An S3 gallop is an extra heart sound that occurs shortly after the normal S2 sound. It is a low-pitched, brief vibration heard early in diastole, during the rapid filling phase of the ventricles. This sound is sometimes called a “ventricular gallop” because the three sounds (S1, S2, and S3) in quick succession create a rhythm similar to a galloping horse.
The cadence of an S3 gallop is often compared to the word “Ken-TUCK-y,” with the “cky” syllable representing the S3 sound. It is thought to arise from the sudden deceleration of blood as it rapidly fills an already distended or less compliant ventricle, causing vibration of the ventricular walls.
Causes and Clinical Significance
The presence of an S3 gallop is often linked to conditions that cause rapid ventricular filling or volume overload. In adults over 40, an S3 gallop is an abnormal finding, indicating ventricular dysfunction or heart failure, such as congestive heart failure where the heart struggles to pump blood efficiently.
Conditions such as dilated cardiomyopathy, where the heart’s lower chambers enlarge and cannot pump effectively, can lead to an S3 gallop. Other causes include coronary artery disease, heart valve issues like mitral or tricuspid regurgitation, and chronically high blood pressure. These conditions increase the volume load on the ventricles, contributing to the sound.
In contrast, an S3 gallop can be a normal or “physiological” finding in certain individuals. This includes children, young adults, and pregnant women. Highly trained athletes may also exhibit a physiological S3 sound due to their increased cardiac output and efficient heart function.
Detection and Evaluation
Medical professionals primarily detect an S3 gallop through auscultation, which involves listening to the heart with a stethoscope. The S3 sound is low-pitched, making it best heard using the bell of the stethoscope, applied lightly to the skin. It is most audible at the cardiac apex, the pointed tip of the heart, located to the left of the sternum between the fourth and fifth ribs.
To enhance detection, the patient may be asked to lie in a left lateral decubitus position. This positioning can bring the heart closer to the chest wall, making the faint sound more discernible. If an S3 gallop is identified, further diagnostic tests are performed to determine its underlying cause. Tests include an echocardiogram, which uses sound waves to image the heart’s structure and function, and various blood tests.