When Is S3 Heard

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When is S3 heard? As a technical expert, I am often asked this question. S3, also known as the third heart sound, is a unique sound that can be heard during a cardiac examination. It is an important diagnostic clue for identifying certain cardiovascular conditions. In this article, I will explain what S3 is, when it is heard, and its significance in clinical practice.

Understanding S3

S3 is an extra heart sound that occurs during diastole, the phase of the cardiac cycle when the heart is relaxed and filling with blood. It is caused by the rapid deceleration of blood flow in the ventricles as they fill. This deceleration causes vibrations within the heart chambers, producing an audible sound.

The S3 sound is best heard with the bell of the stethoscope placed at the apex of the heart, which is the area where the heart is closest to the chest wall on the left side. It is typically heard immediately after the second heart sound (S2), which corresponds to the closing of the aortic and pulmonic valves.

When is S3 Heard?

S3 is most commonly heard in individuals with certain cardiac conditions, such as heart failure. It is particularly prevalent in patients with dilated cardiomyopathy, a condition characterized by the enlargement of the heart chambers. In these patients, the S3 sound is often indicative of impaired ventricular function and increased fluid volume in the heart.

However, it’s important to note that S3 can also be heard in individuals without any underlying cardiac pathology. In children and young adults, the presence of an S3 sound may be considered normal and benign. This physiological S3 is commonly referred to as a “physiologic gallop” and is more commonly heard in athletes or individuals with increased blood volume.

The Significance of S3

In clinical practice, the presence or absence of S3 can provide valuable information about a patient’s cardiac health. When evaluating a patient, healthcare providers listen for S3 as part of a comprehensive cardiovascular examination. The presence of an S3 sound can help confirm or raise suspicion for certain conditions, such as heart failure, while its absence can help rule out these conditions.

Moreover, the intensity and timing of the S3 sound can provide additional insights. A loud and easily heard S3 sound, often referred to as a “ventricular gallop,” is more indicative of impaired ventricular function and fluid overload. On the other hand, a soft and difficult-to-audible S3 sound, known as a “atrial gallop,” may suggest other cardiac abnormalities, such as atrial fibrillation or stiff ventricles.


S3, the third heart sound, plays a crucial role in the assessment of cardiac health. It is a unique sound that can be heard during diastole and provides valuable diagnostic information. While it is most commonly associated with heart failure and dilated cardiomyopathy, it can also be heard in individuals without underlying cardiac pathology. As healthcare providers, listening for S3 and interpreting its characteristics can help guide clinical decision-making and provide insights into a patient’s cardiovascular status.