From the Guidelines
An S3 heart sound is characterized as a low-pitched, early diastolic sound that occurs just after the S2 heart sound during ventricular filling, often indicating heart failure, volume overload, or decreased ventricular function in adults over 40 years old. This sound is best heard with the bell of the stethoscope placed at the apex of the heart with the patient in the left lateral decubitus position. The presence of an S3 in older adults correlates with elevated ventricular filling pressures and is considered a significant clinical finding that may warrant further cardiac evaluation, as noted in studies such as 1.
Some key points to consider when evaluating an S3 heart sound include:
- The sound is often described as having a "gallop" quality or sounding like "ken-tuck-y" when heard in sequence with S1 and S2
- It is typically abnormal in adults over 40 years old, but can be normal in children, young adults, and during pregnancy
- The sound is produced by rapid ventricular filling against a stiff or non-compliant ventricle, causing vibrations of the ventricular wall
- An S3 can be a manifestation of the volume load in conditions such as severe aortic regurgitation, and is not necessarily an indication of heart failure, as mentioned in 1
In clinical practice, the presence of an S3 heart sound should prompt further evaluation, including a thorough physical examination, electrocardiography, and potentially advanced diagnostic imaging, as outlined in guidelines such as 1 and 1. The management of patients with an S3 heart sound will depend on the underlying cause and severity of the condition, and may involve medical therapy, lifestyle modifications, and potentially surgical intervention.
From the Research
Characterization of S3 Heart Sound
The S3 heart sound is characterized as an abnormal heart sound component that is an indicator of heart failure during the diastolic period 2. It is often described as a ventricular gallop, which can be a sign of cardiac decompensation 3. The presence of S3 may be the earliest clue to the presence of left ventricular failure 4.
Clinical Significance
- The S3 heart sound is a predictor of response to digoxin in patients with congestive heart failure 4.
- It predicts a high risk of postoperative complications in the setting of noncardiac surgery 4.
- The presence of S3 is associated with coronary heart disease, hypertensive heart disease, and dilated cardiomyopathy 3.
Detection and Interobserver Variability
- The detection of S3 can be challenging, with high interobserver variation even among experienced clinicians 5, 4.
- The use of adaptive methods based on time-frequency analysis, such as Hilbert-Huang Transform (HHT), can improve the detection of S3 and S4 heart sounds 2.
- The interobserver agreement on the presence of S3 can range from 48% to 73% 5.
Physiological Mechanisms
- The S3 heart sound is thought to be due to cardiohemic vibrations powered by rapid deceleration of transmitral blood flow 6.
- The kinematics of filling requires that all hearts have oscillations of the cardiohemic system during E-wave deceleration, but the oscillations may not have high enough amplitude or frequency to be heard as an S3 unless there is sufficiently rapid fluid deceleration 6.