S3 and S4 Heart Sounds: Clinical Significance by Patient Population
S3 is abnormal in adults (except during pregnancy), indicating cardiac decompensation with elevated left ventricular filling pressures, while S4 is abnormal when it signals underlying pathology such as coronary heart disease, left ventricular hypertrophy, or impaired diastolic function. 1
S3 Heart Sound: When It's Abnormal
Pathologic S3 Populations
S3 is a reliable indicator of cardiac decompensation and substantially increases perioperative risk in adults with heart failure. 1 The sound occurs during rapid ventricular filling and reflects volume overload with elevated filling pressures. 1
Adults with cardiac pathology where S3 is abnormal:
Heart failure patients: S3 indicates left ventricular dysfunction when heard over the mitral area, or right ventricular dysfunction when heard over the tricuspid area. 2 The presence of S3 combined with history of heart failure, pulmonary edema, bilateral rales, or pulmonary vascular redistribution independently predicts perioperative complications. 1
Valvular regurgitation: S3 serves as a marker of severe regurgitation (regurgitant fraction ≥40%) in patients with mitral regurgitation, aortic regurgitation, or primary left ventricular dysfunction. 3 In mitral regurgitation specifically, S3 associates with marked ventricular dilatation. 3
Reduced ejection fraction: The sensitivity and specificity of S3 for detecting ejection fraction <50% are 51% and 90% respectively, with positive predictive value of 95%. 4 For ejection fraction <30%, sensitivity increases to 78% with specificity of 88%. 4
Elevated filling pressures: S3 correlates with mean pulmonary pressure of 55±15 mm Hg versus 41±11 mm Hg in those without S3, and associates with elevated left ventricular end-diastolic pressure. 3, 5
Restrictive filling patterns: S3 associates with restrictive filling in primary left ventricular dysfunction (odds ratio 3.0). 3
Perimyocarditis: A new S3 indicates myocardial involvement. 1
Chronic thromboembolic pulmonary hypertension: S3 gallop may be auscultated over the right ventricle as right-sided heart failure develops. 2
Normal S3 Populations (Key Exceptions)
Pregnant women: S3 is present in most pregnant patients as a normal physiologic finding due to increased circulating blood volume and cardiac output—this represents a critical exception where S3 does not indicate pathology. 6, 1
Young healthy individuals: Those with hyperdynamic circulation can have S3 due to rapid early filling velocity without underlying cardiac disease. 1
S4 Heart Sound: When It's Abnormal
S4 occurs during atrial contraction and is most frequently found in patients with coronary heart disease. 1 Unlike S3, S4 does not independently predict heart failure but signals underlying cardiac pathology. 1
Populations where S4 is abnormal:
Coronary artery disease patients: S4 is most commonly associated with coronary heart disease. 1
Left ventricular hypertrophy: S4 commonly associates with LVH and should prompt echocardiographic assessment of ventricular hypertrophy and diastolic function. 1
Hypertensive patients: Improved blood pressure management may lead to resolution of S4, and monitoring for LVH is essential. 1
Impaired diastolic function: S4 may signal increased risk for developing heart failure if the underlying condition is not addressed. 1
Aortic stenosis: S4 is rather common in obstructive hypertrophic cardiomyopathy and valvular aortic stenosis. 6
Clinical Pitfalls and Diagnostic Considerations
The absence of S3 does not exclude cardiac dysfunction—the negative predictive value is only 32% for ejection fraction <50%. 4 S3 has only intermediate sensitivity (41% for elevated LVEDP, 52% for reduced LVEF) but high specificity (92% for elevated LVEDP, 87% for reduced LVEF). 5
Optimal detection requires proper technique: The patient should be positioned in the left lateral decubitus position, which brings the cardiac apex closer to the chest wall—critical for detecting low-frequency, low-amplitude sounds like S3. 7 The patient must be relaxed and quiet during auscultation to minimize artifact. 7
Both S3 and S4 warrant echocardiographic evaluation as the first-line diagnostic test to assess ventricular function, chamber dimensions, valvular pathology, and diastolic function. 2, 1 Consider cardiac MRI in selected cases to evaluate for infiltrative processes or myocardial fibrosis. 1
Perioperative risk stratification: Patients with S3 require careful perioperative fluid management and hemodynamic monitoring, as S3 substantially increases surgical risk. 1 The combination of S3 with signs of heart failure is associated with substantially increased risk during noncardiac surgery. 1