What do S3 and S4 heart sounds indicate?

S3 and S4 Heart Sounds: Clinical Significance and Management

What They Are

S3 is a mid-diastolic heart sound occurring during rapid ventricular filling that indicates volume overload and elevated left ventricular filling pressures, while S4 is a late-diastolic sound occurring during atrial contraction that most commonly signals coronary heart disease and reduced ventricular compliance. 1

S3 (Third Heart Sound)

• Occurs during the rapid filling phase of ventricular diastole 1
• When heard over the mitral area, indicates left ventricular dysfunction; when heard over the tricuspid area, suggests right ventricular dysfunction 2
• Highly specific (92-97%) but poorly sensitive (29-41%) for left ventricular dysfunction 3, 4
• Strongly associated with elevated left ventricular end-diastolic pressure, reduced ejection fraction, and elevated B-type natriuretic peptide 4
• In hypertrophic cardiomyopathy, S3 is highly associated with myocardial fibrosis on cardiac MRI (86% incidence of late gadolinium enhancement) 5

S4 (Fourth Heart Sound)

• Occurs during atrial contraction in late diastole 1
• Most frequently found in patients with coronary heart disease 6
• Constant finding in patients with hypertension 6
• Does NOT indicate heart failure, unlike S3 6
• Moderately specific (72-80%) but poorly sensitive (40-46%) for left ventricular dysfunction 4

Clinical Significance for Risk Stratification

The presence of S3 is a reliable indicator of cardiac decompensation and substantially increases perioperative risk, while S4 does not independently predict heart failure. 7, 1

• Both S3 and signs of heart failure are associated with substantially increased risk during noncardiac surgery 7
• S3 gallop is an independent predictor of perioperative risk when combined with history of congestive heart failure, pulmonary edema, paroxysmal nocturnal dyspnea, bilateral rales, or pulmonary vascular redistribution on chest X-ray 7
• S3 combined with intermediate BNP levels (100-500 pg/mL) improves diagnostic accuracy, increasing positive predictive value from 53% to 80% 3

Diagnostic Workup

Perform echocardiography in all patients with S3 or S4 to assess ventricular function, as this is the first-line diagnostic test recommended by major cardiology societies. 1, 2

Mandatory Testing

• Echocardiography to evaluate:
  • Left ventricular systolic and diastolic function 1, 2
  • Ventricular dimensions and wall thickness 2
  • Valvular abnormalities 1
  • Presence of left ventricular hypertrophy (commonly associated with S4) 1

Additional Assessment

• Measure B-type natriuretic peptide, especially when S3 is present, as elevated levels correlate with the presence of S3 4
• Assess jugular venous pressure (often elevated with S3), pulmonary rales, peripheral edema, and hepatomegaly 1
• Consider cardiac MRI in selected cases to evaluate for infiltrative processes (sarcoidosis, hemochromatosis, amyloidosis) or myocardial fibrosis 7, 5

Management Approach

For S3 (Indicates Heart Failure)

Treat the underlying heart failure with standard guideline-directed medical therapy, as S3 reliably indicates cardiac decompensation requiring aggressive management. 1

• Initiate or optimize diuretics for volume overload 1
• Start or uptitrate ACE inhibitors or angiotensin receptor blockers 1
• Initiate or optimize beta-blockers 1
• Add aldosterone antagonists when appropriate 1
• Monitor for resolution of S3 as a marker of treatment response 1

For S4 (Does Not Indicate Heart Failure)

Focus on blood pressure control and management of the underlying condition (typically coronary disease or hypertension), as improved blood pressure management may lead to resolution of S4. 1, 6

• Optimize antihypertensive therapy if hypertension is present 1
• Evaluate and treat coronary artery disease if suspected 6
• Assess for and manage left ventricular hypertrophy 1
• Monitor for progression to heart failure, as S4 may signal increased future risk 1

Important Clinical Pearls

Detection Techniques

• An S4 gallop is eliminated with firm pressure on the stethoscope, but pressure does not eliminate ejection sounds or splitting of S1 6
• In patients with emphysematous chest or increased anteroposterior diameter, listen over the xiphoid or epigastric area where gallops may be more easily detected 6
• Use the "inching" technique: keep S2 in mind as reference and move the stethoscope from aortic area to apex to accurately time extra sounds 6

Combination Findings

• Both S3 and S4 may be present simultaneously in cardiac decompensation associated with coronary disease, hypertensive heart disease, or dilated cardiomyopathy 6
• When S3 and S4 occur in close proximity, they may create a short rumbling murmur that can be confused with valvular lesions 6
• When both sounds occur exactly simultaneously, a single loud "summation gallop" results, which is rare but can be misinterpreted as a valvular abnormality 6

Perioperative Considerations

• In perimyocarditis, auscultation of a new S3 is indicative of myocardial involvement 7
• Patients with S3 require careful perioperative fluid management and hemodynamic monitoring 7