What does the presence of an S3 (third heart sound) indicate in adults and how is it managed?

S3 Heart Sound: Clinical Significance and Management

What S3 Indicates in Adults

An S3 heart sound in adults is a reliable indicator of cardiac decompensation, signaling elevated left ventricular filling pressures, volume overload, and substantially increased risk for adverse outcomes. 1

Pathophysiologic Significance

• S3 occurs during the rapid filling phase of ventricular diastole and reflects elevated left ventricular filling pressures with volume overload, as stated by the European Society of Cardiology 1

• The sound correlates with severe hemodynamic alterations including higher pulmonary pressures (mean 55 vs 41 mm Hg in those without S3) and more severe symptoms (55% with class III-IV symptoms vs 18% without S3) 2

• S3 is associated with higher early filling velocity due to greater filling volume, restrictive filling patterns, or both 2

Clinical Context Matters

• In young healthy individuals with hyperdynamic circulation, S3 can be physiological without underlying cardiac disease, occurring in approximately 23% of persons approaching age 40, particularly those who are lean with high early diastolic filling velocities 1, 3

• In adults over 40 years with cardiac disease, S3 indicates severe pathology: it is a marker of severe regurgitation (regurgitant fraction ≥40%) in primary left ventricular dysfunction, mitral regurgitation, and aortic regurgitation 2

• S3 is more prevalent in primary left ventricular dysfunction (46%) compared to organic mitral regurgitation (16%) or aortic regurgitation (12%) 2

Diagnostic Accuracy

• Phonocardiographic S3 has high specificity (87-92%) but low sensitivity (32-52%) for detecting left ventricular dysfunction, elevated left ventricular end-diastolic pressure, or elevated BNP 4

• Physician auscultation has even lower sensitivity (16%) but maintains high specificity (97%), though interobserver agreement is only moderate at best (kappa 0.40-0.50) 5, 6

Management Approach

Primary Treatment Strategy

Treat the underlying heart failure with standard guideline-directed medical therapy including diuretics, ACE inhibitors/ARBs, beta-blockers, and aldosterone antagonists, as recommended by the European Society of Cardiology 1

Immediate Diagnostic Workup

• Perform echocardiography to assess ventricular function, as S3 correlates with both systolic and diastolic dysfunction, per the American College of Cardiology 1

• Obtain comprehensive quantitative Doppler echocardiography to evaluate: 2

  • Left ventricular ejection fraction
  • Severity of valvular regurgitation
  • Filling patterns (restrictive vs non-restrictive)
  • Chamber dimensions and wall thickness

• Consider cardiac MRI in selected cases to evaluate for infiltrative processes or myocardial fibrosis 1

Clinical Assessment

• Monitor jugular venous pressure, which is often elevated in patients with S3 1

• Assess for other signs of heart failure: pulmonary rales, peripheral edema, hepatomegaly, and evidence of volume overload 1

• Evaluate for precipitating factors: uncontrolled hypertension, ischemia, arrhythmias, medication non-adherence, or dietary indiscretion 7

Risk Stratification

S3 substantially increases perioperative risk and requires careful perioperative fluid management and hemodynamic monitoring, as stated by the American Heart Association 1

• S3 combined with history of heart failure, pulmonary edema, bilateral rales, or pulmonary vascular redistribution is an independent predictor of perioperative complications, per the American College of Cardiology 1

• In perimyocarditis, a new S3 indicates myocardial involvement, according to the European Society of Cardiology 1

Diagnostic Utility in Emergency Settings

• When combined with BNP levels in the indeterminate range (100-500 pg/mL), an electronic S3 improves diagnostic accuracy: the positive likelihood ratio increases from 1.3 to 2.9, and positive predictive value from 53% to 80% 6

Key Clinical Pitfalls

• Do not dismiss S3 as benign in adults over 40 years without thorough evaluation, as physiological S3 becomes increasingly rare with age and pathological causes predominate 3

• Do not rely solely on auscultation for diagnosis given poor interobserver reliability; confirm with echocardiography when S3 is suspected 5

• Do not overlook S3 as it mandates comprehensive hemodynamic assessment and consideration of vigorous medical or surgical treatment 2

• Recognize that absence of S3 does not exclude heart failure given its low sensitivity (32-52%) 4