What does it mean when S3 and S4 heart sounds are heard over the mitral and tricuspid areas?

S3 and S4 Heart Sounds Over Mitral and Tricuspid Areas: Clinical Significance

The presence of S3 and S4 heart sounds over the mitral and tricuspid areas typically indicates significant cardiac pathology, most commonly heart failure, ventricular dysfunction, or valvular heart disease. These extra heart sounds are important clinical findings that warrant comprehensive cardiac evaluation.

S3 (Third Heart Sound) Significance

• S3 is a low-pitched, early diastolic sound that occurs during the rapid filling phase of ventricular diastole, representing abrupt deceleration of ventricular filling 1
• The presence of an S3 is strongly associated with:
  • Heart failure and cardiac decompensation 2, 3
  • Severe left ventricular dysfunction with decreased compliance 1
  • Elevated left ventricular filling pressures 3, 1
  • Restrictive filling patterns 3
• When heard over the mitral area (apex), S3 typically indicates left ventricular dysfunction; when heard over the tricuspid area (lower left sternal border), it suggests right ventricular dysfunction 4
• S3 is highly specific (97%) for the presence of myocardial fibrosis in conditions like hypertrophic cardiomyopathy, though with lower sensitivity (29%) 5

S4 (Fourth Heart Sound) Significance

• S4 is a late diastolic sound occurring just before S1, associated with atrial contraction against a non-compliant ventricle 2
• The presence of an S4 is commonly associated with:
  • Coronary heart disease 2
  • Hypertensive heart disease 2
  • Hypertrophic cardiomyopathy (HCM) - S4 is classically present in HCM patients 4, 5
  • Decreased ventricular compliance without overt heart failure 2
• Unlike S3, S4 does not necessarily indicate heart failure but reflects increased resistance to ventricular filling 2

When Both S3 and S4 Are Present

• The combination of S3 and S4 is commonly found in:
  • Cardiac decompensation associated with coronary heart disease 2
  • Hypertensive heart disease 2
  • Dilated cardiomyopathy 2
• When S3 and S4 occur in close proximity, they may create a short rumbling murmur that can be confused with valvular pathology 2
• If both sounds occur exactly simultaneously, they produce a summation gallop, which can be louder than either S1 or S2 2

Diagnostic Approach

• Echocardiography is the recommended first-line diagnostic test to evaluate the underlying cause 4
• For patients with suspected heart failure, assessment should include:
  • Evaluation of ventricular function and dimensions 4
  • Assessment of valvular function, particularly for mitral and tricuspid regurgitation 3
  • Measurement of E/E' ratio (early mitral inflow velocity to diastolic velocity of mitral annulus), which correlates with the presence of S3 1
• Dynamic auscultation can help differentiate S3 and S4 from other heart sounds:
  • S4 is eliminated with pressure on the stethoscope, while ejection sounds or split S1 are not 2
  • Timing relative to S2 is critical - sounds after S2 are diastolic (S3), while those before S1 are presystolic (S4) 2

Clinical Pearls and Pitfalls

• An S3 in a patient with valvular regurgitation (mitral or aortic) is a marker of severe regurgitation (regurgitant fraction ≥40%) 3
• In patients with chronic thromboembolic pulmonary hypertension, an S3 or S4 gallop may be auscultated over the right ventricle as right-sided heart failure develops 4
• The presence of S3 in patients without symptoms of heart failure may indicate subclinical myocardial fibrosis, particularly in hypertrophic cardiomyopathy 5
• S3 can persist even after replacement of native mitral and tricuspid valves, indicating that it's not solely generated by the valve leaflets but by ventricular wall motion during rapid filling 6

Understanding the significance of these extra heart sounds is crucial for early detection of cardiac pathology and appropriate management to improve morbidity and mortality outcomes.