Is an S4 heart sound usually indicative of dilated cardiomyopathy?

S4 Heart Sound and Dilated Cardiomyopathy

An S4 heart sound is not specifically indicative of dilated cardiomyopathy, but rather is most frequently associated with conditions that reduce left ventricular compliance, particularly coronary heart disease and hypertension.

Understanding the S4 Heart Sound

The S4 heart sound (atrial gallop) is a late diastolic sound that occurs just before S1. It has the following characteristics:

• Results from decreased ventricular compliance causing resistance to ventricular filling
• Can be distinguished from other sounds (split S1, ejection sounds) as it is eliminated with pressure on the stethoscope 1
• Most commonly found in patients with:
  • Coronary heart disease
  • Hypertensive heart disease
  • Left ventricular hypertrophy

S4 in Different Cardiomyopathies

Dilated Cardiomyopathy

• S4 can be present in dilated cardiomyopathy (DCM), but it is not a defining or characteristic feature
• Both S3 and S4 gallops may be present in patients with cardiac decompensation associated with DCM 1
• When both S3 and S4 occur in close proximity, they can create a summation gallop that might be confused with other cardiac sounds

Hypertrophic Cardiomyopathy

• S4 is actually more commonly heard in patients with hypertrophic cardiomyopathy (HCM)
• Research shows S4 is present in approximately 75% of HCM patients 2
• Unlike S3, the presence of S4 in HCM was not associated with myocardial fibrosis as assessed by late gadolinium enhancement on MRI 2

Clinical Significance of Heart Sounds

S3 (Ventricular Gallop)

• Indicates ventricular dysfunction and heart failure
• In HCM, S3 is associated with myocardial fibrosis (86% of patients with S3 had fibrosis on MRI) 2
• Highly specific (97%) for detection of myocardial fibrosis in HCM patients

S4 (Atrial Gallop)

• Indicates reduced ventricular compliance
• Does not necessarily denote heart failure (unlike S3)
• Constant finding in patients with hypertension 1
• Can be present in various cardiac conditions including:
  • Coronary artery disease
  • Hypertensive heart disease
  • Hypertrophic cardiomyopathy
  • Aortic stenosis

Diagnostic Approach for Cardiomyopathies

When evaluating patients with suspected cardiomyopathy:

1. Perform a thorough cardiac examination, listening for extra heart sounds

   • S3 suggests ventricular dysfunction
   • S4 suggests reduced ventricular compliance but is not specific for DCM

2. Obtain a 12-lead ECG to assess for conduction abnormalities and arrhythmias 3

3. Perform echocardiography to assess:

   • Ventricular size and function
   • Wall thickness
   • Valvular function

4. Consider cardiac MRI for tissue characterization and differentiation between types of cardiomyopathy 3

5. Exclude coronary artery disease through appropriate testing 3

Key Points to Remember

• The presence of an S4 alone is not diagnostic of DCM
• S4 is more commonly associated with conditions causing reduced ventricular compliance, particularly hypertension and coronary artery disease
• In cardiomyopathies, S4 is more characteristic of HCM than DCM
• When both S3 and S4 are present, this combination may be found in advanced DCM with decompensation
• Proper auscultation technique is essential - listen at different areas of the precordium, including the xiphoid or epigastric area in patients with emphysematous chest 1

In summary, while an S4 can be present in dilated cardiomyopathy, it is not a specific diagnostic feature of DCM and is more commonly associated with other cardiac conditions that reduce ventricular compliance.