What does the murmur of anemia sound like?

Characteristics of Anemia Murmurs

The murmur of anemia typically presents as a soft, systolic ejection murmur that is best heard at the left sternal border and apex, without radiation into the carotids. 1

Acoustic Characteristics

• Grade I-II/VI systolic murmur on the Levine scale, rarely exceeding grade II intensity in uncomplicated anemia 1, 2
• Soft, blowing quality without the harshness associated with structural cardiac abnormalities 2
• Does not radiate to the carotids (unlike aortic stenosis murmurs) 3
• May be accompanied by a third heart sound (S3) or gallop rhythm due to increased cardiac output and ventricular volume 3
• Often associated with tachycardia as a compensatory mechanism 1

Location and Timing

• Best heard at the lower left sternal border and apex 1
• Systolic timing (occurs during ventricular contraction) 1, 2
• Early to mid-systolic, not holosystolic 2
• May increase with exercise or other conditions that increase cardiac output 4

Physiological Basis

• Results from increased blood flow velocity across normal cardiac valves due to:
  • Decreased blood viscosity from reduced hemoglobin concentration 1
  • Hyperdynamic circulation with increased stroke volume 3
  • Increased cardiac output as a compensatory mechanism 1

Associated Findings

• Tachycardia is almost universally present as a compensatory mechanism 1
• Hyperdynamic precordium may be palpable 3
• Wide pulse pressure may be present in chronic severe anemia 3
• Bounding peripheral pulses due to decreased peripheral vascular resistance 3

Distinguishing Features

• Disappears when the underlying anemia is corrected with appropriate therapy (e.g., iron supplementation in iron deficiency anemia) 1
• Increases with inspiration (unlike left-sided murmurs which typically decrease) 4
• No associated diastolic murmurs (which would suggest structural valve disease) 3

Clinical Significance

• In pediatric populations, innocent murmurs due to anemia are common and resolve with treatment of the underlying anemia 1
• The presence of a grade III or higher murmur, even in anemic patients, should raise suspicion for underlying structural heart disease 2
• When evaluating a new murmur, anemia should be ruled out before proceeding to more extensive cardiac workup 1

Diagnostic Approach

• Complete blood count to confirm and characterize the anemia 5
• If the murmur persists after correction of anemia, echocardiography is warranted to evaluate for structural heart disease 1
• Dynamic auscultation (listening during different patient positions and respiratory phases) can help differentiate anemia murmurs from pathological ones 4

Remember that while anemia can cause a murmur, the presence of a murmur in an anemic patient does not exclude concurrent structural heart disease, particularly if the murmur is grade III or higher or has other concerning characteristics 2.