What are the different types of heart murmurs?

Types of Heart Murmurs

Heart murmurs are primarily classified as systolic, diastolic, or continuous based on their timing in the cardiac cycle, with diastolic and continuous murmurs almost always representing pathological conditions requiring further cardiac evaluation. 1

Primary Classification of Heart Murmurs

Systolic Murmurs

• Holosystolic murmurs: Occur throughout systole and are almost always pathological 1

  • Examples: Mitral regurgitation (apex, radiating to axilla), tricuspid regurgitation (left lower sternal border, increases with inspiration) 1
  • Require complete cardiac evaluation

• Midsystolic murmurs: Characterized by crescendo-decrescendo configuration 1

  • Can be innocent or pathological
  • Most innocent murmurs in children and young adults are midsystolic 1
  • Typically grade 1/6-2/6 in intensity when innocent 2

Diastolic Murmurs

• Almost always pathological and require further evaluation 1, 2
• Examples include:
  • Mitral stenosis: Often accompanied by an opening snap 1
  • Aortic regurgitation

Continuous Murmurs

• Present throughout systole and diastole 1
• Almost always require further cardiac evaluation except for benign cases:
  • Venous hums
  • Mammary souffles 1, 3

Innocent vs. Pathological Murmurs

Innocent Murmurs

• Common in up to 80% of school children and 52% of adults 2

• Characteristics:

  • Usually grade 1/6-2/6 in intensity
  • Midsystolic, crescendo-decrescendo pattern
  • Position-dependent
  • No radiation
  • Lower frequencies (below 200 Hz) 4
  • More harmonic frequency structure 4

• Types of innocent murmurs 3:

  1. Pulmonary systolic murmur
  2. Vibratory systolic murmur
  3. Supraclavicular systolic murmur
  4. Mammary souffle
  5. Venous hum

Pathological Murmurs

• Red flags suggesting pathology 5:
  • Holosystolic or diastolic timing
  • Grade 3 or higher intensity
  • Harsh quality
  • Abnormal S2
  • Maximal intensity at upper left sternal border
  • Systolic click
  • Increased intensity upon standing
  • Contains frequency components over 200 Hz 4
  • Length exceeding 80% of systolic duration 4

Hyperdynamic Flow Murmurs

• Causes include 1:
  • Pregnancy (increased blood volume and cardiac output)
  • Thyrotoxicosis (increased metabolic rate and cardiac output)
  • Arteriovenous fistulas (creating low-resistance circuits)

Diagnostic Maneuvers

The response of murmurs to different maneuvers helps determine their origin 1:

Maneuver	Effect on Murmur
Respiration	Right-sided murmurs increase with inspiration; left-sided murmurs louder during expiration
Valsalva	Most murmurs decrease in intensity, except HCM (increases) and MVP (becomes longer/louder)
Standing	Most murmurs diminish, except HCM and MVP which become louder
Squatting	Most murmurs become louder, except HCM and MVP which soften
Handgrip	Increases murmurs of mitral regurgitation, VSD, and aortic regurgitation

Clinical Pearls and Pitfalls

• Diastolic and continuous murmurs almost always warrant further evaluation 1, 2
• Less than 1% of murmurs in children are pathological, yet they remain a common source of referral to pediatric cardiologists 6
• Echocardiography is the definitive diagnostic tool for evaluating suspected pathological murmurs 1, 5
• Using quantitative criteria (frequency >200 Hz or duration >80% of systole), 90% specificity and 91% sensitivity can be achieved in distinguishing innocent from pathological murmurs 4
• Neonatal heart murmurs should be evaluated more carefully as they are more likely to represent structural heart disease 5