What is the description of Still's murmur?

Still's Murmur Description

Still's murmur is best described as an innocent murmur with a medium pitched, vibratory character heard at the apex, left lower sternal border, left middle sternal border, and right upper sternal border that disappears or becomes quieter and localizes to the left lower sternal border on upright position. 1

Characteristics of Still's Murmur

• Still's murmur is classified as an innocent murmur, meaning it is not associated with any structural cardiac defects 1
• It has a medium pitched, vibratory quality that is distinctive in its sound 1
• The murmur is typically heard at multiple locations including:
  • Apex of the heart
  • Left lower sternal border
  • Left middle sternal border
  • Right upper sternal border 1
• When the patient assumes an upright position, the murmur either:
  • Disappears completely, or
  • Becomes quieter and localizes specifically to the left lower sternal border 1

Physiological Basis

• Research suggests that Still's murmur is related to a small ascending aortic diameter with concomitant high aortic blood flow velocity 2
• The average peak ascending aortic velocity in patients with Still's murmur (133 cm/s) is significantly higher than in those without the murmur (107 cm/s) 2
• The ascending aortic diameter relative to body surface area is significantly smaller in individuals with Still's murmur 2

Clinical Significance

• Still's murmur is the most prevalent innocent heart murmur of childhood 3
• It is frequently misdiagnosed, leading to unnecessary referrals to pediatric cardiologists 3, 4
• Unlike pathologic murmurs, Still's murmur does not indicate underlying structural heart disease 1, 5

Differentiation from Pathologic Murmurs

• Still's murmur can be distinguished from pathologic murmurs by:
  • Its vibratory quality (rather than harsh) 1
  • Its response to positional changes (quieter when standing) 1
  • Its medium pitch 1
  • Absence of other abnormal cardiac findings 5

Common Pitfalls in Identification

• Still's murmur may be confused with other innocent murmurs or mild pathologic conditions 5
• Red flags that would suggest a murmur is NOT an innocent Still's murmur include:
  • Holosystolic or diastolic timing
  • Grade 3 or higher intensity
  • Harsh quality
  • Abnormal S2
  • Increased intensity when standing (Still's murmur typically decreases) 5
• Primary care providers are often less successful than pediatric cardiologists in distinguishing Still's murmur from pathologic murmurs 3