Functional murmur

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: Innocent murmur

Overview

A functional murmur (innocent murmur, physiologic murmur) is a heart murmur that is primarily due to physiologic conditions outside the heart, as opposed to structural defects in the heart itself. Serious conditions can arise even in the absence of a primary heart defect, and it is possible for peripheral conditions to generate abnormalities in the heart. Therefore, caution should be applied to use of the terms "innocent" or "benign" in this context.

Natural history, Complications and Prognosis

Innocent murmurs are inconsequential and usually disappear as the child grows.

Physical Exam

• The characteristics of the murmur:
  • Soft, less than 3/6 in intensity (although note that even when structural heart disease is present, intensity does not predict severity.)
  • Often position-dependent: Murmurs are heard while supine and may disappear when upright or sitting.
  • Occurs during systole or continuously during both systole and diastole. (Murmurs occurring only during diastole are always pathologic.)
• Physiologic splitting of S2 (A2 and P2 components should only be resolvable during inspiration and should merge during expiration.)
• No palpable thrill