Overview of Heart Murmur

A heart murmur is an abnormal "whooshing" or "swishing" sound heard with a stethoscope when there is unsteady blood flow near the heart. This sound is different from the usual "lub-dub" heartbeat sound.

Heart murmurs can be loud or soft. Most of the time, they are harmless, but heart murmurs can sometimes indicate a heart condition that needs treatment. People of any age can have a heart murmur and the condition may come and go throughout a person's lifetime.

Types of Heart Murmur

Heart murmurs are classified in two ways: innocent and abnormal. Innocent heart murmurs, also called normal, benign flow, functional, or physiologic murmurs, occur when blood flow moves quickly through the heart or there is extra blood flow in the heart.

Patients with innocent murmurs have healthy, normal hearts and usually do not need treatment. Innocent heart murmurs frequently are detected in children. Innocent heart murmurs may become louder or softer when the heart rate changes from exercise, excitement, or anxiety; however, this usually is not cause for concern.

Abnormal heart murmurs, also called pathologic murmurs, usually indicate an underlying heart condition (e.g., congenital heart defect, heart valve defect, infection) that needs further evaluation.

Heart murmurs also can be classified into these subcategories:

  • Diastolic murmurs occur between heartbeats, as the heart relaxes and fills with blood.
  • Systolic murmurs happen when the heart contracts and pumps blood out.
  • Continuous murmurs occur throughout the heartbeat cycle.
  • Heart murmurs during pregnancy are usually innocent. Women's bodies make more blood during pregnancy, which can cause extra blood flow through the heart. These murmurs often go away after the pregnancy.
  • Still's murmur is a common type of innocent murmur that usually occurs in children between the ages of 3 and 7.

Heart Murmur Incidence and Prevalence

Innocent heart murmurs are common. They affect 40–45 percent of children and about 10 percent of adults at some point during their lifetimes. Innocent heart murmurs are more common in women during pregnancy. Abnormal heart murmurs occur most often in people who have certain heart conditions, such as a defective heart valve (e.g., aortic stenosis, mitral regurgitation).

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 18 Nov 2008

Last Modified: 18 Sep 2015