Health Library Explorer

Heart Murmurs

What causes a heart murmur?

A heart murmur is caused by the turbulent movement of blood moving through the heart valves and chambers. Normally, the blood flows from one chamber to the next and valves close tightly to prevent blood from flowing backwards. In some cases, the valves can become narrowed or stiffened, or leak (regurgitate) and this causes the blood to flow abnormally creating the sound that is heard with a stethoscope when your healthcare provider does a physical exam.


  • Defective heart valves


  • Pregnancy (increased blood volume)

  • Fever


  • Thickening of pumping chamber of the heart (ventricular hypertrophy)

  • During times of rapid growth in children (innocent murmur)

What are the different types of murmurs?


Types of murmurs include:



  • Continuous murmur. This happens throughout the cardiac cycle.

Some murmurs can be heard best when listening on the front of the chest, while others can be heard best when listening with a stethoscope on your back. Your healthcare provider may ask you to hold your breath so that the sound of your heart beating can be heard without the sounds of your breathing interfering with the assessment. You may also be asked to lay on your side or to stand and squat to see how the chambers of the heart and valves react to the increased blood flow through the heart chambers and the heart valves.

Online Medical Reviewer: Glenn Gandelman MD MPH
Online Medical Reviewer: Lu Cunningham
Online Medical Reviewer: Mandy Snyder APRN
Date Last Reviewed: 11/1/2018
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