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Heart Murmurs

What causes a heart murmur?

Heart murmurs may be caused by a number of factors or diseases, including:

  • Defective heart valves

  • Holes in the walls of your heart (atrial septal defect or ventricular septal defect)

  • Pregnancy (increased blood volume)

  • Fever

  • Anemia (a decrease in the red cells in the blood)

What are the different types of murmurs?

All murmurs are analyzed for pitch, frequency, and duration. They are also graded according to how loud they are (on a scale of 1 to 6  with 1 being very faint and 6 being very loud).

Types of murmurs include:

  • Systolic murmur. This occurs during a heart muscle contraction. Systolic murmurs are divided into ejection murmurs (due to blood flow through a narrowed vessel or irregular valve) and regurgitant murmurs (backward blood flow into one of the chambers of the heart).  

  • Diastolic murmur. This occurs during heart muscle relaxation between beats. Diastolic murmurs are due to a narrowing (stenosis) of the mitral or tricuspid valves, or regurgitation of the aortic or pulmonary valves.

  • Continuous murmur. This occurs throughout the cardiac cycle.

Online Medical Reviewer: Foster, Sarah, RN, MPH
Online Medical Reviewer: MMI board-certified, academically affiliated clinician
Date Last Reviewed: 4/17/2014
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