heart murmur

Causes of Heart Murmurs

Knowing the cause of your heart murmur is very important. Depending on its cause, your murmur could be serious or innocent. Its cause can also help determine what treatment option is best for you. Here are the most common causes of heart murmurs in children and adults. 

What Is A Heart Murmur?

A heart murmur is an extra sound that can be heard when auscultating or listening to the heart. A typical heart makes a lub-dub sound. The first sound is heard when the mitral and tricuspid valves close, and the second sound occurs when the aortic and pulmonic valves close. When a heart murmur is present, a swishing or whooshing noise can also be detected. This sound is caused by turbulent blood flow in or near the heart. 

Murmurs are named depending on where in the heartbeat they occur. A diastolic murmur occurs in between beats when the heart is relaxed. A systolic murmur occurs when the muscles of the heart contract. Systolic murmurs are graded on a scale of 6, with a grade 1/6 being a very faint murmur, and a grade 6/6 being a very loud murmur. 

Heart Murmurs In Children

In children, heart murmurs are typically innocent. They sometimes appear randomly and are not related to any conditions in the body. They can also be the result of a congenital heart defect, or an abnormality in the heart's structure (which presents at birth). An example is a ventricular septal defect—an opening between the two ventricles of the heart. Depending of the size of the hole, the shunting of blood through the opening can cause the sound of a murmur.

Heart Murmurs In Adults

In adults, a murmur can also be called an innocent murmur. This can be seen during pregnancy, physical activity, fever, and other conditions that temporarily increase blood flow.

Many common murmurs are related to heart valve changes. A valve may have become stenotic or narrow and hardened from calcifications that make it more difficult for the blood to flow through the heart. As the blood flows through the narrower opening, the friction can cause an extra whooshing sound. This is found in Mitral Valve or Aortic Valve Stenosis. Valve changes can be caused by aging or can be the result of scarring from an infection like Rheumatic Fever or Endocarditis. 

A heart murmur can also be caused by a valve not completely closing, which can lead to regurgitation or backflow of blood into the heart. This can be seen in conditions such as Mitral Valve Prolapse, Mitral Valve Regurgitation, or Aortic Valve Regurgitation. These conditions can lead to more serious heart disease as the heart is forced to work harder to pump blood. 

Some conditions can lead to a heart murmur that are not related to heart valve changes. Hyperthyroidism, high blood pressure, and anemia can cause an increase of blood flow across the valves, leading to the sound of a heart murmur.

Last Updated: September 23, 2016