Heart murmurs are abnormal sounds during your heartbeat cycle — such as whooshing or swishing — made by turbulent blood in or near your heart. These sounds can be heard with a stethoscope.

What is it?

  • Heart murmurs are abnormal sounds during your heartbeat cycle — such as whooshing or swishing — made by turbulent blood in or near your heart. These sounds can be heard with a stethoscope. A normal heartbeat makes two sounds like "lubb-dupp" (sometimes described as "lub-DUP"), which are the sounds of your heart valves closing.
  • Heart murmurs can be present at birth (congenital) or develop later in life. A heart murmur isn't a disease — but murmurs may indicate an underlying heart problem.
  • Most heart murmurs are harmless (innocent) and don't need treatment. Some heart murmurs may require follow-up tests to be sure the murmur isn't caused by a serious underlying heart condition. Treatment, if needed, is directed at the cause of your heart murmurs.

Symptoms

If you have a harmless heart murmur, more commonly known as an innocent heart murmur, you likely won't have any other signs or symptoms.

An abnormal heart murmur usually has no obvious other signs, aside from the unusual sound your doctor hears when listening to your heart with a stethoscope. But if you have these signs or symptoms, they may indicate a heart problem:

  • Skin that appears blue, especially on your fingertips and lips
  • Swelling
  • Shortness of breath
  • Enlarged liver
  • Enlarged neck veins
  • Poor appetite and failure to grow normally (in infants)
  • Weight gain (in adults and children)
  • Heavy sweating with minimal or no exertion
  • Chest pain
  • Dizziness
  • Fainting

Causes

There are two types are heart murmurs: innocent murmurs and abnormal murmurs. A person with an innocent murmur has a normal heart. This type of heart murmur is common in newborns and children. More than half of all children have heart murmurs at some time, and most of those murmurs are harmless.

An abnormal heart murmur is more serious. In children, abnormal murmurs are usually caused by congenital heart disease. In adults, abnormal murmurs are most often due to acquired heart valve problems.

Innocent heart murmurs

An innocent murmur can occur when blood flows more rapidly through the heart. Conditions that may cause rapid blood flow through your heart, resulting in an innocent heart murmur, are:

  • Physical activity or exercise
  • Pregnancy
  • Fever
  • Changes in your heart's structure, such as changes from heart surgery
  • Not having enough healthy red blood cells to carry adequate oxygen to your body tissues (anemia)
  • An excessive amount of thyroid hormone in your body (hyperthyroidism)

Changes to the heart due to aging or heart surgery also may cause an innocent heart murmur. Innocent heart murmurs may disappear over time, or they may last your entire life without ever causing further health problems.

Abnormal heart murmurs

Although most heart murmurs aren't serious, some may result from a heart problem. The most common cause of abnormal murmurs in children is congenital heart disease — when babies are born with structural heart defects. Common congenital defects that cause heart murmurs include:

  • Holes in the heart or cardiac shunts. Many heart murmurs in children are the result of holes in the walls between heart chambers, known as septal defects. These may or may not be serious, depending on the size of the hole and its location. Shunts occur when there's an abnormal blood flow between the heart chambers or blood vessels, leading to a heart murmur.
  • Heart valve abnormalities. Congenital heart valve abnormalities are present at birth, but sometimes aren't discovered until much later in life. Examples include valves that don't allow enough blood through them (stenosis) or those that don't close properly and leak (regurgitation).

Other causes of abnormal heart murmurs include infections and conditions that damage the structures of the heart and are more common in older children or adults. For example:

  • Rheumatic fever. Although rare in the United States, rheumatic fever is a serious condition that can occur when you don't receive prompt or complete treatment for a strep throat infection. In many cases, rheumatic fever may permanently affect the heart valves and interfere with normal blood flow through your heart.
  • Endocarditis. This is an infection and inflammation of the inner lining of your heart and valves. Endocarditis typically occurs when bacteria or other germs from another part of your body, such as your mouth, spread through your bloodstream and lodge in your heart. Left untreated, endocarditis can damage or destroy your heart valves. This condition usually occurs in people who already have heart abnormalities.
  • Valve calcification. This hardening or thickening of valves, called mitral or aortic valve stenosis, can occur as you age. These valves may not work as well as they once did, making it harder for blood to flow through your heart, resulting in murmurs.
  • Mitral valve prolapse. In this condition, the valve between your heart's left upper chamber (left atrium) and the left lower chamber (left ventricle) doesn't close properly. When the left ventricle contracts, the valve's leaflets bulge (prolapse) upward or back into the atrium, which may cause a murmur.

Risk factors

There aren't any risk factors for developing an innocent heart murmur.

While there aren't any risk factors for abnormal heart murmurs either, there are risk factors that increase your chance of having an underlying condition that can cause a heart murmur. These include:

  • Family history of a heart defect. If blood relatives have had a heart defect, that increases the likelihood you or your child may also have a heart defect and heart murmur.
  • Illnesses during pregnancy. Having some conditions during pregnancy, such as uncontrolled diabetes or a rubella infection, increases your baby's risk of developing heart defects and a heart murmur.
  • Taking certain medications or illegal drugs during pregnancy. Use of certain medications, alcohol or drugs can harm a developing baby, leading to heart defects.

Diagnosis

Heart murmurs are usually detected when your doctor listens to your heart using a stethoscope during a physical exam.

To check whether the murmur is innocent or abnormal, your doctor will consider:

  • How loud is it? This is rated on a scale from 1 to 6, with 6 being the loudest.
  • Where in your heart is it? And can it be heard in your neck or back?
  • What pitch is it? Is it high-, medium- or low-pitched?
  • What affects the sound? If you change your body position or exercise, does it affect the sound?
  • When does it occur, and for how long? If your murmur happens when your heart is filling with blood (diastolic murmur) or throughout the heartbeat (continuous murmur), that may mean you have a heart problem. You or your child will need more tests to find out what the problem is.

Your doctor will also look for other signs and symptoms of heart problems and ask about your medical history and whether other family members have had heart murmurs or other heart conditions.

Additional tests

If the doctor thinks the heart murmur is abnormal, you or your child may need additional tests including:

  • Chest X-ray. A chest X-ray shows an image of your heart, lungs and blood vessels. It can reveal if your heart is enlarged, which may mean an underlying condition is causing your heart murmur.
  • Electrocardiogram (ECG). In this noninvasive test, a technician will place probes on your chest that record the electrical impulses that make your heart beat. An ECG records these electrical signals and can help your doctor look for heart rhythm and structure problems.
  • Transthoracic or transesophageal echocardiogram. This noninvasive exam, which includes an ultrasound of your chest, shows detailed images of your heart's structure and function. Ultrasound waves are transmitted, and their echoes are recorded with a device called a transducer that's held outside your body. A computer uses the information from the transducer to create moving images on a video monitor. This test identifies abnormal heart valves, such as those that are hardened (calcified) or leaking, and can also detect most heart defects. If the images from a transthoracic echocardiogram are unclear, the doctor may recommend a transesophageal ultrasound. During this exam, a flexible tube containing a small transducer about the size of your index finger is guided down your throat. The transducer will transmit images of your heart to a computer monitor. Since the esophagus passes close behind your heart, the transesophageal transducer can produce better images than can sound waves transmitted through your chest.
  • Cardiac catheterization. In this test, a short tube (sheath) is inserted into a vein or artery at the top of your leg (groin) or arm. A hollow, flexible and longer tube (guide catheter) is then inserted into the sheath. Aided by X-ray images on a monitor, your doctor threads the guide catheter through that artery until it reaches your heart. The pressures in your heart chambers can be measured, and dye can be injected. The dye can be seen on an X-ray, which helps your doctor see the blood flow through your heart, blood vessels and valves to check for problems.
  • Cardiac computerized tomography (CT) or magnetic resonance imaging (MRI). These tests can help diagnose heart problems and detect heart murmurs. In a cardiac CT scan, you lie on a table inside a doughnut-shaped machine. An X-ray tube inside the machine rotates around your body and collects images of your heart and chest. In a cardiac MRI, you lie on a table inside a long tube-like machine that produces a magnetic field. The magnetic field aligns atomic particles in some of your cells. When radio waves are broadcast toward these aligned particles, they produce signals that vary according to the type of tissue they are. Images of your heart are created from these signals, which your doctor will look at to determine the cause of your heart murmur. 

References:

https://en.wikipedia.org/wiki/Heart_murmur

http://www.nhlbi.nih.gov/health/health-topics/topics/heartmurmur

http://www.medicinenet.com/heart_murmur/article.htm

https://www.heart.org/HEARTORG/Conditions/More/CardiovascularConditionsofChildhood/Heart-Murmurs_UCM_314208_Article.jsp

https://www.irishheart.ie/iopen24/heart-murmurs-t-7_19_64.html