What Are Heart Murmurs?

Medically Reviewed by Zilpah Sheikh, MD on March 23, 2024
9 min read

The "murmur" is the sound of blood flowing. It may be passing through an abnormal heart valve, for instance. Or it may be that a condition makes your heart beat faster and forces your heart to handle more blood quicker than normal.

Within the heart, there are four chambers separated by valves that control how much blood enters each chamber at any time. Healthy valves also help prevent blood from flowing in the wrong direction in your heart.

A healthy heart makes a "lub-dub" sound as it beats. The "lub" (systolic sound) happens when part of the heart contracts, and the mitral and tricuspid valves close. The "dub" (diastolic sound) occurs when part of the heart relaxes, and the aortic and pulmonic valves close. A heart murmur is an extra sound in the heartbeat -- such as a ''whooshing'' -- that is caused by turbulent blood flow through the heart valves.

Heart murmurs happen in many healthy children, who may outgrow them as adults. They may also happen during pregnancy. Such murmurs are called "innocent" heart murmurs. They are not linked to medical or heart conditions and do not need treatment or lifestyle changes.

But there are exceptions. Murmurs can be linked to a damaged or overworked heart valve. Some people are born with valve problems. Others get them as a part of aging or from other heart problems.

Doctors divide heart murmurs into three types by the cause and the part of your heart they affect:

  • Systolic. This murmur happens when your heart muscle contracts. Doctors further divide systolic murmurs into two types. Ejection murmurs happen when blood flows through a narrowed blood vessel or abnormal valve. Regurgitant murmurs occur when blood flows backward into one of your heart’s chambers.
  • Diastolic. This type of murmur happens when your heart relaxes between beats. The cause could be a narrowed heart valve or the backward flow of blood through your heart valves.
  • Continuous. This type of murmur happens both when your heart muscle contracts and relaxes.

An innocent, or harmless, heart murmur means your heart is normal except for the murmur. This type is common in newborns and children.

In teens and adults, an innocent heart murmur can happen from:

  • Pregnancy
  • A fever
  • Low count of red blood cells (anemia)
  • High blood pressure
  • An overactive thyroid gland
  • Growth spurts
  • Exercise

A murmur could also be from a problem with a heart valve. The valves open and close to let blood flow through the heart's two upper chambers (called the atria) and two lower chambers (called the ventricles). Valve problems include:

Mitral valve prolapse. Your mitral valve closes to stop blood from flowing back into the upper left chamber of your heart. In mitral valve prolapse, part of the valve doesn't close all the way, allowing blood to flow backward through the valve. Your doctor may call this backflow regurgitation.

Mitral valve or aortic stenosis. Stenosis is the narrowing of the valves, which makes your heart work harder to pump blood to your body. You might be born with narrowed valves. It can also happen as you get older or after an infection such as rheumatic fever.

Aortic valve sclerosis and stenosis. Sclerosis is when the aortic valve gets scarred, thick, or stiff. The valve can narrow over time. Aortic valve stenosis can lead to chest pain, shortness of breath, or fainting. Sometimes, the valve needs to be replaced.

Mitral or aortic regurgitation. Blood flows the wrong way through your mitral or aortic valve and back into your heart. Your heart must work harder to force blood through the damaged valve. Over time, this can weaken or enlarge your heart and lead to heart failure.

Congenital heart defects. About 40,000 babies are born with heart defects each year. These problems include a hole in the heart walls or abnormal valves. Surgery can correct many heart defects.

Other heart conditions that can cause a murmur include:

  • Endocarditis. The bacteria or other germs that cause this infection attack and damage your heart valves. Lupus causes a type of endocarditis that makes growths form on the heart valves.
  • Calcium buildup. Calcium can deposit on a heart valve and make it stiff and narrow. The valve may not be able to close all the way, which allows blood to flow backward. 
  • Tumors. Carcinoid syndrome is a type of cancer that can affect your heart. The tumor grows slowly and causes symptoms such as weight loss, belly pain, and diarrhea.
  • Marfan syndrome. This inherited condition affects the connective tissue that holds your body together. Marfan syndrome can make your valves larger than normal. Blood flows backward through the faulty valves when your heart pumps.
  • Rheumatic fever. This is a complication of untreated strep throat. Rheumatic fever is rare in the U.S., but it can damage the heart valves and cause a murmur.

Many people with heart murmurs have no symptoms. But when they do happen, symptoms of heart murmur include:

  • Chest pain
  • Fast heartbeat (palpitations)
  • Shortness of breath
  • Tiredness
  • Heavy sweating without doing much activity
  • Fainting
  • Bluish color to the skin or fingertips
  • Sudden weight gain or swelling
  • Swollen neck veins
  • A cough that doesn’t go away

Heart murmur symptoms in babies

Babies and young children with a heart murmur might also have symptoms such as:

  • Feeding problems and appetite loss
  • Bluish color to the skin, especially on the lips and fingertips
  • Cough
  • Extra fussiness
  • Slow growth
  • Dizziness
  • Swelling in the belly, lower legs, ankles, and feet

Heart murmur sounds

A normal heartbeat makes a lub-dub sound. When you have a heart murmur, your doctor will hear a whooshing or humming sound between beats. The abnormal flow of blood through your heart valves causes this sound.

Usually, doctors find heart murmurs during a physical exam. Your doctor should be able to hear the sound when listening to your heart with a stethoscope. The doctor will listen for these things:

  • How loud is the murmur on a scale of one to six?
  • Is the sound high- or low-pitched?
  • Where in your heart is the sound? Does it spread to your neck or back?
  • Does it happen when your heart pumps, relaxes, or both?
  • Does the sound change when you hold your breath, squat, lie down, or stand up?

Other tests your doctor might do during the physical exam are:

  • Blood pressure. This test measures the force of your blood pushing against your artery walls. High blood pressure can make the condition that caused your heart murmur worse.
  • Blood oxygen level. Anemia can cause your blood oxygen level to drop.
  • Pulse rate. A normal resting heart rate is 60-100 beats per minute.

Your doctor may order one or more of these tests to see whether your heart murmur is innocent, or if a valve disease or heart defect caused it:

  • Echocardiogram. This test uses sound waves to show the blood flow through your heart. A stress echocardiogram shows how well your heart works when it's under stress from exercise.
  • Electrocardiogram (EKG). It measures the electrical activity of your heart. 
  • Chest X-rays. These images show whether your heart is enlarged due to heart or valve disease.
  • Cardiac catheterization. This test shows how well your heart and its blood vessels are working. Your doctor might do cardiac catheterization if they can't find the cause of your murmur. A thin tube goes through a blood vessel to your heart. Sometimes, dye is put into the tube to help your blood vessels show up more clearly on the test.

Heart murmur grading

Doctors grade heart murmurs by how intense or loud they are. The systolic grading system is for murmurs that happen when your heart squeezes. It ranges from 1 to 6:

  • Grade 1 is so faint that your doctor can barely hear it with a stethoscope in a quiet room.
  • Grade 2 is faint, but your doctor can hear it with a stethoscope.
  • Grade 3 is loud enough for your doctor to hear easily with a stethoscope.
  • Grade 4 is very loud and obvious.
  • Grade 5 is so loud that your doctor can hear it with only one side of the stethoscope touching your chest.
  • Grade 6 is so loud that your doctor can hear it when the stethoscope isn't touching your chest.

The diastolic grading system is for murmurs that happen when your heart relaxes. It ranges from 1 to 4:

  • Grade 1 is so quiet your doctor can barely hear it.
  • Grade 2 is soft, but your doctor can hear it.
  • Grade 3 is easy to hear.
  • Grade 4 is loud and clear.

The volume of a heart murmur doesn't always relate to how severe it is. A loud murmur may not be more severe than a quiet one. The type of murmur is a sign of its severity, though. Systolic heart murmurs are often innocent, or harmless.

Your exam and tests should show what caused your heart murmur. If the murmur is related to a heart problem, your doctor may refer you to a heart doctor called a cardiologist. You might need medicine or surgery to treat the cause.

Many children and adults have harmless heart murmurs that don't need treatment. If a condition such as high blood pressure is the cause of your murmur, your doctor will treat the cause.

Treatment for some types of heart valve disease includes medicines such as:

  • Blood thinners. These medicines prevent blood clots from forming in the heart.
  • Antiarrhythmic medicines. They control a fast or irregular heartbeat.
  • Blood pressure lowering medicines. Angiotensin-converting enzyme (ACE) inhibitors and beta-blockers lower high blood pressure to prevent it from making your heart murmur worse.
  • Water pills. Diuretics remove excess water from your blood so it's easier for your heart to pump.

Some of the heart conditions that cause murmurs need surgery to fix. Your surgeon can do the procedure through a large incision with open-heart surgery. Or you might have minimally invasive or robotic surgery that uses smaller incisions. Sometimes, surgeons perform procedures through a catheter.

Surgery can:

  • Close a hole in the heart wall
  • Fix or replace a damaged heart valve
  • Patch a leak in the valve
  • Tighten the ring around a valve so it doesn't leak
  • Remove extra tissue to help the valve close tighter

You can't always prevent heart murmurs. But following a heart-healthy lifestyle and getting regular checkups could help you avoid conditions such as high blood pressure and heart valve problems that cause murmurs.

Not drinking or doing illegal drugs and getting treated for infections during pregnancy can prevent some heart murmurs in children. Most children who do have heart murmurs outgrow them as they get older.

Most heart murmurs aren't serious. But sometimes a murmur can be a sign of a valve or heart problem that does need treatment.

Get medical help if you have symptoms such as:

  • Chest pain
  • Shortness of breath during exercise or when you sleep
  • Tiredness
  • Dizziness or fainting for no obvious reason
  • Heart palpitations
  • Swelling in your ankles or legs

Can you die from a heart murmur?

Sometimes, a murmur does signal a heart problem. In that case, it could be serious if you don't treat it.

A heart murmur is an abnormal sound your doctor might hear if blood flows the wrong way through your heart. Some heart murmurs are harmless. Others are a sign of a valve problem or other type of heart disease.

See your doctor for symptoms such as chest pain, shortness of breath, or a fast heartbeat. You may need medicine or surgery to treat the condition causing your heart murmur.

How serious is a heart murmur?

A heart murmur itself isn't dangerous. Some heart murmurs don't cause any problems. Others are signs of a serious heart condition.

What is the life expectancy of someone with a heart murmur?

A heart murmur shouldn't affect your life expectancy. An innocent heart murmur won't have any effect on your life. If a serious heart problem caused the murmur, treatment can prevent it from affecting your lifespan.