Heart Murmurs


Normal heart sounds are often described as a constant "lub-dub, lub-dub, lub-dub, lub-dub." These are the sounds of the four heart valves closing, and they normally occur in pairs. Using a stethoscope, a trained doctor can hear an abnormal sound in a heartbeat—a heart murmur.

Some heart murmurs, called “innocent” heart murmurs, are harmless, common in children, and do not require treatment or lifestyle changes. Innocent murmurs usually disappear by the time children reach adulthood.

Other murmurs indicate more serious heart problems. In these cases, the sound may indicate blood flowing through a damaged or overworked heart valve, a hole in one of the heart's walls, or a narrowing in one of the heart's vessels.

What Causes a Heart Murmur?

Heart murmurs occur when blood is forced through a narrowed valve (stenosis) or when it leaks backward through a defective valve (regurgitation). These valve problems may be present at birth (congenital) or develop later in life from rheumatic fever, coronary artery disease, infective endocarditis, or aging. A structural defect, such as a hole in a heart wall, can also cause a murmur. Conditions such as pregnancy, anemia, high blood pressure, fever, or an overactive thyroid gland may also cause a temporary or periodic heart murmur.

Symptoms

Most people with a heart murmur have no symptoms. The murmur is usually found during a routine physical examination or when related symptoms arise, such as chest pain, shortness of breath, fatigue, or cyanosis.

Diagnosis

In most cases, a stethoscope is the only tool that a doctor needs to diagnose a heart murmur. Because heart murmurs may change as body position or breathing changes, the doctor may listen for the murmur while the patient is standing up, sitting down, squatting, lying down, breathing deeply, or holding their breath.

A diastolic (di"as-TOL'ik) murmur occurs while the heart is relaxing between beats. A systolic (sis-TOL'ik) murmur occurs when the heart muscle is contracting. Systolic murmurs are graded by intensity (loudness) from one to six. A grade 1/6 is very faint, heard only with special effort. A grade 6/6 is extremely loud and can even be heard with the stethoscope slightly removed from the chest.

To determine whether a heart murmur is innocent or caused by another problem, additional tests may be ordered, including:

• A chest x-ray
• An electrocardiogram (ECG)
• An echocardiogram
• An amyl nitrate test

Treatment

Heart murmur treatment is based on underlying cause. Innocent heart murmurs usually need no treatment. When a heart murmur’s underlying condition is something like high blood pressure, the underlying condition is treated to resolve the murmur. If a heart murmur is caused by heart valve disease or a structural defect, medicine and/or surgery may be needed.

Preventative Antibiotics

It used to be common practice for doctors to prescribe antibiotic medicine to patients with heart murmurs before a dental or surgical procedure in order to prevent heart valve infection (these procedures may cause bacteria to enter the bloodstream). Today, most doctors believe that this practice is unnecessary unless the murmur is caused by intrinsic valve disease.

Medicines

Different medicines are prescribed for heart murmurs, depending on the underlying cause of the murmur and the patient’s individual history and symptoms. The types of medicines that may be used include anticoagulants, beta blockers, antihypertensives, antiarrhythmics, diuretics, and digoxin.

Surgery

Depending on the cause of the heart murmur, surgery may be needed to repair a heart defect or a damaged heart valve. Heart valve surgery is specialized to the individual patient and the structural conditions that exist.

Resources

Texas Heart Institute www.texasheartinstitute.com/HIC/Topics/Cond/murmur.cfm
American Heart Association www.americanheart.org/presenter.jhtml?identifier=4571

Updated December 2009