A heart murmur is an abnormal heart sound that results from the turbulent flow of blood through the heart. Heart murmurs are usually detected by a physician using a stethoscope to listen to the heartbeat. Most heart murmurs are harmless or “innocent,” which means they are not associated with a disease or condition of the heart. Many, if not most, children will have a heart murmur at some point in their lives.
However, heart murmurs may also be the result of an underlying heart condition, such as the narrowing of one of the heart’s four valves (valvular stenosis) or heart disease that has been present from birth (congenital heart disease).
The underlying cause of a heart murmur is usually diagnosed through painless tests such as an echocardiogram and (if necessary) a minimally invasive test such as a cardiac catheterization. A treatment plan will be designed based on the underlying condition.
About heart murmurs
A heart murmur is an abnormal heart sound that results from the turbulent flow of blood through the heart. Heart murmurs are usually detected by a physician listening to the heartbeat with a stethoscope. Although many heart murmurs are unassociated with disease, they may also stem from a cardiovascular problem such as:
Valvular stenosis. A narrowing of one of the heart’s four valves which causes blood flow to become more turbulent as it is forcefully pumped through the smaller opening. The character of the murmur can give the physician clues about which valve(s) is/are affected.
Mitral valve prolapse. A condition in which the flaps of the mitral valve (located between the left atrium and left ventricle) cannot close properly. As a result, blood may leak back through the valve (mitral regurgitation), when it should only move forward.
Aortic regurgitation. A condition in which the aortic valve (located between the left ventricle and the aorta) does not close properly, allowing blood to leak back into the left ventricle rather than being pumped out to the body.
Tricuspid regurgitation. A condition in which the tricuspid valve (located between the right atrium and right ventricle) does not close properly, allowing some blood to leak backward from the right ventricle into the right atrium during contraction
Aortic aneurysm. The dilation, bulging or ballooning out of part of the wall of the aorta, resulting in a murmur caused by aortic regurgitation. Untreated, aortic aneurysm puts the patient at risk for a ruptured aneurysm.
Congenital heart disease. Heart defects or other conditions present since birth. This is the most common cause of non-innocent heart murmurs. Heart murmurs can be caused by septal defects, as well as shunts that allow the blood to travel from one side of the heart to the other inappropriately.
Enlarged heart. An increase in the size of the heart muscle that indicates that the heart is overworked. An enlarged heart due to a non-cancerous tumor called a cardiac myxoma may cause a heart murmur. Heart murmurs may also be caused by hypertrophic cardiomyopathy, a condition in which the heart becomes enlarged and weakened.
Increased transvalvular blood. A condition in which blood is flowing more rapidly than normal through the heart’s lower chambers (ventricles).
Innocent murmurs (sometimes called Still’s or functional heart murmurs) do not represent any long-term heart-related problems and are not related to any structural abnormality of the heart. They are associated with rapid or unusual blood flow through the heart's valves. Such situations are associated with overactive thyroid function, fever, anemia and pregnancy.
Other symptoms related to heart murmurs
Most people do not notice innocent heart murmurs and remain unaware they have one until it is detected during a routine physical examination.
Heart murmurs caused by an underlying cardiovascular condition may be accompanied by other signs and symptoms of that condition, including:
Shortness of breath
Lightheadedness or syncope (fainting)
Arrhythmias (rapid heartbeats)
Chest pain
Fatigue with exertion
Signs of heart failure
Types and differences of heart murmurs
If a murmur is present, it will be categorized as one of three types, depending on when it occurs in the cardiac cycle:
Systolic. Murmurs that occur during the heart’s muscular contraction phase (systole) during which blood is pumped from the heart. Systolic murmurs are further described as early systolic, mid-systolic, late systolic or holosystolic, referring to when they occur during the contraction period. Systolic murmurs may be innocent or may signal potential problems such as aortic stenosis or mitral regurgitation.
Diastolic. Murmurs that occur during the heart’s resting phase (diastole), during which the heart takes in nourishment from oxygen-rich blood. Diastolic murmurs are further classified as early diastolic, mid-diastolic or late diastolic (presystolic). All diastolic murmurs are clinically significant, requiring further investigation to rule out aortic regurgitation or mitral stenosis.
Continuous. Murmurs that occur through both the systolic and diastolic cycles. Continuous murmurs may be innocent and occur in healthy children and pregnant women. However, they may suggest the presence of cardiovascular problems (such as patent ductus arteriosus). Most continuous murmurs are subject to further evaluation.
A heart murmur may also be classified according to how loud it is, as well as its location in the chest. Based on a scale from one to six, with higher designations being more intense (louder), a physician may label a heart murmur as “grade 1,” “grade 2” and so forth. However, since listening to the heart is the physician’s primary tool for distinguishing heart murmurs, such labeling is subjective and not precisely measurable. Heart murmurs are also described by their location in the chest, from their radiation or transmission (to neck or back), and their pitch (low frequency or high pitch, etc.).
Diagnosis methods for heart murmurs
During auscultation (the process of using a stethoscope to listen to the heart), the physician will carefully evaluate several distinct factors, such as the loudness, frequency, configuration and timing of the patient’s murmur with the heartbeat. Each characteristic is matched to established guidelines.
If a patient exhibits symptoms of heart disease along with the discovery of heart murmurs, or if certain murmurs point to a more serious underlying condition, further diagnostic tests will be done. These tests may include:
Echocardiogram. This test uses sound waves to create a picture of the heart, allowing the physician to determine the thickness and/or dilation of the various heart chambers. According to 2006 guidelines issued by the American College of Cardiology and American Heart Association, echocardiography is the standard for discovering the cause of a murmur.
Doppler echocardiogram. This test is very effective, precise and noninvasive. It can show whether a murmur is the result of a significant medical problem. This ultrasound test provides images that indicate the direction and speed of blood flow, as well as the cause of a murmur (such as a heart defect).
Electrocardiogram. This standard and fairly inexpensive test records the electrical patterns of the heart. It can reveal a number of problems with the heart. It may be performed first, but the echocardiogram is considered the best test to evaluate the cause of a murmur.
Chest x-ray. This test may be done to assess heart size, calcification of valves and other information.
Blood test. One or more tests may be administered if the physician suspects inflammation of the heart or valves endocarditis.
Cardiac catheterization. During this test the physician examines the heart's hemodynamics (the pressures and motion of blood flow through the heart). Blood samples will also be taken and a coronary angiogram, including a coronary arteriogram, will be performed. Prior to the test, the physician will inject a special dye (contrast medium) into the coronary arteries through a catheter. This dye is visible under x-ray and allows the physician to precisely locate possible blockages of the coronary arteries. Following the coronary angiogram, the catheter may be moved into the left ventricle and a left ventricular angiogram will be performed. In some cases, an aortogram may be performed
Patients may also be asked to perform simple movements, such as standing suddenly, squatting or gripping an object tightly. These movements may change the nature of heart murmurs in predictable ways that help physicians better diagnose what kind of underlying is present. Medical professionals are well trained to diagnose murmurs and the extent of testing will be based on a careful assessment of many factors.
New technologies are being developed to better differentiate the types of murmurs. For example, electronic stethoscopes use computer technology to record and analyze heart sounds. Another innovation is in the field of telemedicine, where information gathered through electronic stethoscopes is sent as e-mail attachments. This can be useful in pediatric patients who may have murmurs that require further evaluation so the pediatrician can e-mail the information to a cardiologist.
Treatment and prevention of heart murmurs
Heart murmurs, in themselves, are typically not treatable. Nor do they warrant treatment. If, however, the physician determines through careful testing that a murmur is neither innocent nor a natural murmur resulting from fever or pregnancy, the underlying cause will be investigated and treated. Patients with existing valvular heart disease or congenital heart defects may need to receive medical or even surgical treatment.
There is no known method to prevent heart murmurs that are unrelated to other forms of heart disease. Certain conditions, such as pregnancy and rheumatic fever, can cause heart murmurs. A physician may recommend a preventive program focusing on good overall cardiovascular health to reduce the risk of any future heart-related problems or complications.
It is generally recommended in the majority of patients that prophylactic antibiotics should be given prior to dental or surgical procedures. All patients with heart murmurs are advised to speak to their doctor about the need for prophylactic antibiotics before any dental or surgical procedures. Such precautions may prevent infections from occurring on the heart (endocarditis).
Individuals with innocent murmurs have an excellent prognosis and, in the vast majority of cases, will see no disruptions in their normal, everyday routine.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to heart murmurs:
Do you detect a heart murmur when listening to my heartbeat?
What does a heart murmur sound like or feel like?
What are the chances that the heart murmur is harmless?
Could my murmur be the sign of an underlying condition?
How can we tell if my heart murmur is the sign of a serious cardiovascular condition?
Is my heart murmur treatable? If so, what type of treatment do you recommend?
If my murmur is not treatable, what course of action do you advise?
Will I need to take any special precautions during dental procedures?
Will my murmur cause any disruptions in my everyday life? Can I still engage in a normal range of activities?
Could a heart murmur be caused by my pregnancy? Could a murmur be dangerous to my pregnancy?
