Heart murmurs are common, especially in children, with up to 50–70% exhibiting murmurs during childhood, most of which are harmless1 2. These murmurs are sounds caused by turbulent blood flow within the heart and can be present at birth or develop later in life3 . While many heart murmurs are innocent and do not indicate heart disease, others signal underlying structural or functional heart problems that require medical evaluation4 .
Structural Heart Defects
Heart murmurs often arise from congenital or acquired structural abnormalities of the heart1 . In children, many murmurs are due to congenital heart defects present at birth, with septal defects being the most common1 5. Septal defects are holes in the walls dividing the heart chambers that disrupt normal blood flow and produce audible murmurs1 6.
Key congenital structural defects causing murmurs include:
- Atrial Septal Defect (ASD): A hole in the atrial septum allowing abnormal blood flow between the upper heart chambers, leading to a systolic murmur1 7.
- Ventricular Septal Defect (VSD): An opening in the ventricular septum causing turbulent blood flow and a systolic murmur; VSD is the most frequent congenital cardiovascular malformation5 1.
- Patent Ductus Arteriosus (PDA): A fetal blood vessel that fails to close after birth, resulting in continuous abnormal blood flow and a continuous murmur8 1.
These defects alter intracardiac blood flow patterns, producing the characteristic whooshing or swishing sounds heard during auscultation3 . Structural abnormalities can be detected prenatally or during routine pediatric exams1 .
Heart murmurs caused by structural defects often indicate abnormal blood flow through holes or persistent fetal vessels in the heart. Early detection is crucial for managing potential complications1 8.
Heart Valve Issues
Heart valves ensure unidirectional blood flow through the heart chambers. Dysfunction of these valves, such as stenosis (narrowing) or regurgitation (leakage), frequently causes heart murmurs1 9. The four main valves are the aortic, pulmonary, mitral, and tricuspid valves1 .
Aortic Valve
The aortic valve controls blood flow from the left ventricle into the aorta. Malfunction can produce audible murmurs due to turbulent flow1 10. Common aortic valve problems include:
- Aortic Stenosis: Narrowing of the valve that limits blood flow, causing a systolic murmur. This condition can be congenital or develop later in life due to calcification1 9.
- Aortic Regurgitation: Improper closure of the valve allows backward blood flow during diastole, producing a diastolic murmur1 9.
Symptoms of aortic valve disease may include chest pain, shortness of breath, fatigue, syncope, and peripheral edema1 10.
Mitral Valve
Mitral valve problems often involve regurgitation, where the valve does not close completely, causing blood to leak backward into the left atrium during ventricular contraction9 11. This leakage creates a characteristic murmur and may lead to symptoms such as palpitations and fatigue10 .
Pulmonary Valve
Pulmonary valve stenosis or regurgitation can also cause murmurs, though these are less common than aortic or mitral valve issues11 . Stenosis narrows the valve opening, while regurgitation allows backward flow, both producing turbulent blood flow sounds11 .
Tricuspid Valve
Tricuspid valve dysfunction, including regurgitation or stenosis, can result in murmurs heard on the right side of the heart. These conditions may be congenital or acquired and contribute to abnormal heart sounds11 .
Heart murmurs are often the first sign of valve disease, which affects millions annually. Murmurs caused by valve problems may sound like whooshing, swishing, or rasping noises10 .
Cardiomyopathy and Heart Muscle
Cardiomyopathies are diseases affecting the heart muscle's thickness or function and may produce murmurs1 . One important form is hypertrophic cardiomyopathy (HCM), characterized by abnormal thickening of the myocardium1 12.
HCM is often inherited in an autosomal dominant pattern and can cause symptoms such as exertional chest pain, syncope, palpitations, and fatigue1 12. The thickened heart muscle can obstruct blood flow, leading to turbulent flow and audible murmurs11 .
Hypertrophic cardiomyopathy is a genetic condition that thickens the heart muscle, often causing murmurs and symptoms like chest pain and fainting during exercise12 .
Hereditary Heart Murmur Factors
Certain congenital heart defects causing murmurs have genetic origins, though murmurs themselves are not directly inherited1 . Familial patterns exist for underlying heart defects such as septal defects and cardiomyopathies1 .
A family history of cardiomyopathies or congenital heart defects increases the likelihood of murmurs due to structural or muscle abnormalities1 6. Genetic predisposition plays a significant role in the risk of developing murmurs related to these conditions.
Heart Murmur Prevalence and Demographics
Heart murmurs are frequently detected in infants and children, sometimes even before birth1 . Routine pediatric exams often reveal murmurs in asymptomatic children, most of which are innocent and do not require treatment2 1.
Yale has been a leader and innovator in treating children and adults with heart defects since the 1940s. Heart murmurs are carefully evaluated several times a day in clinics, with state-of-the-art workups and interventions provided when necessary6 .
Innocent murmurs may persist or resolve as the child grows, while pathologic murmurs can occur at any age and usually indicate underlying heart disease1 . Abnormal murmurs reflect structural or functional heart abnormalities and warrant further diagnostic evaluation1 .
| Cause | Description | Typical Age Group | Murmur Type |
|---|---|---|---|
| Ventricular Septal Defect | Hole in ventricular septum | Infants, children | Systolic murmur |
| Atrial Septal Defect | Hole in atrial septum | Infants, children | Systolic murmur |
| Patent Ductus Arteriosus | Persistent fetal vessel | Neonates, infants | Continuous murmur |
| Aortic Valve Stenosis | Narrowing of aortic valve | Congenital or adults | Systolic murmur |
| Aortic Valve Regurgitation | Incomplete valve closure | Adults | Diastolic murmur |
| Hypertrophic Cardiomyopathy | Thickened heart muscle, often inherited | Adolescents, adults | Systolic murmur |
| Sources: 158 | |||
The most important test for a heart murmur is a careful exam with a stethoscope. If the murmur is determined to be innocent, no further testing is needed. Patients may participate in all activities with no concerns or restrictions6 .
Heart Murmur Risk Factors
Risk factors for heart murmurs include congenital heart defects and family history of heart problems1 6. Other factors that may increase the likelihood of murmurs are:
- Fever, which increases blood flow velocity3 13
- Anemia, reducing blood oxygen levels and causing turbulent flow3 14
- Overactive thyroid (hyperthyroidism) 313
- Rapid growth phases such as adolescence3 13
- Pregnancy, which increases blood volume and flow3 13
Medical conditions that can increase murmur risk include carcinoid syndrome, cardiomyopathy, endocarditis (infection of the heart lining), autoimmune disorders, pulmonary hypertension, and history of rheumatic fever3 .
Innocent heart murmurs are common during childhood, exercise, and pregnancy due to increased blood flow, and often do not indicate heart disease4 .
Heart Murmur Summary and Review
Heart murmurs are extra or unusual heart sounds caused by turbulent blood flow through the heart valves or chambers3 . They can be innocent, meaning no heart problem exists, or abnormal, indicating underlying heart conditions such as congenital defects, valve disease, or cardiomyopathy4 11.
Key points include:
- Murmurs may be systolic (during heart contraction), diastolic (during relaxation), or continuous3 4.
- Innocent murmurs are common in children and often resolve by adulthood2 6.
- Abnormal murmurs may cause symptoms like chest pain, shortness of breath, fainting, or bluish skin3 13.
- Diagnosis involves auscultation with a stethoscope and may include echocardiography, chest X-ray, and electrocardiogram4 7.
- Treatment depends on the underlying cause and may range from observation to surgery6 10.
