Heart murmur is the medical term for audible blood flow through the heart. There are two main types of heart murmurs: physiologic and pathophysiologic. Flow murmurs are one example of a physiologic murmur.
Murmurs occur whenever the blood flow is turbulent rather than laminar. Physiologic, or innocent, murmurs typically result from benign causes and are part of the body’s normal response. Pathophysiologic, or abnormal, murmurs are the result of a heart abnormality or underlying heart condition.
Physiologic murmurs, such as flow murmurs, can go away on their own, but abnormal murmurs typically require some form of treatment.
In this article, we describe what flow murmurs are, including their causes and symptoms. We also outline the diagnostic procedure for flow murmurs, along with some factors that can increase the likelihood of this type of murmur.
According to the American Heart Association (AHA), a physiologic heart murmur is the result of normal blood flow through the heart or the arteries near the heart. A flow murmur is often due to increased blood flow.
Flow murmurs mostly occur in infants, children, and teens. Reports suggest that up to 72% of children experience physiologic heart murmurs. In some cases, the murmur may continue into and throughout adulthood.
When a flow murmur occurs, a doctor can hear the blood flowing through the heart with a stethoscope. According to The Society for Cardiovascular Angiography and Interventions, fever or anemia may make the sound easier to hear by making the murmur louder.
A physiologic murmur may not produce any symptoms, and it will not increase the risk of heart-related conditions or diseases. It will likely resolve on its own with resolution or treatment of the underlying condition (such as fever or anemia).
Flow murmurs are the result of increased blood flow through the valves of the heart. The valves are small flaps of tissue that open and close to ensure that blood flows through the heart in the correct direction.
Below are several conditions and factors that can temporarily increase blood flow through the heart, causing a flow murmur:
In some cases, a person may need to treat the underlying condition causing the flow murmur. Following successful treatment, the flow murmur should disappear.
It is possible that neither physiologic nor pathophysiologic murmurs will produce any symptoms. A person may not even realize that they have a murmur until a doctor discovers it during a routine examination.
In some cases, though, a person may experience symptoms of a heart murmur. Below are some possible symptoms of physiologic murmurs and pathophysiologic murmurs.
Flow murmurs and other benign murmurs often do not directly cause any symptoms, although a doctor may be able to hear the blood flowing through the heart if they are listening with a stethoscope.
However, people may experience symptoms of conditions that can cause flow murmurs. For instance, anemia is a common cause. While mild anemia may not produce any symptoms, moderate or severe anemia may cause the following:
- pale skin
- increased sweating
- increased thirst
- rapid, weak pulse
- tiredness and fatigue
- dizziness or faintness
- fast breathing
- shortness of breath
- lower leg cramps during exercise
Abnormal murmurs also may not produce any symptoms. If symptoms do occur, they may include:
A person may not realize that they or their child has a heart murmur. Diagnosis often occurs during a routine medical examination.
According to a 2018 review, physiologic heart murmurs are the most common reason for a pediatrician to refer a child to a heart specialist, called a cardiologist. The review indicated that the diagnosis of a heart murmur should include the following:
- an evaluation of the person’s medical history
- a review of the person’s family history
- a full medical assessment
When diagnosing a child, a doctor may also wish to review the child’s birth history and growth chart.
If the doctor can hear a heart murmur or suspects that one is present, they will likely recommend one or more of the following procedures:
- Chest X-ray: Uses radiation to image the heart and surrounding tissues.
- Cardiac MRI: Uses imaging to view the heart as it is pumping blood.
- Electrocardiogram (EKG): Measures the electrical activity of the heart, which allows a doctor to assess a person’s heart rhythm.
- Transthoracic echocardiogram: Emits and receives ultrasound waves through the chest wall to create a moving image of the heart.
- Cardiac catheterization: Involves inserting a long, flexible tube called a catheter into a blood vessel. The end of the catheter contains a tiny camera that allows a surgeon to see inside the heart.
- Transesophageal echocardiogram: Involves inserting a long, flexible tube called an endoscope into a person’s esophagus (food pipe). The tip of the endoscope contains a device that emits and receives sound waves. This device allows a surgeon to see detailed images of the heart’s valves.
If the flow murmur is the result of an underlying medical condition, a person may need to treat the condition to resolve the murmur.
A physiologic flow murmur typically does not require specific treatment in addition to treating the underlying condition causing it.
Physiologic heart murmurs during pregnancy are very common, affecting almost 90% of pregnant women.
Flow murmurs during pregnancy are not usually a cause for concern. In many cases, the murmur is the result of increased blood volume. However, women should see their doctor if they experience the following symptoms while at rest:
- heart palpitations, which may feel like a fluttering in the chest
- shortness of breath
- chest pain
- difficulty breathing when lying down or sleeping
- swelling of the abdomen, ankles, or feet
The above symptoms can sometimes be an indication of heart disease.
Certain factors can increase the risk of heart murmurs.
Risk factors for innocent murmurs
The following medical conditions can increase the risk of a physiologic flow murmur:
- high fever
- a hyperactive thyroid gland
Pregnancy is another factor that can lead to the development of a physiologic murmur.
Risk factors for abnormal murmurs
Abnormal heart murmurs are the result of heart abnormalities or disease. Some risk factors for developing an abnormal murmur include:
- congenital heart or valve abnormalities
- scar tissue from a heart attack
- heart attack
- heart disease
- valve disease
- high blood pressure
- calcium deposits on heart valves
Flow murmurs are common among children and teens. The condition is usually the result of increased blood flow through the heart. It does not indicate an underlying problem with the heart or increase the risk of heart disease.
Often, a person may not even realize that they have a flow murmur. Most cases go away by the time a child reaches adulthood. However, some people may continue to experience a flow murmur into and throughout adulthood.
Flow murmur is the medical term for an unusual sound that occurs as blood flows through the heart or its surrounding arteries. It is a type of physiologic murmur, meaning that the murmur itself is usually harmless.
Flow murmurs are common among children and teens but usually go away by adulthood. However, some people continue to experience them into and throughout their adult years. Pregnancy and certain health conditions can increase the likelihood of developing a flow murmur.
While flow murmurs are harmless, abnormal heart murmurs can indicate an underlying issue with the heart. A medical evaluation is necessary to distinguish a physiologic from a pathophysiologic murmur. As such, a person should see a doctor if they become aware of a heart murmur or experience worrying symptoms relating to their heart.