A heart murmur is a distinct, extra sound—a swishing, whooshing, or rasping noise—heard by a healthcare provider when listening to the heart with a stethoscope. Normally, the heart produces two sounds, often described as “lub-dub,” which represent the closing of the heart valves as blood flows smoothly through the chambers. A murmur occurs when blood flow becomes turbulent instead of smooth. While the presence of a murmur is a sign that blood is moving in an unusual way, it does not automatically indicate a serious heart problem.
The Difference Between Innocent and Abnormal Murmurs
Murmurs are extremely common, especially in childhood, with estimates showing that up to 80% of children will have a murmur detected at some point in their early years. The vast majority of these are classified as “innocent” or “functional” murmurs, which are harmless and not caused by any structural heart disease. Innocent murmurs are temporary and often occur when blood flows faster than usual through the heart. This increased flow can be triggered by normal physiological states such as fever, exercise, excitement, anemia, or phases of rapid growth in adolescence. These murmurs do not require treatment, as they do not affect the heart’s function and frequently disappear on their own as a child matures.
Abnormal, or pathologic, murmurs are significantly less common but signal an underlying heart defect or condition. These are typically caused by structural problems, such as issues with the heart valves or congenital defects in the heart’s walls. In adults, this often relates to acquired valve disease, where valves become stiff and narrowed (stenosis) or fail to close properly, allowing blood to leak backward (regurgitation).
How Turbulent Blood Flow Creates the Sound
The characteristic sound of a murmur is a direct result of the transition from laminar to turbulent blood flow. In a healthy heart, blood moves in smooth, parallel layers, a pattern called laminar flow, which is essentially silent. The normal “lub-dub” sound is only produced when the heart valves snap shut. When flow becomes turbulent, the blood swirls chaotically, creating vibrations loud enough to be heard through a stethoscope. Turbulence can be created in a healthy heart by simply increasing the speed of blood flow, which causes innocent murmurs.
For an abnormal murmur, the turbulence is caused by a physical obstruction or an uneven surface within the heart. For example, a narrowed valve forces blood through a smaller opening at high pressure, or a leaky valve allows blood to rush backward. The location, timing, and intensity of the sound help physicians determine where the turbulence is occurring.
Recognizing Signs That Require Further Evaluation
For most people with an innocent murmur, there are no associated symptoms, and the sound is detected only during a physical examination. However, a heart murmur accompanied by other symptoms can be a warning sign that the heart is struggling to pump blood efficiently. Signs that warrant immediate medical attention include experiencing shortness of breath, especially with activity, or a persistent, unexplained cough. Other concerning symptoms are chronic fatigue, dizziness, or fainting episodes (syncope).
In infants, poor feeding, lack of growth, or heavy sweating with minimal activity are important indicators. Visible signs such as swelling in the ankles, feet, or abdomen, or a bluish tint to the lips or fingernails (cyanosis), also suggest a significant heart issue. If a previously known murmur changes in character or new symptoms develop, a thorough medical follow-up is necessary.
Follow-Up Testing and Treatment Options
If a physician hears a murmur suggesting it may be pathologic, or if concerning symptoms are present, further diagnostic testing is required. The primary test is typically an echocardiogram, which uses sound waves to create moving images of the heart. This non-invasive ultrasound allows doctors to visualize the heart’s structure, check valve function, and see how blood is flowing through the chambers.
Other tests may include an electrocardiogram (EKG), which measures electrical activity to detect problems like chamber enlargement or arrhythmias. A chest X-ray can also provide information about the size of the heart and the condition of the lungs. These tests help confirm whether a structural defect is the cause of the murmur.
For innocent murmurs, the only management required is reassurance and continued routine check-ups. Treatment for a pathologic murmur focuses on addressing the underlying condition. This may involve medications to manage symptoms, such as diuretics to reduce fluid or blood thinners to prevent clots. Severe structural issues, such as a significantly narrowed or leaking heart valve, may ultimately require surgical intervention, like valve repair or replacement.