A heart murmur is a sound detected during a heartbeat, distinct from the normal rhythmic sounds. This sound is often described as a whooshing, swishing, or rasping noise. A murmur is a physical sign, not a diagnosis, and not all murmurs indicate a serious underlying condition. Whether a heart murmur is serious depends on its specific characteristics and ultimate cause.
What Exactly Is a Heart Murmur
The heart’s normal sound, often called “lub-dub,” is created by the closing of the heart valves. The “lub” occurs when the mitral and tricuspid valves close during systole. The “dub” occurs when the aortic and pulmonic valves close as the heart relaxes.
A heart murmur is generated when blood flow becomes turbulent, creating vibrations audible through a stethoscope. This turbulence occurs when blood moves rapidly or unevenly through the heart’s chambers and valves. Disruption in the smooth flow of blood produces this extra sound.
Innocent Murmurs Versus Abnormal Murmurs
The most important distinction in evaluating a heart murmur is determining whether it is innocent or abnormal. An innocent murmur, also known as a functional or physiologic murmur, occurs in a structurally normal and healthy heart. These sounds are common, especially in children, and are caused by a temporary increase in the speed of blood flow.
Conditions that cause the heart to pump blood faster, such as fever, strenuous exercise, rapid growth spurts, or pregnancy, can cause an innocent murmur. Since they are not caused by a structural defect, innocent murmurs require no treatment and typically disappear once the temporary condition resolves. They are generally soft, occur only during systole, and often change in intensity with body position.
Abnormal murmurs, conversely, are caused by an underlying structural problem within the heart or its major blood vessels. These pathological murmurs signal a disturbance requiring further investigation and potential treatment. Doctors distinguish them from innocent murmurs by analyzing the timing and persistence of the sound. Murmurs heard during the heart’s relaxation phase (diastole) or those that persist throughout the entire cardiac cycle are almost always considered abnormal.
The intensity of the sound is graded on a scale from 1 (very faint) to 6 (very loud and palpable). Louder murmurs often suggest a more significant flow disturbance. A doctor notes the precise location where the sound is loudest to pinpoint the specific valve or area involved. Abnormal murmurs will not change or disappear with changes in body position, indicating a fixed structural cause for the turbulence.
Medical Conditions Causing Abnormal Murmurs
An abnormal heart murmur results from a structural issue impeding the normal flow of blood. The most frequent causes involve the heart’s four valves, which suffer from two primary types of dysfunction. The first is stenosis, where a valve becomes stiff, thickened, or narrowed, forcing blood through a smaller opening. This narrowing causes a jet of turbulent flow, such as in aortic stenosis.
The second common valve issue is regurgitation, or insufficiency, where the valve fails to close completely. This leaky closure allows blood to flow backward into the previous chamber, creating a whooshing sound. Both stenosis and regurgitation increase the heart’s workload, potentially leading to progressive heart enlargement or failure over time.
Structural defects in the heart’s walls, known as septal defects, also cause murmurs. These include an atrial septal defect (ASD) or a ventricular septal defect (VSD), which are holes between the upper or lower chambers. These defects allow blood to shunt between the left and right sides of the heart, creating turbulence. Other conditions, such as hypertrophic cardiomyopathy or damage from rheumatic fever, can also lead to a serious murmur.
How Doctors Evaluate a Murmur
Evaluation begins with a careful physical examination using a stethoscope (auscultation). The doctor listens for the sound’s characteristics, including timing, location, pitch, and intensity. Specific maneuvers, such as having the patient stand or squat, are performed to see how the murmur’s intensity changes, providing clues about the cause.
If the exam suggests the murmur is abnormal, or if the patient has symptoms like shortness of breath or chest pain, further testing is required. An electrocardiogram (ECG) checks the heart’s electrical activity for signs of enlargement or rhythm disturbances. A chest X-ray provides an image of the heart’s size and the condition of the lungs.
The echocardiogram (echo) is the primary diagnostic tool, using non-invasive ultrasound to create a moving picture of the heart. The echo visualizes the heart’s structure, confirming chamber size and valve function. It identifies structural defects, such as a narrowed valve or a septal hole, and measures blood flow to assess the severity of the problem.
Managing and Treating Serious Heart Murmurs
Treatment for a serious heart murmur is determined entirely by the underlying structural cause. For patients with mild valve stenosis or regurgitation, the condition may only require regular monitoring by a cardiologist. Lifestyle modifications, such as managing blood pressure and cholesterol, are often recommended to slow the disease progression.
If the defect causes symptoms or negatively affects heart function, medications are prescribed to manage associated issues. These may include:
- Diuretics to help reduce fluid retention and swelling.
- Beta-blockers to slow the heart rate and lower blood pressure, reducing the heart’s workload.
- Anticoagulants (blood thinners) if abnormal blood flow increases the risk of blood clot formation.
When the structural issue becomes severe, intervention is necessary, often involving repairing or replacing a damaged valve. Valve repair is generally preferred, but replacement with a mechanical or biological valve may be required. Procedures can be performed through traditional open-heart surgery or less-invasive transcatheter methods. For septal defects, devices can sometimes be placed via a catheter to close the hole, restoring normal blood flow.