A heart murmur is a sound, often described as a whooshing or swishing, that a physician hears when listening to the heart with a stethoscope. This unusual noise is caused by turbulent blood flow, meaning the blood is moving chaotically instead of in a smooth, linear fashion. While the sound itself is harmless, the underlying cause of the turbulence can range from a benign occurrence to a serious, life-threatening heart problem. Determining the source of this turbulent flow is necessary to understand the true risk a murmur poses to a person’s health.
The Difference Between Innocent and Pathological Murmurs
A major distinction exists between murmurs that are not concerning and those that signal an underlying health issue. Innocent, or functional, murmurs occur when blood flows rapidly through an otherwise structurally normal heart. These murmurs are extremely common, especially in children, and require no medical treatment since they are not associated with heart disease.
Innocent murmurs are typically temporary, arising during periods when blood flow is increased, such as during a fever, intense exercise, or pregnancy. Conditions like anemia or an overactive thyroid gland, which increase the speed of circulation, can also cause this temporary sound. The sound is generally softer and occurs during the heart’s contraction phase, known as a systolic murmur.
Pathological murmurs are caused by structural abnormalities or functional defects within the heart and require further medical investigation. To differentiate between the two types, a physician listens for specific characteristics of the sound. These characteristics include the loudness (often graded on a scale of one to six), the precise location where the sound is heard most clearly, and the pitch.
The timing of the sound within the cardiac cycle is an important differentiator. Murmurs that occur when the heart is relaxing and filling with blood (diastolic murmurs) or those that are continuous are almost always indicative of a structural problem. These features help determine whether the murmur is simply a sound of accelerated flow or a consequence of a serious condition.
Underlying Cardiac Conditions That Create Serious Murmurs
The most frequent source of a serious heart murmur is valvular heart disease, involving one or more of the heart’s four valves malfunctioning. These valves regulate blood flow between the heart chambers and major arteries; their improper function creates the turbulent flow heard as a murmur. The two main types of valvular problems are stenosis and regurgitation.
Stenosis
Stenosis occurs when a valve thickens, stiffens, or narrows, restricting the amount of blood that can flow forward. This obstruction forces the heart muscle to work harder to push blood through the smaller opening, causing strain and potential enlargement of the heart chambers. The aortic and mitral valves are commonly affected by this type of damage.
Regurgitation
Regurgitation (also called insufficiency or incompetence) happens when a valve does not close completely, allowing blood to leak backward into the previous chamber. This backflow reduces the heart’s efficiency and causes a volume overload, which strains the heart muscle. Chronic overwork required to compensate for these valve issues can lead to progressive heart failure and, in severe cases, sudden cardiac events.
Structural issues present from birth, known as congenital heart defects, are another source of pathological murmurs. These often involve holes in the heart wall, such as an atrial septal defect or a ventricular septal defect. These defects allow blood to shunt, or flow abnormally, between the oxygenated and deoxygenated sides of the heart, creating a loud, persistent murmur.
A more immediate cause of a serious murmur is endocarditis, an infection of the inner lining of the heart and its valves. Bacteria or other germs travel through the bloodstream and colonize the valve tissue, rapidly damaging its structure and function. This can quickly lead to severe regurgitation and heart failure, making it a medical emergency that poses a significant threat to life.
Diagnostic Steps and Monitoring the Severity
Once a physician identifies a murmur with pathological characteristics, diagnostic procedures are initiated to pinpoint the cause and severity. The initial physical exam uses the stethoscope to assess the murmur’s timing, pitch, and location. Sometimes the patient performs maneuvers like gripping their hands or squatting, which can alter the sound and offer clues to its origin, guiding the selection of further testing.
The primary tool for investigating a serious murmur is the echocardiogram (Echo). This non-invasive ultrasound provides detailed, moving images of the heart chambers, valves, and surrounding blood vessels. It is the most effective way to visualize the precise structural problem, measure the severity of stenosis or regurgitation, and assess the overall pumping function of the heart muscle.
Other standard tests include an electrocardiogram (EKG), which measures the heart’s electrical activity and can detect chamber enlargement or rhythm abnormalities. A chest X-ray is often used to assess the overall size and shape of the heart and check for signs of fluid buildup in the lungs, indicating heart failure. For stable, mild conditions, the focus shifts to watchful monitoring, with follow-up testing scheduled regularly to detect progression.
Individuals with a known pathological murmur must be vigilant for specific warning signs that signal a worsening condition requiring immediate medical attention. These signs include unexplained shortness of breath (particularly when lying flat), a sudden onset of chest pain, or episodes of fainting (syncope). Peripheral swelling in the ankles or feet and sudden, unexplained weight gain are also concerning, as they indicate fluid retention resulting from the heart’s reduced pumping ability.