During a heart examination, additional sounds called heart murmurs may be detected. These murmurs indicate turbulent blood flow within the heart or its major blood vessels. While some murmurs are harmless, others can signal an underlying cardiac condition that warrants further evaluation.
Understanding Heart Murmur Characteristics
Heart murmurs are characterized by several features that help medical professionals identify their origin and potential significance. These characteristics include pitch, intensity, and timing within the cardiac cycle. Pitch refers to the frequency of the sound, categorized as high, medium, or low. High-pitched murmurs often sound like a “blowing” or “whistling” noise, while low-pitched murmurs are typically described as “rumbling” or “gurgling.”
Intensity, or loudness, of a murmur is graded on a scale from 1 to 6. A Grade 1 murmur is very faint and difficult to hear, whereas a Grade 6 murmur is extremely loud and can be detected even with the stethoscope slightly off the chest. Timing indicates when the murmur occurs during the heartbeat. Systolic murmurs happen when the heart muscle contracts, while diastolic murmurs occur during the heart’s relaxation phase, as the ventricles fill with blood. Continuous murmurs are heard throughout both contraction and relaxation.
Identifying the Low-Pitched Murmur
The abnormal heart sound typically described as a low-pitched murmur is a diastolic murmur. These murmurs occur during diastole, the period when the heart relaxes and fills with blood. The low pitch often gives them a rumbling quality.
The low pitch results from turbulent blood flow through a narrowed opening under a relatively low-pressure gradient. The vibrations produced by this type of flow are of lower frequency, creating the rumbling sound. These murmurs are often best heard using the bell of a stethoscope, which is designed to pick up lower-pitched sounds.
Common Causes of Low-Pitched Murmurs
Low-pitched diastolic murmurs are indicative of an underlying medical condition, commonly involving issues with the heart valves. The most frequent causes are the narrowing of the mitral valve (mitral stenosis) and the narrowing of the tricuspid valve (tricuspid stenosis). Mitral stenosis, a condition where the mitral valve becomes stiff and narrow, impedes blood flow from the left atrium to the left ventricle during filling. This obstruction creates turbulent flow, resulting in the characteristic low-pitched, rumbling diastolic murmur.
Tricuspid stenosis, though rarer, similarly involves the narrowing of the tricuspid valve, which restricts blood flow from the right atrium to the right ventricle. This also produces a low-pitched, rumbling diastolic murmur. Both mitral and tricuspid stenosis are frequently associated with rheumatic heart disease, a complication of untreated strep throat that can damage heart valves. Other less common causes include atrial myxoma, a benign heart tumor that can obstruct blood flow, or very high blood flow through a normal valve.
What Happens After Detection
If a low-pitched heart murmur is detected during a physical examination, it prompts further investigation to determine its cause and clinical significance. A healthcare provider will consider various factors, including the murmur’s timing, location, and intensity, alongside the patient’s medical history and any associated symptoms. Symptoms that may accompany a worrisome murmur include shortness of breath, chest pain, or swelling in the ankles.
The primary diagnostic tool for evaluating heart murmurs and identifying their underlying cause is an echocardiogram. This non-invasive ultrasound of the heart uses sound waves to create detailed images of the heart’s structure and function, allowing visualization of blood flow patterns and valve abnormalities. An echocardiogram can confirm if a valve is narrowed (stenosis) or leaking (regurgitation), or if other structural issues exist.
While some murmurs, particularly in children, can be innocent and require no treatment, diastolic murmurs are generally considered pathological. They necessitate a thorough cardiac evaluation by a heart specialist for proper diagnosis and management.