Heart murmurs are unique heart sounds produced when blood flows across a heart valve or blood vessel. This occurs when turbulent blood flow creates a sound loud enough to hear with a stethoscope. The sound differs from normal heart sounds by their characteristics. For example, heart murmurs may have a distinct pitch, duration and timing. The major way health care providers examine the heart on physical exam is heart auscultation; another clinical technique is palpation, which can detect by touch when such turbulence causes the vibrations called cardiac thrill. A murmur is a sign found during the cardiac exam. Murmurs are of various types and are important in the detection of cardiac and valvular pathologies (i.e. can be a sign of heart diseases or defects). There are two types of murmur. A functional murmur is a benign heart murmur that is primarily due to physiologic conditions outside the heart. The other type of heart murmur is due to a structural defect in the heart itself. Murmurs may be diagnosed as innocent or pathologic, with innocent murmurs all being physiologic, and pathologic murmurs, by contrast, having a wide variety of characteristics and having some sort of pathologic significance. Defects may be due to narrowing of one or more valves (stenosis), backflow of blood, through a leaky valve (regurgitation), or the presence of abnormal passages through which blood flows in or near the heart. It is estimated that 66% of children have heart murmurs at some point during childhood, with up to 60% of these being diagnosed as innocent by a pediatric cardiologist. The most common innocent murmurs include the Still’s murmur, a low-pitched murmur caused by blood flow in the ventricular outflow tract, as well as pulmonary and systolic murmurs. Most murmurs are normal variants that can present at various ages which relate to changes of the body with age such as chest size, blood pressure, and pliability or rigidity of structures. Heart murmurs are frequently categorized by timing. These include systolic heart murmurs, diastolic heart murmurs, or continuous murmurs. These differ in the part of the heartbeat they make sound, during systole, or diastole. Yet, continuous murmurs create sound throughout both parts of the heartbeat. Continuous murmurs are not placed into the categories of diastolic or systolic murmurs.
Diagnostic approach and diagnosis
Classification
Murmurs have seven main characteristics. These include timing, shape, location, radiation, intensity, pitch and quality.
Timing refers to whether the murmur is a systolic, diastolic, or continuous murmur. Shape refers to the intensity over time. Murmurs can be crescendo, decrescendo or crescendo-decrescendo. Crescendo murmurs increase in intensity over time. Decrescendo murmurs decrease in intensity over time. Crescendo-decrescendo murmurs have both shapes over time. These have progressive increase in intensity, peak, and progressive decrease in intensity. Crescendo–decrescendo murmurs resemble a diamond or kite shape. Location refers to where the heart murmur is usually heard best. There are four places on the anterior chest wall to listen for heart murmurs. Each location roughly corresponds to a specific part of the heart. Health care providers listen to these areas with a stethoscope.
Position for auscultation: The patient is most often lying on their back (supine) with the head of bed at slight upward angle. The head of the bed is usually at a 30 degree upward angle. Usually the health care provider is standing to the right of the person they are examining. Below are positional changes that one may use: Left lateral decubitus (lying on the left side). This will decrease the distance from wall of the chest to the apex of the heart. This will help to examine the point of maximal impulse. Also, this will help to hear extra heart sounds (S3 or S4). With the patient sitting upright. With the patient seated, leaning forward and holding breath after exhalation. This will decrease the distance of the chest wall to the left ventricular outflow tract. By doing so this will help find the presence of an aortic regurgitation murmur. Radiation refers to where the sound of the murmur travels. The rule of thumb is that the sound radiates in the direction of the blood flow. Intensity refers to the loudness of the murmur with grades according to the Levine scale, from 1 to 6:
Pitch may be low, medium or high. This depends on whether auscultation is best with the bell or diaphragm of a stethoscope. Quality refers to unusual characteristics of a murmur. For example, blowing, harsh, rumbling or musical.
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