Heart murmur

Murmurs are extra heart sounds that are produced as a result of turbulent blood flow that is sufficient to produce audible noise. Most murmurs can only be heard with the assistance of a stethoscope ("on auscultation").

A functional murmur or "physiologic murmur" is a heart murmur that is primarily due to physiologic conditions outside the heart, as opposed to structural defects in the heart itself. Functional murmurs are benign (an "innocent murmur").^[1]

Murmurs may also be the result of various problems, such as narrowing or leaking of valves, or the presence of abnormal passages through which blood flows in or near the heart. Such murmurs, known as pathologic murmurs, should be evaluated by an expert.

Heart murmurs are most frequently categorized by timing, into systolic heart murmurs and diastolic heart murmurs. However, continuous murmurs cannot be directly placed into either category.^[2]

Classification

Murmurs can be classified by seven different characteristics: timing, shape, location, radiation, intensity, pitch and quality.^[3]

• Timing refers to whether the murmur is a systolic or diastolic murmur.
• Shape refers to the intensity over time; murmurs can be crescendo, decrescendo or crescendo-decrescendo.
• Location refers to where the heart murmur is usually auscultated best. There are six places on the anterior chest to listen for heart murmurs; each of the locations roughly corresponds to a specific part of the heart. The first five of the six locations are adjacent to the sternum. The six locations are:
  • the 2nd right intercostal space
  • the 2nd to 5th left intercostal spaces
  • the 5th left mid-clavicular intercostal space.
• Radiation refers to where the sound of the murmur radiates. The general rule of thumb is that the sound radiates in the direction of the blood flow.
• Intensity refers to the loudness of the murmur, and is graded on a scale from 0-6/6.
• Pitch can be low, medium or high and is determined by whether it can be auscultated best with the bell or diaphragm of a stethoscope.
• Quality refers to unusual characteristics of a murmur, such as blowing, harsh, rumbling or musical.

The use of two simple mnemonics may help differentiate systolic and diastolic murmurs; PASS and PAID. Pulmonary and aortic stenoses are systolic while pulmonary and aortic insufficiencies (regurgitation) are diastolic. Mitral and tricuspid defects are opposite.

Grading of murmurs

Interventions that change murmur sounds

• Inhalation leads to drop in intrathoracic pressure, which increases capacity of pulmonary circulation, thereby prolonging ejection time. This will affect the closure of the pulmonary valve. This finding, also called Carvallo's maneuver, has been found by studies to have a sensitivity of 100% and a specificity of 80% to 88% in detecting murmurs originating in the right heart.^[5][6] specifically positive Carvallo's sign describes the increase in intensity of a tricuspid regurgitation murmur with inspiration.^[7]
• abrupt standing
• squatting
• valsalva maneuver. One study found the valsalva maneuver to have a sensitivity of 65%, specificity of 96% in detecting hypertrophic obstructive cardiomyopathy (HOCM).^[5] Both standing and Valsalva maneuver will decrease venous return and subsequently decrease left ventricular filling, resulting in an increase in the loudness of the murmur of hypertrophic cardiomyopathy, since outflow obstruction is increased by decreasing preload. Alternatively, squatting increases venous return and thus decreases the murmur. Maximum handgrip exercise also results in a decreased loudness of the murmur.^[8]
• hand grip
• post ectopic potentiation
• amyl nitrite
• methoxamine
• positioning of the patient. That is, putting patients in the left lateral position will allow a murmur in the mitral valve area to be more pronounced.

Examples of anatomic source of murmur

Stenosis of Bicuspid aortic valve

Symptoms tend to present between 40 and 70 years of age.

Stenosis of Tricuspid Aortic Valve

Symptoms more likely to present after 80 years of age.

Hypertrophic subaortic stenosis

Symptoms are a harsh murmur in mid-systole, often accompanied by S4, Brisk Bifid Carotid upstroke. Murmur increases with standing and valsalva maneuver.

Ventricular septal defect

Symptoms are holosystolic, heard best at left lower sternal border.

Cooing dove murmur

The cooing dove murmur is a cardiac murmur with a musical quality (high pitched - hence the name) and is associated with acute mitral valve regurgitation, preceded by a rupture of the chordae tendinea (the fibrous "strings" that connect the papillary muscle to the cusps of the valves). It is a systolic murmur which is best heard over the left second, third and fourth intercostal spaces.

See also

• Benign paediatric heart murmur
• Precordial examination

References

External links

• Information on heart murmurs in children from Seattle Children's Heart Center
• Heart Murmurs in Pediatric Patients
• Lehrer, Steven. Understanding Pediatric Heart Sounds. Elsevier 2002.
• Hanifin, Christopher. Heart Sounds: A Cardiac Auscultation Primer. CreateSpace, 2010
• Texas Heart Institute Scroll down to listen to heart murmurs.
• The Auscultation Assistant Provides recordings of heart murmurs.