Heart Murmur

About 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 may be benign (an "innocent murmur"), mildly troublesome, or serious.
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 organized by timing, into systolic heart murmurs and diastolic heart murmurs. However, continuous murmurs cannot be directly placed into either category.

Classification
Murmurs can be classified by seven different characteristics: timing, shape, location, radiation, intensity, pitch and quality.
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 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.

Interventions that change murmur sounds
Inhalation will increase the amount of blood filling into the right ventricle, 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.
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).
hand grip
post ectopic potentiation
amyl nitrite
methoxamine
positioning of the patient. ie. positioning 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.
Ventral septal defect
Symptoms are holosystolic, heard best at left lower sternal border.