Last updated on April 7th, 2020
The first indication of heart disease may be the discovery of an abnormal sound on auscultation which is called heart murmur. A heart murmur is defined as the abnormal sounds during the heartbeat cycle which is made by turbulent blood flow in or near the heart.
A heart murmur can be congenital or develop later on in adult life. This may be ancillary – for example, during a routine childhood examination – or may be prompted by symptoms of heart disease.
The aims of clinical assessment are, firstly, to determine if the abnormal sound is cardiac; secondly, to determine if it is pathological; and thirdly, to try to determine its cause.
Is the sound cardiac?
Additional heart sounds and murmurs demonstrate a consistent relationship to a specific part of the cardiac cycle, whereas extracardiac sounds, such as a pleural rub or venous hum, do not. Pericardial friction produces a characteristic scratching noise termed a pericardial rub, which may have two components corresponding to atrial and ventricular systole, and may vary with posture and respiration.
Is the sound pathological?
Pathological heart sounds and heart murmurs are the product of turbulent blood flow or rapid ventricular filling due to abnormal loading conditions of the heart. Some added sounds are physiological but may also occur in pathological conditions; for example, a third sound is ordinary in young people and in pregnancy but is also a feature of heart failure.
Similarly, a systolic murmur due to turbulence across the right ventricular outflow tract may occur in hyperdynamic states such as anemia or pregnancy, but may also be due to pulmonary stenosis or an intracardiac shunt leading to volume overload of the RV, such as an atrial septal defect. Benign murmurs do not occur in diastole and systolic murmurs that radiate or are associated with a thrill are almost always pathological conditions.
What is the origin of the sound?
Timing, intensity, location, radiation, and quality are all useful clues to the origin and nature of an additional sound or murmur. Radiation of a murmur is determined by the direction of turbulent blood flow and is detectable only when there is a high-velocity jet, such as in mitral regurgitation (radiation from the apex of the heart to axilla) or aortic stenosis (radiation from the base of the heart to neck).
Similarly, the pitch and quality of the sound can help to distinguish the heart murmur, such as the ‘blowing’ murmur of mitral regurgitation or the ‘rasping’ murmur of aortic stenosis. The position of a heart murmur in relation to the cardiac cycle is clamorous and should be evaluated by timing it with the heart sounds, carotid pulse, and apex beat.
How to assess a heart murmur?
When does it occur?
- The time in which the heart murmur using heart sounds, carotid pulse, and the apex beat. Is it systolic or diastolic?
- Does the heart murmur extend throughout systole or diastole or is it confined to a shorter part of the cardiac cycle?
How loud is it? (intensity)
Grade 1: very soft (audible only in ideal conditions)
- Grade 2: soft
- Grade 3: moderate
- Grade 4: loud with an associated thrill
- Grade 5: very loud
- Grade 6: heard without a stethoscope
Note: Diastolic murmurs are very rarely above grade 4
Where is it heard best? (location)
Auscultation over the apex and base of the heart, including the aortic and pulmonary areas help to listen best.
Where does it radiate?
Listen at the neck, axilla or back
What does it sound like? (pitch and quality)
- Pitch is determined by blood flow (high pitch indicates high-velocity flow)
- Is the intensity constant or variable?
Ejection systolic murmurs are associated with ventricular outflow tract obstruction and occur in mid-systole with a crescendo–decrescendo pattern, reflecting the changing velocity of blood flow. Pansystolic murmurs maintain a constant intensity and extend from the first heart sound throughout systole to the second heart sound, sometimes obscuring it.
Systolic murmurs occur when blood leaks from a ventricle into a low-pressure chamber at an even or constant velocity. Mitral regurgitation, tricuspid regurgitation, and ventricular septal defect are the only causes of a Pansystolic murmur. Late systolic murmurs are unusual but may occur in mitral valve prolapse if the mitral regurgitation is confined to late systole, and hypertrophic obstructive cardiomyopathy if dynamic obstruction occurs late in systole.
These are due to accelerated or turbulent flow across the mitral or tricuspid valves. They are low-pitched noises that are often challenging to hear and should be auscultated with the bell of the stethoscope.
A mid-diastolic murmur may be due to mitral stenosis (located at the apex and axilla), tricuspid stenosis (located at the left sterna edge), increased flow across the mitral valve (for example, the to-and-fro murmur of severe mitral regurgitation) or increased flow across the tricuspid valve (for example, a left-to-right shunt through a large atrial septal defect).
Early diastolic murmurs have a soft, blowing quality with a decrescendo arrangement and should be auscultated with the diaphragm of the stethoscope. Early diastolic murmurs are due to regurgitation across the aortic or pulmonary valves and are best heard at the left sternal edge, with the patient sitting forwards in held expiration.
These result from a combination of systolic and diastolic flow, such as occurs with a persistent ductus arteriosus, and must be distinguished from extracardiac noises such as bruits from arterial shunts, venous hums (high rates of venous flow in children) and pericardial friction rubs.
If clinical evaluation suggests that the additional sound is cardiac and likely to be pathological, then echocardiography is indicated to determine the underlying cause.
The management of patients with additional cardiac sounds depends on the underlying cause.
Heart murmur may also be the result of various problems, such as narrowing or leaking of heart valves or passage through which blood flows in or near the heart. It is a physical finding and not a structural problem within heart itself. If you have any queries regarding any abnormal heart sounds/heart murmur do contact us through our contact page.