Cardiac murmur is the abnormal  heart sound.

It is also called cardiac bruit.

Cardiac murmur is mainly  heard by stethoscope, along with the normal heart sounds.


-It is produced because of change in the pattern of blood flow.

-Normally,  the blood flows in streamline through the heart and blood vessels.

-However, during abnormal conditions like valvular diseases, the flow of blood becomes turbulent.

-It produces the cardiac murmur.

-Murmur is produced because of  the following like valvular diseases, septal defects and vascular defects

Valvular Diseases

Valvular diseases are of two types:

 1. Stenosis

 2. Incompetence.

1. Stenosis

-Stenosis means narrowing of heart valve.

-The flow of blood is rapid with turbulence through the narrow orifice of the valve, resulting in murmur.

2. Incompetence

-Incompetence refers to weakening of the heart valve.

– Due to the weakness of the value , it cannot close properly.

-Which  causes back flow of blood, resulting in turbulence.

-This disease is also called  valvular insufficiency.


Cardiac murmur is classified into three types:

A. Systolic murmur

B. Diastolic murmur

C. Continuous murmur.


During systole the murmur produced is know as SYSTOLIC MURMUR. It is produced in the following conditions:

1. Incompetence of Atrioventricular Valves

-When the atrioventricular valves become weak, these valves cannot close completely.

-What it causes is like  regurgitation of blood from ventricles to the atria during ventricular systole, producing the murmur.

– The sound is harsh with high frequency.

2. Stenosis of Semilunar Valves

-During  the stenosis of aortic valve, the pressure of the left ventricle rises  to 300 mm Hg during systole.

-It causes a greater turbulence in the flow of the blood.

-In severe conditions, the sound is heard even a few feet away from the affected person.

– The sound is harsh and loud .

3. Murmur due to Anemia

-A systolic murmur is mainly  heard in severe anemia because of reduced viscosity and accelerated flow of blood.

4. Septal Defect

-Blood flows from left ventricle to right ventricle during systole, during the interventricular septal defect.

-It produces a systolic murmur.

– Septal defect is a rare disorder.

5. Coarctation of Aorta

-It is a congenital disorder, characterized by the narrowing of a part of systemic aorta.

-A loud murmur is produced during systole and it is heard in the earlier part of diastole also.


-It is the murmur that is produced during diastole.

-It is produced in the following conditions:

1. Stenosis of Atrioventricular Valves 

When the atrioventricular valves become narrow, the turbulence of blood flow occurs during diastole, i.e. when blood enters the ventricles from atria.

-At mitral area the stenosis of the mitral valve is heard clearly.

-At  tricuspid area the stenosis of the tricuspid valve is heard clearly

-It is a weak sound with low frequency.

-Sometimes, murmur cause by mitral stenosis cannot be heard by stethoscope, because of  low frequency.

-But it can be felt as a mild thrill  mainly over mitral area of the chest.

2. Incompetence of Semilunar Valves

-Murmur is mainly  produced during the regurgitation of blood from aorta into the ventricle, through incompetent semilunar valve during diastole.

– It sounds like a blowing sound; with low frequency.


-Continuous murmur is the murmur that is heard in conditions such as patent ductus arteriosus.

-A continuous murmur is heard in this condition.

-However, intensity of the sound is more during systole and less during diastole.

-Because of this, it is also known as  machinery murmur.

-It is a harsh blowing sound and is heard best in the pulmonary area. The murmur is heard 1 year after birth.




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