[Cardiology] Heart murmurs

This article is about a diagnostic finding from the cardiac examination: murmurs.

 

Auscultation

A cardiac murmur is a disturbance in the blood flow of the heart. It can be heard with a stethoscope. This is called cardiac auscultation.

 

Structural defects

Murmurs often indicate a structural heart defect, particularly when they sound harsh and a thrill is palpable. Structural heart defects are more common in older patients, people with a family history of structural heart disease, or a personal medical history of certain diseases (e.g. rheumatic fever, SLE).

We have to feel the pulse (at the carotid artery) to identify when the heart is in systole (contracting) or diastole (relaxation and filling). A structural defect can produce an audible murmur in either systole, diastole or both, depending on where the defect is and what type of defect it is.

 

Palpation

A thrill is a murmur which can be felt over the turbulence. This is one reason to perform chest wall palpation (feeling the chest wall with the hand).

It can be benign (harmless), particularly when it sounds soft, with no palpable thrill. This is often seen in young children.

 

Accentuation maneuvers

Another important point is accentuation of cardiac murmurs (making them louder). There are 2 important categories of accentuation: breathing, and position.

Some murmurs sound louder when the patient is exhaling (breathing out), but some murmurs sound louder when inhaling (breathing in). This is because the pressure in the thorax (the chest cavity) is relatively low when inhaling (because your ribs rise and diaphragm falls to increase the volume inside the chest). The pressure is relatively high when exhaling (because the thoracic volume is decreasing). When the pressure is low, blood can return to the heart more easily. When the pressure is high, blood can leave the heart more easily.

Some murmurs sound louder when the patient is lying forward, and some sound louder when the patient is lying on the left side of their body. This is because the position of the patient is bringing the diseased valve closer to the surface of the chest wall, so the sound of the turbulence is closer to the stethoscope.

 

Radiation

It is also important to listen over the carotid arteries, and under the left axilla (armpit) with a stethoscope. This is because some murmurs will classically radiate (spread) to the carotids, the back, or the axilla. This is because of the direction of the turbulent jet of blood through the valve. In mitral incompetency (back flow of blood through the mitral valve during systole), there is a systolic murmur. In aortic stenosis (narrowed forward flow through the aortic valve during systole), there is a systolic murmur. How do we tell them apart easily?

In mitral insufficiency (also called mitral incompetence, mitral regurgitation), the jet of blood which is regurgitating is heading towards the left axilla or the left scapula (shoulder blade), so a sound wave is pushed in that direction, and the murmur may be audible at these locations.

In aortic stenosis, the heart is pushing blood upwards through a narrow aortic valve so it can flow through the aorta to reach the body. A sound wave is pushed upwards towards the neck, and may be audible through the carotid arteries, which branch upwards from the aorta.

 

Diagrams

The diagrams below show which defects may cause a systolic or diastolic murmur.

 

Key

Arrows: direction of blood flow
Cylinder: major vessel
Thickened circle: stenotic (narrowed) valve
Backward arrow: regurgitant flow, through incompetent valve
Cloud: septal defect

Murmurs heard during systole

Murmurs heard during diastole

 

Worked example

A patient is brought to the hospital after syncope (fainting). She is in her 60s. Her father had his aortic valve surgically replaced in his 40s. When listening to the chest there is a harsh, crescendo-descrendo, systolic, murmur. It is loudest over the aortic valve. The sound can also be heard over the carotid arteries.

The answer here is aortic stenosis. This patient and her father both had bicuspid aortic valve. This is a congenital abnormality in which the aortic valve has only 2 cusps instead of 3. This means that blood flow through the aortic valve is turbulent, and over many years, the valve can become calcified and stenotic (narrowed). These patients often require a valve replacement when they are in their 40s.

If they are young, it is best to use a mechanical valve replacement. Anti-coagulation is necessary because blood clots will form on the artificial valve more easily than a natural valve. If the patient is old enough, you can use a biological prosthetic valve, since they may die before it degrades.