Article by Dr. Thomas Burnell and Dr. Bethany Turner
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Core
In valve stenosis, there is narrowing of the affected valve. This causes a decreased flow of blood through the valve which results in backing up of blood before the valve.
In valve regurgitation, the valve cannot properly close. This causes some backflow of blood through the valve in the reverse direction when, or after, the heart contracts.
Valve stenosis and regurgitation have different effects depending on which valve they affect. The different pathologies will also have differing sounds and patterns on auscultation.
When auscultating a heart murmur, the sound produced is caused by turbulent blood flow generated by the pathology affecting the heart valve.
Mitral valve stenosis is narrowing of the mitral valve. This most commonly occurs due to rheumatic fever which causes commissural fusion of the valve leaflets.
The effects of this are:
- Backing up of blood into the pulmonary circulation causes damage and fibrosis of the vasculature which leads to increased resistance to blood flow.
- The increased resistance to flow results in pulmonary hypertension.
- The higher pressures within the pulmonary circulation forces fluid out of the capillaries causing pulmonary oedema.
- Left atrial dilation occurs as the left atrium has to pump harder against the stenosed valve to move blood through it.
- Left atrial dilatation leads to fibrosis and remodelling of the atria to repair damaged tissue caused by stretching of the atria.
- Fibrosis interrupts electrical pathways leading to ectopic beats which can cause atrial fibrillation.
- Left atrial dilatation can compress the oesophagus causing dysphagia.
- Left atrial dilatation can also compress the recurrent laryngeal nerve which runs close to the oesophagus. This can cause the patient to present with a hoarse voice.
Mitral valve stenosis is heard as a diastolic rumble murmur between S2 and S1.
Diagram - Mitral valve stenosis and how it affects blood flow through the valve
SimpleMed original by Dr. Bethany Turner
Aortic valve stenosis is narrowing of the aortic valve. There are several causes of this:
- Degeneration of the valve, e.g. due to calcification or fibrosis with age
- Congenital bicuspid valve
- Chronic rheumatic fever which causes commissural fusion of the valve leaflets
The effects of an aortic valve stenosis are:
- Left ventricular hypertrophy as the ventricle must pump harder to force the blood through the narrowed valve.
- This can lead to left sided heart failure.
- Microangiopathic haemolytic anaemia (MAHA) - RBCs are sheared/damaged as they are pumped through the stenosed valve.
Aortic valve stenosis is heard as a crescendo-decrescendo murmur between S1 and S2.
Diagram - How aortic stenosis affects blood flow
SimpleMed original by Dr. Bethany Turner
Mitral valve regurgitation is pathology affecting the mitral valve resulting in blood flowing backwards through it on ventricular contraction. There are several causes:
- Myxomatous degeneration - there is degeneration of the valve. It is often idiopathic.
- Damage to the papillary muscle after a myocardial infarction. Damage to the papillary muscle means it is less effective at anchoring the chordae tendineae and therefore less effective at preventing the valves from prolapsing. This allows blood to flow backwards through the prolapsed mitral valve.
- Left sided heart failure which causes left ventricular dilation. This dilation causes stretching of the valve so it no longer forms a tight seal, allowing blood to leak through.
- Rheumatic fever causes fibrosis of the valve which disrupts the seal of the valve, allowing blood to leak through.
Mitral valve regurgitation allows blood to leak back into the left atrium. This increases the preload of the ventricle as more blood enters the ventricle on diastole. The left ventricle hypertrophies to cope with the increased volume of blood which can lead to left sided heart failure.
Mitral valve regurgitation is heard as a holosystolic murmur heard between S1 and S2.
Diagram - The flow of blood in mitral regurgitation
SimpleMed original by Dr. Bethany Turner
Aortic valve regurgitation is pathology affecting the aortic valve resulting in blood flowing backwards through it after ventricular contraction. There are several causes:
- Aortic root dilatation which causes the leaflets to be pulled apart so they no longer form a tight seal.
- Valve damage caused by endocarditis or rheumatic fever.
- Connective tissue disorder, e.g. Marfan’s syndrome.
The effects of aortic valve regurgitation are:
- Blood flows back into the left ventricle during diastole causing a reduced diastolic pressure. The systolic pressure is often increased due to the increased stroke volume.
- The decreased diastolic pressure increases the pulse pressure, and this can be felt as a bounding pulse.
- Blood flows back into the left ventricle which increases the stroke volume. The heart hypertrophies to cope with the increased stroke volume. This can result in left sided heart failure.
Aortic valve regurgitation is heard as a decrescendo early diastolic murmur between S2 and S1.
Diagram - The flow of blood in aortic regurgitation
SimpleMed original by Dr. Bethany Turner
Heart murmurs are often caused by pathology affecting the heart valves, although some murmurs can occur in structurally normal hearts. In order to locate which valve is affected, you must auscultate each of the valves individually with a stethoscope.
The aortic valve can be auscultated on the right side in the 2nd intercostal space on the sternal edge.
The pulmonary valve can be auscultated on the left side in the 2nd intercostal space on the sternal edge.
The tricuspid valve can be auscultated on the left side in the 4th intercostal space on the lower left sternal border.
The mitral valve can be auscultated on the left side in the 5th intercostal space, in the midclavicular line.
Right sided heart murmurs are louder in inspiration as there is decreased pressure in the chest. This increases cardiac return to the right atrium and so there is more blood. Increased volume of blood being pumped means the effect of stenosis or regurgitation is increased so can be heard louder.
Left sided heart murmurs are louder in expiration as there is increased pressure in the chest. This increases the cardiac return to the left atrium as blood from the lungs is pushed into the left atrium due to the increased chest pressure. The volume of blood being pumped from the left atrium is increased, so the stenosis or regurgitation can be heard louder.
This can be remembered using the mnemonic RILE: Right Inspiration, Left Expiration.
Edited by: Dr. Ben Appleby
Reviewed by: Dr. Marcus Judge
In this article
Stenosis and regurgitation of the heart valves can result in different sounds. Stenosis makes it harder for blood to flow through valves while…
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