(USMLE topics, cardiology) Aortic stenosis and regurgitation: pathology, symptoms, risk factors, diagnosis and treatment.
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The aortic valve serves to ensure ONE-WAY flow of oxygen-RICH blood from the LEFT ventricle to the aorta and to the body. It OPENS when the left ventricle contracts and pumps blood; and CLOSES when the ventricles refill, to prevent blood from flowing BACK to the left ventricle. The aortic valve consists of three leaflets, or cusps.
A defective valve is one that FAILS to either OPEN or CLOSE properly. Aortic STENOSIS happens when the aortic valve does not OPEN fully, REDUCING blood flow. Aortic REGURGITATION, on the other hand, occurs when the valve does not CLOSE tightly, causing BACKWARD flow to the ventricle.
The common outcome of both situations is that the heart does NOT pump enough blood to the body, and heart failure may result. Symptoms may develop suddenly or SLOWLY over decades, and may include: fatigue, shortness of breath, especially when exercising; chest pain or tightness; dizziness, fainting, swelling in the ankles and feet; and poor feeding and growth in children.
In attempts to compensate for the low blood output, the left ventricle grows LARGER to generate higher pressures and pump harder. This enlargement may help to relieve symptoms at first, but eventually it causes the ventricle to become weak and fail.
Risk factors for both conditions include:
- Congenital heart valve disease: some people are born with ABnormal structures that increase the risks of valve MALfunctioning. Common defects include having two leaflets, instead of three; fused leaflets, and dilation of the aortic root.
- STIFFENED valve due to calcium deposits, as a result of AGING.
- and valve DAMAGE due to infection or inflammation in conditions such as endocarditis and rheumatic fever.
Aortic valve diseases produce characteristic heart murmurs that are useful for diagnosis.
Aortic stenosis gives rise to a crescendo-decrescendo systolic murmur which starts shortly after the first heart sound. It is often preceded by an ejection click caused by the opening of the STENOTIC valve. The murmur is loudest in the aortic area and the sound radiates to the neck.
Aortic regurgitation produces a diastolic murmur which is heard along the left sternal border. It peaks at the beginning of diastole when the flow is largest, then rapidly decreases as the ventricles are filled.
Diagnosis is usually confirmed by echocardiography.
A damaged valve usually requires surgical repair or replacement. Several repair procedures are available depending on the type of defect. Valve replacement is often preferred as a long-term solution, especially for aortic stenosis, in which the valve tends to become narrow again after a repair procedure. Artificial valves can be mechanical or bio-prosthetic. Mechanical valves last longer but usually require life-long administration of anticoagulant medications to prevent formation of blood clots.