Aortic stenosis: Narrowing of the valve between the left ventricle and aorta
What causes aortic stenosis?
In the developing world, an important cause of aortic stenosis is rheumatic fever. But the disease if fast becoming almost unknown in developed countries. Degenerative aortic valve disease is the common cause of aortic stenosis in the older population of the developed world. An abnormal aortic valve with two leaflets instead of the normal three leaflets (bicuspid aortic valve) is an important cause of aortic stenosis in younger individuals. This is a birth defect and valve with only two leaflets can get damaged as years go by and can become either leaky or narrowed. Very high levels of cholesterol in familial hypercholesterolemia has also been associated with aortic stenosis.
What are the important symptoms?
As the valve orifice gets progressively narrowed it becomes more and more difficult for the left ventricle to pump blood into the aorta (largest blood vessel carrying oxygenated blood to the whole body). This causes thickening of the heart muscle of the left ventricle. A thick muscle requires more oxygen, especially during exercise. If the heart is not able to deliver the increased demand, it causes chest pain (angina pectoris). When there is a sudden increase in demand with rapid exercise like running, the individual with severe aortic stenosis may also faint, because brain does not get enough blood as more blood is being diverted to the exercising muscles. In severe cases of aortic stenosis, they may develop heart failure with increasing breathlessness. Sudden death can also occur in very severe aortic stenosis, mostly due to life threatening disorders of heart rhythm.
Can aortic stenosis be treated?
Mild cases need only follow up and prompt treatment of infections to prevent infections from reaching the valve which can cause a dangerous disease known as infective endocarditis. Severe cases can be treated by valve replacement, which can be surgical or by interventional techniques. Surgery for aortic valve replacement is an open heart surgery. Two types of artificial valves can be used: mechanical prosthetic valve and bioprosthetic valve (biological valve). Mechanical valves have better longevity, but needs lifelong medications to prevent blood clotting which needs close monitoring and has a significant bleeding risk. Bioprosthetic valves need medications to prevent blood clotting (anticoagulants) for an initial short period. But their longevity is less compared to mechanical prosthetic valves and is more suited for older individuals. They can also be considered in females planning pregnancy as the difficulties of taking anticoagulants in pregnancy can be avoided.
Alternative option, especially in those elderly individuals with high risk for surgery is transcatheter aortic valve implantation (TAVI).