|This article needs additional citations for verification. (October 2008)|
Frontal view of the Aortic valve
The aortic valve is one of the two semilunar valves of the heart, the other being the pulmonary valve. The heart has four valves and the other two are the mitral and the tricuspid valves. The aortic valve normally has three leaflets, although in 2% of the population it is found to congenitally have two leaflets. It lies between the left ventricle and the aorta.
The aortic valve normally has three cusps – a left, right and posterior cusp.
During ventricular systole, pressure rises in the left ventricle. When the pressure in the left ventricle rises above the pressure in the aorta, the aortic valve opens, allowing blood to exit the left ventricle into the aorta. When ventricular systole ends, pressure in the left ventricle rapidly drops. When the pressure in the left ventricle decreases, the aortic pressure forces the aortic valve to close. The closure of the aortic valve contributes the A2 component of the second heart sound (S2).
There are two prototypical processes that can affect the aortic valve - aortic stenosis in which the valve fails to open fully, thereby obstructing blood flow out from the heart, and aortic insufficiency, also called aortic regurgitation, in which the aortic valve is incompetent and blood flows passively back to the heart in the wrong direction. These two conditions frequently co-exist. Common causes of aortic regurgitation include vasodilation of the aorta, previous rheumatic fever, infection, i.e. infective endocarditis, degeneration of the aortic valve, and Marfan's syndrome.
The most common congenital abnormality of the heart is the bicuspid aortic valve. In this condition, instead of three cusps, the aortic valve has two cusps. This condition is often undiagnosed until later in life when the person develops symptomatic aortic stenosis. Aortic stenosis occurs in this condition usually in patients in their 40s or 50s, an average of 10 years earlier than can occur in people with normal aortic valves. Aortic stenosis can also be caused by rheumatic fever and degenerative calcification.
Turner syndrome a congenital condition that affects females, can often have a bicuspid aortic valve as one of its symptoms.
Aortic Valve Replacement
Aortic valve replacement means that a patient's aortic valve is replaced by a different valve. The aortic valve can be affected by a range of diseases and require aortic valve replacement. The valve can become either leaky (regurgitant or insufficient) or stuck partially shut (stenotic). Aortic valve replacement currently requires open heart surgery. Research is being done now to develop valves that can be implanted using a catheter without open heart surgery. There are two basic types of artificial heart valve, mechanical valves and tissue valves. Tissue heart valves are usually made from animal tissues, either animal heart valve tissue or animal pericardial tissue. The tissue is treated to prevent rejection and to prevent calcification.
There are alternatives to animal tissue valves. In some cases, a human aortic valve can be implanted. These are called homografts. Homograft valves are donated by patients and recovered after the patient expires. The durability of homograft valves is probably the same as for porcine tissue valves. Another procedure for aortic valve replacement is the Ross procedure (after Donald Ross) or pulmonary autograft. The Ross procedure involves going to surgery to have the aortic valve removed and replacing it with the patient's own pulmonary valve. A pulmonary homograft (a pulmonary valve taken from a cadaver) or a valvular prothesis is then used to replace the patient's own pulmonary valve.
The first minimally invasive aortic valve surgery took place at the Cleveland Clinic in 1996.
Another option for aortic valve replacement is Transcatheter Aortic Valve Replacement (TAVR). This procedure is for patients who are not candidates for surgery or who have high risk for surgery.
- Anatomy photo:20:29-0104 at the SUNY Downstate Medical Center - "Heart: The Aortic Valve and Aortic Sinuses"
- Aortic Valve, Bicuspid at eMedicine
- Anatomy figure: 20:07-02 at Human Anatomy Online, SUNY Downstate Medical Center