Aortic regurgitation (aortic incompetence, or aortic
insufficiency) is leakage of blood back through the aortic valve
each time the left ventricle relaxes. As the left ventricle
relaxes to fill with blood from the left atrium, blood leaks
backward from the aorta into the left ventricle because the
aortic valve does not seal completely. The backward leakage of
blood increases the volume and pressure of blood in the left
ventricle. As a result, the amount of work the heart has to do
increases. To compensate, the muscular walls of the ventricles
thicken (hypertrophy), and the chambers of the ventricles
enlarge (dilate). Eventually, despite this compensation, the
heart may be unable to meet the body's need for blood, leading
to heart failure, with fluid accumulation in the lungs.
Rheumatic fever and syphilis used to be the most common causes
of aortic regurgitation in North America, Australasia, and
Western Europe, where both disorders are now rare because of the
widespread use of antibiotics. In regions where an