Bicuspid aortic valve
A normal aortic valve has three cusps. A bicuspid aortic valve has only two cusps, and this is mostly due to congenital malformation. About 1-2% of the population have bicuspid aortic valves, and the majority will cause no problems. However, especially in later life, a bicuspid aortic valve may become calcified, which may lead to varying degrees of severity of aortic stenosis and aortic regurgitation, which will manifest as murmurs. If these become severe enough, they may require surgery.
Reference: Cohn LH, Edmunds LH Jr. Cardiac Surgery in the Adult. McGraw-Hill, 2003.