**1. Introduction**

Bicuspid aortic valve (BAV) is one of the most common congenital heart diseases. It is phenotypically variable and genetically heterogeneous. The prevalence of the disease has been determined according to the results of echocardiographic screening and necropsy studies. Some patients with isolated BAV may remain asymptomatic throughout their lives, so they may be diagnosed accidentally in echocardiographic screening. Although it is difficult to define the real incidence of BAV, it is accepted to have a prevalence of 0.5–2% in the general population, with a higher prevalence in males than females: M/F = 3/1 [1, 2]. The clinical presentation of BAV is highly variable. Its major manifestations are aortopathy, valvular

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

dysfunctions, endocarditis, and dissection. In the patients presenting with valvular dysfunction earlier in life, aortic regurgitation (AR) is more common, whereas aortic stenosis (AS) is more prevalent later in life, after the fourth decade. Valve phenotypes, genetic, and hemodynamic factors have been proposed as underlying mechanisms of aortopathy. Ascending aortic aneurysm is generally due to aortopathy and hemodynamics; however, the aortic root aneurysm is considered to be a consequence of aortopathy rather than hemodynamics, especially in younger patients. The asymptomatic BAV patients with normal valvular function require surgical treatment less frequently than those with valvular dysfunction and aortopathy during their lives.

Moreover, BAV may be associated with several genetic disorders with cardiovascular manifestations such as hypoplastic left-heart syndrome, congenital left-sided obstructive lesions (coarctation of aorta, Shone complex), ventricular septal defect, and syndromic conditions (Turner, Loeys Dietz). This chapter enrolls only the isolated bicuspid aortic valves.
