Surgical Treatment of Bicuspid Aortic Valve Disease

Abstract

Bicuspid aortic valve (BAV) disease is the most common congenital cardiac abnormality, occurring in 0.5% to 2% of the general population (Ward, 2000; Braverman et al., 2005), and in 0.9% as reported in autopsy studies (Roberts, 1970). It may be sporadic or familial and sporadically transmitted through families by an autosomal dominant pathway with a 4:1 male predominance (Cripe et al., 2004). The BAV may be associated with significant valvular dysfunction (Ward, 2000), will develop aortic stenosis and regurgitation, and will be at risk for infective endocarditis (Braverman et al., 2005; Sabet et al., 1999). The bicuspid valve includes different morphologic phenotypes (Sabet et al., 1999; Fernandes et al., 2004). It usually consists of two cusps unequal in size. The cusps are typically oriented right to left, and the larger cusp has a central raphe or ridge (Sievers & Schmidtke, 2007). Notably, pathologic examination of the raphe could not be demonstrated containing the valve tissue (Pomerance, 1972). A review of the echocardiograms of 1135 children with BAV revealed that the most common morphologic pattern is the fusion of the right and left cusps in 70% of all patients (Fernandes et al., 2004). Sievers & Schmidtke (2007) also reported that 71% of 304 BAV surgical specimens had right and left leaflet fusion. Raphal position was described between the right and left cusps in 86% of cases in surgical pathology study reported by Sabet et al (1999). Previously, much of the original focus centered on the abnormal bicuspid valve. Actually, BAV is not just only a disorder of valvulogenesis, but is also a coexistent genetic disorder of the aorta (Siu & Silversides, 2010). More recent studies have shown that structural abnormalities occur at the cellular level. The structural abnormalities of the thoracic aorta disclose a deficiency of fibrillin-1, increased activity of matrix metalloproteinases (MMPs), elastin fragmentation, and vascular smooth muscles cell (VSMC) apoptosis (Tadros et al., 2009). Genetic studies have reported that BAV is likely due to mutations in different genes with dissimilar patterns of inheritance (Cripe et al., 2004; Siu & Silversides, 2010). Typically, mutation in the NOTCH1 gene leads to signaling abnormalities, which may be responsible for abnormal development of the aortic valve, and later to accelerated valvular calcium deposition (Garg et al., 2005; Mohamed et al., 2006). In patients with BAV, the presence of BAV is an important risk factor for progressive dilatation of the aortic root and ascending aorta, even in BAV patients with normal valvular function (Nkomo et al., 2003; Gurvitz et al., 2004; Warren et al., 2006). Thus, because of its