Surgical Treatment of Bicuspid Aortic Valve Disease

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


Introduction
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 situation, patients with hypoplastic annuli and functional bicuspid valves may be primarily considered for surgery in order to prevent the risk of aortic regurgtation and the need for valve replacement (Reich et al., 2004).Actually, any type of treatment for aortic stenosis in newborns and infants is palliative, and future aortic valve replacement is inevitable (Vida et al., 2005).Because the bioprosthetic valve has a high structural failure rate in young patients and mechanical valves have a risk of anticoagulant-related morbidity, the better option of aortic valve substitute in infants and children is the pulmonary autograft because of its potential for growth (Vida et al., 2005;Behery et al., 2009).

Aortic valve replacement
As outlined in the 2006 American College of Cardiology/American Heart Association Guidelines for the Management of Patients With Valvular Heart Disease (Bonow et al., 2006), aortic valve repair involves a lack of uniform applicability and lack of widespread experience with surgical techniques.Moreover, there are no clear indications on when repair should be performed and the regarding data demonstrating its safety and durability are limited (Rao et al., 2000;EI Khoury et al., 2006;Aicher et al., 2007;Ashikhmina et al., 2010).In adulthood, the major implication associated with BAV is a tendency toward premature degeneration of the aortic valve with premature presentation of calcific valvular stenosis (Braverman et al., 2005).If aortic valve repair is impossible because of the remarkable structural changes of the aortic valve, the definitive surgical treatment is aortic valve replacement (AVR) (Ali et al., 2010).AVR for aortic valve stenosis is the second most common reason for cardiac surgery in the industrialized countries, and BAV is the second most common cause of aortic valve disease requiring surgery (Etz et al., 2007).In patients with congenital aortic valve disease such as BAV, Klieverik et al. (2008) reported that the durability of allografts for aortic valve replacement is better than that of bioprostheses, and that their hemodynamic profile is superior to that of mechanical prostheses and bioprostheses.However, the increasing reoperation risk within ten to twenty years remains a major concern.Wijesinghe et al. (2010) proved that transcatheter aortic valve implantation (TAVI) in selected high-risk patients with severe BAV stenosis can be successfully performed with acceptable early clinical outcomes, but that its long-term durability will require further evaluation.On the contrary, Zegdi et al. (2008a) proposed that the valvular opening shape tends to be elliptical rather than circular in patients with BAV; elliptical deployment of valved stents will inevitably create valve distortion that may impede their long-term durability.Thus, BAV stenosis has been considered a questionable indication or even a contraindication for endovascular valve implantation (Zegdi et al., 2008a;Zegdi et al., 2008b).Ross (1967) first described replacement of the diseased aortic valve by pulmonary autograft in 1967, and the full root technique with a pulmonary autograft was introduced in 1989 (Stelzer et al., 1989).The Ross operation is an acceptable alternative to conventional aortic valve replacement and has been shown to provide excellent hemodynamic results.The advantages of this therapeutic option are the use of a viable autologous valve and a low incidence of infection and thrombogenicity, avoidance of anticoagulant therapy, as well as its potential to grow in children (Hanke et al., 2007;Brown et al., 2010;Sievers et al., 2010;Ryan et al., 2011).Nevertheless, there is growing concern about autograft failure and surgical revisions because of the frequently concomitant aortic root and tubular ascending aorta pathology observed in many patients with BAV (Hanke et al., 2010), and the intrisic abnormalities in the wall of the pulmonary artery based on the common embryological origin of the aortic and pulmonary root, which may contribute to progressive neoaortic root dilatation and AR, or both, when the pulmonary root is placed in the systemic position (David et al., 2000;Siu & Silversides, 2010;Hanke et al., 2010).Progressive dilatation of the pulmonary autograft with or without regurgitation of the autograft valve is a common indication of reoperation (David et al., 2000;Luciani et al., 2003;Takkenberg et al., 2006;Hanke et al., 2007;Ozaslan et al., 2009;Aljassim et al., 2011).In addition, factors contributing to a limited acceptance are the complexity of the operation and a dearth of long-term clinical information on the durability of the autograft in the aortic position and the durability of the pulmonary conduit substitute (Sievers et al., 2010).This concern has led many to reconsider the indication for the Ross operation in the adult population for whom other surgical options are available (Hanke et al., 2007;David, 2009).There are even some do not advocate the use of the Ross operation in patients with BAV disease (Siu & Silversides, 2010).Nevertheless, freedom from autograft or pulmonary conduit reoperation was 89% at 10-year follow-ups reported from the German-Dutch Registry (Sievers et al., 2010).They concluded that the autograft procedure is a valuable therapeutic option for treating aortic valve disease (including BAV) in children, adolescents, and young adults (Sievers et al., 2010).Recently, Ryan et al. (2011) reported that freedom from pulmonary autograft reoperation for aortic stenosis patients was 95% at 10 years.They concluded that the Ross procedure in adults provides excellent freedom from autograft failure in patients operated for aortic stenosis.Conversely, the freedom from autograft reoperation rate was 67% at 10 years in patients with AR preoperatively.Thus, the Ross operation provided suboptimal results in patients with aortic insufficiency (David et al., 2010;Ryan et al., 2011).Therefore, other therapeutic alternatives should be strongly considered in adults presenting primarily with aortic inssuffciency (Ryan et al., 2011).Pulmonary autograft dilatation is common after the Ross procedure in adults, and this might be a cause of reoperation (David et al., 2000;Aljassim et al., 2011).Patients with BAV and dilated ascending aortas, or patients with dilated aortic root and primarily AR, have been considered the highest-risk groups for dilatation and neo-aortic valvular regurgitation (Tantengco et al., 1999;Simon-Kupilik et al., 2002;Kouchoukos et al., 2004;Brown et al., 2010).Perhaps the modified Ross procedure, as described by Ungerleider et al., in which the autograft is completely encased in a Dacron graft before implantation, may provide better results in patients with preoperative ascending aortic and sinus dilation.A long-term follow-up for successful valve function will be needed for this technique to be recommended for wider use (Ungerleider et al., 2010).In summary, although the early outcomes continue to be excellent, follow-ups after more than 10 years show continued deterioration of the autografts and a need for reoperation in a substantial percentage of patients, particularly those in whom the root replacement technique was used.Thus, some investigators suggested that the Ross procedure should not routinely be used for aortic valve replacement in adults (Kouchoukos, 2011).

Repair of regurgitant valve
Clinically, up to 15% to 20% of patients with BAV are reported to have had significant AR as young or middle-aged adults (Roberts, 1970;Olson et al., 1984;Ward, 2000).Although chronic AR is well tolerated for a long time, progressive left ventricular dilatation is a sign with ominous results if timely intervention is not undertaken (Pretre et al., 2006).This makes the choice of valve substitutes difficult because of the limitations of current prostheses.Mechanical valves have an excellent freedom from reoperation, but the cumulative risk of thromboembolic complications and anticoagulation-related hemorrhage may be substantial due to the long exposure time (Khan, 2002;Salem et al., 2004).The Ross procedure is ideal for young patients with BAV stenosis because of its low operative mortality, excellent hemodynamic performance, low prevalence of infection, avoidance of anticoagulant therapy, and potential to grow in children (El Behery et al., 2009;Takkenberg et al., 2009).However, the presence of preoperative AR and aortic root dilatation are important independent determinants of reoperation for pulmonary autograft failure (Elkins et al., 2008;de Kerchove et al., 2009;Ryan et al., 2011).For these reasons, repairing the BAV is an attractive therapeutic option (Ashikhmina et al., 2010;Boodhwani et al., 2011;Ryan et al., 2011).Reconstruction of the regurgitant bicuspid valve was proposed as early as 1991 by Cosgrove et al. (1991).Subsequently, others have been able to reproduce reconstructive surgery for regurgitant BAV with good results (Aicher et al., 2004); although some others who used the Cosgrove technique proposed that the intraoperative results were rarely predictable and that there was a high reoperation rate in the early phase (Moidl et al., 1995).Cusp prolapse may be an isolated cause of AR or may exist in conjunction with dilatation of the proximal aorta.Prolapse can be corrected by central plication, triangular resection, or pericardial patch implantation (Aicher et al., 2007b).In the case of limited cusp prolapse, Aicher et al. ( 2007b) used plication stitches in the central portion of the free edge of the cusp, which were possibly first used by Spencer et al. (1962).The concept of paracommissural plication has been used in AR with ventricular septal defects (Starr et al., 1960;Garamella et al., 1960).Aicher et al. (2007b) showed that central plication had better valve stability with freedom from recurrent AR and freedom from reoperation at 10 years postoperatively compared with the paracommissural approach.In the presence of a more extensive prolapse, a triangular resection was adopted to avoid excessive bulging of plicated cusp tissue (Aicher et al., 2007b).The reason for their low failure rate may be that they frequently corrected prolapse of both cusps in bicuspid aortic valves.On the other hand, using pericardial patch augmentation to close congenital fenestrations that had led to increase coaptation surface provides reliable early and midterm competence of reconstructed bicuspid aortic valves (Aicher et al., 2007b;Doss et al., 2008).The systemic segmental approach suggested by Pettersson et al. (2008) is based on echocardiographic evaluation.Their findings emphasized that restrictive cusp motion, due to fibrosis or calcification, is an important predictor for recurrent AR following valve repair.On the contrary, redundant or sufficient cusp tissue offers a greater potential for reparability.Several studies have suggested risk factors for failure of BAV repair.Casselman et al. (1999) described left ventricular dysfunction as a predictor of immediate, persistant regurgitation after valve repair.Nash et al. (2005) reported that the paramenters included an eccentric jet of AR, absence of cuspal or commissural thickening, and lack of cusp calcification associated with an increased likelihood of successful valve repair.De Kerchove et al. (2008) suggested that methods of repair of the prolapsed cusp and increased left ventricular end-diastolic diameter were predictors of BAV repair failure.Recently, the size of the aortoventricular junction was also shown to be an independent risk factor for recurrence of regurgitation after repair (Aicher et al., 2011).One should be hesitant to repair a BAV if the aortoventricular diameter is ≥ 29mm, if commissural orientation is < 160°, and if a pericardial patch is required for partial cusp replacement (Aicher et al., 2011).
In summary, bicuspid aortic valve repair is a viable alternative to replacement with a bioprosthesis because durability and safety are similar between both surgical management methods for AR.Nevertheless, after initial repair, approximately half of the patients require aortic valve replacement within 10 years (Ashikhmina et al., 2010).

Surgical treatment of bicuspid aortic valve with aortopathy
Studies on children (Beroukhim et al., 2006;Warren et al., 2006;Holmes et al., 2007) and adults (Yasuda et al., 2003;Davies et al., 2007;Tadros et al., 2009) have reported significantly faster aortic dilatation in the significantly younger with BAV versus trileaflet aortic valve (Figure).BAV is associated with ascending aortic dilatation and enlargement of the aortic root annulus in as many as half of all individuals (Nkomo et al., 2003;Park et al., 2011).Therefore, the size and shape of the ascending aorta should be serially followed.Measurements of the aortic root dimensions should be performed at the level of the ventriculoaortic diameter, sinuses of Valsalva, sinotubular junction, and proximal ascending aorta (Braverman et al., 2005).Surgery to repair the aortic root or replace the ascending aorta has been recommended for those patients with dilated aortic roots or ascending aortas, with possible early prophylactic surgical intervention to prevent dissection or rupture (Bonow et al., 2008;Tadros et al., 2009).

Valve sparing aortic root replacement
Valve-sparing aortic root replacements are becoming more popular in view of the potential thromboembolic, and infection complications after composite graft replacement (Cozijnsen et al., 2011).Currently, there are two different techniques of valve-sparing root replacement.
In the remodeling technique of the aortic root described by Sarsam and Yacoub (1993), the graft is sewn to the remaining aortic wall around the commissures.In the reimplantation technique proposed by David and Feindel (1992), the graft is fixed at the subannular level, and the valve and commissures are reimplanted inside the graft.Both procedures provide an alternative to composite root replacement with excellent short-and medium-term results, but the long-term durability is not yet established (Cozijnsen et al., 2011).Of note, the main limitation of valve-sparing procedures compared with aortic root replacement with a composite graft remains the predominant risk for reoperation on the bicuspid aortic valve due to recurrent regurgitation (Zehr et al., 2004;Badiu et al., 2010).Cattaneo et al. (2004) reported that late results with valve-sparing procedure in children have been compromised by late root dilatation.Kallenbach et al. (2002) reported that some of their patients subsequently required valve replacement after valve-sparing operations because of subsequent increases in AR.On the contrary, Badiu et al. (2010) said that root replacement with aortic valve-sparing should be offered even in the presence of a BAV or severe AR.Aicher et al. (2007a) reported that remodeling of the aortic root can be treated in patients with dilatation of the aortic root and concomitant AR whenever the aortoventricular junction was not dilated.Freedom from reoperation was 96% at 5 and 10 years, and freedom from valve replacement was 98% at 5 and 10 years.Thus, they concluded that root remodeling leads to durable restoration of bicuspid valve function and that the risk of reoperation is low.Therefore, root remodeling is a good option in patients with aortic dilatation and AR undergoing valve-sparing aortic replacement (Aicher et al., 2007a).Cusp pathology is frequently encountered in patients with supracoronary ascending aortic aneurysm and AR.Severe AR is not a contraindication to valve-sparing surgery, but careful identification and repair of cusp pathology, in addition to sinotubular junction reduction, is critical for durable, long-term outcome (Boodhwani et al., 2011).There is no actual recommendation in the ACC/AHA guidelines for valve-sparing aortic root replacement (Bonow et al., 2006).The guidelines indicate that this may be possible in selected patients for valve-sparing procedures at experienced centers when there is no AR or deformed or calcified aortic valves (Bonow, 2008).Despite reports of good mid-term results with valvesparing operations (Doss et al., 2010;De Paulis et al., 2010), some experts believe that leaving behind the abnormal BAV is ill-advised.Therefore, the optimal surgical approach for patients with BAV remains to be defined (Siu & Silverslides, 2010).

Ascending aorta replacement
It is now widely accepted that an inherent aortopathy exists regardless of whether the valve has any functional abnormalities.Ascending aortic dilatation occurs more frequently and at a younger age in patients with a BAV than in patients with a tricuspid aortic valve (Hahn et al., 1992;Nkomo et al., 2003), and, according to Yasuda et al. (2003), the aorta continues to dilate, even after valve replacement.Because of this, reoperation for aortic aneurysm as well as late aortic dissection and sudden rupture are significantly higher in this group of patients (Russo et al., 2002;Borger et al., 2004).Although the proximal ascending aorta is thought to be the most commonly affected segment (Nkomo et al., 2003;Alegret et al., 2003;Westhoff-Bleck et al., 2005;Tadros et al., 2009;Biner et al., 2009), recent computed tomographic angiography or magnetic resonance angiography and echocardiography studies of the thoracic aorta morphology in patients with BAV show more diffuse and distinct patterns of aortopathy extending from the aortic root to the proximal aortic arch (Westhoff-Bleck et al., 2005;Fazel et al., 2008;Nazer et al., 2010).
The two main theories explaining the phenomenon of aortopathy in patients with BAV are: (1) the genetic theory, and (2) the hemodynamic theory.Both genetic and hemodynamic causes of aortic pathology associated BAV have been postulated, and there is still a great deal of controversy about the pathogenesis of the dilatation of the ascending aorta.Given the marked heterogeneity of BAV disease, further studies are required in order to more accurately determine which theory is the correct one for explaining BAV-derived aortopathy (Bonow et al., 2008;Tadros et al., 2009;Girdauskas et al., 2011).
Looking at the time of rupture or dissection on a lifetime basis, it can be seen that there are sharp hinge points when the ascending aorta reaches 6 cm in diameter (i.e., the patient has incurred a 34% risk of rupture or dissection) (Elefteriades & Farkas, 2010).The mortality rate for elective surgical correction of ascending aortic aneurysm in an experienced center is 2.5% to 5.0% (Elefteriades, 2002;Isselbacher, 2005;Tadros et al., 2009).Ascending aortic aneurysms with an annual risk of rupture or dissection higher than the combined risks of perioperative mortality should be repaired electively (Tadros et al., 2009).These data permit evidence-based criteria for surgical intervention.Because rupture or dissection occurs at 6 cm or more, most adverse events can be prevented by operating at a criterion of less than 6 cm (Elefteriades, 2010).Therefore, for idiopathic ascending aortic aneurysms, surgical intervention at up to 5.5 cm has been recommended on the basis.In contrast, to accommodate differences in body size for optimal operative decision making, Elefteriades (2002) proposed using the aortic size indexed to body mass, rather than using absolute aortic dimensions to predict risk.In other words, adults with small body size should undergo earlier intervention because a higher ratio of aortic size to body size is a predictor of increased risk (Svensson & Khitin, 2002;Svensson et al., 2003;Davies et al., 2006;Tadros et al., 2009).The risk of rupture, dissection, or death is high (approximately 20% per year) when the aortic size index is above 4.25 cm/m 2 (Davies et al., 2006).However, an aorta less than 5 cm in diameter does not guarantee freedom form aortic complications.Autopsies and clinical studies have shown that aortic dissection certainly occurs in near-normal-sized aortas that do not fall within current guidelines for elective aneurysm surgery (Neri et al., 2005;Pape et al., 2007;Bajona et al., 2010).Between 2006 and2008, 3 guidelines that focused on advice for patients with a dilating ascending aorta in combination with BAV or AR were published: (1) the 2006 ACC/AHA guidelines for the management of valvular heart disease (Bonow et al., 2006); (2) the 2007 European Society of Cardiology (ESC) guidelines on the management of valvular heart disease (Vahanian et al., 2007); and (3) the 2008 ACC/AHA guidelines for managing adults with congenital heart disease (Warnes et al., 2008).All give practically the same recommendations as the following guidelines.Management Guidelines for Patients with Bicuspid Aortic Valve with Dilated Ascending Aorta proposed by the 2008 ACC/AHA guidelines (Bonow et al., 2008).

Class I
1. Patients with known bicuspid aortic valves should undergo an initial transthoracic echocardiogram to assess the diameters of the aortic root and ascending aorta.(Level of Evidence: B) 2. Cardiac magnetic resonance imaging or cardiac computed tomography is indicated in patients with bicuspid aortic valves when morphology of the aortic root or ascending aorta cannot be assessed accurately by echocardiography.(Level of Evidence: C) 3. Patients with bicuspid aortic valves and dilatation of the aortic root or ascending aorta (diameter greater than 4.0 cm*) should undergo serial evaluation of aortic root/ascending aorta size and morphology by echocardiography, cardiac magnetic resonance, or computed tomography on a yearly basis.(Level of Evidence: C) 4. Surgery to repair the aortic root or replace the ascending aorta is indicated in patients with bicuspid aortic valves if the diameter of the aortic root or ascending aorta is greater than 5.0 cm* or if the rate of increase in diameter is 0.5 cm per year or more.
(Level of evidence: C) 5.In patients with bicuspid valves undergoing AVR because of severe AS or AR repair of the aortic root or replacement of the ascending aorta is indicated if the diameter of the aortic root or ascending aorta is greater than 4.5 cm*.(Level of evidence: C)

Class IIa
6.It is reasonable to give beta-adrenergic blocking agents to patients with bicuspid valves and dilated aortic roots (diameter greater than 4.0 cm*) who are not candidates for surgical correction and who do not have moderate to severe AR. (Level of Evidence: C) 7. Cardiac magnetic resonance imaging or cardiac computed tomography is reasonable in patients with bicuspid aortic valves when aortic root dilatation is detected by echocardiography to further quantify severity of dilatation and involvement of the ascending aorta.(Level of Evidence: B).The recent 2010 ACC Foundation/AHA guidelines (Hiratzka et al., 2010) have provided adjusted indications for prophylactic surgery of asymptomatic patients with ascending aortic anneurysm.

Class I
Patients with Marfan syndrome or other genetically mediated disorders (vascular Ehlers-Danlos syndrome, Turner syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm and dissection) should undergo elective operation at smaller diameters (4.0 to 5.0 cm depending on the condition) to avoid acute dissection or rupture.(Level of Evidence: C)

Class IIa
Elective aortic replacement is reasonable for patients with Marfan syndrome, other genetic diseases, or bicuspid aortic valves, when the ratio of maximal ascending or aortic root area (πr 2 ) in cm 2 divided by the patient's height in meters exceeds 10. (Level of Evidence: C) More recently, Svensson et al. (2011) proposed that an aortic size larger than 4.5 cm or aortic cross-sectional area/height ratio greater than 8 to 10 should be considered triggers for concurrent aortic repair, because there is no added risk, and late survival is better.

Thoracic endovascular aneurysm repair (TEVAR)
TEVAR is a minimally invasive method for managing descending aortic aneurysms in the acute and chronic settings (Dake et al., 1994;Dake et al., 1999) and is becoming more frequently used (Gopaldas et al., 2010;Coady et al., 2010).TEVAR has been suggested as an alternative, although controversial, approach for the elderly with comorbidities because of the high risk of open repair (Tadros et al., 2009).Nevertheless, TEVAR is not currently a definitive approach for managing ascending aortic dilatation with BAV because the contour of the ascending aorta is complex and has inadequate landing zones to anchor the stent grafts, especially when dilatation involves the aortic annulus and extends into the arch (Tadros et al., 2009).Whether future developments in these techniques may render them more widely applicable as therapy for ascending aortic aortopathy is still unknown (Atkins et al., 2006;Vallely et al., 2008).On the other hand, the data are on TEVAR in patients with connective tissue disease, as well as on continued aortic expansion and higher reintervention rates (Geisbusch et al., 2008).Furthermore, patients with BAV aortopathy typically need intervention at a younger age, and currently TEVAR has not been shown to provide as durable long-term results as does open repair (Tadros et al., 2009).

Conclusion
BAV is the most common form of congenital heart defect.Although BAV can be found in isolation because of a disorder of valvulogenesis, it is also represented as coexistent aspects of a genetic disorder of aortopathy, and is most frequently associated with dilatation of the proximal ascending aorta.With or without intervention, patients with BAV require continued surveillance.Because BAV is a disease of both valvular pathology and aortopathy, surgical decision making is more complicated than previously believed.There are several surgical options available to patients with BAV.New surgical techniques have been developed, especially for valve repair and transcatheter aortic valve implantation.The surgical intervention option should be individualized to each patient, depending on the surgical experience and skill of the surgeon.If aortic valve repair for valvular regurgitation or an aortic valve sparing procedure is to be considered, patients should be referred to experienced centers where there is both interest and experience with surgical options available for these patients.Compared with trileaflet aortic valve patients, BAV disease patients have a connective tissue disorder leading to a higher prevalence and faster yearly growth rate of the ascending aorta, which increases the risk of dissection or rupture at a younger age.Thus, ascending aortic dilatation associated with BAV warrants frequent monitoring, with possible early prophylactic intervention to prevent dissection or rupture.