There are three types of aortic valve AR. The first and most common type is the result of a dilatation of the aortic root. The mobility of the leaflets in these patients remains unaffected. The second type of AR is the result of a leaflet prolapse, which is defined as an effective height of less than 9 mm [24], resulting in an eccentric jet. The third type of AR is the result of restriction of the leaflet by a degenerative or rheumatic valvular disease with thickening, fibrosis, and calcification. This is accompanied by a peak gradient of over 20 mm Hg and is a marker for poor durability of its repair [13]. Cusp retraction and a combination of cusp and commissural anomalies are less common [25]. A preoperative distinction of these types by imaging is an important issue for the choice to replace or repair the valve. Aortic valve repair could be performed in the majority of patients with BAV, but this has a higher risk for a need of reintervention [4]. To keep this risk as low as possible, repair of the valve and VSRR should be a part of the armamentarium of the cardiac surgeon. SAVR as treatment for a dysfunctional BAV is more simple and reliable but carries the risks of valve-related complications and the need for anticoagulation [21]. These complications have to be taken into account since BAV patients are younger and have better survival [26].

The main goal of the repair of the regurgitating valve is the restoration of an adequate coaptation zone that remains effective and durable. The introduction of the anatomic repair concept for the valve, with the aim to achieve an effective height of 9–10 mm, has reduced the incidence of reoperation rate threefold, from 24% to 8% [27]. The effective height of the affected cusp and free margin length should thereby be measured during the operation [24,28,29] since these data are critical in the performance of the repair. The need for expertise is illustrated by the improvements in long-term results over time [4]. The different techniques are presented in Table 1. Plication sutures of the cusp can be used in single, conjoined, and bi-leaflet structures but also to close defects [4,22]. Pericardial patches are used to augment the cusps, and reconstruct commissures, as attempts to “tricuspidize” a BAV [24,25], close perforations or treat retractions of raphes [23,26]. The use of pericardium and decalcification during repair can be associated with a higher need for reoperations [24,27]. However, resecting and shaving of a raphe is protective against the development of AS [30]. “Bicuspidization” results in an almost straight line of coaptation a more physiologic flow and lower wall shear stress at the level of the STJ. From a hemodynamic point of view, symmetric valve geometry should be attempted in most BAV repairs [8,31]. A more challenging “tricuspidation” should be attempted in cases with a higher degree of asymmetry and with retraction of the raphe [8]. A higher degree of asymmetry could also affect the time to reoperate [27]. An annuloplasty reduces valve regurgitation in the long term [28]. In patients with a suture annuloplasty, a second band at the STJ, would not be needed if the ascending aorta is replaced, because the proximal anastomosis of the ascending graft would stabilize the STJ [8]. During valve-sparing root procedures, CV-0 sutures are routinely employed to reapproximate cusp edges or reinforce the annulus, providing precise tension control and minimizing tissue stress. Their use is particularly beneficial in BAV repair where cusp asymmetry necessitates delicate realignment.

The evaluation of the surgical result can only be reliably performed during the operation, although TEE before installation of the CPB might be helpful in measuring the angle and planning the repair [8]. A failure to attempt to repair the valve in the first session might be a predictor of the future development of AS [30]. Since the use of a pericardial patch in cases of calcified zones increases the risk for reoperation [28], SAVR seems preferable over the use of a pericardial patch in cases with calcification [27]. In the presence of calcifications, immobile cusps, severe fenestration, or an inadequate geometric height, SAVR should be performed. If an aortic dilatation is present, a Bentall procedure is the best option [32].

The decision for valve surgery in BAV cannot be disentangled from the problems posed by an affected aortic root [32], since aortic valve regurgitation can be a consequence of the aortic dilatation. Dissection is a major complication of aortic dilatation [8,33]. This complication is potentially fatal and can be prevented by timely surgery. The relationship of BAV with aortic complications is illustrated by the observation that patients with an acute type A aortic dissection have a higher association with BAV, compared to the general population, especially when AR is present [33,34,35]. Root replacement is often required in patients with BAV [10]. However, it is still not well established which is the best surgical strategy and when a specific technique should be preferred in root surgery, especially regarding BAV anatomy [6]. For a dilatation limited to the ascending aorta, an intervention (AAI) is indicated, but there is a significant variation in the timing for such a procedure [36]. The decision to perform surgery does not only depend on the size of the aorta but also on the risk factors for dissection such as AR and hypertension. Without these risk factors, the proposed threshold is at 55 mm [5,8]. However, the value of 55 mm might fail to prevent complications [33]. In the presence of risk factors, this threshold is set at 50 mm [8,37]. For specific genetic syndromes, which carry an increased risk for the presence of BAV, separate guidelines have been proposed [23]. In patients with symptomatic AR and ascending aortic diameter >45 mm, a replacement was advocated [5], and more than one-third of patients with a BAV underwent AAI at aortic diameters <45 mm. Patients with higher age and the presence of aortic valve stenosis were more likely to receive SAVR without AAI, but the risk-benefit ratio of routine aortic interventions at smaller diameters needs to be determined [36]. This is in line with the observation that the aortic root does not dilate over time when not replaced. Adherence to the 45 mm size threshold for AAI protects against adverse events after SAVR. The cutoff for AAI might be lowered to 45 mm, without additional short-term risks [38]. Moreover, if the aortic dilatation was a consequence of altered hemodynamics and not by genetic factors, the risk for complications might disappear after valve surgery [35]. Nevertheless, even patients with roots smaller than 35 mm with RL-BAV would require more surveillance after AAI [6]. The balance between the risk for dissection and potential postoperative complications should be based on the patient’s characteristics and also on the available surgical expertise [33]. The absolute size as a parameter might be insufficient to determine the need for aortic intervention. Some authors advocate the use of indexed sizes of the SOV, STJ, and ascending aorta using the patients’ height for indexing. The existence of abnormal indexed sizes with absolute values between 45 and 50 mm holds a significant risk [33]. Moreover, there is the gender effect: female patients with BAV referred for surgery were older, and had a more significantly diseased aortic wall with larger indexed sizes and higher risks for complications. These findings indicated that women should be monitored more closely [39]. All these findings made reproducible serial imaging to monitor the progress of an aortopathy all the more important [8]. There was no consensus to extend the repair into the aortic arch to avoid future risks for arch-related complications. This more complex and longer procedure involved a circulatory arrest. Its necessity was not established, since there is no documented clinical benefit with respect to in-hospital complications, long-term survival, or reintervention rate [16]. A more extensive resection into the arch for patients with non-syndromic BAV seemed generally not justified when the ascending aorta was replaced [8].

The technique for VSRR requires an inspection of the valve cusps for calcification, perforations, fenestrations, elongation of the free margin, and prolapse. The findings determine the repairability of the valve. During a VSRR, the root should be completely dissected free from the surrounding structures, with excision of all abnormal parts of the sinus, leaving a 4–5 mm rim of aortic tissue along with the annulus. The coronary buttons are dissected free and mobilized [5]. Several options are available: (1) a straight tube graft can be reimplanted, without creation of neo-sinuses; (2) a remodeling according to Yacoub, with a three-tongued graft sewn at the annulus and small remnants of the sinuses, (3) with or without annular support and (4) reimplantation by creating a neo-STJ and neo-sinuses by plication of the graft or using separate grafts, the proximal one being the larger [40]. Care should be taken to maintain an optimal coaptation height by an appropriate suturing of the commissures and respecting the native anatomy. Once these positions are finalized, the commissural sutures are tied to the graft, and the coronary buttons are reimplanted. The root is fully inspected to see if any adjunctive cusp repair is needed [5].

In cases with a severe AR and a normal-sized aortic root but a dilatation of an ascending aorta, a valve repair could be performed with an STJ remodeling by using a tube graft and external sutures at the basal ring around a Hegar dilator [24]. Remodeling of the root has become the primary treatment for root enlargement and a noncalcified aortic valve, irrespective of the degree of AR. The remodeling reduces the annular diameter and improves the coaptation height. A suture annuloplasty might improve the durability of the repair. Measurement of an effective height allows the detection of any prolapse. One should be aware of aggravated prolapse by reducing the distance between the commissures [29]. In case of an asymmetrically dilated root with an R-L type BAV, a supra-coronary replacement was proposed with an extension for the replacement of the NC-cusp. Results were good in patients with small roots and only a mild residual AR [6].

The “Florida sleeve” technique was proposed for AR due to the dilatation of the root. This technique involves four sub-annular anchoring sutures placed two to three mm below the nadir of the leaflets. Three sutures are in line with the commissures and the fourth is placed under the noncoronary cusp. The keyhole for the coronary arteries is cut after the sleeve is temporarily seated. After the definitive seating of the sleeve, the slits in the graft below the coronary keyholes are sutured. The running horizontal mattress suture both suspends the aorta and orients the posts of the commissures. Redundant aortic wall at the STJ should be made to overlap with small pleats. The procedure seems safe and offers durable results [41].

A reduction aortoplasty is not recommended as a first-line procedure but seems applicable in patients of higher age who are unfit for extended aortic surgery. Connective tissue disorders are clear contraindications. A longitudinal aortotomy just proximal from the clamp to the NC sinus is followed by a wedge-shaped excision and a double-layered closure, which can be reinforced with a pericardial strip. This technique preserves the Windkessel-effect but there is a risk for recurrent dilatation, especially with high preoperative aortic diameters or with underlying histopathologic aortic wall changes associated with BAV. Support by an external wrapping with a dacron prosthesis aims for stabilization but with a risk for prosthesis dislocation and aortic tissue lesions. The procedure itself is safe, with a low complication rate and a good durability and survival, irrespective of the valve morphology. An adequate pre- and intraoperative tissue quality assessment and patient selection are crucial [37]. Extravascular wrapping of a mildly dilated ascending aorta as a sole procedure in patients with BAV-related aortopathy is also safe and easy to perform. The wrapping excludes the SOV and the coronary arteries. Comparison of SAVR with and wrapping versus ascending aorta replacement showed longer CPB and ACC times for replacement but without difference in adverse postoperative events and good mid-to-long-term outcomes. Wrapping in these cases could be considered as a prophylactic measure [21].

If a dysfunctional valve is repairable, VSRR for aortic dilatation is the preferable option [4,5,42]. This might be better compared to a SAVR or a composite graft, at least in experienced centers [4,5]. The preservation of a native valve avoids potential valve-related complications and the need for anticoagulation [3]. In the presence of calcification, immobile cusps, severe fenestration, or geometric height below 18 mm, a Bentall procedure should be performed [32,42]. A conversion from valve repair to SAVR might be needed in a high degree of asymmetry of BAV and of the root with a higher severity of AR in BAV Sievers type 1, other than L-R fusion [40], although “tricuspidation” could be attempted in these cases [28,29]. The postoperative mortality is lower in VSRR compared to Bentall, but the rate of recurrent AR is higher [42]. Although VSRR with valve repair in young patients with a regurgitating BAV has a good 15-year survival rate, a high reoperation rate of 31% was observed [27]. With proper patient selection, VSRR in BAV is considered a durable option [5]. Selected patients with a diameter of the aorta below 55 mm, undergoing SAVR showed a low rate of rupture, dissection, or sudden death. This seemingly contradicts the guidelines using 45 mm as a threshold. This observation, however, needs confirmation by future studies [35].

The durability of valve and aortic operations has its importance because of the relatively young age of patients with BAV, with a consequently longer life expectancy. In patients with BAV and mild-to-moderate AR, valve dysfunction will not worsen after isolated replacement of the ascending aorta. The need for reintervention was low at 12 years [7]. The 10-year reoperation rate after VSRR was also low [5]. After ARR, the 15-year reoperation rate is increased, especially for the repaired valve. The survival rate was comparable to that of the age and gender-matched general population [10]. Recurrent root dilation after ascending aorta replacement with or without replacement of the NC-sinus in the long term was predicted by an aortic root diameter at discharge > 35 mm, a preoperative AR labeled as more than mild, and no SAVR. Age and replacement of the NC sinus had a borderline effect. Reoperation for aortic root dissection or dilation was extremely rare at follow-up, so full replacement of the aortic root when this was only mildly dilated still does not appear justified [6]. A VSRR of the David V type which creates neo-sinuses showed a good 12-year survival with low reoperation rate in patients with BAV as well as TAV [4]. Conformance to the 45 mm size cutoff for preemptive ascending aortic replacement during SAVR in BAV patients was not associated with an increased risk for early adverse events [38]. A valvuloplasty of BAV showed higher transvalvular gradients compared to a repair of a TAV. These higher gradients did not affect rates of regurgitation and reoperation [24].

The fate of the remaining aorta (i.e., the SOV and remaining distal ascending aorta) after combined SAVR with ascending aorta surgery for BAV after excluding patients with isolated SAVR, aortic root replacement (ARR), aortic arch surgery or connective tissue disease was also a matter for debate. Most patients under study had AS. A mixed AS-AR and pure AR were less common. One-quarter of the patients underwent surgery with circulatory arrest. Serial CT exams showed that the remaining SOV diameters increased hardly, while there was a significant increase in the remaining distal ascending aorta. Only 1 patient required surgery for proximal pseudoaneurysm, and none for dilatation of the remaining distal aorta. Long-term survival was high. Rapid dilatation of the residual aorta rarely occurred in patients with a BAV who underwent SAVR and grafting of the ascending aorta in the mid-term follow-up. For selected patients with a surgical indication for ascending aortic dilatation, simple SAVR and graft replacement of the ascending aorta may be sufficient surgical options [17]. In selected patients with a BAV with a >45 mm ascending aorta and normal roots and arches, the replacement of the ascending aorta by a graft without concomitant root and arch procedure produced excellent survival rates, freedom from MACCEs, and fewer reoperation and aorta-related events in the mid-term follow-up. Rapid dilatation of the residual aorta rarely occurred in patients with a BAV who had undergone SAVR and grafting of the ascending aorta. For selected patients with a surgical indication for ascending aortic dilatation, simple AVR and grafting of the ascending aorta may be sufficient surgical options [17].

Table 2 shows the comparison between the demographic, operative, and postoperative results (survival, reoperation rate) of patients with BAV versus TAV. The included articles had a very different design, which makes a comparative analysis difficult. In all series, the BAV patients were at least 10 years younger, compared to their TAV counterparts. This was also the case in two series before a propensity score match (PSM) analysis was performed. The mean ages were 57 years versus 68 years [43] and 44 years versus 54 years [4]. In these series, patients with BAV had a higher rate of aortic arch procedures. This younger age in patients with BAV translated also in lower mean Euroscores II of 1.8% versus 2.7% [44] and 1.6% versus 2.6% [45]. A low Society of Thoracic Surgeons risk score of about 0.7 was observed in other single-arm series studying BAV patients with mean ages below 40 years [31], while in another small series, mean Euroscores of 2.1 for Sievers type and 2.9 for Sievers type 0 were observed. These patients, however, had mean ages of 62 and 64.5 years [46]. In all series 30-day complication and mortality rates were low. The age of BAV patients also allows for a long follow-up with respect to reoperation rate and survival. The results in Table 2 show that for patients with a TAV morphology, long-term survival varies widely.

In three comparative series, patients were treated with SAVR instead of a repair. Long-term survival was lower in TAV patients, which could be attributed to the age difference. Reoperation rate differed in one series, where a stentless device was implanted. In one series, where a propensity score match analysis was performed between patients with BAV and TAV, the presence of BAV was identified as an independent predictor in favor of long-term survival. Because of the research design, preoperative and operative characteristics were comparable for both patient groups. The reoperation rate for BAV patients was higher, but a higher mortality rate in TAV patients, as a competing event, could contribute to this observation [43]. Biological valve prostheses should be used with caution in these patients. A Resilia valve, which is designed to prevent or at least delay calcification by capping residual aldehyde groups, showed encouraging results with respect to durability [44]. The use of rapid deployment valves such as Intuity seemed less favorable in patients with BAV [43] and was more appropriate in older and higher-risk patients because of the shorter operation times. The presence of BAV in patients with infective endocarditis was also identified as an independent protective predictor for short- and long-term mortality. These patients were also younger and healthier compared to their TAV counterparts since infective endocarditis occurs generally sooner in patients with BAV [11].

Comparative series concerning repair with pericardial tissue showed worse results, especially in patients with BAV [25]. Aortic valvuloplasty with annuloplasty and a tube graft showed better early postoperative results in patients with TAV compared to those with BAV. Patients with a repaired BAV have a higher transvalvular gradient, but this did not affect mid-term outcomes nor the reverse remodeling of the left ventricle [24]. However, VSRR for patients with BAV, such as the Florida-sleeve technique [41], a tube graft [29] with external annuloplasty and STJ remodeling [24], a Valsalva graft with the commissural resuspension and other necessary valve repair procedures [4], showed acceptable outcomes.

The existence of BAV has also consequences beyond the valve and the aorta. The eccentric opening of a BAV and the altered elasticity of the aorta can contribute to a chronically elevated afterload imposed on the left ventricle (LV). This leads to the observation that an impaired LV function is more common in patients with BAV, compared to age and sex-matched controls with dysfunctional TAV [47,48]. Especially adolescents and young adults with a BAV have early echocardiographic signs of LV remodeling [49]. In patients with predominantly AR, an eccentric LV hypertrophy was observed [1]. Patients with isolated severe AS had, compared to TAV counterparts, a higher degree of ventricular systolic and diastolic dysfunction [50].

There were also other differences between patients with a dysfunctional TAV and BAV. Table 2 shows that patients with BAV dysfunction are mostly younger compared to those with TAV disease and have fewer comorbid conditions. The increased LV compliance in younger BAV patients could lead to a more prominent dilatation of the LV. This is an important observation since about half of the operations on the aortic valve are based on an increased end-diastolic diameter of the LV [41,42,43,44,45,46,47,48,49,50,51,52,53,54]. Patients with BAV show also a higher risk for early congestive heart failure [55,56]. If a severely reduced left ventricular ejection fraction (LVEF) is present in patients with AR, the risk for persisting lower LVEF is higher after corrective surgery [57]. Early valve surgery should be recommended since survival is reduced with a decreased preoperative LVEF [58].

The extent of postoperative reverse remodeling of the LV depends on the preoperative size of the LV [59]. Early surgery should occur because of its beneficial effect [47,59]. It should be noted that many patients with LV end-diastolic dimensions below the current surgical thresholds for surgery, did not experience a normalization LV size. Compared to patients with isolated AS in patients with TAV, those with BAV had a lower preoperative LV function and higher LV mass index. Patients with BAV required significantly more postoperative inotropic support [60]. They also had a higher cumulative incidence of postoperative admissions for congestive heart failure compared with patients with TAV. However, survival was not different between these groups. Patients who had BAV with AS might benefit from closer surveillance and possibly earlier intervention. For these reasons, patients with BAV and TAV with isolated severe AS should not be regarded as one entity [60].

BAV disease also affects LA remodeling and function to a stronger degree than a diseased TAV. Aortic valve morphology is associated with preoperative LA reservoir function [48,58]. Even with an earlier intervention a more severely affected LA function in patients with BAV, has the consequence of a higher risk for postoperative atrial fibrillation. Ischemic neurologic events during follow-up are more common in AS patients with BAV morphology, probably due to the effect of a diseased BAV on the LA function [61].