Rationale behind symmetrical BAV repair: time to generalize a standardized approach of bicuspid valve repair

Arimura et al. should be congratulated for an elegant in vitro study, which delves into the scientific evidence behind the effects of sinus plication in repair of the bicuspid aortic valve (BAV) that was intuitively performed by Schäfers et al. [1, 2]. This study shows that improving the commissural angle towards a symmetrical valve design both improves valve opening and reduces the transvalvular gradient. Nature has shown us that a type 0 symmetrical bicuspid valve can be functioning perfectly well even in advanced age. This study is the first to confirm the logic behind a symmetrical design for bicuspid valve repair to improve valve dynamics postoperatively and also to reduce flow turbulence through the valve for long-term durability. All parameters influencing BAV repair are now well understood and rationally demonstrated: annulus diameter, effective height, commissural orientation, and STJ diameter. First, a dilated aortic annulus >25 mm, if left untreated, has been clearly shown to be a major risk factor for failure of bicuspid and tricuspid aortic valve (AV) repair procedures [3, 4]. As a result, since 2014, European Association for Cardio-Thoracic Surgeons/European Society of Cardiology guidelines’ recommendation for management of aortic root aneurysm (originally called annulo-aortic ectasia) is to use ‘reimplantation or remodelling with aortic annuloplasty’ for valve-sparing root replacement, referring to the need to address the annulus [5, 6]. Indeed, aortic annuloplasty efficiently addresses this issue, aiming at a sustained long-term outcome by reducing the dilated aortic annulus and improving the surface of coaptation, much like the role of mitral annuloplasty in mitral valve repair. Second, the need to address the STJ was documented by Frater et al. for ascending aorta aneurysm with a supracoronary tube, by Yacoub and David for valve-sparing root replacement (remodelling or reimplantation) and more recently by Zakkar et al. for repair of isolated aortic insufficiency (AI), which demonstrated the superiority of isolated AV repair using double sub and supra (STJ) annuloplasty as compared to single subvalvular annuloplasty alone [4]. The present study demonstrates for the first time the rationale behind symmetrical BAV repair. Effective height is tightly correlated to commissural orientation. By placing the commissures in a symmetrical 180° configuration, the free edge of the non-fused cusp will be stretched and lifted up, thereby increasing its effective height. This has the advantage of addressing the mild–moderate prolapse present in the non-fused cusp of most BAVs with AI. By increasing the effective height of the non-fused cusp and treating this prolapse, this avoids the need to perform central cusp plication, thereby preserving the free edge length of the non-fused cusp. In BAV repair, the vast majority of cases will have significant prolapse of the fused cusp, which will require cusp plication. This means that the non-fused cusp becomes the work-horse for opening dynamics of the valve, much like the anterior leaflet of the mitral valve in posterior leaflet prolapse MR. Avoiding plication of the non-fused cusp will reduce the transvalvular gradient as shown in the present study and preserve maximum opening of valve for long-term durability. Following the rationale described above, it is possible to standardize symmetrical BAV repair according to the aorta phenotype [7, 8]: Dilated aortic root (sinus of Valsalva >45 mm): remodelling root repair with 2 symmetrical sinuses along with external ring annuloplasty; Ascending aortic dilatation (>45 mm) in a right–left fusion BAV: hemi-remodelling with replacement of the non-coronary sinus along with sinus plication and external ring annuloplasty; and Normal root and ascending aorta (all diameters ≤40–45 mm): double sub- and supra-valvular (STJ) aortic ring annuloplasty with sinus plication. Regarding valve-sparing root replacement, despite an annuloplasty being provided by both the reimplantation technique and the remodelling + ring technique, we prefer to use remodelling + ring based on a number of reasons. The first is related to superior haemodynamics in the remodelling technique with regard to vortical flow formation with preserved root expansibility and more physiological valve movements [9]. Second, there are advantages to remodelling + ring with regard to the standardization and reproducibility of the technique. Whereas in the reimplantation technique the surgeon has to make a judgement on how high to place the commissures and how to place them circumferentially inside the graft, the commissures will follow the graft in the remodelling technique and will therefore be placed at the same level as well as at 180° for bicuspid valve or 120°for tricuspid valve. Furthermore, as the annuloplasty is the first step carried out in the reimplantation technique through the proximal suture line, this means that subsequent eH measurement is hampered by having to measure within a small reduced annulus, making accurate measurements difficult. In contrast, the annuloplasty ring is the last step of the technique in remodelling + ring; therefore, cusp eH is measured in an untouched (often large) annulus, making accurate measurement easier. Third, the fallback option in aortic root repair if there is persistent AI after the cross-clamp is removed is to re-clamp and replace the AV. In the case of reimplantation, this may mean inserting a prosthetic valve into a reduced small annulus, implying a small valve may be inserted. In remodelling + ring, the external ring could simply be cut and removed, thereby making the annulus enlarge again. This would provide space for inserting a large prosthetic ring. Despite this scenario being a relatively rare occurrence, it is of particular importance to new surgeons embarking on these techniques in their learning curve. This standardization provides 94% freedom from valve-related reoperation at 12 years for BAV repair including all phenoptype of the aorta similar to tricuspid AV repair with similar life expectancy to the general population (data under submission). Long-term evaluation of patients’ outcomes after bicuspid repair will be essential to raise the level of evidence of current European Society of Cardiology/European Association for Cardio-Thoracic Surgeons guidelines for heart valve disease for valve repair. One of the most important key factors is uniform clinical reporting in all available AV repair techniques. One such example of this is the open Heart Valve Society (HVS) aortic surgery database (AVIATOR registry) [10] and we encourage all teams to join this effort of evaluation. Conflict of interest: Emmanuel Lansac has consultant agreements with CORONEO, Inc (www.coroneo.com), in connection with the development and patent of an aortic ring bearing the trade name ‘Extra-Aortic’. The other author reports no conflicts of interest.