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INTRODUCTION
Following the first descriptions by Tirone David and Magdi Yacoub 1,2 the valve-sparing aortic replacement (VSAR) has been established as a successful procedure for aortic root aneurysms.
There are specific advantages of VSAR when compared to conventional aortic root replacement with a valved conduit, and include decreased possibility of valve thrombosis, thromboembolism, bleeding events associated with anticoagulation, structural valve deterioration, and endocarditis. 3,4 Preservation of the native aortic valve has become an attractive option to avoid these undesirable events.
There are mainly two types of VSAR techniques: reimplantation and remodeling. In both, the aortic root is excised preserving the native valve, but there are differences in terms of technical aspects. In reimplantation, the Dacron graft is attached at the level of the aortic annulus, giving support to this structure. In remodeling, the graft is sutured at the level of the aortic sinuses. This last one requires less time and is easier, but there is a lack of aortic annulus support, increasing the rate of aortic regurgitation during the follow-up. Adding external support for the annulus (i.e., ring, suture, etc.) can solve this disadvantage.
The VSAR technique has become an accepted operation for patients with Marfan’s syndrome and other connective tissue disorders as well as for patients with aortic dissection. It has also gained increasing use in patients with bicuspid aortic valves. 5-9
Over the years several modifications have been proposed and opinions differ amongst surgeons regarding technical aspects, indications, and the future of VSAR. We believe there is a need for a consensus opinion regarding key aspects of VSAR, as well as what skills are necessary for a surgeon to safely and effectively perform VSAR.
This survey of surgeons with known expertise in VSAR operations provides a summary of their views.
METHODS
A literature review was performed regarding the most frequent debates and controversies in VSAR. List of relevant questions was prepared and evaluated by experts. Authors with known expertise in VSAR operations were identified and asked to participate in the project. A survey was developed, and questions were reviewed and chosen by the authors (GF, MM, TD, CF, EL, RM). Inclusion criteria required that surgeons have performed VSAR with a minimum of 25 cases, either reimplantation or remodeling technique.
A total of 25 surgeons with known experience in this field spanning 10 countries and 15 different institutions were identified and selected. They were contacted through email and asked to participate voluntarily in the survey. In total, 5 participants´ answers were excluded for incomplete/ inconsistent survey responses. An online platform was developed using 46 multiple-choice questions. The questions were focused on:
1. Indications and patient-related factors,
2. Technical and anatomy-related aspects
3. Echocardiography findings
4. Research, training, and the future.
RESULTS
Of the 20 responders, 13 (65%) have ≥ 100 VSAR in their expertise, 3 (15%) more than 50, and 4 (20%) between 25 and 50. Everyone accepted to participate voluntarily in this financially unfunded project.
Indications and patient-related factors (Table 1) (Fig. 1)
(Q.4) Severe left ventricular dysfunction was a contraindication for VSAR: 14/20 of the responders.
(Q.5) The aortic annulus diameter cutoff for the remodeling procedure was heterogenous between the options: 8/20 believe there is no limit for a remodeling technique; however, 3/20 prefer this method for small annulus (20-22 mm), 4/20 would consider the cutoff in 24-26 mm and 5/20, ≥ 28 mm.
(Q.6) Severity of aortic regurgitation (AR) was not considered a limitation for the VSAR.
(Q.7-8) 11/20 (55%) responders decided to perform prophylactic VSAR in Marfan group when the aorta measured ≥ 5 cm and 8/20 when it was ≥ 4.5 cm. Moreover, everyone (100%) considered the VSAR as a safe operation for this population.
(Q.9-10) 12/20 responders are willing to bicuspid valves especially if the surgeon has expertise in the field; besides 14/20 considered that cusps anatomy (type 0 vs 1) as a predictor of AR recurrence.
(Q.11-12) There was a strong tendency to avoid VSAR in type III lesions (17/20). In acute aortic dissections, more than half (11/20) preferred to perform the VSAR only in patients consider younger or below 50 years; nonetheless, 18/20 accept this procedure when is feasible even in this scenario.
Technical and anatomy-related aspects (Table 2) (Fig. 2)
(Q.13-16) Of the asked surgeons, 9/20 believe that the lack of neo-sinuses in the reimplantation technique adds stress to the cusps but does not affect the general results. Interesting, half of the participants think it is useful to standardize an external ring in the remodeling technique, and most of them use Hegar when tying to maintain annular size.
(Q. 17-18) The majority (13/20) believed that a minimum target of cusps effective height to assume successful the procedure must be >8 mm. When asked if annulo-aortic ectasia is a contraindication for remodeling, 14 preferred to do reimplantation; however, 7 of them still prefer a remodeling with external stabilization.
(Q. 19-22) Notoriously, almost half of the responders assured that a Dacron non-compliant graft increases the risk of distal aortic disruption, and 11 out of 20 prefer a Dacron rather than a Valsalva graft. More than half (65%) use mid-leaflet plication for excessive valve prolapse.
(Q. 23) According to graft sizing, the height of the interleaflet triangle as a basis for graft sizing (8/20) and the measure of the sino-tubular junction with a Hegar (7/20) were the most selected choices.
(Q. 24) Regarding stabilization of the aortic annulus in the remodeling technique, only the group of surgeons who perform this technique answered this question, and 7/20 use an extra-aortic ring for stabilization.
(Q. 25-27) When there are more than 2 leaflets with fenestration, 80% will not try to preserve the valve, and for those who accepted to repair a calcified valve, the major part will only do it if it is mild.
(Q.28) Eleven out of twenty don´t use the caliper routinely.
(Q. 29-31) Most of the participants agree that in bicuspid valves, the tricuspidization is reasonable only if the commissure presents orientation near 120º, and shaving is the most frequent technique used for the raphe (14/20). Moreover, 15 out of 20 are convinced that the pericardial patch used for cusp restoration after raphe resection is not advisable.
(Q. 32) The surgical strategy decided preoperatively changed due to intraoperative findings in 29% on average.
(Q. 33) The estimated VSAR failure rate, with conversion to a Bentall procedure was almost 7%.
(Q. 34) Sixty percent of the responders would consider switching to a Bentall procedure when the post- VSAR echocardiography reveals AR ≥ mild.
(Q. 35) In redo operation in failed VSAR, a minority (3/20) are willing to re-repair the valve, but the majority prefer a Bentall/aortic valve replacement.
Echocardiography Findings (Table 3) (Fig. 3)
(Q. 36-38) The majority of the participants (16/20) think that echocardiography provides accurate anatomy assessment and is predictive of valve repairability; however, they still need to re-check intraoperatively to decide definitively what to do. Additionally, for fifteen of the responders, the echocardiography findings correlate with the intraoperative findings.
(Q. 39-40) With regard to the AR predictors, most of the participants have chosen the effective height, coaptation length, and immediate post-VSAR residual AR as the most important factors.
Research, training, and the future (Table 3) (Fig. 3)
(Q. 41) Most of the surgeons believed that doing this procedure with a resident does not affect the results.
(Q. 42) Interestingly, almost all the responders (19/20) affirmed that a minimally invasive approach (MICS) doesn’t improve the postoperative results or even make any difference.
(Q. 43) Most of the surgeons assured that VSAR must only be performed either by high-volume centers or by experienced surgeons.
(Q. 44-46) 75% of the participants think that 3D printing could be helpful sometimes or even is the future for preoperative decisions, and 16 out of 20 considered that the intention to repair the aortic valve should be the standard for all candidates for a VSAR.
DISCUSSION
Both re-implantation and remodeling techniques have been shown to adequately preserve aortic valve function in patients with aneurysms of the aortic root, Marfan´s syndrome, and type A aortic dissection. 2,9-12
This survey mirrors the controversies regarding indications, technical aspects, echocardiography use, and the future.
Even though a broad variety of experienced surgeons worldwide have participated in this questionnaire, it is still difficult to reach a final consensus on some key aspects of VSAR operations. However, we believe that the opinion based on the clinical experience of the most experienced surgeons of the world on this topic has a fundamental value. The broad spectrum of the results reflects the different surgeon specific criteria when performing VSAR.
It has been demonstrated that aortic annular dilatation is a risk factor for early and late failure. 13 Hanke et al. proved that patients who underwent remodeling technique with an aortic annulus greater than 28-30 mm presented worse results at follow-up compared to those who underwent reimplantation.
14 Notoriously, 8/20 participants (40%) will proceed with a remodeling technique regardless of the aortic annulus diameter, undoubtedly due to the personal preference for one technique over the other one, but more importantly, this could be explained because surgeons who prefer the remodeling technique, have performed the ¨modified remodeling¨ which includes the external aortic annulus support with the aim to avoid the AR during the follow-up. The lack of this annulus support was the Achilles heel in aortic annulus greater than 28 mm.
While more than 90% don´t believe that preoperative AR is a limitation, David and colleagues have suggested that patients with preoperative severe AR are not good candidates since they often have damaged cusps. 10
Contrary to surgeons' thoughts decades ago, most now feel (100% in this survey) that VSAR is a safe procedure for the Marfan’s syndrome population. There is a discrepancy between European and American guidelines regarding when to treat the Marfan population. The ESC 2014 guidelines consider treating after ≥5 cm in the Marfan population (Ic) and 4.5 cm with risk factors (IIa), whereas 2018 AATS guidelines recommend treating at 5 cm with risk factors (IIa). In this survey, almost half and half have chosen one of those options, most likely related to where they do their practice. 15,16
All the participants believe in treating the aortic root in bicuspid valves whenever feasible. Boodhwani and colleagues 17 presented freedom from aortic valve reoperation for bicuspid valve repair at 5 and 8 years of 94% and 83% respectively. The ACC/AHA 2020 guidelines established for the first time the valve repair with/without reimplantation technique (IIb) in bicuspid aortic valves by experienced centers. 18
Interestingly, 15% would take an aggressive approach to type III injuries or at least consider treating them initially. We believe this is a challenging scenario and should only be performed by highly experienced surgeons.
Regarding VSAR in acute type A dissections (ATAD), the majority (55%) will prefer to do this procedure in young patients only, and another 35% will try it always when possible. This shows how surgeons have gained confidence with this technique, even in undesirable situations like ATAD. Khachatryan and the Leipzig group have shown excellent results with the David technique in ATAD with in-hospital and 30- day mortality of 4% and 9% respectively. 19 Mosbahi, et al. 20 also showed that the David procedure was superior to the Bentall technique for the ATAD population after analyzing 27 studies with a total of 3058 patients. David procedure was superior in terms of inhospital mortality (2% vs 8%), midterm survival (99% vs 81%), early postoperative stroke (2.7% vs 5.1%) and thromboembolic events (0.5% vs 4.9%).
The association of valve plication on previously diagnosed prolapse reflects the combination of lesions commonly observed (annuloectasia, sinus dilation, and proper valve disease; type 1 and type 2 lesions on Carpentier classification).21
The minority of the participants uses routinely the Valsalva graft; however, it has been shown by some authors 22 in a finite element study that re-creation of the sinuses reduces leaflet stress during valve closure, consequently improving leaflet long-term durability.
It is worth mentioning the significance of the effective height (eH) and coaptation area to achieve good postoperative results.
An eH range between 7 -12 mm is believed to be normal for adults 23
It has been shown by Bierbach and colleagues 24 that 96% of all patients with moderate or more severe AR had an eH of less than 9 mm.
One of the most relevant aspects of these techniques is graft sizing. Since the original method based on the Feindel-David formula 2, several different methods have been proposed and surgeons tend to use whatever they feel is more reliable as we can see in this survey.
Most of these formulas are based on relative proportions of the normal aortic root, but patients requiring the VSAR no longer have normal root anatomy; therefore, choosing the size of the graft based merely on fixed normal aortic valve dimensions, may generate mistakes.
One of the most relevant answers collected from this study is related to the failure rate of VSAR, with conversion to Bentall (7%) and the change of strategy intraoperatively (26%), especially since surgeons may feel uncomfortable when asked about the results.
Although 7% is not a negligible number (certainly biased by surgeons' experience), VSAR has demonstrated so many advantages that proves to be an excellent surgery for aortic root aneurysms. 3,10,20.
Some authors as Lansac 21 have proposed a useful lesion classification by echocardiography, to standardize surgical management and planning. Overall, almost all the responders accept the importance of the pre and intraoperative echocardiography assessment. However, there are aspects to consider. For instance, this may not always be clearly visible by echocardiography or could be inaccurate (eg. measure of effective height) and the caliper could be helpful in this scenario; therefore, these tools allow further standardization of valve repair by supporting the surgeon in his assessment of cusp prolapse. Additionally, it is mandatory on these cases to have a high-experienced echo operator for aortic valve and root pathology.
Interestingly, the MICS approach was not considered at all to improve results or even make any difference; however, more than half of the surgeons confessed that patients ask for it. Why has it not prospered? It could be that today’s surgeons do not wish to adopt MICS techniques because they are more complex, take more time and there is a lack of data showing real benefits for the mini-David procedure.
The need of a long learning curve and advanced surgical expertise present a certain disadvantage for the VSAR. For such reasons, it should be performed in specialized cardiac centers with enough experience in the field.
There are still groups that opt for one variant over the other one; nonetheless, we believe that it should be adapted to every single case while taking care of the minimal technical aspects and details.
Finally, in the most comprehensive long-term analysis performed to date of the surgical management of aortic root dilation by Ouzounian et al., 25 it has been shown the superiority of VSAR when compared to tissue-Bentall or mechanical-Bentall at long-term follow-up (15 years) in terms of major adverse valverelated events (18.9% vs. 38.5% vs 35%, p<0.001), anticoagulation-related hemorrhage (6.3 %vs. 2.4 % vs. 11.6%,p<0.001), and with a risk of reoperation similar between VSAR and mechanical-Bentall, but inferior with tissue-Bentall (4.6 % vs 20 %, p<0.001). VSAR procedures were associated with reduced cardiac mortality and valve-related morbid events compared to tissue or mechanical Bentall at 15 years (15.8 % vs. 23.7% vs. 25.3%, p 0.04).
These estimates of time-related freedom from valve-related complications are certainly superior to those obtained with bioprosthetic or mechanical valves.
CONCLUSION
These results suggest that VSAR, regardless of variants, has been accepted as a treatment option for aortic root aneurysm when the valve is feasible to preserve with remarkable results. Although it is not yet possible to reach a final consensus, this survey showed that technical aspects are the most critical factors in achieving outstanding results. Nonetheless, the personal preference of the surgeon based on his own experience will also determine which technique will use.
