Discussion

AVNeo is an important treatment alternative that has gained popularity in recent years and has been used in various pathological conditions related to the aortic valve in both adult and children. ^{Reference Buratto and Konstantinov2,Reference Polito, Albanese and Cetrano5} With AVNeo surgery, one or more aortic valve leaflets can be replaced using autologous or heterologous pericardial tissue. ^{Reference Chivers, Pavy, Vaja, Quarto, Ghez and Daubeney6} Numerous studies, especially in the adult age group, have shown that this surgical method is associated with low mortality, morbidity, and reoperation in the early, medium, and long term. ^{Reference Ozaki, Kawase, Yamashita, Uchida, Takatoh and Kiyohara3,Reference Pirola, Mastroiacovo and Arlati7} After the experiences in adult patients, the AVNeo technique has been frequently used in the childhood age group. Although the early and mid-term results are successful, data for long-term morbidity and reoperation rate have not yet been published. ^{Reference Baird, Marathe and Del Nido8,Reference Jia, Zhang and Huang9}

A wide variety of surgical repair techniques are available for congenital or acquired aortic valve stenosis and insufficiency in children. ^{Reference Buratto and Konstantinov2} These techniques have acceptable results in the medium and long term. ^{Reference Wiggins, Mimic and Issitt10} However, replacement is the only option for aortic valve pathologies that are unsuitable for surgical repair. There are various alternatives for aortic valve replacement in children, and these are pulmonary autograft implantation (Ross procedure), aortic homograft implantation, and mechanical valve replacement. ^{Reference Myers, Mokashi and Horgan11} Although the Ross procedure has excellent results in the early and medium term, it has some drawbacks such as high mortality in the neonatal and infant period, the need for reoperation for root dilatation in the long term, and the need for long-term intervention for stenosis developing in valve conduits placed in the pulmonary position. ^{Reference Moroi, Bacha and Kalfa12} Homografts are reasonable alternatives for the aortic position in children. However, they are not the best option due to the lack of limitations in availability and a high rate of structural deterioration in the long term. ^{Reference Horke, Bobylev and Avsar13} Mechanical valves, on the other hand, have various disadvantages such as the life-long need for anticoagulation, risk of thromboembolism, possible need for additional aortic root expansion in patients with narrow annulus, and the need for reoperation due to pannus formation in the long term. ^{Reference Bouhout, Ba, El-Hamamsy and Poirier14}

The AVNeo technique has recently been used more frequently in children. The advantages of this surgical method can be listed as follows: it can be applied using autologous or xenografted pericardium; single or multiple valve leaflets can be replaced; it can be applied in isolation or using annulus expansion techniques; it allows the native aortic annulus to grow; it does not require life- long warfarin anticoagulation due to the use of biological material; it offers an effective orifice area as good as an aortic bioprosthesis without a stent; and it has a low risk of thromboembolism. Thanks to these advantages, it seems to be suitable for children.

On the other hand, the AVNeo technique also has its drawbacks. First of all, a significantly long learning period may be required. Additionally, special sizing apparatus are needed for this technique to ensure valve competency. Since the surgical field in infants is inherently narrow, the reconstruction of the valve leaflets might be challenging in these patients and additional annular enlargement surgery might be required in some of them. Besides, the issues regarding the need for long-term anticoagulation and valvular durability have yet to be clarified.

In major studies recently published, we have seen that the AVneo technique has rarely been applied in the infant age group. This may be due to successful aortic valve repair techniques which provide enough time for patients to grow for a potential future Ross or valve replacement operation. Another possible reason may be that the surgeon has extensive experience with the Ross or Ross–Konno operation and also the lack of long-term results with AVNeo.

Two surgical options could have been performed on this patient. The first one was the Ross operation and the second, which was our choice, was the AVNeo surgery. The first reason we chose the AVNeo surgery was that the diameter of the pulmonary annulus was significantly larger than the diameter of the aortic annulus and an additional annular expansion operation would have been required for the patient. The second reason was due to the known disadvantages of the Ross operation. The third reason we favoured the AVNeo procedure was because the patient had severe heart failure requiring immediate intervention and was not in a good enough clinical condition to tolerate an extensive and lengthy operation such as the Ross procedure.

Although the experience in the adult and paediatric age groups has shown that AVNeo may be a safe alternative for aortic valve pathologies that are otherwise irreparable, we still have concerns about the durability of the replaced leaflets. It is evident that the calcium turnover is high in children and valve degenerations due to calcification are common when biological materials are used in valve repairs. This situation is more intense, especially in the systemic atrioventricular and semilunar valves. Since autologous pericardium treated with glutaraldehyde is used in the AVNeo technique, any potential degeneration risk is inevitable. That is why we decided to replace only the damaged valves rather than all three valves. We assumed that the more native leaflet tissue we preserve, the less calcification will develop. However, due to a lack of knowledge about the long-term valvular durability of the leaflets and the extent of calcific degeneration, we cannot say whether the original Ozaki procedure with three leaflet replacement is safer in the paediatric population or the limited leaflet replacement procedure that we conducted. We believe that all children who have undergone any type of AVneo surgery should be followed very closely.

To the best of our knowledge, this was the youngest infant to receive the AVNeo technique, who was not suitable for any other kind of repair due to the extensive destruction of the aortic valves. We believe that in case of urgency the AVNeo technique may be an alternative technique to Ross surgery in the infant age group with aortic valve endocarditis.