Results of the Aortic Valve Reconstruction in Children

Overview

Aortic valve disease counts up to 5% of cases of congenital heart disease being one of the most common congenital malformations of the cardiovascular system. This disease requires replacement of the damaged valve which in itself is not a trivial task to complete in children as there is still no available best practice for valve replacement. Today, the following alternative variants are performed in children: mechanical aortic prosthesis, xenografts, allografts, and pulmonary autograft (Ross procedure) and each has its potential advantages and disadvantages. Mechanical aortic prostheses require lifelong anticoagulation therapy and repeated surgeries to replace mechanical valves during child growth. Available xenografts in children also has suboptimal results not only because of absence of growth potential, but also due to development of degenerative changes in biological tissue of the graft leaflets. Allograft tissues are exposed to rapid biodegradation in the recipient body and thus requiring repeated surgeries associated with higher difficulty, high risk of hemorrhages, and injury of the coronary injuries. Ross procedure was proposed as theoretically the most evidence-based reconstruction of the aortic valve in children. Even successfully performed Ross operation transforms one-valve disorder into two-valve disease. The accumulation of knowledge on the anatomy of the aortic root and improvement of surgical techniques led to the development of new methods for reconstruction of the valve function. The technique is widely applied in adult cardiac surgery, uses glutaraldehyde-treated autopericardium for augmentation of the leaflets. Absence of foreign material provides no need for anticoagulation therapy. Potentially, reconstruction of the aortic valve with autopericardium can be widely used in children. Aim is to study safety, clinical and hemodynamic efficacy of the method of the aortic valve reconstruction with autopericardium in children with aortic valve disease. Patients aged 29 days to 12 years will be included into the study. The data according to the protocol of the study will be assessed at the stage of inclusion, during the surgery, in 30 days after the surgery, and in 1, 2, and 3 years after the surgery. Data about all the patients included into the research will be analyzed in order to study the endpoints and achieve the research aim.

Aortic valve disease amounts to approximately 5% of the total number of cases of congenital heart disease, thus being one of the most common congenital malformations of the cardiovascular system. This disease requires replacement of the damaged valve, which in itself is not a trivial task to complete in children as there is still no available perfect option for valve replacement. Today, the following alternative variants for the aortic valve reconstruction in children are known: mechanical aortic prosthesis, xenografts, allografts and pulmonary autograft (Ross procedure); each of the above-mentioned variants has its potential advantages and disadvantages. Mechanical aortic prostheses are widely available, including in small sizes (16 and 18 mm) appropriate for young children. However, the available sizes still do not allow to perform the surgical reconstruction in children of the first year of life. Besides these patients need lifelong anticoagulation therapy and necessity for repeated surgeries in order to replace mechanical valves with a child's growth. Available xenografts have various types but usually, their sizes begin from 19 mm which does not fit for the majority of young children. Aortic xenografts are characterized by low risk of thromboembolism complications and do not require lifelong antithrombotic therapy. However, application of these grafts in children also has suboptimal results not only because of the absence of growth potential but also due to the development of degenerative changes in biological tissue of the graft leaflets. Allografts are characterized by perfect hemodynamic parameters which are similar to the native healthy aortic valve. Risk of thromboembolic complications in implantation of allografts is very low, so there is no need for anticoagulation therapy. As in xenografts, allograft tissues are exposed to rapid biodegradation in the recipient body with the following development of obstruction or insufficiency and thus requiring a repeat operation. Implantation of allografts is associated with higher difficulty and high risk of hemorrhages and injury of the coronary injuries. Ross procedure was proposed as theoretically the most justified choice for reconstruction of the aortic valve in children. As a conduit for reconstruction of the aortic valve the host's intact native pulmonary valve - autograft - is used; and the pulmonary valve is usually replaced by xenograft. Even successfully performed Ross operation, according to some authors, resolves the problem of the aortic valve only for a while; moreover, it causes another problem with the pulmonary valve, thus transforming one-valve disorder into two-valve disease. The accumulation of knowledge on the anatomy of the aortic root and improvement of surgical techniques has led to the development of new methods for reconstruction of the valve function. The experience of various options for interventions on the aortic valve leaflet gained in adult cardiac surgery allowed to consider such interventions as an alternative method to valve reconstruction in children. About ten years ago, Professor Shigeyuki Ozaki brought the reconstruction of the aortic valve with the patient's own tissues to a completely new technological level. This technique includes the use of glutaraldehyde-treated autopericardium for augmentation of the leaflets; the reproducibility of the method was significantly increased due to usage of the template sets and special tools for the measurement of the native valve. Since no foreign material is used, there is no need for anticoagulation therapy after such intervention, which the authors of the method referred to as the valve reconstruction, not implantation of the graft. Potentially, reconstruction of the aortic valve with autopericardium can be widely used in children. In this population of patients, the various variants of the leaflets dysmorphogenesis are much more common, a wide range of morphological diversity of structure with inadequate hemodynamics can be found: monocuspid, bicuspid and pseudobicuspid valves; which does not allow to perform the valve reconstruction by restoring the original anatomy. The normal anatomy of the aortic valve assumes three-valve structure, and most augmentation techniques suppose formation of tricuspid anatomy. At the same time, there is an alternative variant of hemodynamically adequate valve structure in the human body - bicuspid anatomy of the venous valves in the vena cava inferior system. Theoretical calculations obtained through computer simulation show that the neo-valve formed by three artificial leaflets will retain its locking function with increasing the diameter of the fibrous ring only by 8%. At the same time, the bicuspid valve with an increased height of the leaflets is able to maintain the shut-off function with an increase in the diameter of the fibrous ring by 67%. The aim is to study safety, clinical and hemodynamic efficacy of the method of the aortic valve reconstruction with autopericardium in children with aortic valve disease. Primary endpoints: patient's death due to various causes during the first 30 days after the surgery. Secondary endpoints for efficacy assessment: аreedom from repeated surgeries on the aortic valve; mean gradient at the aortic valve over 40 mmHg; аortic insufficiency over 2 degree; effective area of the neo-aortic valve less than 1.0 cm2/m2 Secondary endpoint for safety assessment: acute disorders of cerebral circulation within the first 30 days after the surgery; hemorrhage needing revision surgery; acute kidney injury, stages 2 or 3, including the necessity for renal replacement therapy; acute coronary syndrome; dysfunction of the neo-valve requiring repeated surgery. Patients aged from 29 days to 12 years old with dysfunction of the native aortic valve with and without manifestations, with indications for the aortic valve reconstruction, and without concomitant supravalvular and subvalvular aortic stenosis and major congenital heart diseases, will be included into the study. The study design is planned to be prospective, cohort, single-center, observational. In total 40 patients will be included into the study. The data according to the protocol of the study will be assessed at the stage of inclusion, during the surgery, in 30 days after the surgery, and in 1, 2, and 3 years after the surgery. Data about all the patients included in the research will be analyzed in order to study the endpoints and achieve the research aim. The first report on safety of the operation will be published when all the patients included in the study are carried out the procedure of augmentation of the aortic valve with autopericardium and all of them are examined within 30 days after the surgery. A report about the efficacy of the operation within the first year after the performed surgery of augmentation of the aortic valve with autopericardium; it will be published after all the patients included in the study are examined at the control visit in one year after the surgery. Report about clinical and hemodynamic efficacy of the operation within three years after the performed reconstruction of the aortic valve with autopericarduim; it will be published after all the patients included in the study are examined in three years after the surgery. Final report on the study will be published when for all patients included in the study all the follow-up periods are completed, or patients are excluded from the study due to other causes. For compensation for the lost quantitative or qualitative data, statistical methods will not be applied. If there is a lack in patient's data due to any causes, such a patient will be excluded from this block of analysis. A number of patients included in each analysis will be represented in the report, so readers could themselves assess the influence of the lost data on the published result.