Reconstruction of the pulmonary posterior wall using in situ autologous tissue for the treatment of pulmonary atresia with ventricular septal defect

Pulmonary atresia with ventricular septal defect (PA-VSD) is a rare and complex cyanotic congenital heart malformation that has a high incidence of early mortality. Although surgical interventions have been employed successfully for a number of years, the long-term prognosis has remained poor with an increased incidence of sudden death [1]. In 1955, Lillehei et al. successfully corrected an atresia of the main pulmonary artery (MPA) and a ventricular defect in a patient who had been diagnosed with PA-VSD by anastomosing the distal pulmonary artery with the right ventricle [2]. A decade later, Rastelli and colleagues reported a case in which a cardiac conduit from the right ventricle to the pulmonary trunk was used to treat the abnormality [3]. Various extracardiac valved conduits have subsequently been used to correct a right ventricle to pulmonary artery discontinuity since Ross and Somerville successfully employed a homograft aortic valved conduit in 1966 [4]. Weldon et al. reported the same result 2 years later [5]. In 1973, PA-VSD was successfully employed by Bowman and colleagues, who used a Dacron conduit containing a porcine heterograft aortic valve [6]. Despite these improvisations to the Rastelli procedure, most patients with PA-VSD have had to undergo repeated surgeries resulting from first conduit failure because of either calcification or degeneration of the extracardiac graft or a mismatch of biologic prosthesis. Thus, treating a ventricle-pulmonary artery discontinuity remains a major challenge; surgeons have tried to develop an ideal prosthesis while concomitantly developing techniques to reconstruct the right ventricular outflow tract (RVOT) [7, 8]. Herein, we describe a strategy that was performed on 24 patients who were diagnosed with PA-VSD in which autogenous tissue was preserved in situ as the posterior part of a newly reconstructed pulmonary artery. Forty PA-VSD patients underwent control surgeries using the Rastelli procedure of connecting a bovine jugular venous conduit (BJVC) between the right ventricle and the bifurcation of the MPA.

PA-VSD accounts for approximately 2% of all congenital heart disease cases and is one of the most common causes of cyanosis and hypoxemia in neonates. The pathological anatomic characteristics of PA-VSD include VSD, intramuscular or valvar atresia of the pulmonary artery, an overriding of the aorta, and PDA or MAPCAs. According to the classification presented by Castaneda et al., there are four types of PA-VSD [9]. In this study, 48 of the patients were type A, and 16 patients were type B (Table 1). Selection of the surgical procedure for treatment of PA-VSD depends mainly on development of the right ventricle and the pulmonary artery [10]. There are two evaluation indices for pulmonary artery development that can be considered: the McGoon index and the pulmonary artery index (PAI) [11]. A patient is considered suitable for radical repair if the McGoon index is greater than 1.2 or the PAI is greater than 150 mm²/m², suggesting no severe hypoplasia of the pulmonary artery, which indicates that a patient would be a suitable candidate for radical repair.

Currently, the most common method of radical repair for the treatment of PA-VSD is the classical Rastelli procedure, in which a right ventriculotomy is repaired with an artificial patch. Following the ligation of the co-existing PDA or MAPCAs, the remnant pulmonary trunk is excised, the proximal end is closed, and a vascular prosthesis is then used to connect the right ventricle and the pulmonary artery.

Despite the short-term success of employing different conduit modifications of the Rastelli procedure [7, 8, 12–14], many common complications remain. These include conduit dilation, twisting, thrombosis, calcification, endocarditis, arrhythmia and re-stenosis [15–17]. Shebani et al. [12] found that the early mortality rate resulting from conduit dilation, complete conduit thrombosis, and sudden arrhythmia was 6.4%, as determined from a retrospective analysis of 62 cases of RVOT and pulmonary trunk reconstruction using a bovine Contegra valved conduit. Distal conduit stenosis at the suture line associated with a size-mismatch with the conduit being too small was the main indicator for conduit-related secondary intervention. The high incidence of conduit-related complications, particularly with smaller conduits, included characteristics such as neointimal proliferation, thrombosis, calcification, and chronic inflammation. Reoperation is therefore inevitable for some patients with pulmonary atresia (PA) who receive a heterograft or homograft in a primary Rastelli operation. To treat PA-VSD, Chiu and colleagues [13] adopted a method used in the repair of Fallot’s tetralogy, a congenital heart defect that is understood to involve four anatomical abnormalities, in which a piece of fresh pericardium is harvested and sutured to cover the anterior part of the RVOT. However, pulmonary regurgitation and tricuspid regurgitation are common complications of this procedure. Schreiber et al. [14] replaced the traditional conduit with the Shelhigh No-React (NR-4000PA series)-treated porcine pulmonic valve conduit (SPVC). However, they concluded that a small-sized SPVC cannot be considered an ideal conduit in the reconstruction of the RVOT because although the No-React-treated valve largely resisted calcification, pseudointimal peel formation was found in all explanted conduits and led to multilevel conduit stenosis. Moreover, after reviewing the long-term results of RVOT and pulmonary trunk reconstruction with homografts, Kim et al. [7] determined that although long-term survival was excellent, freedom from reoperation was unsatisfactory, particularly in patients who had small grafts in the initial repair. After analyzing a large patient cohort, Sekarski et al. concluded that smaller pulmonary arteries increase the risk of surgical intervention when using a BJVC to reconstruct the RVOT [8]. Thus, alternative surgical strategies that do not employ small grafts must be considered for young children. In most Chinese areas, especially in rural areas, because of economic considerations, the patient’s custodian tends to refuse to repeat surgical procedures; thus, the BJVC were more commonly used in older children, and BJVP were used more in young children, as shown in Table 1.

Another problem with using an extra-cardiac conduit is that it is difficult to achieve a physiologic linear flow. In the 1920s, Dean [18] described the phenomenon of secondary flow when he used a constant and circular cross-section curved vessel model in a study of the streamline motion of fluid in a curved pipe. As a result, scholars later defined \( \mathrm{D}\mathrm{e}=4\ \mathrm{R}\mathrm{e}\sqrt{2 a/ R} \) as the Dean number, where Re is the parameter of Reynolds, a is the radius of the pipe, and R is the curvature radius of the curved pipe (Fig. 5). The lower the degree of curvature is, the smaller the resulting Dean number is. This implies a smaller impact force against the wall with resultant lower energy losses. When parameter R approaches infinity, the pipe tends to be straight, and the flow tends to be linear. On the one hand, energy consumption of blood flow is partially used for the vascular wall, leading to an additional right ventricular load; on the other hand, the force against the wall brought by deviating blood flow can itself induce the dilation and failure of a vascular prosthesis. Moreover, secondary flow can lead to the accumulation of blood cells, resulting in conduit failure resulting from a build-up of platelets on the outer side of the curve.

To address the problems described, the 24 cases in this study were radically repaired using a procedure in which autogenous tissue was preserved in situ to reconstruct the pulmonary posterior wall. During the follow-up care period, only mild regurgitation of the bovine jugular vein valve was observed in all patients. In the control group, two patients had severe anastomotic stenosis and underwent a further conduit replacement procedure in the early postoperative stage, four patients underwent balloon valvuloplasty and two patients underwent conduit replacement due to stenosis of the BJVC. The most significant differences between the procedures described in the observation group and the control group are as follows: 1. The was a more efficient relief of the right ventricular outflow tract obstruction. 2. The linear bloodstream flow solved the problem of right ventricular overload compared with a traditional conduit that involves the grade climbing of non-linear bloodstream flow. 3. A valved conduit reduced regurgitation, even when there was a gap present between the posterior wall and the bovine valve leaflets. It is important to note, however, that the minimal pulmonary regurgitation did not affect the function of the right ventricle. 4. This technique avoided the severance of remnant pulmonary trunk. Because the preserved autologous vascular bed could stimulate the continual development of the residual pulmonary trunk, young patients, especially children, who receive this procedure will generally not require future conduit replacement. 5. This surgical technique is suitable for PA and does not carry a risk of the major coronary arteries crossing the RVOT.

Reconstructing the pulmonary posterior wall by using in situ autologous tissue is a satisfactory method for treating PA-VSD. Increasing the sample size and continued follow-up care are necessary to fully assess the long-term benefits and advantages of the procedure.