Innominate vein reconstruction in patients with bilateral superior vena cava undergoing bilateral bidirectional superior cavopulmonary anastomosis

Abstract

A 4.5-year-old patient with tricuspid atresia, pulmonary stenosis, bilateral superior vena cava veins with absent innominate vein, and hypoplasia of the left pulmonary artery required a bidirectional superior cavopulmonary anastomosis. An innominate vein was fashioned out of a 6 mm polytetrafluoroethylene graft. The technique is briefly discussed.

INTRODUCTION

A 4.5-year-old child presented with a diagnosis of tricuspid atresia, pulmonary stenosis, bilateral superior caval veins (SVCs), absent innominate vein, and hypoplasia of the left pulmonary artery (LPA). A bilateral bidirectional superior cavopulmonary anastomosis (BCPA) was required as the first stage of surgical palliation. The LPA was diffusely hypoplastic, and a left superior BCPA that entailed an anastomosis of the left SVC (LSVC) to this hypoplastic LPA was not considered a feasible option. Hence, an artificial innominate vein was fashioned out of a 6 mm polytetrafluoroethylene (PTFE) graft, and this graft was connected to the right SVC (RSVC). When this graft was anastomosed end to side to the right pulmonary artery (RPA), the BCPA was easily constructed. This technique is briefly presented, and its advantages are discussed.

PATIENT PROFILE

Informed consent was obtained from the parents of this patient to publish this case report. Because the patient confidentiality was preserved, a formal institutional ethics committee approval was not needed.

A 4.5-year-old male child weighing 10 Kg presented to us with a history of cyanosis for 9 months of age, for which the parents had not sought surgery earlier. On examination, there was central cyanosis, Grade 2 clubbing, and the apex beat was felt at the right fifth intercostal space just medial to the midclavicular line. First heart sound was normal, and pulmonary component of the second heart sound was absent. Oxygen saturation (SpO₂) on room air was 45%.

Chest X-Ray showed dextrocardia and pulmonary oligemia [Figure 1a]. Electrocardiogram showed normal sinus rhythm and left axis deviation. Echocardiogram showed situs solitus, dextrocardia, tricuspid atresia, with double-outlet left ventricle, hypoplastic right ventricle, large atrial septal defect, ventricular septal defect, and severe pulmonary valvular stenosis. The pulmonary blood flow was dependent on the small patent arterial duct (PDA). There were separate RSVC and LSVC; the inferior caval vein was placed slightly to the left of the midline and entered the systemic venous atrium. Computed tomography angiogram confirmed the above findings. Main pulmonary artery (MPA) measured 6.8 mm, and both pulmonary arteries were confluent. The RPA measured 9.3 mm. There was long segment stenosis at the origin of the LPA, and it was diffusely hypoplastic intrapericardially. Beyond this, it was uniformly small and measured only 2 mm up to the hilum of the left lung [Figure 1b and c]. There were no significant aortopulmonary collaterals. As un ultimate univentricular palliation was decided, BCPA was planned.

Figure 1: (a) Chest X-ray showing dextrocardia and pulmonary oligemia. (b) CECT axial section at the level of bifurcation of main pulmonary artery showing contrast opacified LSVC, unopacified RSVC due to the absence of interconnecting vein and diffusely hypoplastic LPA. (c) Reconstructed CECT image showing right and LSVC with absent interconnecting vein. LPA – left pulmonary artery, LSVC – left superior vena cava, RPA – right pulmonary artery, RSVC – right superior vena cava, CECT – Contrast-enhanced computed tomography

OPERATIVE STEPS

Following a standard median sternotomy, normothermic cardiopulmonary bypass (CPB) was instituted using a cannula in the aorta and a single venous cannula in the right atrial appendage. The PDA was ligated and divided, and both pulmonary arteries were mobilized extensively up to the hilum of both the lungs. As the intrapericardial LPA had diffuse long segment stenosis and was also uniformly small up to the lung hilum, its augmentation and a systemic to pulmonary artery shunt to rehabilitate it was thought to be not beneficial. Similarly, in the setting a very small LPA, a left-sided BCPA was thought not to be a desirable option. We also anticipated that, because distal LPA was also quite small, it could be worsened by suturing a patch onto it and that a transcatheter dilatable stent placement in future going through the Glenn shunt would be a better option to avoid losing the LPA completely.

Creation of a “New Innominate vein” to connect both the LSVC and RSVC and perform a right BCPS was therefore planned. To achieve this, the RSVC was mobilized, and the azygous vein was divided. To gain maximum length, the LSVC was extensively mobilized, and its tributaries including the hemiazygous were divided. We anticipated that, after mobilizing the LSVC, we could divide it close to its cardiac end with the latter being closed so that it could be anastomosed to the RSVC to create this “New Innominate vein.”

However, we were not able to obtain the desirable length of the LSVC to permit this. Therefore, a 6 mm PTFE conduit (7 cm in length) was anastomosed between the LSVC and RSVC by partially side clamping both cavae using a continuous 7–0 polypropylene suture. The size of the PTFE graft was selected to match the size of the SVCs, and this graft was placed anterior to aorta considering the relative position of the LSVC and RSVC to avoid compression by the aorta and kinking at the anastomotic site. The sternal retractor was approximated to confirm the lie of the conduit and assess if there was any sternal compression. Following this, the RSVC was anastomosed to the RPA in an end-side fashion [Figure 2a]. For this purpose, the RSVC was not cannulated; instead, an open technique was used by placing a sump sucker placed in the SVC. This technique has been described by us earlier.^[1] The LSVC was ligated at its junction with left atrium (LA). Dobutamine intravenous infusion (5 μg/kg/min) was started following which the patient was weaned off CPB. The SpO₂ increased to 90% on an FiO₂ of 50%. The pressure in Glenn circuit was 15 mmHg. The antegrade MPA flow was interrupted by the ligation of the MPA as per the criteria laid down by us in a prior publication.,^[2]

Figure 2: (a) Intraoperative picture showing 6 mm polytetrafluoroethylene graft (***) connecting LSVC to the RSVC. End-to-side cavopulmonary anastomosis can be seen between RSVC and the RPA. (b) CECT axial section at the level of arch of aorta showing the patent polytetrafluoroethylene graft (***) connecting LSVC to the RSVC. (c) Reconstructed CECT image showing the unobstructed flow in the polytetrafluoroethylene graft (***) connecting LSVC to the RSVC. LSVC – left superior vena cava, RPA – right pulmonary artery, RSVC – right superior vena cava, CECT – Contrast-enhanced computed tomography

Postoperative course was uneventful, and he was extubated 3 h after surgery; there was no facial puffiness or engorgement of neck and facial veins. SpO₂ at the time of discharge from the hospital was 87% on room air. Clopidogrel, aspirin, and Warfarin were advised with a target range of prothrombin time-international normalized ratio of 2–2.5. An echocardiogram at discharge showed that the neo-innominate vein, i.e., interposed Gortex-Tube was patent with normal flow in BCPA circuit and systemic ventricular function was normal.

Follow-up computed tomography showed the patent PTFE graft connecting the LSVC to the RSVC with unobstructed flow through it and the BCPA circuit [Figure 2b and c].

DISCUSSION

The Fontan circulation is the common destination pathway for patients with a functional single ventricle.^[3] An essential component of the staged Fontan procedure is the BCPA that is aimed at volume unloading of the single ventricle at an early age before venturing into the final palliative surgery of total cavopulmonary anastomosis or the Fontan procedure.^[4,5] The presence of bilateral SVC may pose technical difficulties in performing BCPA.^[6] Previous reports indicate that a bilateral BCPA is associated with a higher perioperative mortality, an increased risk of thrombus formation, and a lower conversion rate to the ‘‘Fontan type’’ circulation, when compared to standard BCPA^[7,8] Furthermore, size discrepancy between two SVCs, low mean SpO₂ immediately after BCPA, and hypoplasia of pulmonary artery branches have also been identified as significant risk factors of perioperative mortality and morbidity in patients with bilateral BCPA.^[7]

The ideal operation to rehabilitate the LPA in such a patient would have been by augmenting it with patch material along with a systemic to pulmonary artery shunt. However, we did not elect to perform this because even the intrapericardial LPA had a long segment stenosis with it being uniformly small (2 mm) even up to the hilum of the left lung. It has been reported earlier^[9] that, in older patients, the growth of the pulmonary arteries following a systemic to pulmonary artery shunt is unpredictable. In addition, the latter does not produce significant unloading of the single ventricle. Hence, we preferred a cavopulmonary anastomosis to achieve unloading of the ventricle and to prepare him for the second stage Fontan completion. In addition, we also anticipated that, because distal LPA was also quite small, any attempt at augmenting it could be worsened by suturing a patch onto it and that a transcatheter dilatable stent placement in the future going through the Glenn shunt would be a better option to avoid losing the LPA completely.

The subsequent single lung Fontan in this patient is, however, expected to be suboptimal.

We opted for the interposition of a PTFE graft between the LSVC and RSVCs and interrupting LSVC-LA junction, to allow the adequate decompression of LSVC into the right BCPA circuit through the PTFE graft/neo-innominate vein. We did not elect to use a tube of pericardium for this purpose. As indicated above, we had planned to divide the LSVC extensively so that it could be divided and anastomosed end to side to the RSVC. However, even after extensive mobilization of the LSVC, an adequate length of latter could not be achieved; hence, we disregarded the option of performing a direct end-to-side anastomosis of the LSVC to the RSVC in view of a long distance between both SVCs, possibility of kinking of the LSVC and decrease in lumen size due to stretching and flattening of the SVC.

A BCPA to a hypoplastic pulmonary artery with a neo-innominate vein to decompress the venous system has previously been demonstrated to result in further growth of the hypoplastic pulmonary artery.,^[10] However, owing to the anatomical aspects of the LPA as described above, we did not perform an arteriorplasty and left-sided cavopulmonary anastomosis in our patient.

Various conduits used in the reconstruction of SVC and its tributaries, especially in association with surgeries for thoracic malignancies are externally stented PTFE conduit, tubularized autologous or bovine pericardium, bovine jugular vein conduits, and spiral vein grafts.^[11] We chose to use PTFE conduit due to its easy availability and good midterm patency rates.^[12] The latter observation is further reinforced by this report.

The risk of thrombosis of prosthetic materials interposed within the SVC system has been reported as up to 30% at 3-year follow-up studies.^[13] Another study by Okereke et al.^[12] reported radiologically evident graft thrombosis in two patients among 38 patients who underwent externally stented PTFE grafts for SVC reconstruction following thoracic malignancies. They used only aspirin for the prevention of thrombosis. However, none of them were clinically significant. They avoided Vitamin K antagonists such as Coumadin for anticoagulation in such settings because they considered these drugs to be of no additional advantage because of gradual graft thrombosis and adequate collaterization.

Factors affecting early thrombosis of PTFE conduit in the venous system are kinking of the graft, anastomosis technique, branched Y-graft, smaller size of the graft, and the presence of distal obstruction to flow. Instead of ligating both the azygous and hemiazygous veins, we preferred to divide them to ensure straight lie of both SVC to prevent PTFE graft thrombosis. In addition, because the size of the PTFE conduit used by us was only 6 mm, we opted for continued oral anticoagulation with warfarin along with dual antiplatelet drugs (clopidogrel and aspirin) in this patient. At 7-month follow-up, the PTFE graft was patent, and the SpO₂ on room air was 85%. Construction of the neo-innominate vein between bilateral SVCs along with interruption of LSVC-LA junction and performing right bidirectional cavopulmonary anastomosis alleviated the symptoms in this patient. However, more experience with a larger group of patients and a longer follow-up period is required to draw definite conclusions.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.