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Total Cavopulmonary Connection with Off-Pump Technique

Department of Cardiovascular Surgery, Fu Wai Hospital, Peking Union Medical College, Beijing, China

For reprint information contact: Xin-Jin Luo, MD Tel: 86 10 6831 4466 Fax: 86 10 6833 2376 Email: luoxinjin{at}yahoo.com, Department of Cardiovascular Surgery, Fu Wai Hospital, Peking Union Medical College, No.167, Beilishi Road, Beijing 100037, China.

	ABSTRACT

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The aim of this study was to evaluate an off-pump technique for total cavopulmonary connection. Between May 2000 and June 2004, 16 patients underwent total cavopulmonary connection without cardiopulmonary bypass. There were 8 males and 8 females, with a mean age of 9.8 ± 6.2 years and a mean weight of 27.7 ± 14.9 kg. Preoperative percutaneous oxygen saturation was 75% ± 6%, and pulmonary arterial pressure was 12.6 ± 2.7 mm Hg. Postoperative outcomes were retrospectively compared with a group of 17 patients who underwent total cavopulmonary connection with an extracardiac conduit under cardiopulmonary bypass. Two patients died early postoperatively. Chylothorax occurred in 2 patients and 3 underwent reoperation for fenestration between the extracardiac conduit and the right atrium in the early postoperative period. All survivors were acyanotic. On discharge from hospital, the percutaneous oxygen saturation breathing air was 95% ± 3%. Patients in the off-pump group demonstrated significantly shorter extubation time and intensive care unit stay. This connection technique is easy to perform and helpful in the early management of patients with a functional univentricular heart. However, much remains to be learned about this unique physiologic system.

	INTRODUCTION

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A total cavopulmonary connection (TCPC) diverts systemic venous return from the vena cava directly to both lungs, bypassing a hypoplastic or absent right ventricle. This surgical connection provides excellent palliation in complicated malformations associated with low pulmonary blood flow, low pulmonary artery (PA) pressures, and low pulmonary vascular resistance. This connection enhances systemic arterial oxygen saturation by increasing the effective pulmonary blood flow. At the same time, it can relieve the volume load on a functional single ventricle, and improve the geometry of the ventricle.¹ If intracardiac repair is not necessary, the cavopulmonary connection can be created without cardiopulmonary bypass (CPB) using an extracardiac conduit technique.^2–3 CPB is known to activate inflammatory mediators, increase lung water, and decrease ventricular compliance. These unfavorable effects can increase pulmonary vascular resistance and decrease pulmonary blood flow after TCPC.

	PATIENTS AND METHODS

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Sixteen patients, 8 males and 8 females, underwent TCPC without CPB between May 2000 and June 2004. Their mean age was 9.8 ± 6.2 years (range, 3–24 years), mean weight was 27.7 ± 14.9 kg (range, 14–60 kg), and mean body surface area was 0.96 ± 0.34 m² (range, 0.59–1.66m²). All patients were examined preoperatively by electrocardiography, chest radiography, echocardiography, and angiocardiography. Eight patients had a single ventricle with transposition of the great arteries and pulmonary stenosis; 6 of these had tricuspid atresia, a ventricular septal defect, atrial septal defect, and pulmonary stenosis; 2 had double-outlet right ventricle and hypoplastic left ventricle, transposition of the great arteries, and pulmonary stenosis. Preoperative percutaneous oxygen saturation (SpO₂) ranged from 60% to 82% (mean, 75% ± 6%).

The PA pressure and oxygen saturation were monitored during and after the operation. The operation was performed through a median sternotomy with systemic heparinization (150 units·kg^–1) and normothermia. A temporary shunt was established between the superior vena cava (SVC) and the right atrium. The SVC was cannulated near the innominate vein with a right-angled venous cannula. Another venous cannula placed in the right atrium and connected to the SVC cannula, avoiding kinking. With this venous shunt open, the SVC was test occluded, producing no change in blood pressure, SVC pressure, or oxygen saturation. The SVC was clamped and transected above the cavoatrial junction. The cardiac end of the SVC was closed carefully, avoiding damage to the sinus node area. A large side-biting clamp was applied to the right pulmonary artery, and a 1.5–2.0 cm longitudinal incision was made on the superior aspect of the right pulmonary artery. The distal end of the SVC was anastomosed end-to-side to the right pulmonary artery with a running suture to the posterior wall and with an interrupted suture to the anterior wall, to avoid a pursestring effect. Pericardium was applied at the anterior wall to widen the anastomosis in 9 patients. The clamp was released and the temporary shunt was removed. The inferior vena cava (IVC) was dissected free from the diaphragm and cannulated just above the diaphragm with a right-angled venous cannula. The previously placed right atrial cannula and the IVC cannula were connected. With this venous shunt open, the IVC was test occluded, producing no change in blood pressure, IVC pressure, or oxygen saturation. A snare was passed around the IVC and tightened on the venous cannula. After a clamp was placed at the base of the right atrium, avoiding the coronary sinus, the atrium was transected below the clamp, leaving a beveled cuff of atrial wall attached to the IVC. The stump of the right atrium was oversewn with 6/0 polypropylene suture. The extracardiac conduit was anastomosed end-to-end to the IVC with a running suture. In 10 patients, the main PA was posterior and immediately behind or to the right of the aorta; the main PA was transected and its proximal end closed directly, the other end could be anastomosed to the extracardiac conduit without any distortion. In another 6 patients, the PA was to the left of the aorta, so the extracardiac conduit was anastomosed to the inferior aspect of the right PA in end-to-side fashion, and the main PA was ligated at the root. The clamp was released and the temporary shunt was removed. Heparin was reversed. The material used to construct the IVC-to-PA channel in this group was a Hemashield graft (Meadox Medicals Inc., Oakland, NY, USA), diameter 14–20 mm in 14 cases, and homografts of 20 and 22 mm diameters in 2 cases.

This was the primary operation in 12 patients and a final-stage operation in 4. Two patients had received a bidirectional Glenn shunt without CPB 3 years earlier, one had undergone a modified Blalock-Taussig shunt when he was 1-year old and TCPC when he was 3-years old, and one had PA banding at 2-years old, a bidirectional Glenn shunt without CPB at 4-years old, and TCPC at 6-years old. A fenestration (diameter, 4–8 mm) between the extracardiac conduit and the right atrium was created in 5 patients; it was created during the operation in 2 patients and the other 3 were re-operated for fenestration within 16 hours after TCPC because of unstable hemodynamics. These 3 patients suffered low blood pressure and high central venous pressure during the early postoperative period. After fenestration, they all recovered well.

The data are expressed as mean ± standard deviation and were analyzed using SPSS statistical software (SPSS Inc., Chicago, IL, USA). Student’s t test was used to compare mean values, and differences of p < 0.05 were considered significant.

	RESULTS

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There were 2 hospital deaths. The first patient died of cerebral embolism. The second patient suffered poor cardiac output after the operation, which failed to improved by any means. A fenestration had been created during his operation. He died 7 days later from multiorgan failure.

All patients had an immediate improvement in arterial oxygen saturation. The mean duration of respirator support postoperatively was 18.0 ± 13.4 (5–47) hours. Chylothorax occurred in 2 patients. A 2-week course of hyperalimentation with nothing by mouth was required for cure. During the first 5 postoperative days, thoracic drainage was 15.2 ± 10.2 (4.8–43.5) mL·kg^–1 per day. The PA pressure was 12.6 ± 2.7 (8–16) mm Hg at the beginning of the operation and increased to 16.0 ± 2.1 (12–19) mm Hg in the early postoperative period. All patients received a low dose of aspirin (50–100 mg daily) for postoperative antiplatelet treatment. Cyanosis was notably relieved when the patients were discharged, and SpO₂ increased to 95% ± 3% (89% 98%) on breathing air.

On follow-up (3–48 months), there was no late death and no episode of arrhythmia. Echocardiographic studies showed no thrombus formation in the extracardiac conduits. The data of the 16 patients in this study were compared with 17 patients who underwent extracardiac conduit TCPC under CPB between May 2000 and April 2003 in the same hospital. The results of the 2 groups are summarized in Table 1.

	DISCUSSION

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Although CPB plays a vital role in cardiac surgery, it may activate the inflammatory mediators and lead to lung injury and blood destruction. These adverse effects can increase pulmonary vascular resistance and decrease pulmonary blood flow after cavopulmonary connection. Most studies analyzing risk factors for poor outcome after the Fontan operation have demonstrated that longer CPB times are associated with an increased risk of Fontan failure or mortality.^7–8 The postoperative course after the Fontan procedure is also significantly affected by the duration of CPB. By multivariable analysis, prolonged CPB time was the only independent predictor of length of intensive care unit stay and the need for prolonged ventilatory support.⁹ For this reason, we try whenever possible to create TCPC off-pump at normal temperature. The results have so far been satisfactory. Comparing the results of this study with those of patients who underwent TCPC under CPB, although the operative mortality was similar, the off-pump group had better postoperative results in terms of hemodynamic status, duration of ventilatory support, and intensive care unit stay. Patients in both groups had increased oxygen saturation when they were discharged. It was concluded that performing TCPC off-pump offers more benefits.

There are two ways of connecting the IVC to the PA: an extracardiac conduit and an intracardiac tunnel.^1,7,9–12 The respective merits of these two approaches remain to be determined. For TCPC without CPB, an extracardiac conduit should be chosen. In our previous study, we compared outcomes of an extracardiac conduit (n = 25) and an intracardiac tunnel (n = 21) between February 1993 and October 2001. The extracardiac conduit group had lower operative mortality than the intracardiac tunnel group. Holter analysis showed a higher incidence of atrial arrhythmias in the intracardiac tunnel group. Azakie and colleagues⁹ also suggested that an intracardiac tunnel is an independent risk factor for the development of early and midterm atrial rhythm disturbances. A symmetric extracardiac conduit for cavopulmonary connection may reduce turbulence between the IVC and the pulmonary arteries, thereby improving hydrodynamic flow. An extracardiac conduit should reduce the incidence of later dysrhythmia, not only because there are no extensive atrial incisions and suture lines and no surgery in the vicinity of the sinus node, but also because no part of the right atrial wall is exposed to the elevated systemic venous pressure.^12–13 However, the extracardiac conduit has no growth potential. In addition, the conduit poses a risk of obstruction by thrombus formation or the development of fibrosis, neointimal hyperplasia, or calcification. Use of an adult-sized conduit may avoid future reoperations and may accommodate flow rates necessary for exercise. This limits the use of an extracardiac conduit connection to patients of a minimum age, weight and size.

Additional points should be taken into account when managing TCPC with the off-pump technique at normal temperature. The patient’s age, weight, and body size should be considered; by waiting until the patient weighs at least 15 to 20 kg before instituting TCPC, an adult-sized conduit (20–22 mm) can be used, which may accommodate future growth.¹² The need for other intracardiac repairs should be considered; if atrioventricular valve regurgitation requires intracardiac repair, CPB is necessary. The position of the IVC should be carefully examined during the operation; in some patients, the IVC may be displaced posterior to the heart or even to the left of the vertebral column, and be difficult to expose. Such patients are unsuitable candidates for TCPC with the off-pump technique.

To optimize the early results, it is now firmly established that a staging strategy with early relief of volume load on the functional single ventricle is required. Azakie and colleagues⁹ were moving toward instituting a bidirectional cavopulmonary shunt at an earlier age (3–6 months). The second-stage operation was finished later. Some research has indicated that fenestration does not affect early survival, resource use, or chest tube drainage.^8,14 In our experience, fenestration is necessary for patients with unstable hemodynamics during the early postoperative period, but we are not in favor of its use in all patients. In the extracardiac conduit procedure, there is an obvious increased risk of thrombus formation inside the conduit, which may carry a high risk of multiple pulmonary emboli, and if a fenestration is placed, systemic emboli. Chylothorax, pleural effusion, and chest tube drainage in the early postoperative period are the problems to be considered in TCPC patients. These are assumed to be related to the increase in central venous pressure due to the loss of right ventricular pumping after the connection.

It was concluded that TCPC with the off-pump technique provides excellent palliation for selected patients with cyanotic congenital heart disease. It is easy to perform and helpful in the early management of patients with functional univentricular heart. The postoperative recovery is usually uneventful, but long-term follow-up is needed and much remains to be learned about this unique physiologic system.

	REFERENCES

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