Asian Cardiovasc Thorac Ann 2006;14:402-406
© 2006 Asia Publishing EXchange Ltd
Intrapulmonary Channel for One-Stage Correction of Aortic Arch Obstruction
Yong-Qiang Lai, MD,
Qi-Wen Zhou, MD,
Hua Wei, MD,
Chun Zhang, MD,
Zhao-Guang Zhang, MD
Division of Cardiac Surgery, Beijing Anzhen Hospital, Capital University of Medical Sciences, Beijing, China
For reprint information contact: Yong-Qiang Lai, MD Tel: 86 10 6445 6384 Fax: 86 10 6441 9691 Email: yongqianglai{at}yahoo.com, Division of Cardiac Surgery, Beijing Anzhen Hospital, Capital University of Medical Sciences, 36 Wuluju, Chaoyang District, Beijing 100 029, China.
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ABSTRACT
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There are several methods of surgical repair of aortic coarctation or interruption; the optimal technique is still controversial. The purpose of this study was to assess a new surgical method: intrapulmonary channel for one-stage repair of aortic coarctation or interruption associated with intracardiac anomalies. Between 1993 and 1995, 4 patients with aortic coarctation or interruption and intracardiac anomalies received one-stage surgical correction. Their ages ranged from 5 to 26 years (mean, 16 years). The aortic arch lesions were preductal coarctation in 2, and type B interruption in 2. Coexisting anomalies consisted of patent ductus arteriosus in 4, ventricular septal defect in 3, and aortopulmonary window in 1. An intrapulmonary channel was constructed in all patients, and co-existing anomalies were corrected simultaneously. There was no hospital death or late mortality. A cerebral complication occurred in one patient because of air embolism. Mean follow-up was 9.5 years (range, 8.5–11.5 years). There was no evidence of recoarctation or late aneurysm formation. For selected patients with aortic coarctation or interruption and intracardiac anomalies, an intrapulmonary channel might be an option for one-stage correction.
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INTRODUCTION
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Surgical methods of correction of aortic coarctation or interruption associated with intracardiac anomalies have evolved significantly over recent decades. Although most patients receive surgical repair in the neonatal period or in infancy, in developing countries, some operations are postponed until late childhood or adulthood. The optimal management of these patients remains controversial. Both one-stage and two-stage approaches have been recommended.1–6 One-stage correction enables almost normal cardiac development, but it carries substantial risk of perioperative mortality and morbidity. The traditional two-stage procedures involve repair of the aortic coarctation or interruption as an initial procedure, and correction of intracardiac lesions as a second procedure. The choice of operative technique is influenced by the pathology and anatomy of the lesion, the age of the patient, and the personal preference of the surgeon. Surgical results differ with the choice of procedure, and there is no single optimal method to correct these complicated anomalies. For selected patients, we adopted the intrapulmonary channel procedure for one-stage repair.
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PATIENTS AND METHODS
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The study was approved by our Institutional Review Board, and individual consent was obtained before the operation. Between 1993 and 1995, 4 patients with aortic coarctation or interruption and intracardiac anomalies received one-stage surgical correction. There were 3 females and 1 male. Their ages ranged from 5 to 26 years (mean, 16 years). The aortic arch lesions were preductal coarctation in 2, and type B interruption in 2. Co-existing anomalies consisted of a large patent ductus arteriosus (PDA) in 4, a ventricular septal defect (VSD) in 3, and an aortopulmonary window (APW) in 1. Physical examination showed the blood pressure of the lower limbs was slightly higher than that of the upper limbs in all patients. The electrocardiograms showed right ventricular hypertrophy in 3 patients, and left ventricular hypertrophy in one. Echocardiography was a useful diagnostic modality for demonstrating the morphological details of intracardiac anatomy and aortic arch obstruction. Cardiac catheterization revealed severe pulmonary hypertension in all patients. Angiography was performed in 2 patients with aortic arch interruption (Table 1
).
All patients were operated on through a median sternotomy with the use of deep hypothermic circulatory arrest. Right radial and femoral artery pressures were continuously monitored, and a Swan-Ganz catheter was used to monitor pulmonary artery (PA) pressure. Ascending aortic and femoral arterial cannulas were inserted separately to maintain optimal perfusion of the upper and lower body. Two venous cannulas were used for drainage. When cardiopulmonary bypass was initiated, the main PA was incised. A Foley catheter was placed into the PDA, and the balloon was filled with saline solution to prevent over-perfusing the lungs. The aorta was crossclamped, and the heart was arrested by injecting cold crystalloid cardioplegia through the aortic root. In patient no. 1, the ascending aorta was opened and cardioplegia was infused directly. Patients were cooled to a nasopharyngeal temperature of 18°C. Deep hypothermic circulatory arrest was initiated for construction of the intrapulmonary channel. In patient no. 1, the diameters of the APW and PDA were 20 and 18 mm, respectively. A woven polyester graft (Hemashield; Meadox Medical, Inc., Oakland, NJ, USA) was split vertically and trimmed. A continuous suture of 4/0 Prolene was used to anastomose the graft to the PDA. Three-quarters of the PDA orifice was anastomosed to the graft, leaving the posterior edge of the PDA orifice. The posterior edge of the graft was fixed to the posterior wall of the main PA. The graft was then anastomosed along three-quarters of the APW orifice, except for the posterior edge of the APW. The intrapulmonary channel was established with blood flowing from the ascending aorta to the descending aorta through the APW, intrapulmonary channel, and PDA (Figure 1). A Dacron patch lined with autologous pericardium was used to enlarge the main PA, to avoid obstruction by the intrapulmonary channel.
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Figure 1. The intrapulmonary channel constructed using the patent ductus arteriosus and aortopulmonary window. Blood flowed from the ascending aorta to the descending aorta through the aortopulmonary window, intrapulmonary channel, and ductus arteriosus.
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In patients 2, 3, and 4, there was no APW, but the PA was significantly dilated. Their PDA diameters were 12, 20, and 13 mm, respectively. Collagen-impregnated woven polyester grafts of 14, 20, and 14 mm (Hemashield) were used for construction of the intrapulmonary channels. The pulmonary terminus of the graft was anastomosed to the PDA using 4/0 Prolene. After completing this anastomosis, the graft was clamped, cardiopulmonary bypass was restored, and the patient was rewarmed. The graft exited from the anterior wall of the PA, which was anastomosed to the lateral wall of the graft with 4/0 Prolene. The graft was then end-to-side anastomosed to the lateral wall of the ascending aorta, so part of the graft was in the PA and part was outside the PA; blood could flow from the ascending to descending aorta through the channel and the PDA (Figures 2, 3, and 4). These patients had an associated VSD and severe pulmonary hypertension. To prevent pulmonary hypertensive crisis and acute right heart failure, a unidirectional valved patch was applied to repair the VSD, as described previously.7 After weaning from cardiopulmonary bypass, protamine was infused through the ascending aorta to reduce the risk of protamine-induced acute pulmonary hypertensive crisis. Dobutamine (4–8 µg·kg–1·min–1), nitroglycerin (1–3 µg·kg–1·min–1), and prostaglandin E1 (0.02–0.1 µg·kg–1·min–1) were routinely used to maintain hemodynamics and reduce PA pressure.
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Figure 3. A collagen-impregnated woven polyester graft was applied for construction of the intrapulmonary channel. The pulmonary terminus of the graft was anastomosed to the patent ductus arteriosus.
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Figure 4. The anterior wall of the pulmonary artery enclosed the graft and was anastomosed with the lateral wall of the graft. The aortic terminus of the graft was end-to-side anastomosed with the lateral wall of the ascending aorta. Part of the graft was in the pulmonary artery and part was outside it. Blood could flow from the ascending to descending aorta through the channel and the ductus arteriosus.
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RESULTS
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One-stage correction of aortic coarctation or interruption with intracardiac anomalies using an intrapulmonary channel was feasible in all patients. There was no hospital death or late mortality. Pulmonary artery pressures decreased significantly after the operations. The changes in systolic arterial and PA pressures before and after the operation are shown in Figure 5. Patient no. 3 developed a neurological complication due to air emboli during surgery. She also underwent a tracheotomy because of pneumonia and pulmonary atelectasis. She recovered well with antibiotics and supportive treatment. There were no late neurological deficits or seizures in this patient.
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Figure 5. Changes in systolic arterial blood pressure (SABP) and systolic pulmonary arterial pressure (SPAP) before and after the operation.
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The follow-up ranged from 8.5 to 11.5 years (mean, 9.5 years). Blood pressure in the upper and lower limbs was measured (Table 1
). Each patient was examined by echocardiography during follow-up. The grafts were patent and no obvious obstruction was found. There was no significant change in the aortic coarctation or interrupted segments. A small apical muscular VSD and moderate tricuspid regurgitation were noted in patient no. 3. There was no evidence of recoarctation or aneurysm formation in any of our patients.
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DISCUSSION
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Aortic arch obstruction is a severe congenital defect usually diagnosed in newborns or infants. The natural history is related to any associated intracardiac anomalies, patency and size of the ductus arteriosus, and width of the ascending aorta. The natural history of untreated aortic coarctation is of premature death from stroke, coronary heart disease, or sudden death.8,9 Aortic interruption is defined as complete absence of flow between two portions of the aorta. If the condition is not treated, 90% of patients die at a median age of 4 days.10 As the prognosis is very poor, most patients received early correction. When surgery is postponed, there is usually associated severe pulmonary hypertension because of the long-term left-to-right shunt. It is a great challenge to decide on the optimal procedure to deal with these patients.
Surgical correction of aortic coarctation or interruption associated with intracardiac anomalies has improved significantly; however, the mortality and morbidity remain relatively high. One important reason is comorbid factors. Currently, there are several surgical approaches for correction of aortic coarctation and for rebuilding the continuity of the aortic arch. A one-stage procedure is superior in terms of mortality and morbidity compared with a two-stage procedure, and has evolved as the standard approach. Choosing a suitable procedure for a particular patient mainly depends on the aortic arch lesion and co-existing intracardiac anomalies.
The intrapulmonary channel was designed to correct aortic arch obstruction associated with intracardiac anomalies in selected patients. A large PDA and dilated PA are crucial in this unique procedure. Blood pressure of the lower limbs the same as or slightly higher than that of the upper limbs indicates sufficient perfusion of the lower body through the PDA and collateral arteries. Use of the PDA to correct the aortic obstruction will thus not cause ischemia of the lower body. If the PA is not dilated to a sufficient extent, an intrapulmonary channel will interfere with the pulmonary circulation, and refractory right heart failure will occur. For patient no. 1, we used the PDA and APW to construct the intrapulmonary channel, and a Dacron patch to ensure it was large enough to avoid interference with the pulmonary circulation. The graft diameter should match the orifice of the PDA to avoid restriction of either systemic or pulmonary blood flow. We used this method in older children and adolescents because retained ductal tissue might play a less important role in recoarctation. Many studies have confirmed that recoarctation is predominantly associated with repair during infancy, and is uncommon after repair in adulthood.11–14 We do not recommend this method in neonates and infants because of the risk of recoarctation, and an intrapulmonary channel might cause obstruction of the PA, with inevitable re-operation. Our patients demonstrated no evidence of recoarctation during a mean follow-up of 9.5 years.
Severe pulmonary hypertension was a significant characteristic in these patients. Avoiding a pulmonary hypertensive crisis is very important to the success of the operation. For patients with a co-existing VSD, we utilized a unidirectional valved patch to repair the defect.7 When a pulmonary hypertensive crisis occurs in the postoperative period, PA pressure exceeds systemic pressure, and the unidirectional valve opens to allow blood flow from the right to left ventricle, thus ensuring the output of the left ventricle. When PA pressure decreases, the unidirectional valve closes and blocks the left-to-right shunt. Cardiopulmonary bypass and infusion of protamine could result in the release of vasoconstrictors during the operation, inducing a pulmonary hypertensive crisis. We usually administer protamine through the aortic root to neutralize heparin. This might be beneficial in decreasing the occurrence of pulmonary hypertensive crisis. Nitroglycerin and prostaglandin E1 are routinely used to reduce PA pressure. The latter drug is a relatively selective pulmonary vasodilator and useful for patients with severe pulmonary hypertension. Perioperative hemodynamics showed PA pressure decreased significantly after the operation.
Aneurysm formation after surgical correction of aortic arch obstruction is a serious late complication.11,15–18 It may occur either at the site of repair or within the proximal aorta. It is associated with a risk of aortic rupture; 9% of patients develop aortic aneurysms late after operation, with a 36% mortality rate if left untreated. Changes in aortic compliance, increased wall stress at the repair site, and prosthetic patch-plasty repair are associated with aneurysm formation. The aneurysms are usually very thin walled with histologic evidence of cystic medial necrosis.19 Utilizing the PDA in constructing the intrapulmonary channel guarantees intima and media integrity of the aortic wall, and does not increase wall stress at the repair site. In our limited experience, no evidence of aneurysm formation was found in our patients on long-term follow-up.
It was concluded that the intrapulmonary channel procedure for one-stage correction of aortic coarctation or interruption associated with intracardiac anomalies can be used in selected patients with satisfactory long-term results.
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ACKNOWLEDGMENTS
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The authors thank Dr. Gus J Vlahakes, Chief, Division of Cardiac Surgery, Massachusetts General Hospital, for reviewing our article.
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REFERENCES
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ABSTRACT
INTRODUCTION
