Conversion of Atriopulmonary to Cavopulmonary Anastomosis in Management of Late Arrhythmias and Atrial Thrombosis

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1 Conversion of Atriopulmonary to Cavopulmonary Anastomosis in Management of Late Arrhythmias and Atrial Thrombosis Jane M. Kao, MD, Juan c. Alejos, MD, Peter W. Grant, MD, Roberta G. Williams, MD, Kevin M. Shannon, MD, and Hillel Laks, MD Division of Cardiothoracic Surgery, Department of Surgery and Division of Pediatric Cardiology, Department of Pediatrics, University of California, Los Angeles Medical Center, Los Angeles, California The original atriopulmonary connection or "classic" Fontan operation is associated with several late complications such as arrhythmias, right atrial dilatation, and thromboembolism. This report describes our experience with 3 patients who presented with the acute onset of atrial arrhythmias and upon further evaluation were found to have significant hemodynamic lesions. After failing medical management, all 3 patients were treated successfully with surgical conversion of their atriopulmonary connection to a lateral tunnel cavopulmonary Fontan. The postoperative course of these patients was uneventful. However, long-term evaluation is needed to assess the efficacy of this technique in the prevention of postoperative morbidity. (Ann Thorae Surg ) A nastomosis of the right atrial appendage to the pulmonary artery has become a common approach for directing systemic venous return to the pulmonary arteries. Progressive loss of sinus rhythm, right atrial dilatation, and thromboembolism have been noted in long-term survivors of this technique. Among the later modifications of the Fontan procedure, a significant alteration was introduced by de Leval and associates [1] when they described the total cavopulmonary connection. This technique has been known to offer many advantages that theoretically reduce the risk of early and late arrhythmias. There is also a reduction of turbulence that should minimize the risk of atrial thrombosis. We describe our experience with 3 patients who presented several years after their atriopulmonary connection with atrial flutter. On further evaluation, all 3 patients were found to have significant hemodynamic lesions, such as the presence of a right atrial thrombus (2 of 3), severe mitral regurgitation (l of 3), and progressive right atrial enlargement (3 of 3). On the basis of the theoretical hemodynamic advantages of the cavopulmonary connection, these patients were treated with conversion of their "classic" Fontan procedure to a modification involving a lateral tunnel. Patients and Methods Between January 1, 1993 and July 1, 1993, 3 patients were referred to our institution after having had a classic Fontan operation, which included a direct atriopulmonary anastomosis through the right atrial appendage (Table 1). Each patient presented with the acute onset of arrhythmias Accepted for publication May 13, Address reprint requests to Dr Laks, Division of Cardiovascular Surgery, University of California-Los Angeles Medical Center, Le Conte Ave, Los Angeles, CA by The Society of Thoracic Surgeons between 7 years and 91J3 years after their original operation. A right atrial thrombus was demonstrated in 2 cases and a dilated right atrium was demonstrated in all 3 patients. Each patient was evaluated by transthoracic echocardiogram and in 1 case a transesophageal echocardiogram was required to confirm the extent of the thrombus. Patients PATIENT 1. Patient 1 underwent an atriopulmonary anastomosis on May 15, 1986 at our institution; the procedure also included an atrial septectomy, bulboventricular foramen resection, pulmonary valve closure, and tricuspid valve annuloplasty. His postoperative course was complicated by atrial flutter, atrial fibrillation, and transient complete heart block requiring placement of a pacemaker on postoperative day 6. He was in good health until 7 years later, when he presented with cyanosis, diaphoresis, and chest pain. He was noted at that time to have a heart rate of 300 beats/min. The tachycardia was secondary to atrial flutter with 2:1 heart block. He was given quinidine and digoxin. Seven days later he presented again with tachycardia associated with shortness of breath and chest pain. A transthoracic echocardiogram was performed and a large right atrial thrombus was suspected. A transesophageal echocardiogram was then performed, which demonstrated a large (7 em X 2.5 ern) thrombus along the lateral and anterior walls of the right atrium (Fig 1). Two days after admission, the patient underwent reoperation with creation of a lateral tunnel and conversion to a cavopulmonary anastomosis, removal of the large atrial thrombus (6 ern x 8 cm x 4 em), and replacement of his pacemaker. He was discharged home on postoperative day 9 on a regimen of warfarin. He was given no antiarrhythmic medications. He was readmitted 9 days after discharge in atrial flutter. He was converted to normal sinus rhythm /94/$7.00

2 Ann Thorae Surg KAO ET AL 1511 CONVERSION TO CAVOPULMONARY ANASTOMOSIS Table 1. Patient Characteristics Interval Patient Between Clinical No. Sex Cardiac Anatomy Initial Operation Operations Presentation M t-transposed great arteries, double-inlet Atriopulmonary 6 y 11 mo Supraventricular left ventricle, restrictive anastomosis, atrial tachycardia, bulboventricular foramen, pulmonic septectomy, tricuspid cyanosis, right and subpulmonic stenosis valve annuloplasty atrial thrombus, at 6 y 2 mo diaphoresis, chest pain 2 F L-Transposed great arteries, double-inlet Atriopulmonary 10 y 6 mo Atrial flutter, right left ventricle, restrictive anastomosis and atrial thrombus, bulboventricular foramen Stansel at 8 y 5 mo syncope 3 M Tricuspid atresia, transposed great Atriopulmonary 8yO mo Atrial flutter, mitral arteries, pulmonic stenosis atrial anastomosis at 4 y 6 valve septal defect, ventricular septal defect mo regurgitation with adenosine and then started on procainamide therapy with adequate control of his arrhythmias. He is now 8 months after conversion to a lateral tunnel Fontan. He is currently receiving warfarin and procainamide with no recurrence of his atrial flutter by report. PATIENT 2. Patient 2 underwent an atriopulmonary anastomosis with a Stansel procedure at our institution on October 6, Her postoperative course was uneventful and she was discharged home on postoperative day 9. Nine years later, she began to experience occasional orthostatic dizziness. An electrocardiogram at a referring institution demonstrated short periods of atrial flutter with 3:1 heart block. Eight months after her initial symptoms, she presented with atrial flutter with variable heart block requiring cardioversion. Upon further evaluation by trans- Fig 1. Transesophageal eehoeardiogram in patient 1 taken in the longitudinal plane. A large atrial thrombus (7 em x 2.5 em) is present along the lateral and anterior walls of the right atrium. A dilated right atrium is also present. thoracic echocardiogram, she was noted to have a 3 em X 4 em thrombus in the floor of the right atrium. The echocardiogram also demonstrated a dilated right atrium. After the echocardiogram, she was admitted for anticoagulation and medical treatment of her atrial flutter. Because she demonstrated no response to anticoagulation or standard antiarrhythmic therapy, she underwent conversion to a cavopulmonary anastomosis with removal of the large atrial thrombus 9 days after admission. Postoperatively, she continued in atrial fibrillation and was therefore given procainamide with eventual placement of a pacemaker. She was discharged home on postoperative day 9 on a regimen of warfarin and procainamide. A Holter monitor recording obtained 6 months postoperatively demonstrated normal sinus rhythm without ectopy. Follow-up echocardiogram has demonstrated good ventricular function without recurrence of an atrial thrombus and a marked decrease in right atrial enlargement. She is now 7 months after conversion to a lateral tunnel Fontan. She continues to receive procainamide and warfarin. However, there are plans to discontinue procainamide administration within the next 6 months if she continues to be free of arrhythmias. PATIENT 3. Patient 3 underwent an atriopulmonary anastomosis on March 1985 at another institution. Six years later, he was noted to have a markedly dilated right atrium and mitral regurgitation secondary to mitral valve prolapse. Eighteen months thereafter, a Holter monitor recording demonstrated new onset atrial flutter with alternating periods of 1:1 and 2:1 conduction and intermittent brief episodes of atrial fibrillation. He underwent placement of a pacemaker with the aim of overdrive suppression of his tachyarrhythmia. Two months after pacemaker insertion, he was noted to have atrial flutter with 2:1 conduction requiring cardioversion and suppression with quinidine. A cardiac catheterization was performed at this time to evaluate the severity of his mitral valve regurgitation and to determine his candidacy for a lateral tunnel Fontan conversion. His hemodynamic data were significant for a mean right atrial pressure of 14 mm Hg, a mean right transpulmonary gradient of 4 mm Hg, and a mean left

3 1512 KAO ET AL CONVERSION TO CA VOPULMONARY ANASTOMOSIS Ann Thorae Surg transpulmonary gradient of 3 mm Hg. One month later, he electively underwent a conversion to a lateral tunnel Fontan with placement of an adjustable atrial communication and a mitral valve annuloplasty. He was discharged home on postoperative day 8 on a regimen of warfarin and quinidine. However, the atrial communication was not well tolerated secondary to episodes of desaturation. It was therefore snared closed 2 months after his surgical conversion in the cardiac catheterization laboratory. Hemodynamic data also were obtained and were significant for a mean right atrial pressure of 11 mm Hg, a mean right transpulmonary gradient of 2 mm Hg, and a mean left transpulmonary gradient of 3 mm Hg. Two months postoperatively, his medications were discontinued. A Holter evaluation performed 7 months postoperatively demonstrated no recurrence of his atrial arrhythmias. He is now 8 months after conversion to a lateral tunnel Fontan. Operative Procedure A redo median sternotomy is made, cardiopulmonary bypass is instituted, and blood cardioplegia is given. The markedly enlarged right atrium is opened with a longitudinal incision. Thrombus material, if present, is removed. The previously placed intraatrial Dacron baffle between the systemic venous atrium and the pulmonary venous atrium is completely removed and the atrial septal defect is enlarged if necessary. At this point, the left atrioventricular valve can be repaired, as was required in one case (patient 3). A Gore-Tex (W.L. Gore & Assoc. Flagstaff, AZ) patch taken from a Gore-Tex graft then is used to create a lateral tunnel connecting the orifices of the superior and inferior vena cava with the previous connection between the right atrium and the pulmonary artery, which is a Dacron tube graft (Figs 2, 3). Full thickness bites are taken to avoid a Fig 3. Lateral tunnel Fontan conversion. Arrows demonstrate the direction of systemic venous blood flow. suture line leak. The coronary sinus remains on the left side of the atrial baffle. Portions of the redundant right atrial wall are excised before closing the atriotomy. The right atrium is closed with a running suture of 5-0 Prolene (Ethicon, Somerville, NJ). At the upper end, the right atrium is sutured to the external surface of the Gore-Tex tunnel using a running suture of 5-0 Prolene. One patient (patient 2) required further augmentation of the right atrium to pulmonary artery connection that had narrowed from the buildup of pseudointima on the posterior Dacron patch. The patch was removed, leaving an adequate bed of tissue posteriorly. A triangular Gore-Tex patch then was fashioned and sutured over the roof of the connection between the previously placed Gore-Tex intraatrial tunnel and the pulmonary artery. One patient (patient 3) had a snare-controlled adjustable atrial communication placed on the posterior aspect of the Gore-Tex patch and adjacent to the right superior pulmonary vein. This was accomplished using 1-0 Prolene and an 8F snare, which was brought out through the lateral atrial wall. Fig 2. Atriopulmonary anastomosis and the site of thrombus formation in the dilated right atrium. Comment The original atriopulmonary anastomosis described by Fontan and Baudet [2] and the various modifications of the atriopulmonary connection may be complicated by supraventricular arrhythmias, which contribute to the early and late postoperative morbidity and mortality in these patients [3]. This is the result of elevated pressures transmitted to the systemic venous atrium [1]. The incidence of supraventricular arrhythmias in Fontan patients has been reported to be between 32% and 57% [3, 4]. Further analysis by Gewillig and colleagues [5] has demonstrated that elevated preoperative mean pulmonary artery pres-

4 Ann Thorae Surg KAO ET AL 1513 CONVERSION TO CA VOPULMONARY ANASTOMOSIS A B Fig 4. (A) Transthoracic two-dimensional echocardiogram in patient 3 demonstrating a massively dilated right atrium (arrow) before surgical conversion. (B) Transthoracic two-dimensional echocardiogram in the same patient demonstrating the reduction in right atrial size (arrow) after surgical conversion to a cavopulmonary anastomosis. sures and decreased systemic saturations are significant risk factors for atrial flutter. The maintenance of normal sinus rhythm is particularly important in the early postoperative period to minimize left atrial pressures, which thereby reduce systemic venous pressures. Arrhythmias in the early postoperative period are poorly tolerated, with a reported mortality rate as high as 58% [3]. The occurrence of late arrhythmias are thought to be secondary to elevated right atrial pressures as well as late ventricular dysfunction after the Fontan operation. Other risk factors include older age and increased atrial size [5]. Previous studies [6, 7] have shown that the incidence of early arrhythmias and their associated morbidity is lower for a total cavopulmonary anastomosis as compared with the atriopulmonary anastomosis. The risk of atrial arrhythmias is reduced because a major portion of the right atrium continues to function at low pressures. Thus, the total cavopulmonary connection appears to be a favorable alternative to the atriopulmonary anastomosis, particularly in the group of patients who are at higher risk for postoperative supraventricular arrhythmias. In patients who have undergone previous atriopulmonary anastomosis, significant hemodynamic lesions often present as atrial arrhythmias. Peters and co-workers [3] have reported that 86% of postoperative Fontan patients presenting with atrial arrhythmias have evidence of right atrial obstruction and 57% of patients have a right atrial thrombus. Our approach to these patients involves complete hemodynamic evaluation with particular emphasis on excluding surgically remedial causes for elevated systemic venous pressures. These include an obstructed conduit between the right atrium and the pulmonary artery, a right atrial thrombus, subaortic obstruction, and atrioventricular valve regurgitation. If reoperation is indicated to correct these conditions, a conversion to a lateral tunnel should be considered. However, when ventricular function is severely impaired or when the pulmonary vascular resistance is elevated, the operative risk may outweigh the benefits of conversion. The results of lateral tunnel conversion in these 3 patients were not immediate. Two of the 3 patients continued to require treatment for atrial arrhythmias in the early postoperative period. However, it is noteworthy that the arrhythmias were more easily controlled with medical therapy after surgical conversion. Two patients are receiving standard antiarrhythmic medication without recurrence and 1 patient has been weaned off all antiarrhythmics without evidence of relapse. The other major advantage of the total cavopulmonary connection is the decreased risk of atrial thrombosis. In the Fontan circulation, the right atrium plays a passive role in the systemic venous return and creates low velocity turbulence. This flow disturbance along with a large distended atrium leading to the stasis of blood are the major factors influencing the development of atrial thrombosis [1]. In the case of total cavopulmonary anastomosis, the size of the right atrium is markedly reduced since flow patterns are mainly laminar. This therefore reduces the risk of thrombus formation. The lateral tunnel conversion was effective in reducing the size of the right atrium in all 3 of our patients (Fig 4). Two of our 3 patients who presented with atrial arrhythmias were found to have a large right atrial thrombus. We therefore recommend extensive imaging of the entire systemic venous system in this clinical setting. Removal of the thrombus with conversion to a lateral tunnel, as well as long-term anticoagulation, is warranted. When the presence of a right atrial thrombus is suspected, the diagnosis can usually be made with transthoracic echocardiogram [8]. However, when the thrombus is not easily visualized by transthoracic echocardiogram, a transesophageal echocardiogram may be helpful [9]. The first 2 patients in our group did not undergo a cardiac catheterization before surgical conversion because they were thought to be clinically stable and there were no hemodynamic contraindications to surgical conversion.

5 1514 KAO ET AL CONVERSION TO CAVOPULMONARY ANASTOMOSIS Ann ThoraeSurg With the exception of their arrhythmias, all of our patients were thought to be low-risk candidates for this operation. In addition, because both of the first 2 patients demonstrated a large thrombus in their right atrium, a cardiac catheterization would put them at high risk for a thromboembolic event from catheter manipulation. The third patient did undergo cardiac catheterization 1 month before his surgical conversion to evaluate his candidacy for a lateral tunnel Fontan procedure as well as to evaluate the severity of his mitral valve regurgitation. In addition, patient 3 was the only patient in our group who did not demonstrate the presence of an atrial thrombus. His hemodynamic data were remarkable for a decrease in his mean right atrial pressure from 14 mm Hg preoperatively to 11 mm Hg postoperatively and a decrease in the mean right transpulmonary gradient from 4 to 2 mm Hg. The mean left transpulmonary gradient, however, remained the same postoperatively. Although cardiac output by thermodilution was not obtained from either catheterization, it may be interesting to observe if cardiac output actually improves with a lateral tunnel Fontan. This demonstrates that there may be a significant hemodynamic advantage in surgical conversion. Cardiac catheterization for collection of hemodynamic data both before and after surgical conversion will need to be considered for future candidates of this procedure to confirm the possibility of these hemodynamic advantages. The actual operative technique used to convert the atriopulmonary anastomosis to the lateral tunnel is similar to that of the de novo operation with one exception. The new atrial baffle connects the inferior vena cava to the orifices of both the superior vena cava and the right atrium and pulmonary artery junction. This avoids fairly extensive pulmonary artery reconstruction, which is necessary when performing a total cavopulmonary connection. We conclude that in the long-term management of these post-fontan patients, the physician should be made aware of these potential complications related to the operative technique. The appearance of an atrial tachyarrhythmia should prompt a search for the presence of right atrial enlargement, atrial thrombosis, or other hemodynamic abnormalities. If surgical intervention is required, conversion to a cavopulmonary connection should be considered. Longer evaluation will be needed to determine the efficacy of such a conversion in the maintenance of normal sinus rhythm and the prevention of a thrombotic complication. References 1. De Leval MR, Kilner P, Gewillig M, Bull C. Total cavopulmonary connection: A logical alternative to atriopulmonary connection for complex Fontan operations. J Thorac Cardiovasc Surg 1988;96: Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971;26: Peters N, Somerville J. Arrhythmias after the Fontan procedure. Br Heart J 1992;68: Cromme-Dijkhuis AG, Hess J, Hahlen K, et al. Specific sequelae after Fontan operation at mid- and long-term follow-up. J Thorac Cardiovasc Surg 1993;106: Gewillig M, Wyse RK, de Leval MR, Deanfield JE. Early and late arrhythmias after the Fontan operation: predisposing factors and clinical consequences. Br Heart J 1992;67: Balaji S, Gewillig M, Bull C, de Leval M, Deanfield JE. Arrhythmias after the Fontan procedure. Circulation 1991;84(Suppl 3): Pearl J, Laks H, Stein D, Drinkwater D, George B, Williams R. Total cavopulmonary anastomosis versus conventional modified Fontan procedure. Ann Thorac Surg 1991;52: Dobell A, Trusler G, Smallhorn J, Williams W. Atrial thrombi after the Fontan operation. Ann Thorac Surg 1986;42: Fyfe DA, Kline CH, Sade RM, Gillette Pc. Transesophageal echocardiography detects thrombus formation not identified by transthoracic echocardiography after the Fontan operation. J Am Coli Cardiol 1991;18: