Ann Thorac Surg 2000;69:181-185
© 2000 The Society of Thoracic Surgeons
Original Articles
Right atrioventricular extracardiac conduit as a Fontan modification: late results
Annie Dore, MDa,
Jane Somerville, MDa
a Grown-up Congenital Heart Unit, Royal Brompton Hospital, National Heart and Lung Institute, Imperial College, London, England, United Kingdom
Address reprint requests to Dr Dore, Institut de Cardiologie de Montréal, 5000 Belanger est, Montreal QC, H1T 1C8, Canada;
e-mail: annie.dore{at}sympatico.ca
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Abstract
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Background. The right ventricle, when incorporated in the Fontan circulation, might enlarge and function as a pump to the pulmonary circulation. Experience has shown that over the long-term, this operation can be associated with major difficulties.
Methods. The late results, (13 ± 6 years) after right atrioventricular connection as a Fontan modification, were reviewed in 14 patients with tricuspid atresia (11), ventricular septal-defect with small right ventricle (2), and double inlet left ventricle (1) to assess the long-term survival, the right ventricular size, and the need and timing of reoperations. Operations used a valved conduit (7), a valveless Dacron (E.L. Bard, Haverhill, PA) tube (5) and a direct right atrium-right ventricle anastomosis (2).
Results. Death occurred in 5 by 8 ± 5 years. Conduit obstruction occurred in 10 by 9 ± 3 years equally in patients with valved (6 of 7) compared to patients with valveless conduits (4 of 5) and irrespective of right ventricular size (3 of 4 with enlarged right ventricle versus 4 of 6 with small ventricle). Patients with direct atrioventricular anastomosis had no obstruction. Reoperation was performed in 9 but failed to relieve the obstruction in 4 because of external compression (4) with or without thrombosis (1).
Conclusions. Right atrioventricular connection as a Fontan modification can provide good early palliation, but is a poor long-term solution, as it is associated with a high incidence and difficulties in relieving the obstruction.
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Introduction
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Since the first description of a palliative operation for tricuspid atresia by Fontan and Baudet in 1971 [1], several surgical modifications of this technique have been reported [2–10]. In one, the right atrium is connected to a subpulmonary ventricular chamber either by direct anastomosis or by interposition of valved or valveless extracardiac conduits [6]. The rationale for this approach was the hope that incorporation of the right ventricle would make it grow (enlarge) and function as a pump to the pulmonary circulation. Authors have confirmed that there is growth of the right ventricle after atrioventricular connection, and better hemodynamic results with improved functional status for the patient have been claimed [11–14]. However, as the length of follow-up increases, reoperations for obstruction of the surgically created pathways are more prevalent [11, 13, 15–17]. Experience in the grown-up congenital heart (GUCH) unit has shown that the anterior conduits between the right atrium and the right ventricle, with or without valves, can be compressed beneath the sternum as the right ventricle enlarges and causes significant obstruction. This study reviews the long-term outcome of 14 adults with atrioventricular connections for Fontan-type operations, to determine the long-term benefits and difficulties that may occur with this modification.
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Material and methods
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The records of all patients with right atrial to right ventricular connection, as a Fontan-type repair, who have been followed at the GUCH unit of the National Heart Hospital (now Royal Brompton Hospital) since 1974 were reviewed. The type of atrioventricular connection (valved and nonvalved), duration of survival, Ability Index [18], size of the right ventricle, incidence of late arrhythmias, and the need and timing of reoperation, were evaluated. The most recent angiographic, echocardiographic, or magnetic resonance imaging scan, the original operation report, and the postmortem report were reviewed. The size of the right ventricle was compared to the size of the left ventricle on echocardiography, in apical four-chamber view. The right ventricle was considered enlarged if its size was at least 50% the size of the left ventricle. Continuous variables are presented as mean ± one standard deviation.
Patient population
Fourteen patients (9 men, 5 women) with a right atrium to subpulmonary ventricular connection have been followed at the GUCH unit of the National Heart Hospital since 1974. These patients have been referred by different cardiologists and pediatric cardiologists across the country. The Fontan operations were performed between February 1974 and May 1987 at the National Heart Hospital (10), Great Ormond Street Hospital (2), and elsewhere in the country (2) at a mean age of 11.4 ± 5.6 years (5 to 23). The Fontan operations were performed by 6 different cardiac surgeons, all having specific training in congenital heart disease (with 1 surgeon doing 7 operations). May 1987 was the last date on which an atrioventricular connection was constructed on our patients. The basic lesions were tricuspid atresia (11), double-inlet left ventricle (1), ventricular septal defect with hypoplastic right ventricle (1), and atrioventricular septal defect with hypoplastic right ventricle (1). All had ventriculoarterial concordance. Ten patients had 1 or more previous palliative procedures: Blalock-Taussig shunt (5), Waterston anastomosis (3), Glenn procedure (3), pulmonary artery banding (2), enlargement of a ventricular septal defect (1), and repair of an atrioventricular septal defect (1). Extracardiac valved conduits were used in 7 patients (6 homografts, 1 Hancock) and 1 patient also had a Gore-Tex (W.L. Gore & Assoc, Flagstaff, AZ) tube between the right ventricle and the pulmonary artery. Valveless conduits (Dacron [E.L. Bard, Haverhill, PA] tubes) were used in 5 patients and 1 also had an inverted aortic valve homograft at the junction of the inferior vena cava. There were 2 direct right atrial appendage to right ventricle anastomosis. Patients were followed annually with physical examination, 12-lead electrocardiogram, chest roentgenograms, and transthoracic echocardiograms (10 patients). Twenty-four hour ambulatory monitoring was performed for symptoms of arrhythmias (4 patients). Cardiac catheterization (12 patients) was performed for suspicion or confirmation of conduit obstruction. Since 1988, a magnetic resonance imaging scan (6 patients) has been routinely performed in Fontan patients for the diagnosis and follow-up of obstructed atrioventricular pathways. Patients were followed for 1 (death) to 22 years (12.6 ± 5.8).
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Results
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Mortality
Five patients died 1 to 14 years (7.6 ± 4.7) after the procedure (Tables 1, 2). Two patients died suddenly, and 3 died after a reoperation for obstruction of the conduit. A 23-year-old woman (case 14) died 1 year after her Fontan, having been completely well before becoming unconscious during a severe vomiting attack. Her Dacron conduit was lined with peel but was not obstructed. A 22-year-old man (case 8) died suddenly 8 years after the Fontan and on postmortem examination, the homograft was stenosed, calcified, and flattened. A 13-year-old boy (case 9) died in low cardiac output and renal failure after a Dacron conduit was replaced with a homograft. His Dacron conduit was heavily calcified, rigid, flattened behind the sternum, and filled with peel. A 16-year-old boy (case 10), who had chronic wound infection presented in his ninth postoperative year with sternal osteomyelitis and obvious serious obstruction of the Dacron conduit, died a few hours after reoperation in low cardiac output. A 26-year-old woman (case 7) had a first reoperation to replace a flattened calcified obstructed homograft conduit 14 years after the original operation, and remained with obstruction and clot floating in the right atrium 2 months later. She died after an attempt to put a tricuspid valve in the correct anatomical position as the right ventricle had been almost normal in size.
Conduit obstruction
Obstruction of the atrioventricular connection was recognized in 10 patients, 5 to 13 years (8.8 ± 2.6) postoperatively (Table 1) and was reported to be due to (but not mutually exclusive to) calcification (6), extracardiac compression (5), intimal peel (2), thrombosis (1), and infection (1). The mean age at the time of the obstruction was 20 ± 7.2 years (12 to 36 years). Conduit obstruction was present in patients with valved conduits (6 of 7), patients with valveless conduits (Dacron tubes) (4 of 5), but not in the 2 patients with direct right atrial appendage to right ventricle anastomosis. Nine patients had a reoperation. The time from the initial Fontan to reoperation was 9.9 ± 2.8 years (6 to 14 years). Time from the diagnosis of the obstruction to reoperation was 14.2 ± 14 months (1 to 48 months). Of the 9 patients who had a reoperation, 2 died postoperatively, 3 had a successful relief of the obstruction, and 4 remained obstructed 2 to 84 months later because of extracardiac compression (4) and thrombus in the right atrium (1). A second reoperation was performed in 2 patients; 1 (case 4) had a successful replacement of the conduit but the surgeon had to remove part of the sternum to avoid compression, and the other (case 7) died after an attempt to put in a tricuspid valve. Poor ventricular function (1) and a first reoperation made technically very difficult because of fibrosis and calcification in the outflow tract (1) limited further surgery in 2 other obstructed patients. Two patients (cases 3, 4) had, before their reoperation, an unsuccessful attempt to relieve the obstruction with balloon angioplasty and stenting. Reoperations included ligation of a Blalock-Taussig shunt (1), pacemaker insertion (2), reclosure of the tricuspid valve (1), and sternal debridement (1). Clinical data on the 4 patients who did not present conduit obstruction are summarized in Table 2.
Right ventricular size
Recent echocardiographic exams were reviewed in 10 patients. No echocardiographic information was available for review in 3 patients who died more than 12 years ago and in a patient who is now followed abroad. Four patients had almost a normal size right ventricle with a right ventricle around 70% of the size of the left ventricle. The right ventricle functioned but was hypokinetic. The other 6 patients had a small (less than 50% the size of the left ventricle) or inexistent right ventricle. Conduit obstruction was present in patients with enlarged right ventricles (3 of 4), and in patients with small subpulmonary chamber (4 of 6). Two patients who remained obstructed after a reoperation had an enlarged right ventricle and 2 had a small ventricle.
Arrhythmias
Atrial flutter occurred in 4 patients 9 to 17 years after the initial Fontan-type procedure [Tables 1, 2]. All were symptomatic and 2 had conduit obstruction. One patient (case 2) was treated with amiodarone and had a reoperation to relieve the obstruction, and 1 (case 10) had verapamil preoperatively but died a few hours after surgery. A third patient (case 6) presented with atrial flutter 9 years after a reoperation and was treated with amiodarone. The fourth patient (case 12) presented 17 years after the Fontan with atrial flutter, severe left ventricular dysfunction, moderate left atrioventricular valve regurgitation but no evidence of obstruction. He improved with amiodarone, diuretics, and angiotensin-converting enzyme inhibitors. A patient (case 4) with atrioventricular septal defect had transient second degree heart block after the Fontan operation needing an epicardial pacing system, and 1 patient (case 11) with large ventricular septal defect and hypoplastic right ventricle needed a permanent pacemaker for complete heart block, 8 years after the initial repair.
Follow-up status
The 9 survivors were Ability Index 2 (5), 3 (2), and 4 (2) at the last follow-up visit. No patient was event-free in the long-term. One patient took no medication, the others took a combination of diuretics, angiotensin converting enzyme inhibitors and digoxin; 6 took warfarin. Patient 12 had a Glenn procedure followed by a direct right atrial appendage to right ventricle anastomosis, and now has mild cyanosis secondary to pulmonary arteriovenous fistulae, severe left ventricular dysfunction, and moderate left atrioventricular valve regurgitation. Patient 13 has severe protein losing enteropathy.
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Comment
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The right ventricle, when incorporated in the Fontan circulation, presents a real potential for growth [11, 12, 14]. In some series, this occurs in 85% of the patients [11, 14]. The enlargement seems to be more important in ventricles with a trabecular portion. The ventricular chamber might eventually work as a pump, thereby improving the hemodynamic results, the left ejection fraction, and the patient’s functional class [11–14], thus providing a more physiologic type of repair. Lee and colleagues [19] did not report any clinical advantages of the atrioventricular over the atriopulmonary connection but Coles and associates [13] demonstrated a survival advantage with repair that incorporated the residual right ventricle. The follow-up period of both studies was limited to 2 and 3 years, which is inadequate to judge the success of any operation for congenital heart disease. Monro and associates [17] reported their experience with antibiotic sterilized aortic homograft, used as an atrioventricular connection in 9 patients. Only 2 of these patients had their original homograft in the long-term, and reoperations were difficult. There is little information about the late results in patients with right atrial to right ventricular anastomosis for Fontan-type repair. The main concern, on the long-term, is the potential for conduit obstruction as the right ventricle enlarges and the need for reoperation increases.
These results show that conduit obstruction is a major complication, and even if a different type of conduit was used, some more rigid than others, there was no difference between patients having a valved or valveless conduit. Replacement of a valved (homograft or heterograft) conduit is certainly inevitable as the follow-up lengthens, but conduit calcification, sternal compression with or without thrombosis can also be present in valveless connections. More than half of the patients remained obstructed after a reoperation in this series, and the difficulties encountered in relieving the obstruction are definitely an important concern in the long-term. The role of sternal compression can not be overemphasized. As the right ventricle enlarges (or any other cardiac cavity), the conduit is more and more compressed beneath the sternum and soon becomes obstructed. Surprisingly, the size of the right ventricle alone does not seem to influence the incidence of obstruction. Most of these patients had enlarged right atrium or systemic ventricle, which can participate in the compression phenomenon beneath the sternum.
Reoperation is a serious event in patients with complex anatomy. It is inevitably complicated by the presence of fibrosis, adhesions, and calcification. The ventricular function is often decreased because of the combined effects of previous cyanosis, systemic to pulmonary artery shunts, the deleterious effects of earlier bypass operations and chronic restriction of inflow caused by the obstructed conduit. Furthermore, in patients with anterior lying pathways, there is always the risk of entering the conduit and damaging the right atrium or right ventricle with the resternotomy. Mair and coworkers [20] clearly showed that reoperation was a cause of late death in the Fontan population. It is interesting to note that the 2 patients with a direct right atrial appendage to right ventricle connection did not develop obstruction in the long-term, but had other problems (ventricular dysfunction and protein losing enteropathy) well-recognized in the Fontan population.
Atrial flutter may be the first clinical manifestation of conduit obstruction [21]. It is important that when a patient with a Fontan circulation presents an arrhythmia to not only to cardiovert to sinus rhythm, but also to investigate and treat any potential hemodynamic sequelae, such as an obstruction. There are conflicting data about the need for chronic anticoagulation in Fontan patients. As thrombosis and clot formation in the right atrium occur, either before or during atrial flutter, and play a role in the pathogenesis of the obstruction, these patients (certainly those who present arrhythmias) should be anticoagulated. The policy of our unit is to anticoagulate all Fontan patients.
None of these patients was event-free 10 years after the operation, again showing the palliative nature of the Fontan-type repair. Although the number of patients in this series is small, these poor results, along with high incidence of obstruction and difficulties in relieving the obstruction, suggest that atrioventricular connections as a modification of the Fontan operation should be discouraged. The theoretical advantage of increased size of the right ventricular cavity may in fact become a disadvantage particularly as there is no space for an anterior extracardiac conduit between the heart and the sternum. Compression beneath the sternum is inevitable, and the geometry of the valve or the conduit must be preserved. Although it seems attractive to develop a larger right ventricle, it is likely to predispose to obstruction that is difficult to relieve. Right atrioventricular connections are thus associated with unsatisfactory long-term results, and we would not recommend this type of modification of the Fontan operation.
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Accepted for publication June 18, 1999.
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Abstract
Introduction
