Modification of the Fontan Procedure
Superior Vena Cava to Left Pulmonary Artery Connection and Inferior Vena Cava to Right Pulmonary Artery Connection With Adjustable Atrial Septal Defect
Background A modification of the Fontan procedure with unidirectional cavopulmonary connection is described in which the superior vena cava (SVC) is connected to the left pulmonary artery (PA) and the inferior vena cava (IVC) is connected to the right PA via a lateral tunnel with a snare-controlled, adjustable atrial septal defect (ASD). This allows matching of the SVC and IVC flows with the lung of appropriate size. The obligatory left Glenn shunt provides an adequate arterial oxygen saturation, and the elevation in SVC pressure is well tolerated. The adjustable ASD allows selective decompression of the IVC that maintains cardiac output and reduces fluid accumulation in the serous cavities.
Methods and Results Since March 1992, we have performed this procedure in 18 patients. There were 17 children and 1 adult. Median age was 3 years and 9 months (range, 13 months to 36 years). Six patients had been staged with a previous bidirectional Glenn shunt. Preoperative cardiac catheterization revealed a PA pressure of 13±2 mm Hg and a transpulmonary gradient of 5±3 mm Hg. Ventricular function was satisfactory in all patients. At the completion of bypass, the pressures in the SVC and IVC were 16±4 mm Hg and 10±3 mm Hg, respectively (P<.01). The left atrial pressure was 6.0±3.0 mm Hg and the arterial O2 saturation on 100% oxygen was 93±3%. There was one death as a result of intractable atrial arrhythmias. The remaining 17 patients had a mean hospital stay of 9.7 days (6 to 18 days). The length of pleural drainage was 7±3 days. The ASD was adjusted in 11 patients before discharge. Oxygen saturation at discharge was 85.4±4%. Nine patients had repeat catheterization. The ASD was completely closed in 6 patients, an average of 2.5 months after surgery (range, 3 weeks to 5 months). After ASD closure, the arterial oxygen saturation was 96±3%, and the SVC and IVC pressures were both 13±3 mm Hg.
Conclusions The Fontan procedure with unidirectional cavopulmonary connection and adjustable ASD has several advantages that may reduce mortality and morbidity for the high-risk Fontan candidate.
The Fontan procedure is associated with a high mortality in patients with significant risk factors.1 2 3 4 The bidirectional Glenn shunt has been used as a preparatory step in the high-risk candidate combined with correction of factors that contribute to the increased risk such as severe AV valve regurgitation, severe subaortic obstruction, or an excessively large shunt.5 6 7 For those patients undergoing the Fontan procedure, the use of a residual communication between the systemic and pulmonary venous circulation has proved useful either with the snare-controlled, adjustable atrial septal defect (ASD)8 9 10 11 or the fenestrated Fontan with late clamshell device occlusion.12 13 The residual communication reduces venous pressure and ensures adequate cardiac output at the expense of arterial oxygen saturation. Elevation of the venous pressure in the superior vena cava (SVC) is generally better tolerated than an excessive pressure in the inferior vena cava (IVC) and hepatic veins. We describe a modification of the Fontan procedure in which the SVC is connected to the left pulmonary artery (PA) and the IVC is connected via a lateral tunnel with an adjustable ASD to the right PA. We call this the Fontan procedure with unidirectional cavopulmonary connection. The blood flow is thus matched to the size of the lungs, as the SVC carries between one third and one half of the venous return to the left PA, which supplies 40% of the pulmonary vascular bed, while the IVC is connected to the right PA, which supplies 60% of the pulmonary vascular bed. The left-sided Glenn shunt provides an obligatory source of pulmonary blood flow, and the lateral tunnel has an adjustable ASD that selectively decompresses the IVC. It is therefore possible to have a Fontan patient with a higher SVC than IVC pressure and with an adequate arterial oxygen saturation. This type of cavopulmonary connection was first described by Lins et al14 as a modification of the right atrial to PA connection. DeLeon and associates15 more recently described its use with the snare-controlled, adjustable ASD in 5 patients. We describe our experience with the unidirectional cavopulmonary connection in 18 patients undergoing the Fontan procedure.
Starting in March 1992, we performed a lateral tunnel Fontan procedure with unidirectional cavopulmonary connection in 18 patients. This modification was used in patients undergoing Fontan procedures in whom the intracardiac and PA anatomy were suitable. The IVC was connected via an intra-atrial tunnel to the right PA, and the SVC was connected directly to the left PA. All patients had placement of an adjustable ASD. The clinical profile, surgical techniques, and results were analyzed.
There were 17 children and 1 adult; 9 were female. The median age was 3 years and 9 months (range, 13 months to 36 years). Primary diagnoses were univentricular heart (15), unbalanced AV canal (2), and tricuspid atresia (1). Right ventricular morphology was present in 8 patients. Associated diagnoses are shown in Table 1⇓. Previous procedures had been performed in 13 patients and are listed in Table 2⇓. Six patients had been staged with a previous bidirectional Glenn shunt.
Preoperative cardiac catheterization revealed a PA pressure of 13±2 mm Hg and a transpulmonary gradient of 5±3 mm Hg. The arterial oxygen saturation ranged from 68% to 92%, with a mean of 86±5%. Ventricular function was satisfactory in all patients (ejection fraction, 65±9%). Left ventricular end-diastolic pressure ranged from 2 to 12 mm Hg, with a mean of 9±3 mm Hg. AV valve regurgitation was graded mild to moderate in 2 patients. Ventricular outflow obstruction was present in 4 patients, with gradients ranging from 10 to 29 mm Hg. Mild subaortic obstruction was present in 1 patient. Two patients had a restrictive bulboventricular foramen, and 1 patient had a residual gradient across a Damus-Kaye-Stansel repair. Coil embolization of significant aortopulmonary collaterals was required in 3 patients before the Fontan procedure.
The operation was performed using cardiopulmonary bypass with an ascending aortic cannula and bicaval venous cannulas with the SVC cannula placed proximally at the level of the innominate vein. Moderate hypothermia (24°C rectal) was used. Intermittent cold blood cardioplegia was given both antegrade and retrograde, with warm blood cardioplegia reperfusate given before removal of the cross clamp. Any residual atrial septum was excised so that a large interatrial communication was created. An expanded polytetrafluoroethylene (ePTFE) patch was fashioned and sutured within the right atrium to create a lateral tunnel. Full-thickness bites were taken to avoid a suture line leak. Posteriorly, an adjustable ASD was constructed adjacent to the right superior pulmonary vein, as shown in Fig 1⇓. A No. 1 polypropylene mattress suture was passed through pericardial pledgets, through the wall of the atrium at the interatrial groove, and through the edge of the ePTFE patch. The suture was buttressed outside the atrium with a pericardial pledget. The suture ends were passed through an 8F polyethylene tube. The No. 1 polypropylene was sutured to the edge of the ePTFE patch with a 5-0 polypropylene. The ASD was opened and measured with a 6- or 8-mm Hegar dilator. Medium clips were placed on the end of the polyethylene tubing to fix the ASD in the open position. The lateral tunnel suture line was then completed anteriorly along the lateral aspect of the right atrium, thus connecting the orifice of the IVC to the orifice of the SVC.
The SVC and right PA were divided obliquely in the region where they cross, as shown in Fig 1⇑. The proximal SVC was anastomosed to the end of the divided right PA with an absorbable suture. In two cases, a pericardial patch was used to augment this anastomosis. The distal SVC was anastomosed to the right side of the divided right PA (Fig 1⇑). The anterior aspect of this anastomosis was augmented with a large pericardial patch in all except two cases, one of which developed a late stenosis that was successfully balloon-dilated. Additional procedures were required in 6 patients and included resection of subaortic obstruction (4), AV valve annuloplasty (2), aortic valve repair (1), and pacemaker insertion (1). A significant left SVC was present in 1 patient, and this was anastomosed to the left PA in an end-to-side fashion. One patient had atrial situs inversus and dextrocardia. In this patient, the IVC return was directed to the larger left lung and the SVC return directed to the smaller right lung.
As the patient was weaned from bypass, the ASD was partially closed to achieve an arterial O2 saturation of between 88% and 92% on an Fio2 of 100% and an IVC pressure of no higher than 15 mm Hg, preferably 12 mm Hg. The objective was to achieve an arterial oxygen saturation of 85% or higher on room air with an IVC pressure of 15 mm Hg or less. If the arterial O2 saturation subsequently dropped below 85% in the presence of an IVC pressure below 15 mm Hg, the ASD was snared further in the postoperative period. Patients generally returned for follow-up echocardiography in 3 months. If the ASD was closed or trivial, the patient was followed further to see if spontaneous closure would occur. If the ASD was open, the patient underwent cardiac catheterization for a trial of balloon occlusion and, if appropriate, closure of the ASD with the snare in the catheterization laboratory.
At the completion of bypass, pressures in the SVC, IVC, and left atrium were 15.7±3.5 mm Hg, 10.3±2.8 mm Hg, and 5.9±3.1 mm Hg, respectively. The differences in SVC and IVC pressures were statistically significant (P<.01). The arterial O2 saturation was 93±3%.
There was one early death in a 3-year, 9-month-old boy with the diagnosis of double-inlet left ventricle, coarctation, and obstructed bulboventricular foramen. He was initially palliated with coarctation repair and PA banding as a neonate. He later had a bidirectional Glenn shunt, a Damus-Kaye-Stansel procedure, and a central shunt at 26 months of age. His preoperative PA pressure was 11 mm Hg, and there was a 29 mm Hg gradient across the Stansel. The subaortic obstruction was resected at the time of modified Fontan operation with unidirectional cavopulmonary connection. He required a pacemaker for postoperative heart block. He subsequently developed intractable atrial arrhythmias that produced a low-output state. He died as a result of intractable ventricular arrhythmias.
The remaining 17 patients had hospital stays ranging from 6 to 18 days, with a mean of 9.7 days. One patient developed a low-output state after surgery. The ASD had been virtually closed in the operating room, with a postoperative arterial oxygen saturation of 98%. At 18 hours, the chest was opened and the adjustable ASD opened with transatrial balloon dilatation. Cardiac output improved, and the chest was closed on day 3. The patient subsequently did well. Another patient was anticoagulated for a thrombus in the right internal jugular vein. He also required a pacemaker for persistent complete heart block. Patients were ventilated for an average of 3±3 days. Prolonged ventilation of 13 days’ duration was required for the management of bronchospasm in 1 patient, aged 14 months. Another patient, aged 13 months, developed significant upper body edema with high SVC pressures. This responded to an infusion of prostaglandin E1 into an upper-extremity vein. No significant pleural effusions occurred. The chest tubes were taken out 4 to 13 days after surgery (average, 7±3 days).
The ASD was adjusted after surgery in 11 patients. It was partially closed with the snare once in 7 patients and twice in 3 patients. It was reopened in 1 patient. The arterial O2 saturation at the time of discharge was 85.4±4%.
All patients were discharged on acetylsalicylic acid. One patient, aged 15 years, developed tachybrady syndrome with syncope several months after the operation. He was placed on digoxin and is being evaluated for a pacemaker. His ASD has been closed.
Thus far, 9 patients have had repeat cardiac catheterization. During the procedure, 7 patients underwent further snaring of the adjustable ASD, with 6 being completely closed. Two patients were not snared; 1 patient had a trivial ASD, and the other patient was catheterized at a center not familiar with the technique of snaring. The time interval to catheterization ranged from 1 week to 72 weeks. Table 3⇓ shows the catheterization data before and after closure of the ASD. Cineangiograms revealed stenosis at the SVC–right PA junction in 1 patient, which was successfully balloon-dilated. Figs 2⇓ and 3⇓ show a postoperative angiogram in the unidirectional cavopulmonary connections. The remaining 8 patients are doing well and await recatheterization and closure of the adjustable ASD. One patient developed a left-sided pleural effusion 2 months after surgery. This resulted in an arterial O2 saturation of 80% without SVC syndrome. Drainage of the effusion resulted in an improved arterial O2 saturation.
Since the original reports of the Fontan procedure by Fontan and Baudet16 and Kreutzer et al,17 there have been many modifications, including those by Bjork et al18 and Puga et al.19 Of interest is the fact that the original Fontan connection was unidirectional, with a Glenn shunt directing SVC flow to the right lung and the IVC flow directed via the right atrium to the left lung. There was thus a mismatch between SVC flow, which comprises 33% to 40% of venous return in adults and older children, and the size of the right lung, which comprises 60% of the pulmonary vascular bed. Conversely, the IVC flow, which comprises two thirds of the venous return, was directed to the smaller left lung with 40% of the vascular bed. The classic Glenn procedure20 also entailed a mismatch, with the SVC flow directed to the larger right lung. The bidirectional SVC to PA connection avoided this mismatch and has been widely adopted. The so-called “total cavopulmonary connection” or “lateral tunnel Fontan” described by Puga et al19 and De Leval et al21 has also been widely accepted, with the advantages of avoiding exposure of the entire right atrium to high pressures and directing both the SVC and IVC blood to either lung.
Together with the evolution of anatomic connections, there has been a growing awareness that the relatively high mortality and morbidity associated with the Fontan procedure was related to the sudden increase in systemic venous pressure due to the pulmonary vascular resistance, which must be passively overcome, in addition to an elevation in pulmonary venous pressure, which could be elevated due to ventricular dysfunction. These pressures were commonly transiently elevated by many factors occurring in the perioperative period. This resulted in loss of fluids to the extravascular space and a reduced cardiac output. Provided that the patient survived the early postoperative course, the pulmonary vascular resistance usually fell and ventricular function usually improved, resulting in an improved cardiac output and lower systemic venous pressures. To ameliorate these effects, the snare-controlled, adjustable ASD was first used in 1987 and reported in 1988 (Reference 8) to allow a controlled right to left shunt that would reduce the systemic venous pressure but still maintain an acceptable arterial oxygen saturation and adequate cardiac output. The “fenestrated” Fontan in which a punched hole is left in the ePTFE patch and then closed by a transcatheter device was subsequently reported.12
For the high-risk Fontan candidate with elevated pulmonary vascular resistance or reduced ventricular function, a bidirectional Glenn shunt is now used as a first stage. At the same time, associated defects are corrected. Patients are then reevaluated, and a Fontan procedure is performed only in those found to have acceptable hemodynamics. The Fontan procedure with adjustable ASD or fenestration was another alternative for the patient who was acceptable for a Fontan procedure but who had additional risk factors. These techniques are now used in many centers on all Fontan patients. Despite the use of the ASD, there are still some patients in whom adequate decompression of the systemic venous system results in an unacceptably low oxygen saturation.15 In this situation, mortality from low output or morbidity as a result of fluid accumulation still occurs. The unidirectional cavopulmonary connection was devised to avoid this by selectively decompressing the IVC while still having obligatory pulmonary blood flow via the SVC to left PA anastomosis. The connection we describe in this report connects the SVC to the left PA, providing an obligatory Glenn shunt to the lung of appropriate size. This alone should provide an acceptable arterial oxygen saturation of between 78% and 82%. SVC venous hypertension is generally better tolerated than IVC venous hypertension and results in less massive fluid shifts. The IVC is connected to the appropriately sized right PA but is decompressed to a varying degree with the adjustable ASD, thus maintaining an adequate cardiac output and avoiding excessive fluid accumulation. We use the term “Fontan with unidirectional cavopulmonary connection” for this modification.
A unidirectional connection was first used by Fontan,16 but with the sides reversed as described above. Lins et al14 described a unidirectional Fontan with the right atrium connected to the right lung and the SVC to the left lung. DeLeon and associates15 reported their experience with 5 patients in whom the usual “lateral tunnel Fontan” resulted in excessive venous pressure with inadequate arterial oxygen saturation. Conversion to an “obligatory Glenn shunt” resulted in improved hemodynamics. An adjustable ASD was used in their patients. This was the first report describing a technique similar to the one used in our patients.
We now consider the Fontan with unidirectional cavopulmonary connection to be the preferred connection for patients at increased risk provided that the match of venous return and pulmonary vascular bed size and resistance is appropriate. In cases of situs inversus, the connection is to the opposite PA, as was done in 1 patient. If the IVC cannot be connected to the larger pulmonary vascular bed with the lower resistance, then a bidirectional connection is used.
The adjustable ASD is always left partially open after weaning from bypass, aiming for an arterial oxygen saturation of between 88% and 91% on an Fio2 of 100% and an IVC pressure of no more than 12 mm Hg. Pressures of as high as 22 mm Hg are acceptable in the SVC. Most patients require one adjustment of the ASD within the first few days, and some require two adjustments. After discharge, the ASD is electively closed at 4 to 6 weeks if it has not closed spontaneously. All patients have been maintained on aspirin, and there have been no thromboembolic events in this series.
There are potential pitfalls with this type of connection. There is concern that collapse of one lung or a massive effusion could cause severe venous congestion of the SVC or IVC. Early after surgery, this has not occurred but would require immediate treatment. Late after surgery, venous collaterals will probably develop between the two vascular beds and a unilateral pulmonary process is less likely. Blood flow to the left lung does not contain hepatic venous blood. It has been suggested that the absence of hepatic venous blood could contribute to the development of pulmonary AV fistulae. The evidence for this is indirect, and it remains to be seen whether the left lung will develop AV fistulae. So far, there has been no evidence of this in our patients. They will be followed carefully over the long term.
The Fontan procedure with unidirectional cavopulmonary connection (SVC to left PA and IVC to right PA) and adjustable ASD offers several advantages. It provides an obligatory source of pulmonary blood flow, ensuring an acceptable arterial oxygen saturation. There is selective decompression of the IVC with maintenance of adequate cardiac output and avoidance of large fluid shifts. These advantages may afford more control over the Fontan physiology. It is a further refinement of the partial Fontan and appears indicated for the high-risk Fontan candidate with increased pulmonary vascular resistance, borderline-sized pulmonary arteries, or infants who tolerate venous hypertension poorly. Further clinical experience will be required to determine if it should be applied as the Fontan connection of choice.
Presented in part at the 66th Scientific Sessions of the American Heart Association, Atlanta, Ga, Nov. 8-11, 1993.
- Received March 2, 1995.
- Accepted April 1, 1995.
- Copyright © 1995 by American Heart Association
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