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Ann Thorac Surg 2001;71:1541-1546
© 2001 The Society of Thoracic Surgeons
a Departments of Surgery and Pediatrics, Division of Cardiovascular Surgery, The Hospital For Sick Children, University of Toronto School of Medicine, Toronto, Ontario, Canada
b Department of Cardiology, The Hospital For Sick Children, University of Toronto School of Medicine, Toronto, Ontario, Canada
Accepted for publication January 19, 2001.
Address reprint requests to Dr Williams, Division of Cardiovascular Surgery, The Hospital For Sick Children, 555 University Ave, Rm 1525, Toronto, ON, M5G-1X8, Canada
e-mail: bill.williams{at}mailhub.sickkids.on.ca
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Abstract |
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Methods. From August 1993 to January 2000, 45 patients (mean age 2.6 ± 1.1 years, weight 12.7 ± 2.8 kg) who were palliated with staged Norwood procedures (hypoplastic left heart syndrome, n = 32; nonhypoplastic left heart syndrome, n = 13) underwent a modified Fontan operation. Preoperative features included moderate/severe atrioventricular valve regurgitation (n = 5, 11%), reduced ventricular function on echocardiography in 11 patients, McGoon index 1.56 ± 0.38, and pulmonary artery distortion in 18 patients (40%).
Results. A lateral tunnel (n = 16) or an extracardiac conduit (n = 29) connection with fenestration in 38 patients (84%) was used. Concomitant procedures included pulmonary artery reconstruction (n = 24, 53%), atrioventricular valve repair (n = 4, 9%) or replacement (n = 1). Before Fontan, 12 patients (27%) had an intervention to address neoaortic obstruction, and 7 patients required balloon dilation/stenting of the left (n = 5) or right pulmonary artery (n = 5). Intraoperatively, left (n = 5) or right pulmonary artery (n = 1) stenting was performed in 5 patients (11%). On follow-up, 8 patients required additional interventional procedures to address left pulmonary artery narrowing (n = 5), or venous (n = 5) or arteriopulmonary collaterals (n = 1). Perioperative mortality was 4.4% (n = 2). There were 2 late deaths at a mean follow-up of 39 ± 20 months.
Conclusions. In relatively high-risk patients, midterm results of the Fontan operation for children initially palliated with the Norwood procedure were good. Combined interventional-surgical treatment algorithms can lead to improved outcomes.
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Introduction |
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Optimizing outcomes of the Fontan procedure in children initially palliated with the Norwood operation requires close monitoring of and combined catheter-based interventional and surgical procedures to address these and other potential complications. Children with hypoplastic left heart syndrome represent a particularly high-risk group for the Fontan operation. A morphologic right ventricle and tricuspid valve, functioning as the systemic atrioventricular valve, have been identified as predictors of adverse outcome after the Fontan procedure [4–6]. To determine the outcomes of the Fontan operation in this group of patients and the strategies used to optimize those outcomes, we reviewed our experience with the Fontan procedure in children initially palliated with a modified Norwood operation.
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Preoperative hemodynamics are summarized in Table 1. Mean preoperative pulmonary artery pressure was 11 ± 2 mm Hg with an average room air oxygen saturation of 83% ± 4%. The anatomic diagnoses for which the Fontan operation was performed are summarized in Table 2. The diagnosis of hypoplastic left heart syndrome was present in 32 patients (71%), and 73% of patients (n = 33) had a dominant morphologic right ventricle. Two patients had an associated diagnosis of isomerism/heterotaxy syndrome. An interrupted aortic arch was present in 1 patient and pulmonary venous stenosis in 2.
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Neoaortic obstruction was present in 12 patients (27%) and was addressed with percutaneous balloon dilatation (n = 10) or patch augmentation of the arch (n = 4). Patch augmentation was performed before (n = 2) or at the time of bidirectional cavopulmonary anastomosis (n = 2). The indication for intervention on the neoaorta included the clinical presentation of congestive heart failure or low output syndrome, with an arch gradient of 30 ± 9 mm Hg and a mean diameter of 3.9 ± 0.8 mm. After intervention on the neoaorta, the averaged arch gradient was 7 ± 5 mm Hg and mean diameter was increased to 7 ± 1 mm. Two of the 10 patients initially managed by balloon dilation required subsequent patch enlargement for recurrent arch obstruction.
Before the Fontan operation, diagnostic cardiac catheterization in 7 patients included planned interventions to their pulmonary arteries to relieve (1) mean pressure gradients ranging from 2 to 4 mm Hg, (2) focal stenoses of the left or right pulmonary artery (at the modified Blalock–Taussig shunt site), or (3) central and left pulmonary artery hypoplasia. Five left pulmonary arteries and 5 right pulmonary arteries in the 7 patients were augmented by balloon dilatation or endovascular stenting. Significant aortopulmonary collaterals (n = 10) or venous collaterals (n = 6) were occluded with spring coils in a total of 12 patients. In 1 patient an endovascular stent was placed in a left superior vena cava to relieve focal stenosis at its anastomosis to the left pulmonary artery.
Operative approach
Standard cardiopulmonary bypass techniques were used to perform the Fontan operation with ascending aortic and bicaval venous cannulation. In 29 patients (65%) an extracardiac conduit (20 ± 2 mm) was used to construct the Fontan circuit. Either Gore-tex (W. L. Gore and Assoc, Flagstaff AZ) (n = 8) or aortic homograft tissue (n = 21) was used for the reconstruction. In 16 patients (35%) cardioplegic cardiac arrest was required to perform a lateral tunnel intracardiac baffle. Most patients (84%, n = 38) received a fenestration between the Fontan circuit and neopulmonary venous atrium with a median size of 4 mm (range 3 to 5 mm). A fenestration was not used if hemodynamic measurements, ventricular and atrioventricular valve function, and pulmonary artery size and pressures were all optimal both before and at the time of the Fontan procedure. If a fenestration is used, then reevaluation in the catheterization laboratory is generally performed 6 to 12 months after the operation. If favorable hemodynamics are present at the time of test occlusion, then the fenestration is closed at that time.
The mean cardiopulmonary bypass time was 107 ± 46 minutes. In the 16 patients who required aortic cross-clamping, the average ischemic time was 53 ± 29 minutes. A number of associated procedures were performed at the time of the Fontan procedure. More than half of the patients (n = 24) received pulmonary artery augmentation with pericardial patch angioplasty. In 11 of the 16 patients who received the lateral tunnel connection, the atrial septal defect was enlarged. Significant atrioventricular valve regurgitation was managed by repair in 4 children (suture commissuroplasty, n = 3; partial ring annuloplasty, n = 1) or replacement (bileaflet mechanical valve, n = 1) of the atrioventricular valve. Intraoperative stent placement for hypoplastic or compressed segments of the Fontan circuit was added to relieve narrowing of the right pulmonary artery (n = 1), left pulmonary artery (n = 5), and the superior vena cava (n = 1, right). Additionally, resection of subaortic stenosis or enlargement of a ventricular septal defect was necessary in 3 patients.
Statistical methods
Data are described as frequencies, medians with ranges, and means with standard deviations. Where data are missing, the number of nonmissing values is given. Time-related survival estimates were calculated using the Kaplan–Meier method [7]. Factors associated with time to extubation from mechanical ventilation, discharge from intensive care unit, removal of chest drainage tubes, and discharge from hospital were sought in Cox proportionate hazard modeling, with patients censored at the time of death as appropriate. The variables assessed as predictors of these outcomes included age, sex, weight, body surface area, date of Fontan procedure, diagnosis of hypoplastic left heart syndrome, ventricular morphology, presence of isomerism/heterotaxy syndrome, mean pulmonary artery pressure, atrial pressure, transpulmonary pressure gradient, room air oxygen saturations, ventricular end-diastolic pressure, pulmonary artery distortion, presence of atrioventricular valve regurgitation, McGoon index, Nakata index, and estimated ejection fraction. Other preoperative predictors used in the analysis included type of Fontan connection, fenestration, cardiopulmonary bypass time, need for aortic cross-clamping, need for pulmonary artery augmentation, age at which the bidirectional cavopulmonary anastomosis was performed, and the need for coiling aortopulmonary collaterals or venous collaterals. All analyses were performed using SAS statistical software Version 7 (SAS Institute, Cary, NC) using default settings. A p value less than 0.05 was set as the level of statistical significance.
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Results |
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In the early postoperative period, mean systolic blood pressure was 80 ± 9 mm Hg, mean Fontan circuit pressure was 14 ± 3 mm Hg, and mean atrial pressure was 6 ± 2 mm Hg.
Median duration of mechanical ventilation (n = 44) was 1 day, and ranged from 0.25 to 8 days. In Cox proportionate hazard modeling, only earlier date of Fontan procedure was significantly associated with a longer time to extubation (hazard ratio 0.83 per 1-year increment; 95% confidence interval 0.70 to 0.99; p = 0.038). After controlling for this variable, no other variable was significantly associated with time to extubation.
Median length of stay in the intensive care unit (n = 44) was 2.25 days, and ranged from 1 to 8 days. In Cox proportionate hazard modeling, no variable was significantly associated with time to discharge from the intensive care unit, including duration of cardiopulmonary bypass.
Median duration of chest tube drainage (n = 44) was 8.5 days, and ranged from 4 to 51 days. In Cox proportionate hazard modeling, only higher preoperative atrial pressure was significantly associated with a longer time to removal of chest tube drains (hazard ratio 1.25 per 1-mm Hg increment; 95% confidence interval 1.07 to 1.47; p = 0.006). After controlling for this variable, no other variable was significantly associated with time to removal of chest tube drains, including duration of cardiopulmonary bypass or use of Fontan connection fenestration.
Median length of stay in hospital (n = 45) was 11 days, and ranged from 7 to 52 days. In Cox proportionate hazard modeling, no variable was significantly associated with time to discharge from hospital.
Postoperative arrhythmias
Five patients had preoperative atrial rhythm disturbances that persisted after Fontan procedure—4 patients with junctional rhythm and 1 patient with complete heart block who had a permanent pacemaker. Of the remaining 40 patients, 34 remained in sinus rhythm during their postoperative course and 6 patients developed postoperative atrial rhythm disturbances. Five patients had a junctional rhythm, 4 of whom required temporary pacing and 2 of whom also developed a junctional ectopic tachycardia. The remaining patient developed junctional ectopic tachycardia followed by atrial ectopic tachycardia.
Protein-losing enteropathy
Three patients developed protein-losing enteropathy. In 1 patient, protein-losing enteropathy developed after an aortic homograft extracardiac conduit Fontan connection for hypoplastic left heart syndrome. To address progressive protein-losing enteropathy, a fenestrated Fontan revision was performed with a 20-mm Gore-Tex tube. The patient died 1 month later from progressive protein-losing enteropathy, extensive intravascular thrombosis, and multisystem organ failure. In another patient with protein-losing enteropathy, catheter-based refenestration of a lateral tunnel Fontan connection resulted in normalization of serum albumin concentrations and resolution of the enteropathy. At the time of follow-up, a third patient with protein-losing enteropathy is being managed medically and awaiting heart transplantation.
Follow-up
Of the 43 hospital survivors, 2 patients were lost to follow-up. Follow-up was 95% complete and averaged 39 ± 20 months. There were 2 late deaths. One patient died suddenly of unclear etiology. The other patient developed protein-losing enteropathy and died 1 month after a Fontan revision. Kaplan–Meier survival was 96% at 1 month, 93% at 1 year, and 90% at 5 years (Fig 1).
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Diagnostic and interventional cardiac catheterization was performed in 25 patients at a mean interval of 12 ± 4 months after hospital discharge to assess hemodynamics and the status of the fenestration. In 10 patients (40%) the fenestration had closed spontaneously. Test occlusion and subsequent device closure of the fenestration was performed in the remaining 15 patients. At the time of late postoperative cardiac catheterization, 8 patients required additional procedures, including balloon dilatation/stenting of pulmonary artery stenoses in 5 patients, and coil occlusion of collateral vessels in 6 patients (arterial to pulmonary in 1, venous collaterals in 5).
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Comment |
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TopAbstractIntroductionPatients and methodsResultsCommentReferences |
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Mortality after the Fontan operation in the current series is 4% and compares favorably with other reports [4–6, 11]. No patient in the current series had a Fontan take-down, and because only 2 of 45 patients did not survive the operation we did not perform a multivariable analysis to assess potential risk factors for Fontan failure in this group of patients.
Outcomes evaluated, however, included intensive care unit length of stay, ventilatory requirement, hospital length of stay, and duration of chest tube drainage. We found no predictors of increased hospital and intensive care unit length of stay. Other authors have shown that prolonged cardiopulmonary bypass time correlates with increased resource use including intensive care unit length of stay and duration of ventilatory support [9]. Cardiopulmonary bypass time did not correlate with these outcomes based on our analysis. Duration of ventilatory support did correlate with date of Fontan and may have resulted from an era effect, reflecting our more aggressive, recent approach to early extubation.
Prolonged chest tube drainage may result from elevated Fontan/pulmonary artery pressures and has been correlated with prolonged cardiopulmonary bypass time and use of fenestration. Our analysis showed that duration of chest tube drainage correlated only with preoperative atrial pressure. Perioperative elevations in pulmonary venous atrial pressures may in fact be an important and sensitive indicator of ventricular or atrioventricular valve dysfunction. Theoretically, the resultant transient elevations in pulmonary artery or Fontan pressures may favor the development of pleural effusions and potentially explain the observed relationship between elevations in atrial pressures and prolonged duration of chest tube drainage.
Staging toward a Fontan circulation appears to allow for improved overall outcomes. The timing of second- and third-stage cavopulmonary connections, however, remains variable. Whereas the mean age at which second-stage reconstruction was performed was 8 ± 5 months in this review, we currently favor performing a bidirectional cavopulmonary anastomosis between 3 and 6 months of age. This approach is supported by a recent review of all patients receiving a Norwood reconstruction at our institution. We noted a 10% attrition rate of stage 1 survivors during the interstage period, suggesting that a move toward earlier second-stage reconstruction may reduce interstage death (unpublished data).
Before second-stage reconstruction, diagnostic catheterization allows for evaluation of the aortic arch and pulmonary arteries. The type of arch reconstruction used in the first-stage reconstruction may influence the subsequent development of neoaortic obstruction or pulmonary artery compression [2, 13]. Most patients (40 of 45) received an arch reconstruction with a homograft gusset. Recently the Brawn modification [2], in which all ductal tissue is excised and primary autogenous tissue anastomoses are used for arch reconstruction, has been used more frequently.
Neoaortic obstruction is an important complication after the stage I Norwood reconstruction and occurs in 10% to 25% of patients after first-stage operation [2, 13]. Of the 45 patients who received a completion Fontan operation, neoaortic obstruction was an important issue in a significant number (27%), although approximately 10% to 15% of all patients who required Norwood reconstruction at our institution over the past 10 years have developed such neoaortic obstruction (unpublished data). The primary approach to neoaortic recoarctation at our institution is balloon dilation. Angiographically discrete and significant narrowing (less than 4 mm mean diameter in this series) of the distal arch or a gradient greater than 20 mm Hg (30 mm Hg mean in this series) are standard indications for catheter-based approaches. When arch morphology is such that the recoarctation is not discrete, or there is tubular hypoplasia of an arch segment, then surgical correction at the time of bidirectional cavopulmonary anastomosis is favored. In two-thirds of patients (n = 8) with neoaortic obstruction, balloon dilation was sufficient to relieve the recoarctation. There have been no occurrences of aneurysm formation at the recoarctation site after balloon angioplasty. The remaining 4 patients required surgical reconstruction under deep hypothermic circulatory arrest.
The presence of moderate to severe systemic atrioventricular valve regurgitation is an indication for valve repair in the Fontan candidate. Although 5 of our patients had undergone repair (n = 4) or replacement (n = 1) at the time of the Fontan operation, we currently favor performing valve repair at the second-stage reconstruction or before the Fontan procedure. Limiting the third-stage reconstruction to completion of the cavopulmonary connections without having to address other anatomic lesions may impact favorably on Fontan outcome. In other words, performing additional procedures at the time of the Fontan operation may only add risk to the procedure by prolonging the duration of cardiopulmonary bypass, and should instead be done before the final stage reconstruction.
At the time of bidirectional cavopulmonary anastomosis, liberal pulmonary artery augmentation is performed. If the central and left pulmonary artery segments are compressed by the arch or diffusely hypoplastic, then augmentation of the pulmonary artery with atrial tissue by hemi-Fontan reconstruction is preferred over bidirectional cavopulmonary anastomosis.
Small pulmonary arteries, distorted pulmonary arteries, or elevated pulmonary artery pressure or pulmonary vascular resistance are indications of increased risk of Fontan failure, death, and prolonged pleural effusions [12]. As such, our approach to pulmonary artery issues in this group of patients has also been aggressive. At the time of pre-Fontan catheterization, pulmonary artery narrowing or distortion is occasionally identified at the Blalock–Taussig shunt site or in the central/left pulmonary artery region between the undersurface of the arch and left main stem bronchus. Almost one-third of patients underwent preoperative or intraoperative balloon dilation or stenting of 16 pulmonary arteries to address pulmonary artery compression at these sites. At the time of Fontan operation, more than 50% of patients had pulmonary artery patch augmentation. The indications for perioperative intervention on the pulmonary arteries included a gradient across the pulmonary artery segment of 2 to 4 mm Hg. Irregular contour or a discrete area of pulmonary artery narrowing have also been indications for pulmonary artery augmentation or stenting, even in the absence of a gradient across the stenosis, as a low flow state at the time of catheterization may not produce a measurable gradient that would potentially become hemodynamically significant with exercise.
Although concerns arise with the use of pulmonary artery stenting in the Fontan circulation, few actual complications have arisen. Patient growth requires the use of stent implants that can be further enlarged with time. The development of neointimal hyperplasia at the stent site and potential Fontan pathway obstruction has not occurred, nor have we observed any thromboembolic, erosive, or fracture complications of endovascular stents used in this setting.
Our operative approach to Fontan reconstruction includes standard cardiopulmonary bypass techniques with the construction of a lateral tunnel or extracardiac conduit. Mosca and coworkers [6] have recently reported their experience with 100 consecutive patients with hypoplastic left heart syndrome receiving a staged hemi-Fontan/lateral tunnel Fontan procedure. Two different surgical strategies were used, one using standard cardiopulmonary bypass and the second profound hypothermia and circulatory arrest. They found that duration of aortic cross-clamping and cardiopulmonary bypass time were important determinants of morbidity and mortality. Patients receiving primarily a Fontan reconstruction with a cardiopulmonary bypass strategy had a mortality of 11%, versus 2% in patients managed with deep hypothermic circulatory arrest. The authors favor the notion that reduction of cardiopulmonary bypass and aortic cross-clamp time using the circulatory arrest strategy accounted for the improved mortality rates in the deep hypothermic circulatory arrest group.
We did not use a deep hypothermic circulatory arrest strategy for Fontan construction in this cohort of patients. Our current approach is to avoid or minimize the duration of cardiopulmonary bypass and myocardial ischemia with the application of the extracardiac conduit technique. The lateral tunnel Fontan construction is used for patients with previously staged hemi-Fontan, or in the smaller symptomatic child.
Protein-losing enteropathy is a serious problem after the Fontan operation [14]. In a multicenter study, development of protein-losing enteropathy after the Fontan was associated with a 5-year mortality of 40% despite various forms of treatment. Medical treatment alone resulted in resolution of symptoms in 25% of patients, no improvement in 29%, and death in 46% of patients. Surgical treatment resulted in a 40% survival, with relief of protein-losing enteropathy in only 20%. Interventional treatment by catheter-based refenestration of the Fontan circuit consistently showed some positive effect.
Three patients in the current series developed protein-losing enteropathy (7%). One patient was managed by refenestration in the catheter laboratory and experienced complete relief of protein-losing enteropathy. Another has been managed medically with anticoagulation and is in stable condition. Fontan revision in another patient resulted in persistence of protein-losing enteropathy, multisystem organ failure, and death.
Relatively few patients in this series developed sinoatrial node dysfunction or atrial tachyarrhythmias in the early postoperative period [15–17], and although only 13% of patients developed new atrial arrhythmias in the early postoperative period, by midterm follow-up these self-limited rhythm disturbances had resolved. Survival was 90% at 5 years with well-preserved ventricular function and atrioventricular valve function on echocardiography. Nutritional issues and neurodevelopmental outcomes were not reviewed in this study and merit consideration [18–20]. Long-term follow-up of patients receiving a Fontan operation after successful stage I and II Norwood palliation is required to assess the development of late complications. The impact that technical modifications to the Fontan operation [9] and timing of the operation [19] may have on outcomes represent issues that need continued evaluation.
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