Amplatzer occlusion of accessory ventriculopulmonary connections

Background: Children with complex congenital heart disease often require staged palliation to regulate systemic and pulmonary blood flow. Accessory sources of pulmonary blood flow including aortopulmonary collaterals, aortopulmonary shunts, and ventriculopulmonary connections following Glenn or Fontan palliation can be associated with elevated central venous pressures and persistent pleural drainage. Occlusion of accessory ventriculopulmonary connections in this setting has traditionally been accomplished surgically. Objective: To review the efficacy of Amplatzer devices in transcatheter occlusion of accessory ventriculopulmonary connections in children with complex congenital heart disease. Methods: Patients were identified and their records retrospectively reviewed for indication, procedural details, and clinical efficacy and outcome. Results: Between December 2004 and March 2008, seven patients underwent occlusion of accessory ventriculopulmonary connections using an Amplatzer Septal Occluder (3), an Amplatzer Duct Occluder (3), or an Amplatzer Vascular Plug (1). Underlying single ventricle physiology was present in six of these patients. The site of occlusion was the right ventricle to pulmonary artery (Sano) conduit in two patients, the native main pulmonary artery in three patients, the pulmonary valve in one patient, and a left ventricle to pulmonary artery homograft in one patient with biventricular physiology. There were no complications associated with these procedures. Conclusions: Amplatzer occlusion devices provide a safe and effective means of eliminating accessory ventriculopulmonary connections in children who have undergone surgical palliation of congenital heart disease. © 2008 Wiley‐Liss, Inc.     

Somatic growth in children with single ventricle physiology impact of physiologic state.

OBJECTIVES: We sought to define somatic growth patterns for patients with single ventricle (SV) physiology and associated factors. BACKGROUND: Infants with SV physiology might have somatic growth retardation associated with volume overload and hypoxemia, which might improve after surgical palliation. METHODS: We reviewed 126 patients (35% male) who underwent the Fontan procedure from 1994 to 2004. Demographic data, hemodynamic variables, and surgical procedures were recorded. Serial weights and heights were converted to z-scores. Linear regression analysis adjusted for repeated measures was used to model growth trends. RESULTS: Median z-score for weight was -0.7 at birth, -1.6 before bidirectional cavopulmonary shunt (BCPS), -0.7 before Fontan procedure, and -0.7 after Fontan procedure. A significant decline in z-scores for weight was seen before BCPS, which was reversed after the hemi-Fontan and stabilized after Fontan procedure. The z-scores for weight before the BCPS were lower in patients with lower birth weight (p < 0.01), nutritional difficulties (p = 0.01), and higher right atrial pressures (p = 0.02). After the BCPS, impaired growth was seen in patients who had systemic venous collaterals (p < 0.01). Patients who had collaterals embolized had the same growth trends as patients with no collaterals (p = 0.29). CONCLUSIONS: Infants with SV physiology show impaired somatic growth before BCPS. Although catch-up growth occurs after BCPS, effective interventions such as more intensive nutritional strategies before BCPS might be targeted at this high-risk population. The presence of systemic venous collaterals might impede growth secondary to hemodynamic impairment. Embolization of collaterals might allow for maximum growth potential.     

Baffle fenestration with subsequent transcatheter closure. Modification of the Fontan operation for patients at increased risk

Ventricular dysfunction, elevated pulmonary vascular resistance, and residual distal pulmonary artery distortion contribute to early mortality after a Fontan operation; they may be transient or reversible. A baffle fenestration, allowing right-to-left shunting, maintains cardiac output and limits right atrial pressure. A baffle fenestration was surgically created at the time of a modified Fontan repair in 20 consecutive patients. Risk factors included pulmonary artery pressure of 18 mm Hg or more, end-diastolic pressure of 12 mm Hg or more, valvar regurgitation, pulmonary artery distortion, pulmonary vascular resistance of 2 Woods' units or more, ventricular outflow obstruction, and complex anatomy. Nineteen of 20 patients survived. After the operation, mean arterial oxygen saturation was 86%, mean right atrial pressure was 15 mm Hg, and mean duration of pleural effusions was 6 days. Twelve of 19 survivors tolerated early test occlusion and had permanent transcatheter umbrella closure. Four patients failed early test occlusion, with a significant decrease in venous O2 saturation and a rise in central venous pressure, due to ventricular dysfunction, pulmonary artery distortion, or aortopulmonary collaterals. Three of four had successful late closure of the fenestration after correction of these abnormalities.     

Evaluation of Fontan liver disease: Correlation of transjugular liver biopsy with magnetic resonance and hemodynamics

Introduction: Liver fibrosis and cirrhosis are late complications in Fontan palliation. Liver biopsy is the gold standard. The goal of this study is to correlate transjugular liver biopsy (TJLB) in the setting of Fontan palliation with noninvasive testing and hemodynamics.
Methods: Between August 2014 and July 2017, 49 Fontan patients underwent TJLB. All the patients had hemodynamic evaluation, 28 patients had MRE (magnetic reso‐ nance elastography) and 40 patients had cardiopulmonary exercise test. Histologic liver fibrosis was quantitated using traditional histologic scoring systems and a modi‐ fied Ishak congestive hepatic fibrosis score.
Results: Median age 17.8 years, median time since Fontan 15.2 years. Primary diagnosis and Fontan type were variables, but predominantly LV morphology (30/49), lateral tun‐ nel Fontan (29/49), originally fenestrated (37/49), and 11/49 had a pacemaker. Histologic fibrosis correlated with MRE (R = 0.62, P ≤ .001). Histologic fibrosis and MRE correlated with Fontan pressure (R = 0.38, P = .008 & R = 0.59, P ≤ .001). Morphology of the single ventricle did not correlate with liver fibrosis. The presence of a fenestration resulted in a higher cardiac index (P = .026) but did not resulted in lower liver fibrosis (P = .64).
Conclusion: Noninvasive tests, such as MRE, may be suitable for longitudinal follow‐up in patients with single ventricle physiology. Our data suggest that there is reasonable cor‐ relation of MRE liver stiffness with biopsy scoring systems and Fontan pressures. We demonstrated the feasibility of TJLB in the setting of Fontan palliation and demonstrated its correlation with noninvasive measures particularly MRE. We recommend selective use of TJLB when MRE score is >5 KPa or when there are other clinical signs of cirrhosis.     

Somatic Growth after Fontan and Mustard Palliation

Objective. Patients with complex congenital heart disease frequently develop early growth failure; however, the long‐term outcome for growth after surgery for single ventricle or anatomic right ventricle as systemic ventricle is not clear. This study was designed to determine long‐term growth in patients following the Fontan and Mustard operations. Method. We retrospectively reviewed the growth parameters of children who had previously undergone the Fontan (n = 80) or Mustard (n = 66) palliation at the Riley Hospital for Children, Indiana. Results. Both the Fontan and Mustard groups had normal height and weight at birth. At the time of their Fontan or Mustard palliation, there was a significant retardation in weight (Z‐score: ?0.98 and ?1.79, respectively) and height (Z‐score: ?0.96 and ?1.03, respectively). Both cohorts postoperatively demonstrated significant catch‐up in their weights. Although the Mustard group normalized their heights, the Fontan patients continued to demonstrate short statures in long‐term follow‐up. Conclusion. Children with single ventricles and those with palliated d‐loop transposition of the great arteries suffer somatic growth delay prior to definitive surgery, despite being of normal size at birth. Catch‐up growth in weight occurs after the Fontan and Mustard operations. In the Mustard population, height also normalizes, whereas in patients with univentricular circulation, height remains abnormally low.     

Considerations in Critical-Care and Anesthetic Management of Adult Patients Living With Fontan Circulation

The Fontan procedure is a staged palliation for various complex congenital cardiac lesions, including tricuspid atresia, pulmonary atresia, hypoplastic left heart syndrome, and double-inlet left ventricle, all of which involve a functional single-ventricle physiology. The complexity of the patients’ original anatomy combined with the anatomic and physiologic consequences of the Fontan circulation creates challenges. Teens and adults living with Fontan palliation will need perioperative support for noncardiac surgery, peripartum management for labour and delivery, interventions related to their structural heart disease, electrophysiology procedures, pacemakers, cardioversions, cardiac surgery, transplantation, and advanced mechanical support. This review focuses on the anesthetic and intensive care unit (ICU) management of these patients during their perioperative journey, with an emphasis on the continuity of preintervention planning, referral pathways, and postintervention ICU management. Requests for recipes and doses of medications are frequent; however, as in normal anesthesia and ICU practice, the method of anesthesia and dosing are dependent on the presenting medical/surgical conditions and the underlying anatomy and physiologic reserve. A patient with Fontan palliation in their early 20s attending school full-time with a cavopulmonary connection is likely to have more reserve than a patient in their late 40s with an atriopulmonary Fontan at home waiting for a heart transplant. Each case will require an anesthetic and critical care plan tailored to the situation. The critical care environment is a natural extension of the anesthetic management of a patient, with complex considerations for a patient with Fontan palliation.     

First implantable hemodynamic monitoring device placement in single ventricle fontan anatomy

The Fontan anatomy leads to elevated central venous pressure along with chronic venous congestion and low cardiac output; this is felt to be responsible for deterioration of exercise tolerance and functional capacity over time. Real‐time hemodynamic evaluation of the Fontan anatomy has not been evaluated until now. Here, we report the technical aspects of the first two adult Fontan patients to undergo placement of an invasive hemodynamic monitor (IHM). We validate IHM readings with invasive pulmonary artery catheter derived hemodynamics in the Fontan and show successful home transmission of pulmonary artery hemodynamic tracings. This technology has the capacity to change current understanding of Fontan hemodynamics and treatment in patients with complex single‐ventricle anatomy. © 2016 Wiley Periodicals, Inc.     

Factors influencing survival of patients with heterotaxy syndrome undergoing the Fontan procedure.

OBJECTIVES. This study was undertaken to determine those factors that may influence survival in patients with heterotaxy syndrome undergoing the Fontan procedure. BACKGROUND. The Fontan procedure remains the preferred palliative procedure for patients with heterotaxy syndrome. Although the mortality rate has improved for patients without this syndrome undergoing the Fontan procedure, it remains high for patients with heterotaxy syndrome. METHODS. The medical records of 20 consecutive pediatric patients with asplenia (n = 12) and polysplenia (n = 8) who underwent the Fontan procedure between January 1, 1986 and December 31, 1990 were reviewed. Anatomic and hemodynamic data were collected, as well as data on types of surgical palliative procedures and on outcome of the Fontan procedure. RESULTS. There were two early and two late deaths for a total mortality rate of 20% in the patients with heterotaxy syndrome, as compared with 8.5% for the patients without this syndrome who underwent the Fontan procedure during the same time period. Factors that significantly increased the risk of the Fontan procedure in these patients were 1) preoperative findings of greater than mild atrioventricular valve regurgitation, b) hypoplastic pulmonary arteries, and c) mean pulmonary artery pressure greater than or equal to 15 mm Hg after 6 months of age. Systemic and pulmonary venous anomalies coupled with single-ventricle anatomy were not significant risk factors for determining a poor outcome of the Fontan procedure. CONCLUSIONS. This study suggests that the outcome of the Fontan procedure in patients with heterotaxy syndrome may be improved by early protection of the pulmonary vascular bed, despite the existence of other cardiac anomalies.     

Bidirectional cavopulmonary anastomosis in congenital heart disease. Functional and clinical outcome.

The bidirectional cavopulmonary anastomosis is a surgical procedure suitable for patients with cyanotic congenital heart disease and univentricular physiology. This operation is able to increase the effective pulmonary blood flow without any additional load on the cardiac work and without any further distortion on the pulmonary artery branches. The cavopulmonary anastomosis can represent the first stage for patients destined for Fontan repair or a definitive palliative operation in high risk Fontan candidates. In order to test the hypothesis of a definitive palliation by cavopulmonary anastomosis in this kind of patients, we evaluated the hemodynamic data before and after this surgical approach and compared these data with their clinical and functional outcome. We evaluated 74 patients submitted to bidirectional cavopulmonary anastomosis by either hemodynamic or functional evaluation. End-diastolic and end-systolic ventricular volumes were significantly reduced by bidirectional cavopulmonary anastomosis (p less than 0.0005). Despite these data and a normal ambulatory ECG, spirometry and echocardiographic analysis, the stress test showed discouraging results. In fact, mean work time and peak heart rate were significantly different from normal values showing an impaired functional capacity of these children. In conclusion we think that bidirectional cavopulmonary anastomosis can not be considered an adequate definitive palliation but it represents a very good stage to preserve the pulmonary arteries and to prepare the systemic ventricle towards the Fontan repair.     

Five decades of the Fontan operation: A systematic review of international reports on outcomes after univentricular palliation

Almost fifty years after its first clinical application, the modified Fontan operation is among the most frequently performed procedures in congenital heart disease surgery in children today. The objective of this review is to systematically summarize the international evolution of outcomes in regard to morbidity and mortality of patients with Fontan palliation. All studies published over the past five decades with more than 100 Fontan patients included were screened. In eligible studies, information concerning preoperative patients' characteristics, Fontan modifications employed, early mortality, long‐term survival and frequency of relevant complications was extracted. Ultimately, thirty‐one studies published by the largest surgical centers with an overall number of 9390 patients were included in this review. The extracardiac total cavopulmonary anastomosis is the most frequently used Fontan modification. Hemodynamic data demonstrate a rigorous overall adherence to suggested Fontan selection criteria. The analysis showed a clear trend toward improved early and long‐term survival over the time period covered. Although inconsistently reported, severe complications such as arrhythmias, thromboembolic events and protein‐losing enteropathy as well as reoperations and reinterventions were frequent. In conclusion, patients palliated for complex univentricular heart malformations nowadays benefit from the experience and technical developments of the past decades and have a significantly improved long‐term prognosis. However, important issues concerning postoperative long‐term morbidity and mortality are still unsolved and clear intrinsic limitations of the Fontan circulation are becoming evident as the population of Fontan patients ages.     

Hemiazygos vein "steal hypoxic-syndrome" after hemi-Fontan operation: comprehensive four-dimensional flow magnetic resonance visualisation

A 2-year-old boy with hypoplastic left heart syndrome and previous hemi-Fontan palliation surgery was referred for cardiovascular magnetic resonance evaluation because of progressive cyanosis. This case report illustrates the advantages of non-invasive four-dimensional magnetic resonance imaging for comprehensive identification and quantification of venovenous collaterals in patients with palliated hemi-Fontan staged surgery.     

Orthotopic heart transplantation in patients with univentricular physiology

Parallel advancements in surgical technique, preoperative and postoperative care, as well as a better understanding of physiology in patients with duct-dependent pulmonary or systemic circulation and a functional single ventricle, have led to superb results in staged palliation of most complex congenital heart disease (CHD) [1]. The Fontan procedure and its technical modifications have resulted in markedly improved outcomes of patients with single ventricle anatomy [2,3,4]. The improved early survival has led to an exponential increase of the proportion of Fontan patients surviving long into adolescence and young adulthood [5]. Improved early and late survival has not yet abolished late mortality secondary to myocardial failure, therefore increasing the referrals for cardiac transplantation [6]. Interstage attrition [7] is moreover expected in staged palliation towards completion of a Fontan-type circulation, while Fontan failure represents a growing indication for heart transplantation [8]. Heart transplantation has therefore become the potential "fourth stage" [9] or a possible alternative to a high-risk Fontan operation [10] in a strategy of staged palliation for single ventricle physiology. Heart transplant barely accounts for 16% of pediatric solid organ transplants [11]. The thirteenth official pediatric heart transplantation report- 2010 [11] indicates that pediatric recipients received only 12.5% of the total reported heart transplants worldwide. Congenital heart disease is not only the most common recipient diagnosis, but also the most powerful predictor of 1-year mortality after OHT. Results of orthotopic heart transplantations (OHT) for failing single ventricle physiology are mixed. Some authors advocate excellent early and mid-term survival after OHT for failing Fontan [9], while others suggest that rescue-OHT after failing Fontan seems unwarranted [10]. Moreover, OHT outcome appears to be different according to the surgical staging towards the Fontan operation and surgical technique of Fontan completion [12].The focus of this report is a complete review of the recent literature on OHT for failing single ventricles, outlining the clinical issues affecting Fontan failure, OHT listing and OHT outcome. These data are endorsed reporting our experience with OHT for failing single ventricle physiology in recent years.     

Stenting of stenosed aortopulmonary collaterals and shunts for palliation of pulmonary atresia/ventricular septal defect.

Patients with unrepaired pulmonary artery atresia and ventricular septal defect (PA/VSD) depend on aortoplumonary collaterals and surgically created shunts for pulmonary blood flow. These vessels frequently develop stenoses with time, leading to hypoperfusion of lung segments and systemic hypoxemia. The purpose of this article is to describe catheter palliation of hypoxemic patients with PA/VSD who were not candidates for surgical repair. We present our experience with stent implantation for stenosis of aortopulmonary collaterals and shunts in these patients. Three patients with hypoplastic pulmonary arteries underwent stent placement in aortopulmonary collateral arteries (APCAs) or their shunts. Technical aspects of the interventional catheterization procedure are discussed in detail. Case 1 underwent placement of five stents in collateral vessels and one stent in the Blalock-Taussig shunt (BT) with dramatic increase in vessel size and improvement in saturations from 70% to 89%. Case 2 underwent placement of two overlapping stents in a collateral vessel with an increase in diameter of the collateral vessel from 2.3 to 6 mm and an improvement in saturation from 68% to 88%. Case 3 underwent placement of three overlapping stents in a BT shunt with an increase in diameter of the shunt from 2.2 to 6.6 mm and an improvement in saturation from 71% to 89%. All three patients had excellent clinical improvement and stable saturation at follow-up. Stent placement for maintaining patency of APCAs and aortopulmonary shunts is feasible and safe.     

Pulmonary atresia with intact ventricular septum: results and predictive factors of surgical treatment.

Between 1970 and 1989 26 children were operated for pulmonary atresia with intact ventricular septum (PA/IVS). According to the degree of right heart hypoplasia the patients were divided into 3 groups of mild (5), moderate (17) or severe (4) hypoplasia. Palliative operations were performed in 25 children (17 male, 8 female) at a mean age of 10 days: 13 valvotomies (valv.), 5 aortopulmonary shunts, and 7 valv. plus shunt. One patient had total correction as primary procedure. A total of 17 reoperations was necessary in 12 of 26 patients (10 palliations, 7 total corrections). Total corrections were: 2 conduits and 5 patches of the right-ventricular outflow tract (RVOT). Total mortality was 14/26 (54%) children (early 10/26 = 38%, late 4/26 = 16%). After total correction mortality was 3/7 (43%) patients. After a mean follow up of 10.8 years after palliation the 12 survivors are mostly in NYHA class I. Actuarial survival after palliation was 60% after 30 days and 44% after 5 and 10 years. We analyzed 9 clinical and hemodynamic variables by univariate and multivariate analysis to assess the predictive factors of postoperative outcome. Multivariate analysis disclosed the degree of right-ventricular hypoplasia (p = 0.023) as an independent predictor for death whereas the age at palliation only approached significance (p = 0.065). We recommend the following surgical strategy, aiming in the first place at decompressing the right ventricle: in mild hypoplasia valvotomy alone or combined with a shunt for palliation, in moderate hypoplasia shunt plus patch of the RVOT and in severe hypoplasia shunting alone. In case of a restrictive foramen ovale initial balloon septostomy is performed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preliminary Evaluation of Hemodynamic Effects of Fontan Palliation on Renal Artery Using Computational Fluid Dynamics

Background: The assessment of renal function is important to the prognosis of patients needing Fontan palliation due to the reconstructed compromised circulation. To know the relationship between the kidney perfusion and hemodynamic characteristics during surgical design could reduce the risk of acute kidney injury (AKI) and the postoperative complications. However, the issue is still unsolved because the current clinical evaluation methods are unable to predict the hemodynamic changes in renal artery (RA). Methods: We reconstructed a three-dimensional (3D) vascular model of a patient requiring Fontan palliation. The technique of computational fluid dynamics (CFD) was utilized to explore the changes of RA hemodynamics under different possible blood flow rates. The relationship between the kidney perfusion and hemodynamic characteristics was investigated. Results: The calculated results indicated the declined tendency of the pressure and pressure drop as the flow rate decreased. When the flow rate decreased to two-thirds of its baseline, both the pressure of left renal artery (LRA) and the pressure of right renal artery (RRA) dipped below 50%, and the pressure of RRA fell more quickly than that of LRA. Uneven distribution of WSS was observed on the trunk of RA, and the lowest WSS was found at the distal of RA. The average WSS in RA dropped to around 50% as the flow rate reached one-third of its baseline. Conclusions: As a promising approach, CFD can be utilized to quantitatively evaluate the hemodynamic characteristics of RA and contribute to offsetting the drawbacks of clinical assessments of renal function, to help realize better prognosis for the patients with Fontan palliation.     

Serial evaluation of hepatic function profile after Fontan operation

Moderate persistent elevation of the γ-glutamyltransferase (γGT) level is a frequent finding during long-term follow-up of patients with total cavopulmonary connection (TCPC) for palliation of functionally univentricular hearts. Serial intraindividual data revealed a significant increase in the γGT level within a minimum 4-year interval in more than 80?% of cases. The level of γGT elevation showed a significant correlation to hemodynamic parameters such as systemic ventricular end diastolic pressure and mean pulmonary artery pressure, but did not strongly correlate with duration of follow-up or other liver function parameters, which were less frequent and less impressively deranged. None of the patients had signs of synthetic dysfunction. With increasing postoperative follow-up, abnormalities of sonographic hepatic texture including increased echogenicity, inhomogeneity, or liver surface nodularity were found. All 17 patients with liver surface nodularity had a follow-up period of over 10 years. Structural abnormalities did not correlate with biochemical or hemodynamic parameters. Doppler evaluation revealed inspiratory dependence of hepatic vein flow in more than 90?% as a relevant finding after TCPC; a decrease in portal vein flow velocity was observed in many patients. Since long-term survivors after Fontan procedure are at an increased risk of cardiac hepatopathy and cirrhosis, detailed routine investigation and monitoring of hepatic morphology are needed.     

Hybrid approach to pulmonary vein stenting after Fontan palliation

Pulmonary vein stenosis is poorly tolerated in patients who have undergone Fontan palliation and typically requires surgical or transcatheter intervention. Percutaneous transcatheter approaches to intervention can be technically difficult due to challenging anatomy. A hybrid per-atrial transcatheter approach for stenting pulmonary veins provides a direct approach to the pulmonary veins and has the potential to improve safety and efficacy of this complex intervention. We describe our experience with hybrid per-atrial pulmonary vein stenting in three patients with pulmonary vein stenosis following Fontan palliation.     

Additional aortopulmonary collaterals in patients referred for coil occlusion of a patent ductus arteriosus

Coexisting aortopulmonary collaterals in patients diagnosed with a patent ductus arteriosus (PDA) are rare findings. Percutaneous transcatheter closure of PDA and requisite aortography offer an unique opportunity to identify and treat these systemic arterial anomalies, which would be missed by echocardiographic evaluation alone. The significance of these collaterals is unclear, but it may contribute to left heart dilation from additional left to right shunting in patients with an otherwise isolated small PDA. Of 18 patients undergoing transcatheter occlusion of a PDA with Gianturco coils, 2 were found to an additional significant aortopulmonary collaterals, which were also occluded. © 1996 Wiley-Liss, Inc.     

Growth of children with a functionally single ventricle following palliation at moderately increased altitude

The bidirectional Glenn and Fontan procedures are empirically performed as interim and definitive procedures in children with a functionally single ventricle. The optimal stage of palliation, nonetheless, remains unknown. During childhood, growth is a fundamental measure of response to therapy. Growth may be influenced by the degree of cyanosis, the volume load on the ventricle, and cardiac performance. Thus, the weight and stature of children with a functionally single ventricle who underwent a bidirectional Glenn procedure or a Fontan procedure were studied to determine the effect of each intervention on growth. Z scores for weight and stature were retrospectively determined prior to palliation, at yearly intervals for 4 years, and from long-term measurements until 18 years of age in all patients with at least 2 years of observation following palliation. Growth was evaluated in 54 patients with a bidirectional Glenn procedure, and 65 patients with a Fontan procedure. The Z scores for weight were improved after each method of surgical palliation. Stature, however, was improved only following the bidirectional Glenn procedure. Growth was impaired in patients who developed protein losing enteropathy. Weight improved only during the initial 2 years after the Fontan procedure in patients who had a surgical fenestration. Over the long-term, patients who underwent a Fontan procedure were more likely to have a Z score less than -2.0 for weight and stature than patients who underwent only a bidirectional Glenn procedure. Late mortality and the incidence of heart transplantation were increased in patients who experienced a decrease in their rate of growth, defined as a negative change of more than one Z score in weight or stature, following the Fontan procedure. In conclusion, at moderately increased altitude, children with a functionally single ventricle grow more appropriately following the bidirectional Glenn procedure than following the Fontan procedure. A decrease in the rate of growth is associated with a poor prognosis following the Fontan procedure.