Use of heparin in the treatment of protein-losing enteropathy after fontan operation for complex congenital heart disease

Current diagnostic and therapeutic strategies for the management of lymphatic insufficiency in patients with hypoplastic left heart syndrome

Children with hypoplastic left heart syndrome share unique hemodynamic features that alter lymphatic integrity at all stages of palliation. Lymphatic congestion is almost universal in this patient group to some extent. It may lead to reversal of lymphatic flow, the development of abnormal lymphatic channels and ultimately decompression and loss of protein rich lymphatic fluid into extra lymphatic compartments in prone individuals. Some of the most devastating complications that are associated with single ventricle physiology, notably plastic bronchitis and protein losing enteropathy, have now been proven to be lymphatic in origin. Based on the new pathophysiologic concept new diagnostic and therapeutic strategies have recently been developed. Dynamic contrast magnetic resonance lymphangiography is now mainstay in diagnosis of lymphatic insufficiency and allows a thorough assessment of anatomy and function of the main lymphatic compartments through intranodal, intrahepatic and intramesenteric lymphatic imaging. Contrast enhanced ultrasound can evaluate thoracic duct patency and conventional fluoroscopic lymphangiography has been refined for evaluation of patients where magnetic resonance imaging cannot be performed. Novel lymphatic interventional techniques, such as thoracic duct embolization, selective lymphatic duct embolization and liver lymphatic embolization allow to seal abnormal lymphatic networks minimally invasive and have shown to resolve symptoms. Innominate vein turn-down procedures, whether surgical or interventional, have been designed to reduce lymphatic afterload and increase systemic preload effectively in the failing Fontan circulation. Outflow obstruction can now be managed with new microsurgical techniques that create lympho-venous anastomosis. Short term results for all of these new approaches are overall promising but evidence is sparse and long-term outcome still has to be defined. This review article aims to summarize current concepts of lymphatic flow disorders in single ventricle patients, discuss new emerging diagnostic and therapeutic strategies and point out lacks in evidence and needs for further research on this rapidly growing topic.

Comparative pathophysiology and management of protein-losing enteropathy

Protein‐losing enteropathy, or PLE, is not a disease but a syndrome that develops in numerous disease states of differing etiologies and often involving the lymphatic system, such as lymphangiectasia and lymphangitis in dogs. The pathophysiology of lymphatic disease is incompletely understood, and the disease is challenging to manage. Understanding of PLE mechanisms requires knowledge of lymphatic system structure and function, which are reviewed here. The mechanisms of enteric protein loss in PLE are identical in dogs and people, irrespective of the underlying cause. In people, PLE is usually associated with primary intestinal lymphangiectasia, suspected to arise from genetic susceptibility, or “idiopathic” lymphatic vascular obstruction. In dogs, PLE is most often a feature of inflammatory bowel disease (IBD), and less frequently intestinal lymphangiectasia, although it is not proven which process is the true driving defect. In cats, PLE is relatively rare. Review of the veterinary literature (1977‐2018) reveals that PLE was life‐ending in 54.2% of dogs compared to published disease‐associated deaths in IBD of <20%, implying that PLE is not merely a continuum of IBD spectrum pathophysiology. In people, diet is the cornerstone of management, whereas dogs are often treated with immunosuppression for causes of PLE including lymphangiectasia, lymphangitis, and crypt disease. Currently, however, there is no scientific, extrapolated, or evidence‐based support for an autoimmune or immune‐mediated mechanism. Moreover, people with PLE have disease‐associated loss of immune function, including lymphopenia, severe CD4+ T‐cell depletion, and negative vaccinal titers. Comparison of PLE in people and dogs is undertaken here, and theories in treatment of PLE are presented.

A potentially curative fetal intervention for hypoplastic left heart syndrome

Hypoplastic left heart syndrome (HLHS) encapsulates a spectrum of complex congenital cardiovascular malformations involving varying degrees of underdevelopment of the left-sided heart structures. However, despite improved survival rates since the introduction of staged surgical reconstruction, treatment options for HLHS remain palliative rather than curative. A major limiting factor in the development of definitive curative therapy for HLHS is an incomplete understanding of its pathogenesis. Currently, the aetiology HLHS is best conceptualised by the 'flow theory' of cardiogenesis, which states that normal cardiac development is reliant on the interrelationship of normal flow patterns of blood through the developing heart, and appropriate growth of the cardiac valves and myocardium. Thus, congenital cardiac malformations, such as HLHS, are thought to arise when these two processes are incorrectly coupled in utero. The rationale for the hypothesis proposed herein rests upon the flow theory of cardiogenesis. Morphological studies of HLHS indicate that, although underdeveloped, all left-sided cardiac structures are present and anatomically correct. Further, of the various structural abnormalities that can occur within the spectrum of HLHS, the presence of a ventricular septal defect (VSD) is rare. The rarity of a VSD within the morphological spectrum of HLHS suggests the syndrome may not develop in the presence of a functionally significant VSD. Presumably, the presence of a functional VSD establishes a communication between the two ventricles during cardiac development, and preserves the normal pressure-flow-dependent growth of the left ventricular (LV) myocardium, despite inflow/outflow valve defects. It is proposed that surgical creation of a VSD in utero will 'rescue' the LV of hearts with left-sided valvular deformities that render them susceptible to the development of HLHS later in gestation. In evaluating this hypothesis, potential techniques for surgical creation of a VSD in utero are offered. These techniques are based on already established catheter-based in utero interventions, and conventional postnatal percutaneous procedures for VSD creation. Further discussion is also offered on techniques to avoid, and manage, potential complications (i.e. conduction system damage) of the proposed technique(s). Finally, if VSD creation in utero is indeed practically feasible, and successfully establishes the hypothesised hemodynamic and myocardial growth normalisation within the abnormally developing LV, the clinical implications are profound. This procedure may hold a potential cure for almost every sub-type of HLHS.

Diagnosis and Management of Noncardiac Complications in Adults With Congenital Heart Disease: A Scientific Statement From the American Heart Association

Life expectancy and quality of life for those born with congenital heart disease (CHD) have greatly improved over the past 3 decades. While representing a great advance for these patients, who have been able to move from childhood to successful adult lives in increasing numbers, this development has resulted in an epidemiological shift and a generation of patients who are at risk of developing chronic multisystem disease in adulthood. Noncardiac complications significantly contribute to the morbidity and mortality of adults with CHD. Reduced survival has been documented in patients with CHD with renal dysfunction, restrictive lung disease, anemia, and cirrhosis. Furthermore, as this population ages, atherosclerotic cardiovascular disease and its risk factors are becoming increasingly prevalent. Disorders of psychosocial and cognitive development are key factors affecting the quality of life of these individuals. It is incumbent on physicians who care for patients with CHD to be mindful of the effects that disease of organs other than the heart may have on the well-being of adults with CHD. Further research is needed to understand how these noncardiac complications may affect the long-term outcome in these patients and what modifiable factors can be targeted for preventive intervention.

Gastrointestinal haemorrhage due to lymphangiectasia caused by protein-losing enteropathy in the Fontan circulation

We report the case of a 14-year-old boy with severe protein-losing enteropathy after Fontan surgery that led to lymphangiectasia, which caused gastrointestinal haemorrhage and required invasive treatment to stop the bleeding. Through this case and a review of the literature on protein-losing enteropathy after Fontan surgery, we highlight a rare and serious presentation of the disease and the difficulties of diagnosis and management.

Clinical outcomes and improved survival in patients with protein-losing enteropathy after the Fontan operation

BACKGROUND

Patients with protein-losing enteropathy (PLE) following the Fontan operation have a reported 50% mortality at 5 years after diagnosis.

OBJECTIVES

The aim of this study was to review outcomes in patients with PLE following the Fontan operation.

METHODS

From 1992 to 2010, 42 patients (55% male) with PLE following the Fontan operation were identified from clinical databases at the Mayo Clinic. Data were collected retrospectively.

RESULTS

Mean age at PLE diagnosis was 18.9 ± 11.0 years. Initial Fontan operation was performed at 10.1 ± 10.8 years of age. Mean time from Fontan operation to PLE diagnosis was 8.4 ± 14.2 years. Survival was 88% at 5 years. Decreased survival was seen in patients with high Fontan pressure (mean >15 mm Hg; p = 0.04), decreased ventricular function (ejection fraction <55%; p = 0.03), and New York Heart Association functional class >2 at diagnosis (p = 0.04). Patients who died had higher pulmonary vascular resistance (3.8 ± 1.6 Wood units [WU] vs. 2.1 ± 1.1 WU; p = 0.017), lower cardiac index (1.6 ± 0.4 l/min/m(2) vs. 2.7 ± 0.7 l/min/m(2); p < 0.0001), and lower mixed venous saturation (53% vs. 66%; p = 0.01), compared with survivors. Factors were assessed at the time of PLE diagnosis. Treatments used more frequently in survivors with PLE included spironolactone (21 [68%]), octreotide (7 [21%]), sildenafil (6 [19%]), fenestration creation (15 [48%]), and relief of Fontan obstruction (7 [23%]).

CONCLUSIONS

PLE remains difficult to treat; however, in the current era, survival has improved with advances in treatment. Further study is needed to better understand the mechanism of disease and ideal treatment strategy.

Clinical research priorities in adult congenital heart disease

BACKGROUND

Adult congenital heart disease (ACHD) clinicians are hampered by the paucity of data to inform clinical decision-making. The objective of this study was to identify priorities for clinical research in ACHD.

METHODS

A list of 45 research questions was developed by the Alliance for Adult Research in Congenital Cardiology (AARCC), compiled into a survey, and administered to ACHD providers. Patient input was sought via the Adult Congenital Heart Association at community meetings and online forums. The 25 top questions were sent to ACHD providers worldwide via an online survey. Each question was ranked based on perceived priority and weighted based on time spent in ACHD care. The top 10 topics identified are presented and discussed.

RESULTS

The final online survey yielded 139 responses. Top priority questions related to tetralogy of Fallot (timing of pulmonary valve replacement and criteria for primary prevention ICDs), patients with systemic right ventricles (determining the optimal echocardiographic techniques for measuring right ventricular function, and indications for tricuspid valve replacement and primary prevention ICDs), and single ventricle/Fontan patients (role of pulmonary vasodilators, optimal anticoagulation, medical therapy for preservation of ventricular function, treatment for protein losing enteropathy). In addition, establishing criteria to refer ACHD patients for cardiac transplantation was deemed a priority.

CONCLUSIONS

The ACHD field is in need of prospective research to address fundamental clinical questions. It is hoped that this methodical consultation process will inform researchers and funding organizations about clinical research topics deemed to be of high priority.

Oral budesonide as a therapy for protein-losing enteropathy in patients having undergone Fontan palliation

BACKGROUND

  Protein-losing enteropathy is associated with Fontan palliation for single-ventricle physiology and has been difficult to treat. Limited data suggest the successful use of oral budesonide (Entocort, AstraZeneca) as a palliative measure.

METHODS

  We examine our single-institution retrospective experience in eight patients who were treated with this therapy.

RESULTS

  Median pretherapy albumin level was 1.7 g/dL (range 1.0-2.7 g/dL), 3 months after therapy was 3.1 g/dL (range 2-4.8 g/dL), and by the end of the first year was 3.4 g/dL (range 2.1-5.3 g/dL). All patients had at least a transient improvement, and at latest follow-up (median 29 months, range 3-51 months) five patients remain on therapy. Five of eight patients had required pretherapy albumin transfusions; one patient required albumin infusions after therapy. Four patients had side effects associated with the medication.

CONCLUSIONS

  Oral budesonide is an additional therapy that has the potential to improve symptoms and delay need for heart transplantation in this patient population.

The failing Fontan: etiology, diagnosis and management

While the Fontan operation has facilitated the survival of a generation of children born with congenital heart disease resulting in a functional single ventricle, it does not recreate a normal circulation. Over time, survivors of the Fontan operation are at risk for ventricular dysfunction, plastic bronchitis, protein-losing enteropathy and chronic Fontan failure. New techniques and therapies are emerging to address the long-term risks associated with Fontan physiology, but as the number of survivors continues to grow, the recognition of the limitations of this circulation is increasing. Novel investigations of possible mechanical devices designed to function as a subpulmonary ventricle are underway, but are still many years away from clinical use. In the meantime, continued development of medical therapeutics targeted at the specific problems of the Fontan circulation will be beneficial and might reduce the need for cardiac transplantation.

Protein-losing enteropathy: integrating a new disease paradigm into recommendations for prevention and treatment

Protein-losing enteropathy is a relatively uncommon complication of Fontan procedures for palliation of complex congenital cardiac disease. However, the relative infrequency of protein-losing enteropathy belies the tremendous medical, psychosocial and financial burdens it places upon afflicted patients, their families and the healthcare system that supports them. Unfortunately, because of the complexity and rarity of this disease process, the pathogenesis and pathophysiology of protein-losing enteropathy remain poorly understood, and attempts at treatment seldom yield long-term success. The most comprehensive analyses of protein-losing enteropathy in this patient population are now over a decade old, and re-evaluation of the prevalence and progress in treatment of this disease is needed. This report describes a single institution experience with the evaluation, management, and treatment of protein-losing enteropathy in patients with congenital cardiac disease in the current era, follows with a comprehensive review of protein-losing enteropathy, focused upon what is known and not known about the pathophysiology of protein-losing enteropathy in this patient population, and concludes with suggestions for prevention and treatment.

The Fontan pathway: What's down the road?

The Fontan circulation results from routing of the systemic venous blood to the pulmonary circulation without a hydraulic source of a ventricle. Although a hypertrophied right atrium was thought to be essential for this circulation, the current form of the operation has neither the right atrium nor any valves in the venous circulation that is connected to the pulmonary arteries directly. Modifications in the operative model was one of the early steps in improving outcome. Use of fenestration, staging of Fontan completion and better perioperative management have led to a significant drop in mortality rates in the current era. Despite this, there is late attrition of patients with complications such as arrhythmias, ventricular dysfunction, and unusual clinical syndromes of protein-losing enteropathy (PLE) and plastic bronchitis. Management of failing Fontan includes a detailed hemodynamic and imaging assessment to treat any correctable lesions such as obstruction within the Fontan circuit, early control of arrhythmia and maintenance of sinus rhythm, symptomatic treatment for PLE and plastic bronchitis, manipulation of systemic and pulmonary vascular resistance, and Fontan conversion of less favorable atriopulmonary connection to extra-cardiac total cavopulmonary connection with arrythmia surgery. Cardiac transplantation remains the only successful definitive palliation in the failing Fontan patients.

Protein-losing enteropathy after Fontan operation

Protein-losing enteropathy (PLE) is a poorly understood and enigmatic disease process affecting patients with single ventricle after Fontan operation. In those afflicted, PLE after Fontan operation results in significant morbidity and mortality. The pathophysiology of the disease is unknown; however, a proposed mechanism incorporates a combination of phenomena including: (1) altered hemodynamics, specifically low cardiac output; (2) increased mesenteric vascular resistance; (3) systemic inflammation; and (4) altered enterocyte basal membrane glycosaminoglycan make-up. A paradigm for the clinical management of PLE after Fontan operation is proposed.

Heparan sulfate and syndecan-1 are essential in maintaining murine and human intestinal epithelial barrier function

Patients with protein-losing enteropathy (PLE) fail to maintain intestinal epithelial barrier function and develop an excessive and potentially fatal efflux of plasma proteins. PLE occurs in ostensibly unrelated diseases, but emerging commonalities in clinical observations recently led us to identify key players in PLE pathogenesis. These include elevated IFN-gamma, TNF-alpha, venous hypertension, and the specific loss of heparan sulfate proteoglycans from the basolateral surface of intestinal epithelial cells during PLE episodes. Here we show that heparan sulfate and syndecan-1, the predominant intestinal epithelial heparan sulfate proteoglycan, are essential in maintaining intestinal epithelial barrier function. Heparan sulfate- or syndecan-1-deficient mice and mice with intestinal-specific loss of heparan sulfate had increased basal protein leakage and were far more susceptible to protein loss induced by combinations of IFN-gamma, TNF-alpha, and increased venous pressure. Similarly, knockdown of syndecan-1 in human epithelial cells resulted in increased basal and cytokine-induced protein leakage. Clinical application of heparin has been known to alleviate PLE in some patients but its unknown mechanism and severe side effects due to its anticoagulant activity limit its usefulness. We demonstrate here that non-anticoagulant 2,3-de-O-sulfated heparin could prevent intestinal protein leakage in syndecan-deficient mice, suggesting that this may be a safe and effective therapy for PLE patients.

Using heparin therapy to reverse protein-losing enteropathy in a patient with CDG-Ib

BACKGROUND

A 22-year-old female presented with edema, diarrhea, hypoalbuminemia and pancytopenia. She had previously been diagnosed with congenital disorder of glycosylation type Ib, and had a history of congenital hepatic fibrosis, portal hypertension and esophageal varices. In the past she had refused mannose therapy because of associated diarrhea and abdominal pain.

INVESTIGATIONS

Laboratory examinations, abdominal ultrasonography, bacterial and viral cultures of blood, urine and stools, double-balloon enteroscopy and fecal excretion test using 51Cr-labeled albumin.

DIAGNOSIS

Protein-losing enteropathy.

MANAGEMENT

Infusion of albumin followed by intravenous and subcutaneous therapy with unfractionated heparin.

Usefulness of heparin therapy in protein-losing enteropathy associated with single ventricle palliation

This retrospective study was designed to evaluate the effectiveness of subcutaneous heparin therapy for the treatment of protein-losing enteropathy (PLE) associated with single-ventricle palliation and to evaluate the side effects of long-term heparin use. PLE affects 4% to 13% of Fontan operative survivors. Five-year survival after onset of PLE is only 46% to 59%. We studied a cohort of patients with single-ventricle palliation who developed PLE and were treated with subcutaneous heparin. Seventeen patients were included in the study. Symptoms of PLE appeared on average 43 months after surgical palliation. At diagnosis of PLE, mean albumin level was 2.0 +/- 0.4 g/dl. At cardiac catheterization, mean systemic venous pressure was 11.6 mm Hg. Subjective symptomatic improvement on heparin therapy occurred in 13 patients (76%). Three patients (18%) went into clinical remission. Compared with the period before initiation of heparin, there was no significant difference in the number of hospital admissions (p = 0.99) or albumin infusions (p = 0.88) during the first year of heparin therapy. Five patients had x-rays of their thoracolumbar spine, and 9 patients had bone mineral analyses; all scans were grossly abnormal. In conclusion, subcutaneous heparin therapy leads to subjective improvement of PLE symptoms in most patients; however, it does not change the need for frequent albumin infusions and does not increase the rate of remission above that for standard medical therapy.

Resolution of protein-losing enteropathy with low-molecular weight heparin in an adult patient with Fontan palliation

Protein-losing enteropathy is a well-known complication after the Fontan procedure, and unfractionated heparin therapy has been tried with some success as a potential therapy. Low-molecular weight heparin is believed to be ineffective. We now describe a case in which an adult patient with protein-losing enteropathy after Fontan palliation was successfully treated with systemic doses of low-molecular weight heparin, with complete resolution in the 24-hour fecal alpha-1 anti-trypsin level and serum albumin. The patient continues to remain in remission with this therapy. In conclusion, these findings are novel and compel us to re-evaluate our pathophysiologic understanding of this difficult condition.

Results of transcatheter Fontan fenestration to treat protein losing enteropathy

Transcatheter fenestration to create an interatrial communication has been used to treat patients with protein losing enteropathy (PLE) after Fontan operation. No systematic data have been reported assessing the results of this procedure. Our institutional database was queried to identify patients after Fontan operation who had transcatheter fenestration to treat PLE. Clinical notes, laboratory data, echocardiograms, and cardiac catheterization data were reviewed. From 1995 to 2005, 16 transcatheter fenestration procedures were performed in seven patients. Median age at fenestration was 18 years (range 13-41 years). Median duration of follow-up was 3.6 years (range 0.2-10.4 years). Techniques for fenestration included blade/balloon septostomy, stent placement, Amplatzer-fenestrated ASD device, and balloon dilation of previous stent. Size of the fenestration created was 5.2 +/- 1.1 mm. Systemic venous pressure remained unchanged after fenestration. Cardiac index increased significantly. Reduction of ascites and edema was noted after 9 of the 16 procedures. Ten of 16 (63%) of fenestrations spontaneously occluded. Three patients are free of ascites although recurrence of PLE occurred in all. One patient with a patent fenestration continues to have ascites. Two patients had Fontan takedown. One patient had conversion to a fenestrated extracardiac conduit Fontan and died postoperatively. The results of transcatheter Fontan fenestration are often disappointing. Maintaining fenestration patency is difficult. Even after "successful" fenestration, resolution of PLE may be incomplete and recurrences have occurred in all. Early consideration should be given to Fontan takedown or cardiac transplant in severely symptomatic patients with PLE who do not respond to fenestration. Transcatheter fenestration may be a bridge to a definitive procedure.

Applied glycoproteomics—approaches to study genetic-environmental collisions causing protein-losing enteropathy

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a life-threatening symptom associated with seemingly unrelated conditions including Crohn's disease, congenital disorder of glycosylation, or Fontan surgery to correct univentricular hearts. Emerging commonalities between these and other disorders led us to hypothesize that PLE develops when genetic insufficiencies collide with simultaneous or sequential environmental insults. Most intriguing is the loss of heparan sulfate (HS) proteoglycans (HSPG) specifically from the basolateral surface of intestinal epithelial cells only during PLE episodes suggesting a direct link to protein leakage. Reasons for HSPG loss are unknown, but genetic insufficiencies affecting HSPG biosynthesis, trafficking, or degradation may be involved. Here, we describe cell-based assays we devised to identify key players contributing to protein leakage. Results from these assays confirm that HS loss directly causes protein leakage, but more importantly, it amplifies the effects of other factors, e.g., cytokines and increased pressure. Thus, HS loss appears to play a central role for PLE. To transfer our in vitro results back to the in vivo situation, we established methods to assess enteric protein leakage in mice and present several genetically deficient strains mimicking intestinal HS loss observed in PLE patients. Preliminary results indicate that mice with haploinsufficient genes involved in HS biosynthesis or HSPG trafficking develop intestinal protein leakage upon additional environmental stress. Our goal is to model PLE in vitro and in vivo to unravel the pathomechanisms underlying PLE, identify patients at risk, and provide them with a safe and effective therapy.

Heparan Sulfate Plays a Central Role in a Dynamic in Vitro Model of Protein-losing Enteropathy

Protein-losing enteropathy (PLE), the loss of plasma proteins through the intestine, is a symptom in ostensibly unrelated diseases. Emerging commonalities indicate that genetic insufficiencies predispose for PLE and environmental insults, e.g. viral infections and inflammation, trigger PLE onset. The specific loss of heparan sulfate (HS) from the basolateral surface of intestinal epithelial cells only during episodes of PLE suggests a possible mechanistic link. In the first tissue culture model of PLE using a monolayer of intestinal epithelial HT29 cells, we proved that HS loss directly causes protein leakage and amplifies the effects of the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha). Here, we extend our in vitro model to assess the individual and combined effects of HS loss, interferon gamma (IFNgamma), TNFalpha, and increased pressure, and find that HS plays a central role in the patho-mechanisms underlying PLE. Increased pressure, mimicking venous hypertension seen in post-Fontan PLE patients, substantially increased protein leakage, but HS loss, IFNgamma, or TNFalpha alone had only minor effects. However, IFNgamma up-regulated TNFR1 expression and amplified TNFalpha-induced protein leakage. IFNgamma and TNFalpha compromised the integrity of the HT29 monolayer and made it more susceptible to increased pressure. HS loss itself compromises the integrity of the monolayer, amplifying the effects of pressure, but also amplifies the effects of both cytokines. In the absence of HS a combination of increased pressure, IFNgamma, and TNFalpha caused maximum protein leakage. Soluble heparin fully compensated for HS loss, providing a reasonable explanation for patient favorable response to heparin therapy.

Heparan sulfate depletion amplifies TNF-alpha-induced protein leakage in an in vitro model of protein-losing enteropathy

Protein-losing enteropathy (PLE), the excessive loss of plasma proteins through the intestine, often correlates with the episodic loss of heparan sulfate (HS) proteoglycans (HSPG) from the basolateral surface of intestinal epithelial cells. PLE onset is often associated with a proinflammatory state. We investigated whether loss of HS or treatment with the proinflammatory cytokine TNF-alpha directly causes protein leakage and whether a combination of both exacerbates this process. We established the first in vitro model of PLE and measured the flux of albumin/FITC through a monolayer of intestinal HT29 or Caco-2 cells grown on transwells and determined the integrity by transepithelial electrical resistance (TER). Loss of HS from the basolateral surface, either by heparanase digestion or by inhibition of HS synthesis, increased albumin flux 1.58 +/- 0.09-fold and reduced TER by 23.4 +/- 6.5%. TNF-alpha treatment increased albumin flux 4.04 +/- 0.03-fold and reduced TER by 75.7 +/- 4.7% but only slightly decreased HS content. The combined effects of HS loss and TNF-alpha treatment were not only additive, but synergistic, with a 7.00 +/- 0.11-fold increase in albumin flux and a 83.9 +/- 8.1% reduction of TER. Coincubation of TNF-alpha with soluble HS or heparin abolished these synergistic effects. Loss of basolateral HS directly causes protein leakage and amplifies the effects of the proinflammatory cytokine TNF-alpha. Our findings imply that loss of HSPGs renders patients more susceptible to PLE and offer a potential explanation for the favorable response some PLE patients have to heparin therapy.

Acquired combined immunodeficiency associated with protein losing enteropathy complicating Fontan operation

It is vitally important that the immunological aspect of protein losing enteropathy following Fontan procedures is highlighted, in order to decrease significant morbidity and mortality

Successful resection of localized intestinal lymphangiectasia post-Fontan: role of (99m)technetium-dextran scintigraphy

Intestinal lymphangiectasia is a well-recognized complication of the Fontan procedure, occurring in up to 24% of patients. Because of the loss of chylous fluid into the gut lumen, protein-losing enteropathy results as well as lymphopenia and hypogammaglobulinaemia. In some cases, dilated lymphatics in the intestinal serosa or mesentery also rupture, causing chylous ascites. Standard medical and cardiac surgical interventions are generally ineffective and the condition is frequently lethal. We report a case of intractable and life-threatening chylous ascites and chylothorax in a 14-year-old girl, associated with intestinal lymphangiectasia and protein-losing enteropathy after a Fontan procedure for tricuspid atresia. The condition was refractory to all standard medical therapies, including dietary modifications, diuretics, corticosteroid therapy, albumin infusions, octreotide, heparin, bowel rest, and parenteral nutrition. Cardiac surgery to optimize her hemodynamic status was also ineffective and large volume pleural and ascitic fluid losses continued. Having exhausted all other therapeutic modalities, (99m)technetium-dextran scintigraphy was performed to assess the extent of intestinal protein loss and the potential for surgical intervention. Scintigraphy suggested localized protein loss from the proximal jejunum and subsequent segmental resection was effective. Postoperatively, ascites and pleural effusions resolved, and there was no evidence of short bowel syndrome. Growth has accelerated and the patient has entered puberty. There is mild persistent intestinal protein loss requiring diuretic therapy. Ascites or pleural effusions are absent, and the patient remains well >2 years after surgery. Intestinal lymphangiectasia post-Fontan procedures has traditionally been ascribed to hemodynamic factors such as raised systemic venous pressure, which would predispose to a generalized intestinal lesion. However, in this case, scintigraphy demonstrated a localized, surgically correctible lesion. To our knowledge, this is the first reported case of the use of (99m)technetium-dextran scintigraphy for this indication and of successful partial small bowel resection in such a case.

Improvement of protein-losing enteropathy by coil embolization of the left azygos vein

We report a 17-year-old boy with double-outlet right ventricle, atrioventricular septal defect, pulmonary stenosis, and persistent left superior vena cava who developed a protein-losing enteropathy, which was cured by coil embolization of the left azygos vein, thereby interrupting the vein-to-vein shunt.

Protein-losing enteropathy in patients with Fontan circulation: is it triggered by infection?

INTRODUCTION

Protein-losing enteropathy (PLE) is a recognised complication of the Fontan circulation. Its pathogenesis is not fully understood, however, and it is unclear why its onset occurs months or even years after Fontan surgery.

PATIENTS

We report a 4.5-year-old girl with Fontan circulation who developed PLE almost 1 year after surgery. At the time of onset the patient had rotavirus enteritis and streptococcal tonsillitis. We have reviewed the records of seven other patients with longstanding PLE. In six of these patients we identified infections at the onset of symptoms. None of our patients had evidence of opportunistic infection.

DISCUSSION AND CONCLUSION

The immune system of patients with PLE is compromised, but reports on recurrent opportunistic infections are rare. The present observations suggest that infection and inflammation may be associated with the onset of PLE. The mechanism of how infection may trigger PLE warrants further investigation.

Plastic bronchitis in children with Fontan palliation: analogue to protein losing enteropathy?

We studied a 6-year-old boy and a 2-year-old girl with bronchitis fibroplastica following Fontan operation. Large endobronchial casts of rubber-like consistency resulted in life-threatening pulmonary failure. In one patient symptoms improved after optimizing heart function with diuretics, and in the other a dramatic improvement with the resolution of the clinical symptoms and normalized serum albumin followed subcutaneous high-molecular-weight heparin treatment. The severe relapse after discontinuation of the heparin medication and the once more successful treatment with heparin suggest that in addition to optimizing heart function, high-molecular-weight heparin might be a therapeutic option for this poorly understood condition.

The role of the Fontan procedure in the surgical treatment of congenital heart malformations with double-outlet right ventricle

The Fontan procedure in one of its many modifications is applicable to the surgical treatment of those patients with double-outlet right ventricle who are not amenable to bi-ventricular correction. Included in this group are patients with significant hypoplasia of one of the ventricles, patients with distant (non-committed) ventricular septal defect, patients with significant straddling of the atrioventricular valves, patients with abnormal atrioventricular connections (such as absence of one of the valves), or common atrioventricular valve connection. The presence of complex associated lesions such as those seen in the heterotaxia syndromes may, by virtue of the surgical risk of attempts at bi-ventricular repair, make the Fontan approach a suitable option for these patients. The presence of a subaortic conus and the potential for subaortic obstruction, a frequent findings in patients with double outlet right ventricle, plays an important role in the preparation and conduct of the Fontan operation. Copyright 2000 by W.B. Saunders Company

Reversal of protein-losing enteropathy in a child with Fontan circulation is correlated with central venous pressure after heart transplantation

We report on the reversal of protein-losing enteropathy (PLE) after heart transplantation (HTx) in a 10-yr-old boy with Fontan circulation, previously treated unsuccessfully with heparin for several months. The protein loss continued immediately after the Tx. During the following month, however, a gradual decrease in protein loss was observed, which correlated with a decrease in the inferior vena cava (IVC) pressure. The patient is doing well with a normal serum albumin level and a normal IVC pressure, 2 yr after Tx.

The Fontan procedure for tricuspid atresia: early and late results of a 25-year experience with 216 patients

OBJECTIVES

We assessed the operative and late mortality and the present clinical status of 216 patients with tricuspid atresia who had a nonfenestrated Fontan procedure performed at the Mayo Clinic in the 25-year period 1973 to 1998.

BACKGROUND

The Fontan operation eliminates the systemic hypoxemia and ventricular volume overload characteristic of prior forms of palliation. However, it originally did so at the cost of systemic venous and right atrial hypertension, and the long-term effects of this "price" were unknown when the procedure was initially proposed.

METHODS

We reviewed the clinical records of the 216 patients retrospectively. These were arbitrarily grouped into early (1973 through 1980), middle (1981 through 1987) and late (1988 through 1997) surgical eras. Patient outcome was also analyzed according to age at surgery. Operative and late mortality rates were determined and present clinical status was ascertained in 167 of 171 surviving patients.

RESULTS

Overall survival was 79%. Operative mortality steadily declined and was 2% (one of 58 patients) during the most recent decade. Late survival also continues to improve. Age at operation had no effect on operative mortality, and late mortality was significantly increased only in patients who were operated on at age 18 years or older. Eighty-nine percent of surviving patients are currently in New York Heart Association class I or II.

CONCLUSIONS

The initial 25-year experience with the nonfenestrated Fontan procedure for tricuspid atresia has been gratifying, with most survivors now leading lives of good quality into adulthood. These results justify continued application of this procedure for children born with tricuspid atresia.

Protein-Losing Enteropathy and Gastropathy

The diagnosis of protein-losing enteropathy (PLE) should be considered in all patients with hypoalbuminemia and edema without other known causes, and established by plasma alpha(1)-antitrypsin (alpha(1)-AT) clearance or nuclear studies. The therapy for PLE should focus principally on the treatment of the underlying disease after it has been identified. Therapeutic goals should include improvement of hypoalbuminemia, edema, and lymphopenia. The existing primary literature for therapy of PLE syndromes consists mainly of case reports and expert opinions, subject to substantial reporting bias and unknown rates of spontaneous remission; the rarity of and the diversity among this set of diseases make future large randomized trials unlikely. Therapeutic choices, therefore, must involve clinical acumen, empiricism, and understanding of the pathophysiology of the underlying disease process, and must be tailored to each individual patient's syndrome. Dietary interventions including hypolipidic, high-protein regimens, supplemented by medium-chain triglycerides (MCTs), are extremely useful, particularly in protein loss due to increased lymphatic pressure. Corticosteroids can be very useful in certain cases of PLE (though not without substantial long-term toxicity) when clinical serologic or histologic markers of inflammatory disease are present. Octreotide is a well tolerated drug that has been demonstrated to improve PLE in some patients, and is worth consideration. Octreotide is a well tolerated drug that has been demonstrated to improve PLE in some patients, and is worth consideration. Surgery finds its best role in treating gastrointestinal protein loss from neoplasia, inflammatory bowel disease, and hypertrophic gastritis. Most other PLEs are distributed too widely for surgical intervention. Protein-losing gastropathy (PLG) behaves somewhat differently from the general group of PLE, marked by excellent responses to elimination of Helicobacter pylori, antisecretory therapy, and surgical resection. Protein-losing enteropathy stemming from cardiovascular disease is best treated by medical or surgical cardiovascular interventions; however, some patients may respond to mucosa-directed therapy.

Congenital heart disease: current indications for antithrombotic therapy in pediatric patients

This report reviews the current status of antithrombotic therapy, including anti-platelet therapy, in pediatric patients with congenital heart disease. The current medications utilized and dose recommendations are emphasized, and indications for their use are reviewed.

Reduced heparan sulfate accumulation in enterocytes contributes to protein-losing enteropathy in a congenital disorder of glycosylation

Intestinal biopsy in a boy with gastroenteritis-induced protein-losing enteropathy (PLE) showed loss of heparan sulfate (HS) and syndecan-1 core protein from the basolateral surface of the enterocytes, which improved after PLE subsided. Isoelectric focusing analysis of serum transferrin indicated a congenital disorder of glycosylation (CDG) and subsequent analysis showed three point mutations in the ALG6 gene encoding an alpha1,3-glucosyltransferase needed for the addition of the first glucose to the dolichol-linked oligosaccharide. The maternal mutation, C998T, causing an A333V substitution, has been shown to cause CDG-Ic, whereas the two paternal mutations, T391C (Y131H) and C924A (S308R) have not previously been reported. The mutations were tested for their ability to rescue faulty N:-linked glycosylation of carboxypeptidase Y in an ALG6-deficient Saccharomyces cerevisiae strain. Normal human ALG6 rescues glycosylation and A333V partially rescues, whereas the combined paternal mutations (Y131H and S308R) are ineffective. Underglycosylation resulting from each of these mutations is much more severe in rapidly dividing yeast. Similarly, incomplete protein glycosylation in the patient is most severe in rapidly dividing enterocytes during gastroenteritis-induced stress. Incomplete N:-linked glycosylation of an HS core protein and/or other biosynthetic enzymes may explain the selective localized loss of HS and PLE.