Pulmonary AV malformations after superior cavopulmonary connection: resolution after inclusion of hepatic veins in the pulmonary circulation

Hepatopulmonary syndrome: update on recent advances in pathophysiology, investigation, and treatment

Hepatopulmonary syndrome (HPS) is an important cause of dyspnea and hypoxia in the setting of liver disease, occurring in 10-30% of patients with cirrhosis. It is due to vasodilation and angiogenesis in the pulmonary vascular bed, which leads to ventilation-perfusion mismatching, diffusion limitation to oxygen exchange, and arteriovenous shunting. There is evidence, primarily from animal studies, that vasodilation is mediated by a number of endogenous vasoactive molecules, including endothelin-1 and nitric oxide (NO). In experimental HPS, liver injury stimulates release of endothelin-1 and results in increased expression of ET(B) receptors on pulmonary endothelial cells, leading to upregulation of endothelial NO synthase (eNOS) and subsequent increased production of NO, which causes vasodilation. In addition, increased phagocytosis of bacterial endotoxin in the lung not only promotes stimulation of inducible NO synthase, which increases NO production, but also contributes to intrapulmonary accumulation of monocytes, which may stimulate angiogenesis via vascular endothelial growth factor pathway. Despite these insights into the pathogenesis of experimental HPS, there is no established medical therapy, and liver transplantation remains the main treatment for symptomatic HPS, although selected patients may benefit from other surgical or radiological interventions. In this review, we focus on recent advances in our understanding of the pathophysiology of HPS, and discuss current approaches to the investigation and treatment of this condition.

Inhaled nitric oxide improves oxygen saturation in children with pulmonary arteriovenous malformations after the Fontan procedure

OBJECTIVE

To report the utility of inhaled nitric oxide to ameliorate excessive hypoxemia in children with pulmonary arteriovenous malformations after the Fontan procedure.

DESIGN

Case series.

SETTING

A tertiary pediatric cardiac intensive care unit in a freestanding children's hospital.

PATIENTS

Three children with complex congenital heart disease and pulmonary arteriovenous malformations who underwent the Fontan procedure.

INTERVENTIONS

The 3 patients all exhibited moderate-to-severe hypoxemia in the immediate postoperative period. The hypoxemia persisted despite mechanical ventilation and oxygen at an Fio2 of 1.0. Inhaled nitric oxide was initiated with immediate and dramatic improvements in oxygen saturation in all patients. All patients were eventually weaned off inhaled nitric oxide.

CONCLUSIONS

The use of inhaled nitric oxide in patients with pulmonary arteriovenous malformations after having the Fontan procedure improves hypoxemia and may potentially reduce postoperative morbidity, unnecessary testing, and duration of hospital stay.

Challenges of Univentricular Physiology in Heterotaxy

Patients with heterotaxy syndrome exhibit an extensive constellation of congenital cardiac malformations, making these patients a challenging group to manage surgically. Many of these patients' hearts do not lend themselves to separation of the pulmonary and systemic circulations except by some modification of the Fontan procedure. Palliative procedures early in life are directed at creating a satisfactory balance of pulmonary and systemic blood flow and at the same time ensuring unobstructed pulmonary venous return. Early conversion from parallel pulmonary and systemic circulations to superior cavopulmonary connections is important, to reduce volume work of the systemic ventricle. Heterotaxy patients are generally considered a high-risk population with respect to eventual Fontan procedure. It is important to appreciate the unique and variable anatomy of the sinus node and conduction system and the potential for occult pulmonary venous obstruction, atrioventricular valve regurgitation, and recurrent cyanosis, which may be related to the development of pulmonary arteriovenous malformations.

Individualized computer-based surgical planning to address pulmonary arteriovenous malformations in patients with a single ventricle with an interrupted inferior vena cava and azygous continuation

OBJECTIVE

Pulmonary arteriovenous malformations caused by abnormal hepatic flow distribution can develop in patients with a single ventricle with an interrupted inferior vena cava. However, preoperatively determining the hepatic baffle design that optimizes hepatic flow distribution is far from trivial. The current study combines virtual surgery and numeric simulations to identify potential surgical strategies for patients with an interrupted inferior vena cava.

METHODS

Five patients with an interrupted inferior vena cava and severe pulmonary arteriovenous malformations were enrolled. Their in vivo anatomies were reconstructed from magnetic resonance imaging (n = 4) and computed tomography (n = 1), and alternate virtual surgery options (intracardiac/extracardiac, Y-grafts, hepato-to-azygous shunts, and azygous-to-hepatic shunts) were generated for each. Hepatic flow distribution was assessed for all options using a fully validated computational flow solver.

RESULTS

For patients with a single superior vena cava (n = 3), intracardiac/extracardiac connections proved dangerous, because even a small left or right offset led to a highly preferential hepatic flow distribution to the associated lung. The best results were obtained with either a Y-graft spanning the Kawashima to split the flow or hepato-to-azygous shunts to promote mixing. For patients with bilateral superior vena cavae (n = 2), results depended on the balance between the left and right superior inflows. When those were equal, connecting the hepatic baffle between the superior vena cavae performed well, but other options should be pursued otherwise.

CONCLUSIONS

This study demonstrates how virtual surgery environments can benefit the clinical community, especially for patients with a single ventricle with an interrupted inferior vena cava. Furthermore, the sensitivity of the optimal baffle design to the superior inflows underscores the need to characterize both preoperative anatomy and flows to identify the best option.

The Fontan procedure: evolution in technique; attendant imperfections and transplantation for "failure"

Application of the Fontan procedure has allowed the survival of many patients with univentricular cardiac lesions into mid adulthood. Despite its ingenious design, implementation, and thoughtful modifications, its attendant hemodynamic perturbations persist; central venous hypertension and reduced cardiac output. These aberrations in physiology have led to pernicious changes in organ function. A more thorough understanding of these derangements and attempts at Fontan revision have temporized, yet the morbidity and patient attrition persists. Mechanical assistance to normalize the circulation is being investigated and holds some promise. At present, cardiac transplantation remains the last stage of palliation for many.

A rare cause of cyanosis: hepatopulmonary syndrome caused by congenital extrahepatic portosystemic shunt

A 19-year-old male patient presented cyanosis and dyspnoea because of the presence of multiple pulmonary arteriovenous fistulas resulting in oxygen desaturation. The CTA revealed that intestinal and splenic venous blood bypasses the liver and drains into the inferior vena cava. This is the first reported case of hepatopulmonary syndrome caused by congenital extrahepatic portosystemic shunt in which intestinal and splenic venous blood bypasses the liver and drains into the inferior vena cava.

Pulmonary Arteriovenous Malformations in Heterotaxy Syndrome

We report a surgical approach using hepatic vein–to–azygos vein connection without cardiopulmonary bypass or deep hypothermic circulatory arrest in a patient with heterotaxy syndrome and interrupted inferior vena cava with persistence of pulmonary arteriovenous malformations (PAVMs) after previous Fontan completion. We advocate early performance of hepatic vein–to–azygos vein connection following the Kawashima operation for heterotaxy with functionally univentricular heart and interrupted inferior vena cava. We review the physiology of heterotaxy syndrome with congenital heart disease and justify our approach in the context of a review of previous surgical strategies used in this patient population.

Systemic arteriovenous fistulae for end-stage cyanosis after cavopulmonary connection: a useful bridge to transplantation

OBJECTIVE

Intractable cyanosis after partial or complete cavopulmonary connection may rarely be managed by creating a systemic arteriovenous fistula. We investigated the long-term performance of arteriovenous fistulae.

METHODS

All 21 patients who received an arteriovenous fistula at The Hospital for Sick Children since the 1950s were investigated using parametric competing risk techniques. Primary arteriovenous fistula indication was (1) suboptimal pulmonary blood flow (N = 15) or (2) pulmonary shunting via pulmonary arteriovenous malformations (N = 6). Arteriovenous fistula longevity was determined by time to "occlusion" (absence of arteriovenous fistula flow via surgical ligation or spontaneous occlusion).

RESULTS

All 21 patients had previously undergone second-stage palliation (Glenn shunt = 13; bidirectional shunt = 9). Five patients had undergone Fontan completion. Death in the presence of a functioning arteriovenous fistula occurred in 5 patients. Patients with bidirectional shunts had a significantly higher risk of death with a functioning arteriovenous fistula in situ (P = .04). High hemoglobin concentrations were associated with best outcome, and levels less than 170 g/L were associated with a high risk of death despite a functioning arteriovenous fistula (P < .01). Arteriovenous fistula occlusion occurred in 10 patients. Earlier occlusion was associated with previous Fontan completion (P = .02) and pulmonary arteriovenous malformations (P = .03). Surgical ligation during cardiac transplantation was the cause of occlusion in 7 patients. In these 7 patients, the arteriovenous fistula functioned for a median of 4.8 years. After transplantation, survival was 67% + or - 19% at 5 years. Overall survival was 73% + or - 10% 15 years after receiving an arteriovenous fistula (longest survival, 27.3 years).

CONCLUSION

In patients with adequate hematocrit, arteriovenous fistula offers an effective bridge to transplantation when a high-risk Fontan procedure is deferred. Performance is best after unidirectional cavopulmonary connection and worse in the presence of pulmonary arteriovenous malformations. Survival is 75% at 15 years, despite being considered end stage.

Constitutively active endothelial Notch4 causes lung arteriovenous shunts in mice

Lung arteriovenous (AV) shunts or malformations cause significant morbidity and mortality in several distinct clinical syndromes. For most patients with lung AV shunts, there is still no optimal treatment. The underlying molecular and cellular etiology for lung AV shunts remains elusive, and currently described animal models have insufficiently addressed this problem. Using a tetracycline-repressible system, we expressed constitutively active Notch4 (Notch4*) specifically in the endothelium of adult mice. More than 90% of mice developed lung hemorrhages and respiratory insufficiency and died by 6-7 wk after gene expression began. Vascular casting and fluorescent microsphere analysis showed evidence of lung AV shunts in affected mice. Cessation of Notch4* expression reversed these pathophysiological effects. Assessment of the vascular morphology revealed enlarged, tortuous vessels in the lungs that resembled arteriovenous malformations. By using whole lung organ culture, we demonstrated the effects of constitutively active Notch4 on the lung vasculature to be a primary lung phenomenon. Together, our results indicate the importance of Notch signaling in maintaining the lung vasculature and offer a new, reliable model with which to study the pathobiology of lung arteriovenous shunts and malformations.

Development of bilateral diffuse pulmonary arteriovenous fistula after Fontan procedure: is there nonhepatic factor?

The cause of pulmonary arteriovenous fistulas after a cavopulmonary anastomosis is not clearly known, but the previous studies regarding their causes have been focused mainly on the hepatic factors. We report two unusual Fontan cases with multiple bilateral pulmonary arteriovenous fistulas. One of them died of progressive hypoxia, and the other underwent multiple coiling. Our cases suggest that potentially lethal diffuse pulmonary arteriovenous fistulas may develop bilaterally in spite of balanced hepatic effluent flow to pulmonary circulation through factors other than a hepatic factor.

Expression of vascular endothelial growth factor is coordinately regulated by the activin-like kinase receptors 1 and 5 in endothelial cells

Expression of vascular endothelial growth factor (VEGF) is tightly regulated to achieve normal angiogenesis. The objective was to examine regulation of VEGF by the activin-like kinase receptors (ALKs) ALK1 and ALK5. Transforming growth factor beta1 (TGFbeta1) and bone morphogenetic protein-9 (BMP-9) enhanced and suppressed VEGF expression, respectively, in aortic endothelial cells, as determined by real-time polymerase chain reaction, immunoblotting, cell proliferation, and tube formation. The use of small interfering RNA revealed that TGFbeta1 stimulated VEGF expression by activating ALK5, TGFbeta type II receptor, and SMAD2, whereas BMP-9 suppressed it by activating ALK1, BMP type II receptor, and SMAD1. ALK1 signaling occurred independently of ALK5 activity. Partial ALK1 deficiency in vitro and in vivo resulted in elevated VEGF expression. In vitro, increased BMP-9 levels normalized VEGF expression in cells with partial, but not severe, ALK1 deficiency. Time course experiments revealed that an increase in ALK1 expression induced by BMP-4, an angiogenic stimulus, preceded induction of ALK5 and VEGF in control cells. In ALK1-deficient cells, however, VEGF expression occurred earlier and was abnormally high, even though ALK5 was not induced. Our results suggest that ALK1 and ALK5 are both essential for correct regulation of VEGF, and that disruption of either pathway leads to disease.

Inclusion of hepatic venous drainage in patients with pulmonary arteriovenous fistulas

BACKGROUND

It is well known that hepatic vein (HV) inclusion can ameliorate cyanosis in patients with pulmonary arteriovenous fistulas (PAVFs) during the sequence of Fontan type repair. Previously, we reported that most patients with bidirectional cavopulmonary shunt (BCPS) have clinical or subclinical evidence of a right to left shunt through PAVFs.

METHODS

We studied 33 patients who already had clinical and subclinical PAVFs after BCPS. All patients have taken Fontan completion with HV inclusion. The state of PAVFs was reevaluated by pulmonary angiogram, contrast echocardiography, and lung scintigraphy 7.7 +/- 2.4 years after HV inclusion.

RESULTS

After Fontan completion, the mean oxygen saturation increased from 80.2 +/- 7.4% to 91.5 +/- 9.8% in the entire cohort. Moreover, the amount of right-to-left shunting through the PAVFs, measured by lung scintigraphy, was decreased from a mean of 23.8 +/- 15.1 to 13.0 +/- 8.2%. The degree of severity, for most patients, was decreased as demonstrated by contrast echocardiography. However, 5 patients (16.7%) showed persistent PAVFs, even after the HV inclusion. They all had left isomerism with azygous continuation of the IVC and the conduit was positioned on the contralateral side to the SVC with azygous drainage.

CONCLUSIONS

Most PAVFs regressed after Fontan completion. Left isomerism with azygous continuation of the IVC had risk for persistent PAVFs when the HV conduit was positioned at the contralateral side to the SVC receiving the azygous drainage. Therefore, appropriate design avoiding unilateral streaming of HV flow should be considered for HV inclusion surgery.

Progressive intrapulmonary shunting in a child after bidirectional Glenn operation only resolved after total cavopulmonary completion

We report on a girl with progressive intrapulmonary shunting after bidirectional Glenn (BDG) operation and resolution of these microscopic fistulas after completion to total cavopulmonary connection (TCPC).

Morphological studies of pulmonary arteriovenous shunting in a lamb model of superior cavopulmonary anastomosis

We sought to identify and characterize the abnormal vascular structures responsible for pulmonary arteriovenous shunting following the Glenn cavopulmonary shunt. Superior cavopulmonary shunt is commonly performed as part of the staged pathway to total cavopulmonary shunt to treat univentricular forms of congenital heart disease, however, clinically significant pulmonary arteriovenous malformations develop in some patients after the procedure. The causes of pulmonary arteriovenous malformations and other pulmonary vascular changes that occur after cavopulmonary shunt are not known. Using a juvenile lamb model of superior cavopulmonary anastomosis that reliably produces pulmonary arteriovenous malformations, we performed echocardiography and morphological analyses to determine the anatomic site of shunting and to identify the vascular structures involved. Pulmonary arteriovenous shunting was identified by contrast echocardiography in all surviving animals (n = 40) following superior cavopulmonary anastomosis. Pulmonary vascular corrosion casts revealed abnormal tortuous vessels joining pulmonary arteries and veins in cavopulmonary shunt animals but not control animals. In conclusion, unusual channels that bridged pulmonary arteries and veins were identified. These may represent the vascular structures responsible for arteriovenous shunting following the classic Glenn cavopulmonary shunt. Detailed analysis of these structures may elucidate factors responsible for their development.

Multidetector CT evaluation of congenital lung anomalies

Congenital lung anomalies vary widely in their clinical manifestation and imaging appearance. Although radiographs play a role in the incidental detection and initial imaging evaluation in patients with clinical suspicion of congenital lung anomalies, cross-sectional imaging such as computer tomography (CT) is frequently required for confirmation of diagnosis, further characterization, and preoperative evaluation in the case of surgical lesions. Recently, with the development and widespread availability of multidetector CT scanners, CT has assumed a greater role in the noninvasive evaluation of congenital lung anomalies. The combination of fast speed, high spatial resolution, and enhanced quality of multiplanar reformation and three-dimensional reconstructions makes multidetector CT an ideal noninvasive method for evaluating congenital lung anomalies. In this article, the authors review the multidetector CT technique for evaluation of congenital lung anomalies. Important clinical aspects, characteristic imaging features, and key points that allow differentiation among various anomalies are highlighted for a variety of common and uncommon conditions.

Off-pump connection of the hepatic to the azygos vein through a lateral thoracotomy for relief of arterio-venous fistulas after a Kawashima procedure

OBJECTIVE

To connect the hepatic veins to the azygos venous system through a lateral thoracotomy, and without the use of extracorporeal circulation, so as to relieve arteriovenous fistulas after a previous Kawashima operation.

METHODS

Description of the operative technique by which the hepatic veins are anastomosed to the hepatic venous system.

RESULTS

The surgical approach was successfully applied in 3 patients, all of whom showed an excellent rise of saturations of oxygen after redirection of the hepatic venous blood.

CONCLUSION

The operative method presented is an elegant means of redirecting the hepatic venous blood to the pulmonary circulation without the disadvantages of extracorporeal circulation and resternotomy.

Guidelines for the outpatient management of complex congenital heart disease

An increasingly complex group of children is now being followed as outpatients after surgery for congenital heart disease. A variety of complications and physiologic perturbations, both expected and unexpected, may present during follow-up, and should be anticipated by the practitioner and discussed with the patient and family. The purpose of this position article is to provide a framework for outpatient follow-up of complex congenital heart disease, based on a review of current literature and the experience of the authors.

Hemiazygos venous additional pulmonary flow for successful total cavo-pulmonary connection

Patients who underwent only Glenn procedure after being deemed unsuitable candidates for Fontan completion are not small in number, and may develop arterio-venous (AV) pulmonary malformations during the follow-up period. We present the case of a 17-year-old woman with severe systemic desaturation 13 years after Glenn procedure and repair of total anomalous pulmonary venous return. Among other anomalies, the patient disclosed hemiazygos continuation to a persistent left superior vena cava. This case supports the concept that returning flow from the abdominal vein plays an important role in the well-balanced growth of the pulmonary artery and in the inhibition of the pulmonary AV malformation.

Resolution of hepatopulmonary syndrome after ligation of a portosystemic shunt in a pediatric patient with an Abernethy malformation

This report describes a case of Abernethy malformation associated with hepatopulmonary syndrome, which was resolved after shunt ligation. The clinical course indicated that hepatopulmonary syndrome can develop in Abernethy malformation in which liver function and portal pressure is normal, and liver transplantation is not the exclusive therapy for hepatopulmonary syndrome. The levels of endotoxin and endothelin 1 in the shunt blood were high, whereas those of tumor necrosis factor alpha and interleukin-1beta were within reference range. Although pathogenesis of hepatopulmonary syndrome remains unknown, the findings in this case suggest that bacterial translocation as well as elevated endothelin 1 may play a causal role in development of hepatopulmonary syndrome.

New power loss optimized Fontan connection evaluated by calculation of power loss using high resolution PC-MRI and CFD

A new blood vessel configuration was invented to optimize blood flow efficiency and reduce the power loss in the Fontan connection. The current preferred Fontan configuration, the total cavopulmonary connection (TCPC), usually connects the venae cava (VC) to the pulmonary arteries (PA), bypassing the right ventricle. The new connection, called OptiFlo, has two vertical inlets, which both bifurcate then merge into one another to form two horizontal outlets. One of the preliminary configurations of the new OptiFlo model was used for a comparison experiment between computational fluid dynamics (CFD) and high resolution phase contrast magnetic resonance imaging (PC-MRI) with a voxel resolution of 0.23 mmx0.23 mmx0.25 mm. The thin slice thickness was achieved using the ACGI interpolation technique we have used in other applications before. The 2D PC-MRI velocity vectors were mapped into a CFD grid, enabling direct CFD and MRI data comparisons. The mean squared difference was found between the two dataset Using the viscous power dissipation function we calculated the power loss for both CFD and MRI data. The power losses, calculated with the viscous power dissipation function, were 0.66 mW for CFD and 0.46 mW for the PC-MRI data.

Incorporation of the hepatic veins into the cavopulmonary circulation in patients with heterotaxy and pulmonary arteriovenous malformations after a Kawashima procedure

BACKGROUND

In patients with polysplenia syndrome and azygous continuation of an interrupted inferior vena cava (IVC), pulmonary arteriovenous malformations (PAVMs) are relatively common after bidirectional cavopulmonary anastomosis (BCPA, Kawashima procedure). Resolution of PAVMs after hepatic vein (HV) inclusion into the cavopulmonary circulation has been reported, but there has been no systematic investigation of the effects of this therapy in a population of more than 3 patients.

METHODS

We studied 16 patients with heterotaxy, univentricular congenital heart disease, and azygous continuation of the IVC who underwent incorporation of the HV into the cavopulmonary circuit for treatment of significant PAVMs after a Kawashima procedure.

RESULTS

The median preoperative systemic arterial oxygen saturation (SsaO2) was 76% (65%-85%), compared with 89% (85% to 92%) early after BCPA. Among 15 early survivors, the median early postoperative SsaO2 was 76% (56%-85%). In 11 of the 15 survivors, SsaO2 rose to 90% or greater within a year and remained at 93% or greater at follow-up of 2.8 to 10 years. Four patients had persistent hypoxemia and residual PAVMs at follow-up catheterization 1.5 to 8 years postoperatively; these patients had the most severe hypoxemia prior to HV inclusion, and in 2 the residual PAVMs were unilateral, with HV flow streaming to the contralateral lung, in which PAVMs had resolved.

CONCLUSIONS

Hypoxemia resolved after cavopulmonary incorporation of the HV in the majority of our patients with PAVMs after the Kawashima operation, presumably due to a combination of PAVM resolution and elimination of hepatic venoatrial right-to-left shunting. These findings support the theory that development of PAVMs is facilitated by exclusion of HV effluent from the pulmonary circulation.

Redirection of the hepatic venous flow for the treatment of pulmonary arteriovenous malformations after Fontan operation

A 45-month-old boy who had complex cardiac anomalies with interrupted inferior vena cava and polysplenia underwent extracardiac Fontan operation. He redeveloped deep cyanosis postoperatively. Cardiac catheterization showed a preferential flow of the hepatic venous blood to the right lung and arteriovenous malformations (PAVMs) in the left lung. He underwent revision of the conduit to attain balanced hepatic venous drainage with subsequent regression of the PAVMs and disappearance of cyanosis. Our experience shows that deficiency of hepatic venous flow played a crucial role in the development of PAVMs and that redistribution of the flow retained potential to ameliorate the pathological condition.

Surgery for the functionally univentricular heart in patients with visceral heterotaxy

The heterotaxy syndromes are characterized by a high incidence of cardiac anomalies of extreme heterogeneity. Due to this, the surgical management is varied and challenging. Although a minority of patients can undergo biventricular repair, the complexity of the cardiac defects, and the high incidence of ventricular hypoplasia, mandate a surgical approach in the majority of patients depending on the creation of a functionally univentricular heart. Traditionally, the functionally univentricular approach was associated with a high mortality. More recently, the results have been improving as a result of better understanding of these malformations, and logical improvements in surgical technique. In this review, we will make brief comments on the nomenclature and classification of the heterotaxy syndromes, and the range of cardiac anomalies, before concentrating on the surgical treatment for those patients having functionally univentricular hearts in the setting of heterotaxy. More specifically, we will review initial palliation in early life, creation of the cavopulmonary anastomoses, including the Kawashima procedure and the Fontan circulation, and the role of transplantation.

Management of systemic venous anomalies in the pediatric cardiovascular surgical patient

Systemic venous anomalies are rare and heterogeneous entities. Although these anomalies are rare in the general population, they occur more frequently in the subpopulation with congenital heart disease. In and of themselves, most of these lesions have no physiologic significance. However, in the setting of congenital heart disease these lesions may significantly alter surgical treatment. This review is dedicated to these lesions.

Pulmonary Arteriovenous Malformations in Children After the Kawashima Operation

BACKGROUND

Pulmonary arteriovenous malformations are a major cause of progressive late cyanosis in patients treated with cavopulmonary anastomoses. Previous experience suggests that exclusion of the hepatic venous effluent from the pulmonary circulation may cause the development of pulmonary arteriovenous malformations after the Kawashima operation in children with interrupted inferior vena cava with azygous continuation.

METHODS

From January 1990 to November 2004, 21 children (median age, 2 years) with heterotaxy syndrome and interrupted inferior vena cava with azygous continuation underwent Kawashima operation. The average preoperative arterial oxygen saturation was 76% +/- 7% (range, 64% to 90%).

RESULTS

Follow-up was complete in all survivors except 1 at a median duration of 4.5 years. Pulmonary arteriovenous malformations were diagnosed at a median of 5 years after Kawashima operation in 11 patients (58%). Completion Fontan operation has been performed in 15 (79%). Five children who underwent a completion Fontan procedure 1 to 1.5 years after Kawashima operation did not have pulmonary arteriovenous malformations. There were 2 late deaths due to chronic congestive heart failure 4 months and 7 years after Kawashima operation. Overall survival at 10 years is 90%. Univariate and multivariate analysis demonstrated presence of bilateral superior vena cavae (p = 0.002) and interval longer than 2 years between Kawashima operation and completion Fontan operation (p = 0.04) as predictors of developing pulmonary arteriovenous malformations.

CONCLUSIONS

In most patients with heterotaxy and interrupted inferior vena cava with azygous continuation, clinical evidence of pulmonary arteriovenous malformations will develop after Kawashima operation if they are followed up long enough. Early redirection of the hepatic venous effluent to the pulmonary arterial circulation may prevent or lead to regression of pulmonary arteriovenous malformations, with low mortality and morbidity.

Creation of a Brachial Arteriovenous Fistula for Treatment of Pulmonary Arteriovenous Malformations After Cavopulmonary Anastomosis

BACKGROUND

Pulmonary arteriovenous malformations (PAVMs) occur in approximately 20% of patients after unidirectional superior cavopulmonary anastomosis (CPA), and frequently after bidirectional CPA in patients with polysplenia syndrome. It is hypothesized that exclusion of a growth-modulating factor produced in the liver may predispose to PAVM formation. Resolution of PAVMs after inclusion of hepatic venous effluent into the cavopulmonary circulation has been reported. An upper extremity systemic arteriovenous (AV) fistula may be created to augment pulmonary blood flow and improve oxygenation in hypoxemic patients with CPA, but there has been no systematic investigation of the effects of such fistulas on PAVMs after CPA.

METHODS

We studied 11 patients with PAVMs who underwent creation of a brachial AV fistula a median of 11 years after CPA.

RESULTS

Eight patients had discontinuous pulmonary arteries or unilateral flow of a bidirectional CPA and were not considered good candidates for Fontan completion; the other 3 patients had polysplenia and unilateral hepatic venous streaming after Fontan completion. Three patients died of progressive complications of their heart disease 4 to 18 months after AV fistula creation. Pulmonary arteriovenous malformations resolved after creation of a brachial AV fistula in 4 of 5 surviving patients with unilateral flow of a superior CPA, but in none of 3 patients with polysplenia who had unilateral hepatic venous streaming after Fontan completion and PAVMs in the contralateral lung.

CONCLUSIONS

These findings are consistent with the "hepatic factor" hypothesis, according to which the development of PAVMs is facilitated when an unidentified factor produced or metabolized in the liver does not reach the pulmonary circulation before traversing another capillary bed. Patients with unilateral superior CPA flow and PAVMs who are not considered candidates for Fontan completion may benefit from a brachial AV fistula.

Current treatment and prognosis in children with functionally univentricular hearts

For more than 30 years Fontan-type procedures have been performed for surgical treatment in patients with functionally univentricular hearts. Advances in proper patient selection, staging of the Fontan palliation, and modifications of the surgical technique resulted in continuous improvement of the surgical results during the past two decades. However, increasing experience with medium term and long term follow-up of the Fontan circulation has drawn attention to a number of sequelae and chronic complications affecting a significant number of patients.

Nitric Oxide in Pulmonary Arteriovenous Malformations and Fontan Procedure

Pulmonary arteriovenous malformations are a well documented complication of superior cavopulmonary (Glenn) connections. We report the successful management of a case of severe hypoxemia in the early postoperative period of a patient who underwent the Fontan operation. The patient had previously been diagnosed with pulmonary arteriovenous malformations; the use of inhaled nitric oxide was followed up with reversal of life-threatening hypoxemia. At 6-month postoperative follow-up, the patient was asymptomatic with near normal aortic saturation.

Transcatheter occlusion of an intrahepatic venovenous fistula after modified Fontan circulation by implantation of an Amplatzer atrial septal occluder

We report two successful transcatheter closures of intrahepatic venovenous malformations observed after bidirectional cavopulmonary anastomoses. These malformations were detected immediately after surgery in one case and during a 10-year follow-up in the second case. These intrahepatic venovenous malformations were successfully occluded by the implantation of an Amplatzer atrial septal occluder.

Pulmonary arteriovenous shunting in the normal fetal lung

OBJECTIVES

We hypothesized that pulmonary arteriovenous shunting (PAVS) is normally present in fetal lungs and that cavopulmonary anastomosis-induced PAVS may represent a return to an earlier morphologic stage of development.

BACKGROUND

The surgical superior cavopulmonary anastomosis is performed as part of the staged Fontan pathway to treat univentricular forms of congenital heart disease; PAVS is a known sequela after superior cavopulmonary anastomosis and may have important clinical consequences. Although the etiology and true morphology of the structures responsible for PAVS are unknown, a leading theory is that PAVS is caused by absence of normal hepatic venous drainage to the pulmonary circulation.

METHODS

To determine whether normal fetal lungs demonstrate PAVS, we performed contrast echocardiograms on 13 fetal lambs, 8 neonatal lambs, 4 juvenile lambs, and 4 adult sheep using a blended mixture of saline and blood injected directly into the proximal pulmonary artery.

RESULTS

Pulmonary arteriovenous shunting was detected by direct epicardial echocardiography in all fetal lambs (n = 13) and neonatal animals studied at one and three days of life (n = 4) and in two of four animals studied at six to nine days of life. Pulmonary arteriovenous shunting was not present in animals studied at four weeks of life (n = 2) and in adult sheep (n = 5).

CONCLUSIONS

These studies demonstrate that PAVS is normally present in late gestation fetal and early neonatal lambs but then disappears during the later neonatal period. Furthermore, these findings suggest that PAVS associated with cavopulmonary anastomosis or other processes affecting the developing pulmonary circulation may represent a return to an earlier morphologic stage of development.

Partial hepatic vein diversion in pulmonary arteriovenous malformations in congenital heart disease

The late appearance of pulmonary arteriovenous malformations after operations for complex congenital cardiac conditions may be explained in many ways. The necessity of hepatic blood flow to the lungs is now generally accepted for carrying some labile substance that is secreted by the liver and that has not yet been identified. Rerouting of hepatic blood to the lungs in cardiac patients can be accomplished with different methods, most of which are predisposed to thrombosis because of the slow flow in the tunnel. My colleagues and I describe a case of partial diversion of hepatic blood into the pulmonary circulation and suggest a strategy to decrease the likelihood of conduit thrombosis and to treat pulmonary arteriovenous malformations.

The biological "scrabble" of pulmonary arteriovenous malformations: considerations in the setting of cavopulmonary surgery

Pulmonary arteriovenous fistulas are vascular malformations, which, by virtue of producing abnormal vascular connections proximal to the units of gas exchange, result in intrapulmonary right-to-left shunting. These malformations or fistulas reflect at least in part disordered angiogenesis, and less commonly recruitment and dilation of pre-existing vascular channels. Pulmonary arteriovenous fistulas occur in a number of diverse clinical settings. Such fistulas are a well-established feature of the Weber-Osler-Rendu complex, or hereditary haemorrhagic telangiectasia, an autosomal dominant vascular dysplasia characterized by mucocutaneous telangiectasis, epistaxis, gastrointestinal haemorrhage, and arteriovenous malformations in the lung, brain, liver and elsewhere. They are also seen in the patient with acute or chronic liver disease, disease that is usually but not invariably severe, or those with non-cirrhotic portal hypertension. They may occur as congenital malformations, single or diffuse, large or small in isolation, and when large or extensive enough may result in hypoxaemia, clinical cyanosis, and heart failure. Cerebral vascular accidents are also a well-known complication of this disorder. An extensive literature has accumulated with regard to the pulmonary arteriovenous fistulas seen in the setting of the Weber-Osler-Rendu complex, and there is considerable information on the genetics, basic biology, clinical findings, complications and therapeutic interventions of these malformations in the setting of this syndrome. These issues, however, are not the primary considerations of this review, although some aspects of this fascinating disorder will be discussed later. Rather the focus will be on pulmonary arteriovenous malformations that develop in the setting of cavopulmonary surgery, and their relationship to the pulmonary arteriovenous fistulas occurring in the hepatopulmonary syndrome. The complex tapestry of these overlapping and intersecting clinical observations will be unfolded in the light of their chronology.

Regression of severe pulmonary arteriovenous malformations after Fontan revision and “hepatic factor” rerouting

Although previously described in patients undergoing staged palliation for univentricular heart disease, the mechanism by which hepatic venous flow prevents development of pulmonary arteriovenous malformations is still not completely understood. We present a case in which successful H-type Fontan revision with rerouting of hepatic venous flow through a hemiazygous vein successfully reversed the progression of severe left pulmonary arteriovenous malformations.

Pulmonary expression of the hepatocyte growth factor receptor c-Met shifts from medial to intimal layer after cavopulmonary anastomosis

OBJECTIVE

Pulmonary arteriovenous malformations occur in up to 60% of patients after cavopulmonary anastomosis. We compared the effects of cavopulmonary anastomosis and pulmonary artery banding on lung gene expression in an ovine model to study the abnormal pulmonary vascular remodeling after the exclusion of inferior vena caval blood independent of reduced pulmonary blood flow. We previously demonstrated by contrast echocardiography that pulmonary arteriovenous malformations develop by 8 weeks after cavopulmonary anastomosis but not after pulmonary artery banding. Hepatocyte growth factor, a pleiotropic factor with morphogenic, mitogenic, and angiogenic activities, signals via its specific receptor c-Met to induce the antiapoptotic factor Bcl-2. In this study, we examined pulmonary artery expression of these factors and their potential role in pulmonary artery remodeling after cavopulmonary anastomosis and pulmonary artery banding.

METHODS

Eighteen lambs aged 35 to 45 days were placed into 3 groups: cavopulmonary anastomosis, pulmonary artery banding, and control (n = 6/group). In the cavopulmonary anastomosis group, the superior vena cava was anastomosed to the right pulmonary artery in an end-to-end fashion. In the pulmonary artery banding group, the left pulmonary artery was banded to reduce blood flow to 20% of control. The control group had a simple right pulmonary artery clamp for 30 minutes. Lung was harvested for Western blot, reverse transcriptase-polymerase chain reaction, and immunostaining at 2 weeks (n = 3/group) and 5 weeks (n = 3/group) after surgery.

RESULTS

The expression of c-Met mRNA after cavopulmonary anastomosis was increased by twofold compared with the control or pulmonary artery banding group. The total lung expression of c-Met by Western blot was also up regulated at 2 weeks (P <.05). However, total lung expression of hepatocyte growth factor and Bcl-2 by Western and reverse transcriptase-polymerase chain reaction was not different from the control and pulmonary artery banding groups at both 2 and 5 weeks after surgery. Immunohistochemical analysis revealed that c-Met expression was localized to the intimal layer of the pulmonary artery in the cavopulmonary anastomosis, while its expression in the control and pulmonary artery banding lungs was localized to the medial layer. Localization of Bcl-2 on the intimal layer in lambs with cavopulmonary anastomosis followed the same pattern as c-Met.

CONCLUSIONS

After cavopulmonary anastomosis, pulmonary artery expression of the hepatocyte growth factor receptor c-Met and one of its downstream effectors, Bcl-2, had increased in the intimal layer and decreased in the medial layer. Because the hepatocyte growth factor signaling promotes increased endothelial cell survival, it may have a role in pulmonary artery remodeling following cavopulmonary anastomosis. In addition, the change of c-Met expression in the medial layer after cavopulmonary anastomosis suggests a possible mechanism for the smooth muscle cell alteration related to abnormal angiogenesis.

Total cavopulmonary connection to one lung

The status of pulmonary circulation is of utmost importance to the success of the modified Fontan operation. Pulmonary artery distortion, hypoplasia of the total pulmonary vascular bed, and elevated pulmonary vascular resistance are all risk factors for adverse outcome after modified Fontan operations. In cases of irreparable acquired atresia of one or the other branch pulmonary artery, clinicians are forced to contemplate the possibility of total cavopulmonary connection to one lung. The combined experience of the authors with 12 cases suggests that the likelihood of operative survival following Fontan's operation to one lung is predicted based on the usual hemodynamic parameters: pulmonary artery pressure and flow, ventricular end diastolic pressure, transpulmonary gradient, and pulmonary vascular resistance. In this series, there were no operative mortalities among patients undergoing Fontan's operation to one lung, all of whom meet the usual criteria for hemodynamic acceptability. There may, however, be a higher incidence of protein-losing enteropathy than in Fontan patients with normal pulmonary vascular beds. All possible means of resuscitating the lost elements of the pulmonary vascular bed and re-establishing pulmonary artery continuity should be attempted to minimize pulmonary vascular capacitance of patients undergoing Fontan's operation. It is clear, however, that the presence of only one pulmonary artery does not in and of itself preclude satisfactory outcome.

Neonatal hemangiomatosis and atrial septal defect: a rare cause of right heart failure in infancy

Neonatal hemangiomatosis is a well-recognized cause of left ventricular failure. We describe an infant with neonatal hemangiomatosis and an ostium secundum atrial septal defect who developed severe right heart failure. This was due to the combination of increased flow through the right heart as a result of the atrial septal defect, and the background high cardiac output from the massive arteriovenous shunting and multiple hemangiomas. In addition, the multiple hepatic hemangiomas may exert a vasoactive influence on the pulmonary vasculature.

Techniques and applications of transcatheter embolization procedures in pediatric cardiology

Transcatheter embolization of congenital or acquired superfluous vascular structure has become routine procedures performed by interventional pediatric cardiologists. Embolization procedure is often part of a collaborative effort with cardiac surgeons to palliate complex congenital heart defect, such as in embolizing aortopulmonary collateral arteries in patient with single ventricle physiology. In other cases, the procedure is the definitive treatment as in embolizing coronary artery fistula. Pediatric cardiologists performing embolization procedures should be familiar with available technologies as well as understand the underlying cardiac anatomy and pathophysiology. This article provides a comprehensive review of presently available embolization agents and technologies. Some of the technologies are used only by interventional radiologists but may be useful to pediatric cardiologists. Specific clinical applications in pediatric cardiology are also discussed with summary of current literature. With continue advancement in transcatheter technology and operator expertise, all unwanted vascular communication should be amenable to transcatheter embolization.

Pulmonary arteriovenous malformations after cavopulmonary anastomosis

Pulmonary arteriovenous malformations (PAVMs) are a cause of progressive cyanosis after cavopulmonary anastomosis in children with single ventricle physiology who are on the pathway leading to a Fontan procedure. Investigations into possible mechanisms for the etiology of PAVMs are ongoing and suggest that the liver might play a key regulatory role in the development of these lesions.

New approach to the surgical management of pulmonary arteriovenous malformations after cavopulmonary anastomosis

The development of pulmonary arteriovenous malformations after cavopulmonary bypass in patients with congenital heart disease is well documented. We report successful management of pulmonary arteriovenous malformations after cavopulmonary bypass in a patient with an interrupted inferior vena cava (IVC) and multiple hepatic veins utilizing an extracardiac conduit from the hepatic veins to the hemiazygous continuation of the interrupted IVC. This technique, performed without circulatory arrest or an atriotomy, may limit morbidity associated with intracardiac procedures in patients with single ventricle morphology. Furthermore, this case suggests an alternative technique for completion Fontan in patients with an interrupted IVC and multiple hepatic venous drainage.

The fenestrated Kawashima operation for single ventricle with interrupted inferior vena cava

An 8-month-old boy with double outlet right ventricle with hypoplastic left ventricle, heterotaxy, left atrial isomerism, bilateral superior vena cavae without bridging vein, and interruption of the inferior vena cava with azygous continuation to the left superior cava underwent a bilateral bidirectional cavopulmonary anastomosis. A calibrated 3-mm connection between the right pulmonary artery and the common atrium was constructed with the proximal right superior vena cava to allow right to left shunting, analogous to a fenestration in a Fontan operation. We hypothesize that in small young patients undergoing the Kawashima operation a fenestration may improve postoperative hemodynamics.