Angiogenic proteins in the lungs of children after cavopulmonary anastomosis

Pulmonary Vascular Sequelae of Palliated Single Ventricle Circulation: Arteriovenous Malformations and Aortopulmonary Collaterals

Children and adults with single ventricle congenital heart disease (CHD) develop many sequelae during staged surgical palliation. Universal pulmonary vascular sequelae in this patient population include two inter-related but distinct complications: pulmonary arteriovenous malformations (PAVMs) and aortopulmonary collaterals (APCs). This review highlights what is known and unknown about these vascular sequelae focusing on diagnostic testing, pathophysiology, and areas in need of further research.

Abnormalities in the Von Willebrand-Angiopoietin Axis Contribute to Dysregulated Angiogenesis and Angiodysplasia in Children With a Glenn Circulation

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Children with a bidirectional superior cavopulmonary connection (Glenn circulation) develop dysregulated angiogenesis and pulmonary angiodysplasia in the form of arteriovenous malformations (AVMs). No targeted therapy exists.

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The von Willebrand factor (vWF)–angiopoietin axis plays a major role in normal angiogenesis, angiodysplasia, and AVM formation in multiple diseases.

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vWF and angiopoietin-2 (which destabilizes vessel formation) were abnormal in children with a Glenn circulation versus control children. Within Glenn patients, angiopoietin-1 (which stabilizes vessel formation) and angiogenesis were different in the systemic versus pulmonary circulation. Plasma angiopoietin-1 was lower in the pulmonary circulation of Glenn patients with pulmonary AVMs than Glenn patients without AVMs.

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In parallel, differences in multiple angiogenic and inflammatory signaling peptides were observed between Glenn patients and controls, which indicated derangements in multiple angiogenic pathways in Glenn patients.

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These findings support the novel hypothesis that abnormal vWF metabolism and angiopoietin signaling dysregulate angiogenesis and contribute to pulmonary AVM formation in children with a Glenn circulation.

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The vWF-angiopoietin axis may be a target to correct angiogenic imbalance and reduce pulmonary angiodysplasia in Glenn patients.

Children with a bidirectional superior cavopulmonary (Glenn) circulation develop angiodysplasia and pulmonary arteriovenous malformations (AVMs). The von Willebrand factor (vWF)–angiopoietin axis plays a major role in AVM formation in multiple diseases. We observed derangements in global angiogenic signaling, vWF metabolism, angiopoietins, and in vitro angiogenesis in children with a Glenn circulation versus controls and within Glenn pulmonary versus systemic circulations. These findings support the novel hypothesis that abnormalities in the vWF-angiopoietin axis may dysregulate angiogenesis and contribute to Glenn pulmonary AVMs. The vWF-angiopoietin axis may be a target to correct angiogenic imbalance in Glenn patients, for whom no targeted therapy exists.

sVEGFR1 Is Enriched in Hepatic Vein Blood-Evidence for a Provisional Hepatic Factor Candidate?

Background: Pulmonary arteriovenous malformations (PAVMs) are common sequelae of palliated univentricular congenital heart disease, yet their pathogenesis remain poorly defined. In this preliminary study, we used paired patient blood samples to identify potential hepatic factor candidates enriched in hepatic vein blood. Methods: Paired venous blood samples were collected from the hepatic vein (HV) and superior vena cava (SVC) from children 0 to 10 years with univentricular and biventricular congenital heart disease (n = 40). We used three independent protein analyses to identify proteomic differences between HV and SVC blood. Subsequently, we investigated the relevance of our quantified protein differences with human lung microvascular endothelial assays. Results: Two independent protein arrays (semi-quantitative immunoblot and quantitative array) identified that soluble vascular endothelial growth factor receptor 1 (sVEGFR1) is significantly elevated in HV serum compared to SVC serum. Using ELISA, we confirmed the previous findings that sVEGFR1 is enriched in HV serum (n = 24, p < 0.0001). Finally, we studied the quantified HV and SVC serum levels of sVEGFR1 in vitro. HV levels of sVEGFR1 decreased tip cell selection (p = 0.0482) and tube formation (fewer tubes [p = 0.0246], shorter tube length [p = 0.0300]) in vitro compared to SVC levels of sVEGFR1. Conclusions: Based on a small heterogenous cohort, sVEGFR1 is elevated in HV serum compared to paired SVC samples, and the mean sVEGFR1 concentrations in these two systemic veins cause pulmonary endothelial phenotypic differences in vitro. Further research is needed to determine whether sVEGFR1 has a direct role in pulmonary microvascular remodeling and PAVMs in patients with palliated univentricular congenital heart disease.

Hepatic Vein Blood Increases Lung Microvascular Angiogenesis and Endothelial Cell Survival-Toward an Understanding of Univentricular Circulation

To improve our understanding of pulmonary arteriovenous malformations in univentricular congenital heart disease, our objective was to identify the effects of hepatic vein and superior vena cava constituents on lung microvascular endothelial cells independent of blood flow. Paired blood samples were collected from the hepatic vein and superior vena cava in children 0-10 years old undergoing cardiac catheterization. Isolated serum was subsequently used for in vitro endothelial cell assays. Angiogenic activity was assessed using tube formation and scratch migration. Endothelial cell survival was assessed using proliferation (BrdU incorporation, cell cycle analysis) and apoptosis (caspase 3/7 activity, Annexin-V labeling). Data were analyzed using Wilcoxon signed-rank test and repeated measures analysis. Upon incubating lung microvascular endothelial cells with 10% patient serum, hepatic vein serum increases angiogenic activity (tube formation, P = 0.04, n = 24; migration, P< 0.001, n = 18), increases proliferation (BrdU, P < 0.001, n = 32; S-phase, P = 0.04, n = 13), and decreases apoptosis (caspase 3/7, P < 0.001, n = 32; Annexin-V, P = 0.04, n = 12) compared to superior vena cava serum. Hepatic vein serum regulates lung microvascular endothelial cells by increasing angiogenesis and survival in vitro. Loss of hepatic vein serum signaling in the lung microvasculature may promote maladaptive lung microvascular remodeling and pulmonary arteriovenous malformations.

Resting respiratory lung volumes are "healthier" than exercise respiratory volumes in different types of palliated or corrected congenital heart disease

AIMS

Cardiac surgery has improved life expectancy of patients with congenital heart diseases (CHDs). Exercise capacity is an important determinant of survival in patients with CHDs. There is a lack of studies focusing on the role of resting respiratory performance in reducing exercise tolerance in these patients.

OBJECTIVES

To determine the prevalence and severity of respiratory functional impairment in different types of corrected/palliated CHDs, and its impact on an exercise test.

MATERIALS AND METHODS

Retrospective single-center study involving 168 corrected/palliated patients with CHD and 52 controls. Patients CHD were divided into subgroups according to the presence of native pulmonary blood flow or total cavopulmonary connection (TCPC). All subjects performed complete pulmonary function tests and gas diffusion; patients with CHD also performed cardiopulmonary exercise test (CPX).

RESULTS

Mean values of lung volumes were within the normal range in all CHD groups. Comparing to controls, patients with the reduced pulmonary flow and with TCPC had the highest reduction in lung volumes. CPX was reduced in all groups, most severely in TCPC, and it was correlated to decreased dynamic volumes in all CHD groups except in TCPC. Younger age at intervention and number of surgical operations negatively affected lung volumes.

CONCLUSIONS

Respiratory function is within the normal range in our patients with different CHDs at rest but altered in all CHDs during exercise when cardiorespiratory balance is likely to be inadequate. Comparing the different groups, patients with reduced pulmonary flow and TCPC are the most impaired.

Outcomes of Single Ventricle Patients Undergoing the Kawashima Procedure: Can We Do Better?

Objectives:

Current technology advances in virtual surgery modeling and computational flow dynamics allow preoperative individualized computer-based design of Fontan operation. To determine potential role of those innovations in patients undergoing hepatic vein incorporation (HVI) following Kawashima operation, we retrospectively examined historic cohort of patients who underwent HVI following Kawashima with focus on regression of pulmonary arteriovenous malformations (PAVMs).

Methods:

Twenty-two children with single ventricle and interrupted inferior vena cava underwent Kawashima operation (2002-12). Twenty-one (96%) patients had left atrial isomerism and 21 (96%) had undergone prior first-stage palliation. Clinical outcomes were examined.

Results:

Mean O2 saturation (SaO2) increased from 77% ± 8% to 85% ± 6% ( P = .002) after Kawashima. Fifteen (68%) patients developed PAVMs. Eighteen patients underwent HVI (median age and interval from Kawashima: 4.4 and 3.7 years, respectively). Mean SaO2 prior to HVI was 77% ± 8% and increased to 81% ± 10% at the time of hospital discharge ( P = .250), with five patients requiring home oxygen. On follow-up, mean SaO2 increased to 95% ± 4% ( P < .001). Overall ten-year survival following Kawashima was 94%.

Conclusions:

A large number of patients develop PAVMs and subsequent cyanosis after Kawashima operation. Early following HVI, SaO2 is commonly low and insignificantly different from that prior to HVI. Although SaO2 will improve on follow-up in most patients, a number of patients continue to have low saturations, indicating incomplete resolution of PAVMs. Given the heterogeneity of those patients and lack of preoperative predictors for complete PAVM regression, our findings suggest a role for virtual surgery to determine optimal individual procedure design that would provide even distribution of hepatic blood flow to both pulmonary arteries.

Particle embolization of systemic-to-pulmonary collateral artery networks in congenital heart disease: Technique and special considerations

Systemic-to-pulmonary artery collateral networks commonly develop in patients with single-ventricle physiology and chronic hypoxemia. Although these networks augment pulmonary blood flow, much of the flow is ineffective and contributes to cardiac volume loading. This volume loading can have detrimental effects, especially for single-ventricle patients. Some data suggest that occluding collaterals may improve outcomes after subsequent operations, especially when the volume of collateral flow is significant. Traditional practice has been to coil occlude the feeding vessel. We perform particle embolization of these collateral networks for two primary reasons. First, access to the feeding vessel is not blocked as collaterals may redevelop. Second, particles occlude the most distal connections. Thus, embolization with particles should be considered as an alternative to coil occluding the proximal feeding vessel.

Pulmonary arteriovenous malformations after the superior cavopulmonary shunt: mechanisms and clinical implications

Children with functional single ventricle heart disease are commonly palliated down a staged clinical pathway toward a Fontan completion procedure (total cavopulmonary connection). The Fontan physiology is fraught with long-term complications associated with lower body systemic venous hypertension, eventually resulting in significant morbidity and mortality. The bidirectional Glenn shunt or superior cavopulmonary connection (SCPC) is commonly the transitional stage in single ventricle surgical management and provides excellent palliation. Some studies have demonstrated lower morbidity and mortality with the SCPC when compared with the Fontan. Unfortunately the durability of the SCPC is significantly limited by the development of pulmonary arteriovenous malformations (PAVMs) which have been commonly attributed to the absence of hepatic venous blood flow and the lack of pulsatile flow to the affected lungs. Abnormal angiogenesis has been suggested as a final common pathway to PAVM development. Understanding these fundamental mechanisms through the investigation of angiogenic pathways associated with the pathogenesis of PAVMs would help to develop medical therapies that could prevent or reverse this complication following SCPC. Such therapies could improve the longevity of the SCPC, potentially eliminate or significantly postpone the Fontan completion with its associated complications, and improve long-term survival in children with single ventricle disease.

Normal and abnormal pulmonary arteriovenous shunting: occurrence and mechanisms

Severe cyanosis due to pulmonary arteriovenous fistulas occurs often after a bidirectional superior cavopulmonary anastomosis (Glenn operation) and also in some congenital anomalies in which hepatic venous blood bypasses the lungs in the first passage. Relocation of hepatic flow into the lungs usually causes these fistulas to disappear. Similar pulmonary arteriovenous fistulas are observed in hereditary haemorrhagic telangiectasia, and in liver disease (hepatopulmonary syndrome). There is no convincing identification yet of a responsible hepatic factor that produces these lesions. Candidates for such a factor are reviewed, and the possibility of angiotensin or bradykinin contributing to the fistulas is discussed.

Options for the failing ventricle in pediatric heart disease

The management of the pediatric patient with the failing ventricle poses its own therapeutic challenges, not least because patient size limits options available. Once medical management has hit its ceiling, attention is turned to surgical options for mechanical support. The approach to these options has to bear in mind that there may be many potential causes for pump failure, and that these occur often in the context of pulmonary hypertension and poor gas exchange. Although extracorporeal life support has been the mainstay of treatment for acute heart failure, in the last decade, attention has been focusing on longer-term options to bridge to recovery or eventual transplant. Added to this are more novel applications of ventricular assist devices, notable in the management of the failing Fontan circulation where there are no perfect solutions. There is growing interest in the use of such devices to power this delicate circulation and extend the functional capacity of patients without resorting to transplantation. In this review article, we explore the role each of these surgical modalities has to play in the management of the child with acute and chronic heart failure, and explore the recent developments in the rapidly growing field of pediatric ventricular assist.

Pulmonary artery endothelial cell phenotypic alterations in a large animal model of pulmonary arteriovenous malformations after the Glenn shunt

BACKGROUND

Longevity of the superior cavopulmonary connection (SCPC) is limited by the development of pulmonary arteriovenous malformations (PAVM). The goal of this study was to determine whether phenotypic changes in pulmonary artery endothelial cells (PAEC) that favor angiogenesis occur with PAVM formation.

METHODS

A superior vena cava to right pulmonary artery connection was constructed in 5 pigs. Pulmonary arteries were harvested at 6 to 8 weeks after surgery to establish cultures of PAEC and smooth muscle cells, to determine cell proliferation, gene expression, and tubule formation. Abundance of proteins related to angiogenesis was measured in lung tissue.

RESULTS

Contrast echocardiography revealed right-to-left shunting, consistent with PAVM formation. While the proliferation of smooth muscle cells from the right pulmonary artery (shunted side) and left pulmonary artery (nonshunted side) were similar, right PAEC proliferation was significantly higher. Expression profiles of genes encoding cellular signaling proteins were higher in PAECs from the right pulmonary artery versus left pulmonary artery. Protein abundance of angiopoietin-1, and Tie-2 (angiopoietin receptor) were increased in the right lung (both p < 0.05). Tubule formation was increased in endothelial cells from the right pulmonary artery compared with the left pulmonary artery (404 ± 16 versus 199 ± 71 tubules/mm(2), respectively; p < 0.05).

CONCLUSIONS

These findings demonstrate that PAVMs developed in a clinically relevant animal model of SCPC concomitantly with differential changes in PAEC proliferative ability and phenotype. Moreover, there was a significant increase in the angiopoietin/Tie-2 complex in the right lung, which may provide novel therapeutic targets to attenuate PAVM formation after a SCPC.

Acute histological changes of the lung after experimental Fontan circulation in a swine model

Background

Histological changes of the lungs were studied after the establishment of a modified total cavopulmonary connection (TCPC) without the use of cardiopulmonary bypass (CPB) or other means of temporary bypass on a swine model.

Material/Methods

8 open chest-anesthetized pigs Landrace × Large White pigs (mean weight 43kg, mean age 4.5 months) underwent TCPC by the use of an appropriate size Y-shaped conduit connecting the superior and inferior caval veins (end-to-end anastomosis) to the pulmonary trunk (end-to-side anastomosis). After sternotomy, a wedge resection of the lung parenchyma was performed at baseline. Hemodynamic stability was sustained after TCPC establishment and 2 hours later another wedge resection of the lung was performed (from the same anatomic area). Histological studies were conducted by hematoxylin and eosin staining.

Results

All samples (n=8) at baseline were consistent with normal lung parenchyma. After the establishment of TCPC, all samples (n=8) revealed moderate mononuclear infiltration adjacent to pulmonary alveoli and bronchioles, findings compatible with bronchiolitis.

Conclusions

In a normal swine model, 2 hours after the establishment of Fontan circulation without the use of CPB, pathologic examination of the lungs revealed bronchiolitis. Further research is needed to clarify these findings and the potential implications to the Fontan circulation, either immediate or long-term.

Endostatin, an inhibitor of angiogenesis, decreases after bidirectional superior cavopulmonary anastamosis

Pulmonary arteriovenous malformations (PAVMs) are a common source of morbidity after bidirectional superior cavopulmonary anastomosis (Glenn). The diversion of hepatic venous effluent away from the pulmonary circulation after Glenn appears to play a significant role in the pathogenesis of PAVMs. Although the liver is known to produce factors that regulate vascular development, specific hepatic inhibitors of angiogenesis have not been described in the post-Glenn population. Endostatin, produced from its precursor collagen XVIII, is a potent inhibitor of angiogenesis produced by the liver. This study aimed to investigate the hypothesis that endostatin levels decrease in patients after Glenn. Levels of endostatin and its precursor, long-type collagen XVIII, were determined by enzyme-linked immunoassay and immunoprecipitation, respectively, for serum samples from 38 patients undergoing Glenn, total cavopulmonary anastomosis (Fontan), or biventricular repair of cardiac defects. Samples were obtained before surgery and 24 h afterward. In patients undergoing a bidirectional Glenn procedure, endostatin levels decreased after surgery (n = 17; 4.42 vs 3.34 ng/ml; p < 0.001), and long type-collagen XVIII levels increased by 200 % (n = 10; p = 0.0001). However, endostatin levels did not change after surgery in patients undergoing Fontan (n = 13) or biventricular repair (n = 8). In patients undergoing Fontan, long-type collagen XVIII increased by 18 % (p < 0.01), whereas in control subjects, the levels were unchanged. These data suggest that the diversion of hepatic blood flow away from the pulmonary circulation in patients after the Glenn procedure inhibits endostatin production from collagen XVIII, resulting in decreased circulating serum endostatin levels. A decrease in endostatin may promote angiogenesis. The mechanism whereby the pulmonary circulation processes endostatin and its potential role in the pathogenesis of PAVMs warrant further study.

Systemic-to-pulmonary collateral flow, as measured by cardiac magnetic resonance imaging, is associated with acute post-Fontan clinical outcomes

BACKGROUND

Systemic-pulmonary collateral (SPC) flow occurs commonly in single ventricle patients after superior cavo-pulmonary connection, with unclear clinical significance. We sought to evaluate the association between SPC flow and acute post-Fontan clinical outcomes using a novel method of quantifying SPC flow by cardiac magnetic resonance (CMR) imaging.

METHODS AND RESULTS

All patients who had SPC flow quantified by CMR imaging before Fontan were retrospectively reviewed to assess for acute clinical outcomes after Fontan completion. Forty-four subjects were included who had Fontan completion between May 2008 and September 2010. SPC flow prior to Fontan measured 1.5±0.9 L/min/m(2), accounting for 31±11% of total aortic flow and 44±15% of total pulmonary venous flow. There was a significant linear association between natural log-transformed duration of hospitalization and SPC flow as a proportion of total aortic (rho=0.31, P=0.04) and total pulmonary venous flow (rho=0.29, P=0.05). After adjustment for Fontan type and presence of a fenestration, absolute SPC flow was significantly associated with hospital duration ≥7 days (odds ratio [OR]=9.2, P=0.02) and chest tube duration ≥10 days (OR=22.7, P=0.009). Similar associations exist for SPC flow as a percentage of total aortic (OR=1.09, P=0.048 for hospitalization ≥7 days; OR=1.24, P=0.007 for chest tube duration ≥10 days) and total pulmonary venous flow (OR=1.07, P=0.048 for hospitalization ≥7 days; OR=1.18, P=0.006 for chest tube duration ≥10 days).

CONCLUSIONS

Increasing SPC flow before Fontan, as measured by CMR imaging, is associated with increased duration of hospitalization and chest tube following Fontan completion.

Computational fluid dynamics in cardiovascular disease

Computational fluid dynamics (CFD) is a mechanical engineering field for analyzing fluid flow, heat transfer, and associated phenomena, using computer-based simulation. CFD is a widely adopted methodology for solving complex problems in many modern engineering fields. The merit of CFD is developing new and improved devices and system designs, and optimization is conducted on existing equipment through computational simulations, resulting in enhanced efficiency and lower operating costs. However, in the biomedical field, CFD is still emerging. The main reason why CFD in the biomedical field has lagged behind is the tremendous complexity of human body fluid behavior. Recently, CFD biomedical research is more accessible, because high performance hardware and software are easily available with advances in computer science. All CFD processes contain three main components to provide useful information, such as pre-processing, solving mathematical equations, and post-processing. Initial accurate geometric modeling and boundary conditions are essential to achieve adequate results. Medical imaging, such as ultrasound imaging, computed tomography, and magnetic resonance imaging can be used for modeling, and Doppler ultrasound, pressure wire, and non-invasive pressure measurements are used for flow velocity and pressure as a boundary condition. Many simulations and clinical results have been used to study congenital heart disease, heart failure, ventricle function, aortic disease, and carotid and intra-cranial cerebrovascular diseases. With decreasing hardware costs and rapid computing times, researchers and medical scientists may increasingly use this reliable CFD tool to deliver accurate results. A realistic, multidisciplinary approach is essential to accomplish these tasks. Indefinite collaborations between mechanical engineers and clinical and medical scientists are essential. CFD may be an important methodology to understand the pathophysiology of the development and progression of disease and for establishing and creating treatment modalities in the cardiovascular field.

Pulmonary angiogenesis in a rat model of hepatopulmonary syndrome

BACKGROUND & AIMS

Hepatopulmonary syndrome (HPS), defined as intrapulmonary vasodilation, occurs in 10%-30% of cirrhotics and increases mortality. In a rat model of HPS induced by common bile duct ligation (CBDL), but not thioacetamide (TAA)-induced nonbiliary cirrhosis, lung capillary density increases, monocytes accumulate in the microvasculature, and signaling factors in the angiogenesis pathway (Akt and endothelial nitric oxide synthase [eNOS]) are activated. Pentoxifylline (PTX) directly decreases lung endothelial Akt and eNOS activation, blocks intravascular monocyte accumulation, and improves experimental HPS; we evaluated whether pulmonary angiogenesis develops in this model.

METHODS

TAA- and PTX-treated animals were evaluated following CBDL. Lung angiogenesis was assessed by quantifying factor VIII-positive microvessels and levels of von Willebrand factor (vWf), vascular endothelial cadherin (VE-cadherin), and proliferating cell nuclear antigen (PCNA). Angiogenic factors including phospho-Akt, phospho-eNOS, vascular endothelial growth factor (VEGF)-A, and phospho-VEGF receptor-2 (p-VEGFR-2) were compared and monocyte accumulation was assessed.

RESULTS

Following CBDL, but not TAA exposure, rats developed HPS that was temporally correlated with increased numbers of lung microvessel; increased levels of vWf, VE-cadherin and PCNA; and activation of Akt and eNOS. Angiogenesis was accompanied by increased pulmonary VEGF-A and p-VEGFR-2 levels, with VEGF-A staining in accumulated intravascular monocytes and alveolar endothelial cells. Following CBDL, PTX-treated rats had reduced numbers of microvessels, reduced lung monocyte accumulation, downregulation of pulmonary angiogenic factors, and reduced symptoms of HPS.

CONCLUSIONS

A specific increase in pulmonary angiogenesis occurs as experimental HPS develops, accompanied by activation of VEGF-A-associated angiogenic pathways. PTX decreases the angiogenesis, reduces the symptoms of HPS, and downregulates VEGF-A mediated pathways.

Gene array analysis of a rat model of pulmonary arteriovenous malformations after superior cavopulmonary anastomosis

OBJECTIVE

Pulmonary arteriovenous malformations commonly develop in children who have undergone a cavopulmonary anastomosis as part of the palliative sequence for single-ventricle physiology.

METHODS

We developed a rat model of cavopulmonary anastomosis that results in pulmonary arteriovenous malformations that are angiographically and histologically similar to the human condition. We used this model to analyze the gene expression profile associated with pulmonary arteriovenous malformations developing after cavopulmonary anastomosis.

RESULTS

Six Sprague-Dawley rats underwent right superior cavopulmonary anastomosis, allowing the left lung to serve as a control. Total RNA was isolated from each lung at death 8 months postoperatively and compared by using the Affymetrix Rat Microarray RAE230 2.0 GeneChip (Affymetrix, Santa Clara, Calif). One hundred thirty-seven genes demonstrated altered expression in the lungs after cavopulmonary anastomosis compared with that seen in the control lungs: 55 (40%) genes demonstrated increased expression, and 82 (60%) genes demonstrated decreased expression. Modulation of genes associated with angiogenesis and vascular remodeling was found, including angiopoietin-2, placental growth factor, several matrix metalloproteases, and several collagen subtypes. Genes with vasoactive properties, including endothelin 1 and endothelin receptor type B, demonstrated altered gene expression. Several members of the transforming growth factor beta superfamily signaling pathway also demonstrated altered expression.

CONCLUSIONS

These changes in gene expression might have causative implications for pulmonary arteriovenous malformations that develop after cavopulmonary anastomosis.

Elevated vascular endothelial growth factor levels are associated with aortopulmonary collateral vessels in patients before and after the Fontan procedure

BACKGROUND

Aortopulmonary collaterals (APCs) are frequently observed before and after the Fontan procedure. However, the mechanism of the development of APCs is unknown. We hypothesized that one or several antiangiogenic and/or angiogenic growth factors might play a role in the development of APCs.

METHODS

Eighty-five patients were enrolled and divided into 3 groups (Fontan group: 30 patients after the Fontan procedure, cyanotic group: 29 patients with cyanotic heart disease, and control group: 26 patients with cyanotic heart disease after biventricular repair). We measured basic fibroblast growth factor, vascular endothelial growth factor (VEGF), hepatocyte growth factor, and endostatin at catheterization. Angiographic evaluation for the presence of APCs using a 4-point scale (grade 1: absent APCs, > or = grade 2: significantly present APCs) was performed, and the relation of the serum levels of these factors to the presence of APCs was assessed.

RESULTS

The grade of APCs significantly increased in the Fontan group, but it decreased in the control group. The serum VEGF levels were higher in the Fontan group (280 +/- 174 pg/mL) and the cyanotic group (302 +/- 245 pg/mL) than in the control group (111 +/- 91 pg/mL) (P = .0004), and they were higher in patients with APCs (383 +/- 204 pg/mL) than in those without APCs (115 +/- 65 pg/mL) (P < .0001). There was no significant difference in the serum basic fibroblast growth factor, hepatocyte growth factor, and endostatin levels between the 3 groups.

CONCLUSIONS

Aortopulmonary collaterals increase after the Fontan procedure. Serum VEGF levels are associated with the presence of APCs. Vascular endothelial growth factor may play a role in the development of APCs in patients with cyanotic heart disease and after the Fontan procedure.

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.

Increased vascular endothelial growth factor in patients with cyanotic congenital heart diseases may not be normalized after a Fontan type operation

BACKGROUND

To determine the change of serum concentration of vascular endothelial growth factor (VEGF) in patients with cyanotic congenital heart disease (C-CHD).

METHODS

Patients comprised four groups: group A, 19 patients without cyanosis; group B, 24 patients with C-CHD; group C, 17 patients who had C-CHD and underwent biventricular repair; and group D, 15 patients who had single ventricle and underwent a Fontan type operation. Blood samples were obtained from upper arm veins and serum VEGF was determined. We determined correlation between serum VEGF and arterial oxygen saturation and compared levels of serum VEGF among groups. In addition, age and hemodynamic variables derived from cardiac catheterization were analyzed in terms of correlation with serum VEGF.

RESULTS

Serum VEGF significantly negatively correlated with arterial oxygen saturation (r = -0.62, p < 0.0001). Serum VEGF in B and D were significantly higher than those in A and C (median = 443 pg/mL in B and 302 pg/mL in D vs 180 pg/mL in A and 216 pg/mL in C, respectively). Serum VEGF was significantly negatively correlated with patient's age (p = 0.54, p < 0.04) in D, but significantly positively correlated with systemic venous pressure (p = 0.45, p < 0.01) in pooled data.

CONCLUSIONS

Patients with C-CHD have increased serum VEGF in parallel with the degree of cyanosis. With biventricular repair, cyanosis and serum VEGF are normalized. However, with a Fontan type operation, cyanosis disappears but serum VEGF may not be normalized because of elevated venous pressure in association with younger age.

Heparin Accelerates Pulmonary Artery Development in Neonate Rabbits

Pulmonary vascular resistance drops sharply within a few minutes after birth for the survival of neonates. A majority of this resistance is caused by "pulmonary vascular bed" or vessel lacking smooth muscle cells. Heparin is known to promote proliferation and development of endothelial cells and to subsequently decrease their overall vascular resistance, but its detailed features remained unknown. Therefore, in this study we treated neonatal rabbits with heparin, protamine (antagonist of heparin), or saline, and evaluated histopathological features of vascular endothelial cells using two different types of computer assisted image analysis, i.e., CAS200 and NIH image. These two systems detected the percentage of vascular endothelial area per fields (VA) and CD31-positive area per total area of tissue following subtraction of background stain. CD31 was used as an endothelial cell marker. Heparin treated rabbits were associated with significant decrement of pulmonary/systemic artery pressure (Pp/Ps) (21.0 +/- 6.0%) compared to protamine (29.9 +/- 6.1%) or saline (29.4 +/- 3.0%) treated animals. The values of VA obtained by the two image analyses (CAS200 and NIH image) were significantly increased in heparin treated animals (38.4 +/- 3.2% determined by CAS200 and 24.0 +/- 1.3% by NIH image) compared to protamine (30.2 +/- 3.9% and 19.2 +/- 1.8%) or saline (33.2 +/- 1.5% and 20.8 +/- 3.8%) treated animals on 14th day of treatment. The present study indicates that heparin accelerates pulmonary vascular bed development probably by increasing the number and volume of endothelial cells, which subsequently contributes to the decrease in pulmonary vascular resistance.

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.

Induction of pulmonary angiogenesis by adenoviral-mediated gene transfer of vascular endothelial growth factor

BACKGROUND

We hypothesized that gene transfer of vascular endothelial growth factor (VEGF) mediated by an adenovirus vector might induce pulmonary artery angiogenesis in a lamb model of pulmonary artery hypoplasia.

METHODS

Thirteen fetal lambs had left pulmonary artery banding at 106 days of gestation. Following birth, 3 groups were divided: VEGF group (n = 5) and beta-GAL group (n = 4) received an adenoviral vector encoding respectively for human VEGF165 and for galactosidase A. A control group (n = 4) had neither gene nor virus. Viral suspensions were selectively instilled in the left bronchus 6.5 days after birth. Five nonoperated lambs constituted the normal group. Euthanasia was performed at 30 days of age. Gene transfer was confirmed by blue coloration of left lung obtained with Xgal solution in an additional experiment. Histomorphometric evaluation was performed. All groups were compared with ANOVA test and paired test was used to compare right and left lung in each animal.

RESULTS

Left lung was similarly hypoplastic in all operated lambs. Left pulmonary artery hypoplasia present in all operated groups was significantly less pronounced in VEGF group. The number of pleural arteries was similarly increased in left lung of all operated lambs. Left lung arterial density was higher in VEGF group than in all other groups. The percentage of parenchyma of left lung was lower in beta-GAL group than in all others, partially returned to normal in VEGF group.

CONCLUSIONS

In this model, transbronchial VEGF gene transfer induces pulmonary angiogenesis, proximal pulmonary artery growth and contributes to lung parenchyma recovery.

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.

Alterations in plasma angiogenic growth factor concentrations after coronary artery bypass graft surgery: relationships with post-operative complications

To determine whether angiogenic growth factor levels are altered during and after cardiac surgery, plasma concentrations of basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF) and transforming growth factor beta1 (TGFbeta1) were measured in 32 patients undergoing coronary artery bypass graft (CABG) surgery with extracorporeal circulation (ECC). EGF levels significantly decreased during ECC and remained low until the 24th post-operative hour with no difference between complicated and uncomplicated patients. TGFbeta1 and bFGF concentrations significantly increased at the end of ECC and after cross-clamp release, and returned to pre-operative values at the 6th post-operative hour suggesting that the source of these elevations are the lungs and heart. After cross-clamp release bFGF levels but not TGFbeta1 ones were higher in patients with respiratory impairments. VEGF values increased significantly at the 6th and 24th post-operative hours. At the 24th post-operative hour plasma VEGF levels were higher in patients with cardiovascular and hematological impairments. In conclusion, these results highlight that the angiogenic network is profoundly altered in patients undergoing cardiopulmonary bypass as previously demonstrated for lipidic, cytokine and haematopoietic growth factor ones and identify an association between specific post-CABG complications and systemic release of bFGF and VEGF.

Resident research training conducted in a community hospital general surgery residency program

PURPOSE

Research is educationally important for surgical residents. However, little information exists regarding effective methods for teaching residents scientific methodology in a community hospital. This effort describes an effective program conducted in a community hospital for enhancing scientific opportunities of surgical residents.

METHODS

A strong infrastructure that supports research is necessary. Dedicated nonsalaried teaching faculty serve as mentors and co-investigators. Opportunities to engage in basic research are made available in off-campus basic science laboratories.

RESULTS

Research productivity has been prolific, as demonstrated by numerous publications. Residents interested in sub-speciality training have been able to conduct research that has made them competitive for fellowships and a wider range of practice choices.

CONCLUSION

Rigorous research can be effectively taught in a community hospital, provided adequate educational and funding support is provided and faculty actively mentor residents. Having research capabilities provides added incentive for better-qualified medical students to apply to a surgical residency position in a community hospital. Research productivity also enhances the ability to better recruit new faculty.

Rat model of pulmonary arteriovenous malformations after right superior cavopulmonary anastomosis

We developed a rat model of pulmonary arteriovenous malformations after cavopulmonary anastomosis. We sought to determine whether this model reproduces the angiographic and histologic features seen in the human condition. Eight Sprague-Dawley rats underwent a right superior cavopulmonary anastomosis with the use of microsurgical techniques. Between 2 and 13 mo, pulmonary angiography was performed, the animals were euthanized, and the lungs were removed. Microscopic sections of the lung were stained with an endothelial-specific antibody (von Willebrand factor). Microvessel density was determined by counting vessels staining positively for von Willebrand factor, and the shunted and nonshunted (control) lungs were compared for each animal. Pulmonary angiography revealed time-dependent development of arteriovenous malformations. Microvessel density demonstrated a time-dependent increase in the shunted lung compared with the control lung (simple linear regression of the ratio of the microvessel density of the shunted lung divided by the microvessel density of the control lung on time; R(2) = 0.79, P = 0.003). This animal model reproduces the same angiographic and microscopic features of pulmonary arteriovenous malformations that develop in humans after cavopulmonary anastomosis. This appears to be a valid model that may be used to further study etiologic mechanisms for this phenomenon.