Pulmonary Arteriovenous Malformations in Heterotaxy Syndrome

Off-pump direct hepatic veins-to-hemiazygos vein anastomosis after primary Kawashima operation: long-term result

Direct hepatic veins-to-hemiazygos connection offers the balanced distribution of hepatic venous blood to both lungs, not requiring anticoagulation. We report a 13-year follow-up after this type of off-pump Fontan completion. Patient's hepatic veins-to-hemiazygos confluence increased with growth to allow for unobstructed flow. This unique technique can be recommended in heterotaxy patients, if atrial hepatic venous drainage and hemiazygos vein are in close proximity.

A 4D flow MRI evaluation of the impact of shear-dependent fluid viscosity on in vitro Fontan circulation flow

The Fontan procedure for univentricular heart defects creates a nonphysiologic circulation where systemic venous blood drains directly into the pulmonary arteries, leading to multiorgan dysfunction secondary to chronic low-shear nonpulsatile pulmonary blood flow and central venous hypertension. Although blood viscosity increases exponentially in this low-shear environment, the role of shear-dependent ("non-Newtonian") blood viscosity in this pathophysiology is unclear. We studied three-dimensional (3D)-printed Fontan models in an in vitro flow loop with a Philips 3-T magnetic resonance imaging (MRI) scanner. A 4D flow phase-contrast sequence was used to acquire a time-varying 3D velocity field for each experimental condition. On the basis of blood viscosity of a cohort of patients who had undergone the Fontan procedure, it was decided to use 0.04% xanthan gum as a non-Newtonian blood analog; 45% glycerol was used as a Newtonian control fluid. MRI data were analyzed using GTFlow and MATLAB software. The primary outcome, power loss, was significantly higher with the Newtonian fluid [14.8 (13.3, 16.4) vs. 8.1 (6.4, 9.8)%, medians with 95% confidence interval, P < 0.0001]. The Newtonian fluid also demonstrated marginally higher right pulmonary artery flow, marginally lower shear stress, and a trend toward higher caval flow mixing. Outcomes were modulated by Fontan model complexity, cardiac output, and caval flow ratio. Vortexes, helical flow, and stagnant flow were more prevalent with the non-Newtonian fluid. Our data demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.NEW & NOTEWORTHY Although blood viscosity increases exponentially in low-shear environments, the role of shear-dependent ("non-Newtonian") blood viscosity in the pathophysiology of the low-shear Fontan circulation is unclear. We demonstrate that shear-dependent viscosity significantly alters qualitative flow patterns, power loss, pulmonary flow distribution, shear stress, and caval flow mixing in synthetic models of the Fontan circulation. Potential clinical implications include effects on exercise capacity, ventilation-perfusion matching, risk of pulmonary arteriovenous malformations, and risk of thromboembolism.

Characterisation of computed tomography angiography findings in paediatric patients with heterotaxy

BACKGROUND

Heterotaxy refers to the abnormal arrangement of organs across the left-right axis and is typically associated with complex cardiovascular malformations.

OBJECTIVE

To characterise the range of cardiac and extracardiac CT angiography findings in children with heterotaxy using the latest nomenclature consensus and to compare the different types of isomerism.

MATERIALS AND METHODS

We retrospectively analysed the data of 64 consecutive paediatric patients referred to our tertiary paediatric cardiovascular centre who underwent CT angiography for the evaluation of known or suspected heterotaxy within a 52-month period.

RESULTS

Right atrial isomerism was identified in 44 (69%) children, while left atrial isomerism was identified in 18 (28%) children. Atrial appendage anatomy and situs could not be determined in 2 children (3%). Associated heart defects included complete atrioventricular canal (CAVC) in 51 (80%) children, total anomalous pulmonary venous return in 43 (67%) and pulmonary atresia in 23 (36%). The bronchial branching pattern corresponded to atrial appendage morphology in all children except in the two in whom atrial appendage morphology could not be defined. In children with right atrial isomerism, the most common associated abnormalities were CAVC (n=41, 93%) and asplenia (n=34, 77%), while in those with left atrial isomerism, the most common associated abnormalities were polysplenia (n=17, 94%) and an interrupted inferior vena cava with azygos continuation (n=15, 83%).

CONCLUSION

CT angiography provides useful cardiovascular and extracardiac data on heterotaxy, which frequently involves a pattern of side-related findings but has great anatomical variability.

Hepatic Vein Incorporation Into the Azygos System in Heterotaxy and Interrupted Inferior Vena Cava

Background:

Patients with heterotaxy, single ventricle and interrupted inferior vena cava are at risk of developing significant pulmonary arteriovenous malformations and cyanosis, and inequitable distribution of hepatic factor has been implicated in their development. We describe our experience with a technique for hepatic vein incorporation that reliably provides resolution of cyanosis and presumably equitable hepatic factor distribution.

Methods:

A retrospective review of a single-surgeon experience was conducted for patients who underwent this modified Fontan operation utilizing an extracardiac conduit from the hepatic veins to the dominant superior cavopulmonary connection. Preoperative characteristics and imaging, operative details, and postoperative course and imaging were abstracted.

Results:

Median age at operation was 5 years (2-10 years) and median weight was 19.6 kg (11.8-23 kg). Sixty percent (3/5) of patients had Fontan completion without cardiopulmonary bypass, and follow-up was complete at a median of 14 months (range 1-20 months). Systemic saturations increased significantly from 81% ± 1.9% preoperatively to 95% ± 3.5% postoperatively, P = .0008. Median length of stay was 10 days (range: 7-14 days). No deaths occurred. One patient required reoperation for bleeding and one was readmitted for pleural effusion. Postoperative imaging suggested distribution of hepatic factor to all lung segments with improved pulmonary arteriovenous malformation burden.

Conclusions:

Hepatic vein incorporation for patients with heterotaxy and interrupted inferior vena cava should optimally provide equitable pulmonary distribution of hepatic factor with resolution of cyanosis. The described technique is performed through a conventional approach, is facile, and improves cyanosis in these complex patients.

Fontan Conversion

Early survival after the Fontan operation has improved significantly leading to a lifetime of Fontan circulation for patients. There is a natural progression of pulmonary artery pressure during the human lifetime that is easily tolerated in two-ventricle physiology but is deleterious for single-ventricle physiology. Obstructions in the venous to pulmonary artery pathway and pulmonary venous return or ventricular outflow, atrioventricular valve dysfunction (regurgitation), pulmonary arteriovenous malformations, venous thrombosis, and the development of atrial arrhythmias can lead to reduced functional status. These complications have been demonstrated in older patients with largely atriopulmonary connections owing to time accrual and unfavorable flow characteristics. Various surgical and catheter interventions aimed at reducing morbidity and mortality have been attempted to treat these identifiable abnormalities. The purpose of this article is to review the extant literature on Fontan Conversion and to assess the lessons learned over 20 years.

Non-cardiac issues in patients with heterotaxy syndrome

Management of complex congenital heart disease in patients with Heterotaxy syndrome (HS) has steadily improved. However, there is an insufficient appreciation of various non-cardiac issues that might impact the overall status of these patients. This article briefly reviews the implications of gastrointestinal, immunologic, genitourinary, respiratory, and central nervous system involvement in HS patients with a view to aid in their comprehensive clinical management.

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.

Reconstruction of cavopulmonary pathway for the patient with persistent arteriovenous malformations due to offset flow from hepatic vein

The hypoxemia caused by arteriovenous malformations after cavopulmonary shunt in patients with heterotaxy, an interrupted inferior vena cava and single ventricle physiology have been treated by incorporation of hepatic vein flow into the pulmonary circulation. However, some patients have persistent arteriovenous malformations because of offset hepatic venous flow to one pulmonary artery. Various approaches have been used to change offset flow to achieve balanced hepatic flow to the lungs in this patient population. This case report highlights the challenges that may be associated with anastomosis of the azygos vein to the inferior vena cava at the level of the diaphragm and illustrates an alternative technique to direct hepatic venous blood into an affected lung with arteriovenous malformations. The redirection of hepatic venous flow to the affected pulmonary artery resulted in resolution of symptoms within months of surgery.

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.