Lymphodynamics in Congenital Heart Disease

Lymphatic Interventions in Congenital Heart Disease

Lymphatic disorders in congenital heart disease can be broadly classified into chest compartment, abdominal compartment, or multicompartment disorders. Heavily T2-weighted noninvasive lymphatic imaging (for anatomy) and invasive dynamic contrast magnetic resonance lymphangiography (for flow) have become the main diagnostic modalities of choice to identify the cause of lymphatic disorders. Selective lymphatic duct embolization (SLDE) has largely replaced total thoracic duct embolization as the main lymphatic therapeutic procedure. Recurrence of symptoms needing repeat interventions is more common in patients who underwent SLDE. Novel surgical and transcatheter thoracic duct decompression strategies are promising, but long-term follow-up is critical and eagerly awaited.

Preliminary report of a thoracic duct-to-pulmonary vein lymphovenous anastomosis in swine: A novel technique and potential treatment for lymphatic failure

OBJECTIVE

The thoracic duct is the largest lymphatic vessel in the body, and carries fluid and nutrients absorbed in abdominal organs to the central venous circulation. Thoracic duct obstruction can cause significant failure of the lymphatic circulation (i.e., protein-losing enteropathy, plastic bronchitis, etc.). Surgical anastomosis between the thoracic duct and central venous circulation has been used to treat thoracic duct obstruction but cannot provide lymphatic decompression in patients with superior vena cava obstruction or chronically elevated central venous pressures (e.g., right heart failure, single ventricle physiology, etc.). Therefore, this preclinical feasibility study sought to develop a novel and optimal surgical technique for creating a thoracic duct-to-pulmonary vein lymphovenous anastomosis (LVA) in swine that could remain patent and preserve unidirectional lymphatic fluid flow into the systemic venous circulation to provide therapeutic decompression of the lymphatic circulation even at high central venous pressures.

METHODS

A thoracic duct-to-pulmonary vein LVA was attempted in 10 piglets (median age 80 [IQR 80-83] days; weight 22.5 [IQR 21.4-26.8] kg). After a right thoracotomy, the thoracic duct was mobilized, transected, and anastomosed to the right inferior pulmonary vein. Animals were systemically anticoagulated on post-operative day 1. Lymphangiography was used to evaluate LVA patency up to post-operative day 7.

RESULTS

A thoracic duct-to-pulmonary vein LVA was successfully completed in 8/10 (80.0%) piglets, of which 6/8 (75.0%) survived to the intended study endpoint without any complication (median 6 [IQR 4-7] days). Initially, 2/10 (20.0%) LVAs were aborted intraoperatively, and 2/10 (20.0%) animals were euthanized early due to post-operative complications. However, using an optimized surgical technique, the success rate for creating a thoracic duct-to-pulmonary vein LVA in six animals was 100%, all of which survived to their intended study endpoint without any complications (median 6 [IQR 4-7] days). LVAs remained patent for up to seven days.

CONCLUSION

A thoracic duct-to-pulmonary vein LVA can be completed safely and remain patent for at least one week with systemic anticoagulation, which provides an important proof-of-concept that this novel intervention could effectively offload the lymphatic circulation in patients with lymphatic failure and elevated central venous pressures.

Lymphatic failure and lymphatic interventions: Knowledge gaps and future directions for a new frontier in congenital heart disease

Lymphatic failure is a broad term that describes the lymphatic circulation's inability to adequately transport fluid and solutes out of the interstitium and into the systemic venous circulation, which can result in dysfunction and dysregulation of immune responses, dietary fat absorption, and fluid balance maintenance. Several investigations have recently elucidated the nexus between lymphatic failure and congenital heart disease, and the associated morbidity and mortality is now well-recognized. However, the precise pathophysiology and pathogenesis of lymphatic failure remains poorly understood and relatively understudied, and there are no targeted therapeutics or interventions to reliably prevent its development and progression. Thus, there is growing enthusiasm towards the development and application of novel percutaneous and surgical lymphatic interventions. Moreover, there is consensus that further investigations are needed to delineate the underlying mechanisms of lymphatic failure, which could help identify novel therapeutic targets and develop innovative procedures to improve the overall quality of life and survival of these patients. With these considerations, this review aims to provide an overview of the lymphatic circulation and its vasculature as it relates to current understandings into the pathophysiology and pathogenesis of lymphatic failure in patients with congenital heart disease, while also summarizing strategies for evaluating and managing lymphatic complications, as well as specific areas of interest for future translational and clinical research efforts.

Fifth "Jatene Lecture on Surgical Innovation": Innovation in Congenital Heart Surgery: Contributions From South America

We present the fifth "Jatene Lecture on Surgical Innovation" on Innovation in Congenital Heart Surgery, given at the Eighth Scientific Meeting of the World Society for Pediatric and Congenital Heart Surgery and Eighth World Congress of Pediatric Cardiology and Cardiac Surgery in Washington DC in 2023. We highlight what surgical innovation is and how innovation was accomplished in cardiac surgery and particularly in congenital heart surgery. A brief history of the development of congenital heart surgery across the world is summarized and we finally illustrate the South American contributions to congenital heart surgery, acknowledging the great innovations of Adib Jatene and Guillermo Kreutzer to our field.

Understanding the next circulation: lymphatics and what the future holds

PURPOSE OF REVIEW

The lymphatic system was previously considered the forgotten circulation because of an absence of adequate options for imaging and intervention. However, recent advances over the last decade have improved management strategies for patients with lymphatic disease, including chylothorax, plastic bronchitis, ascites, and protein-losing enteropathy.

RECENT FINDINGS

New imaging modalities have enabled detailed visualization of lymphatic vessels to allow for a better understanding of the cause of lymphatic dysfunction in a variety of patient subsets. This sparked the development of multiple transcatheter and surgery-based techniques tailored to each patient based on imaging findings. In addition, the new field of precision lymphology has added medical management options for patients with genetic syndromes, who have global lymphatic dysfunction and typically do not respond as well to the more standard lymphatic interventions.

SUMMARY

Recent developments in lymphatic imaging have given insight into disease processes and changed the way patients are managed. Medical management has been enhanced and new procedures have given patients more options, leading to better long-term results.

Occlusion Pressure of the Thoracic Duct in Fontan Patients With Lymphatic Failure: Does Dilatation Challenge Contractility?

Background

The Fontan circulation challenges the lymphatic system. Increasing production of lymphatic fluid and impeding lymphatic return, increased venous pressure may cause lymphatic dilatation and decrease lymphatic contractility. In-vitro studies have reported a lymphatic diameter-tension curve, with increasing passive stretch affecting the intrinsic contractile properties of each thoracic duct segment. We aimed to describe thoracic duct occlusion pressure and asses if thoracic duct dilation impairs contractility in individuals with a Fontan circulation and lymphatic failure.

Methods

Central venous pressure and thoracic duct measurements were retrospectively collected from 31 individuals with a Fontan circulation. Thoracic duct occlusion pressure was assessed during a period of external manual compression and used as an indicator of lymphatic vessel contractility. Measurements of pressure were correlated with measurements of the thoracic duct diameter in images obtained by dynamic contrast-enhanced MR lymphangiography.

Results

The average central venous pressure and average pressure of the thoracic duct were 17 mm Hg. During manual occlusion, the thoracic duct pressure significantly increased to 32 mm Hg. The average thoracic duct diameter was 3.3 mm. Thoracic duct diameter correlated closely with the central venous pressure. The rise in pressure following manual occlusion showed an inverse correlation with the diameter of the thoracic duct.

Conclusion

Higher central venous pressures are associated with increasing diameters of the thoracic duct. When challenged by manual occlusion, dilated thoracic ducts display a decreased ability to increase pressure. Dilatation and a resulting decreased contractility may partly explain the challenged lymphatic system in individuals with a Fontan circulation.

The Lymphatic System in the Fontan Patient-Pathophysiology, Imaging, and Interventions: What the Anesthesiologist Should Know

The Fontan surgery was developed as a palliative intervention for congenital heart disease (CHD) patients with single-ventricle physiology who are not candidates for a biventricular repair. Improvements in the surgery and medical management of these patients have increased survival, yet this population remains at risk for complications and end-organ dysfunction due to Fontan failure. Lymphatic vessels maintain a fluid balance within the extracellular space, participate in fat reabsorption from the small intestine, and play an important role in the body's immune response. Altered Starling forces at the capillary level, capillary leak, and lymphatic obstruction contribute to lymphatic dysfunction in patients with Fontan physiology. These lymphatic complications include edema, pleural effusions, plastic bronchitis (PB), and protein-losing enteropathy (PLE). Over the past decade, there have been innovations in lymphatic imaging. These new imaging techniques include noncontrast magnetic resonance (MR) lymphangiography, intranodal lymphangiography (IL), dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL), and liver lymphangiography. These imaging techniques help in delineating anatomy and guiding the appropriate therapeutic approach. Lymphatic interventions then may be performed to decompress the lymphatic system or to identify and occlude abnormal lymphatic vessels and drainage pathways. The anesthesiologist should have an understanding of the effects of lymphatic disorders on the Fontan circulation and apply appropriate management techniques for the associated interventions. The Fontan surgery was developed as a palliative intervention for CHD patients with single-ventricle physiology who are not candidates for a biventricular repair. The surgery creates a series systemic and pulmonary circulation with the energy necessary to provide gradient-driven pulmonary blood flow generated by the ventricle.¹ In the past decades, improvements in the surgery and medical management of these patients have increased survival, with 30-year survival rates close to 85%.² Despite these improvements, this population remains at risk for complications and end-organ dysfunction due to Fontan failure, which is characterized by elevated systemic venous pressures and low cardiac output. These complications include arrhythmias, cardiac dysfunction, ascites, liver fibrosis/cirrhosis, renal dysfunction, pulmonary failure, and lymphatic complications such as edema, pleural effusions, PB, and PLE. Complications ultimately contribute to increased risk for hospitalization, death, and need for heart transplantation.^3,4 For this reason, there has been increasing interest in the role of abnormal lymphatic circulation in the genesis of Fontan failure. The authors characterize the lymphatic pathophysiology associated with Fontan physiology and review the imaging and interventional strategies used to treat these patients.

Medical Interventions for Chylothorax and their Impacts on Need for Surgical Intervention and Admission Characteristics: A Multicenter, Retrospective Insight

The incidence of chylothorax is reported from 1-9% in pediatric patients undergoing congenital heart surgery. Effective evidenced-based practice is limited for the management of post-operative chylothorax in the pediatric cardiac intensive care unit. The study characterizes the population of pediatric patients with cardiac surgery and chylothorax who eventually require pleurodesis and/or thoracic duct ligation; it also establishes objective data on the impact of various medical interventions. Data were obtained from the Pediatric Health Information System database from 2004-2015. Inclusion criteria for admissions for this study were pediatric admissions, cardiac diagnosis, cardiac surgery, and chylothorax. These data were then divided into two groups: those that did and did not require surgical intervention for chylothorax. Other data points obtained included congenital heart malformation, age, gender, length of stay, billed charges, and inpatient mortality. A total of 3503 pediatric admissions with cardiac surgery and subsequent chylothorax were included. Of these, 236 (9.4%) required surgical intervention for the chylothorax. The following cardiac diagnoses, cardiac surgeries, and comorbidities were associated with increased odds of surgical intervention: d-transposition, arterial switch, mitral valvuloplasty, acute kidney injury, need for dialysis, cardiac arrest, and extracorporeal membrane oxygenation. Statistically significant medical interventions which did have an impact were specific steroids (hydrocortisone, dexamethasone, methylprednisolone) and specific diuretics (furosemide). These were significantly associated with decreased length of stay and costs. Dexamethasone, methylprednisolone, and furosemide were associated with decreased odds for surgical intervention. These analyses offer objective data regarding the effects of interventions for chylothorax in pediatric cardiac surgery admissions. Results from this study seem to indicate that most post-operative chylothoraxes should improve with furosemide, a low-fat diet, and steroids.

Pulmonary Manifestations of Congenital Heart Disease in Children

This review addresses how anomalous cardiovascular anatomy imparts consequences to the airway, respiratory system mechanics, pulmonary vascular system, and lymphatic system. Abnormal formation or enlargement of great vessels can compress airways and cause large and small airway obstructions. Alterations in pulmonary blood flow associated with congenital heart disease (CHD) can cause abnormalities in pulmonary mechanics and limitation of exercise. CHD can lead to pulmonary arterial hypertension. Lymphatic abnormalities associated with CHD can cause pulmonary edema, chylothorax, or plastic bronchitis. Understanding how the cardiovascular system has an impact on pulmonary growth and function can help determine options and timing of intervention.

Lymphatic Disorders and Management in Patients with Congenital Heart Disease

Congenital heart disease can lead to significant lymphatic complications such as chylothorax, plastic bronchitis, protein losing enteropathy and ascites. Recent improvements in lymphatic imaging and the development of new lymphatic procedures can help alleviate symptoms and improve outcomes.

An international survey of the nutrition management of chylothorax: a time for change

INTRODUCTION

Although chylothorax is an uncommon complication following paediatric cardiothoracic surgery, it has significant associated morbidities and increased in-hospital mortality, as well as results in higher costs. A lack of prospective evidence or consensus guidelines for management of chylothorax further hinders optimal management. The aim of this survey was to characterise variations in practice in the management of chylothorax and to identify areas for future research.

MATERIALS AND METHODS

A descriptive, observational survey investigating conservative management practices of chylothorax was distributed internationally to health-care professionals in paediatric intensive care and cardiology units. The survey investigated five domains: the first providing general information about health-care professionals and four domains focusing on clinical practice including diet composition and duration.

RESULTS

In total, sixty-four health-care professionals completed the survey, representing 38 organisations from 16 countries. The respondents were dietitians (80%), physicians (19%), and nurses (1%). In Australia and New Zealand, management was most commonly directed by physicians' preference (67%) as compared to unit protocols in Europe (67%), United States of America (67%), and Other regions (55%). Dietitians in Australia/New Zealand, United Kingdom, and Ireland followed the most restrictive diet therapy recommending <5 g long chain triglyceride fat per day (p < 0.00001). The duration of diet therapy significantly varied between regions: Australia/New Zealand: 4 weeks (36%) and 6 weeks (43%); Europe: 4 weeks (25%) and 6 weeks (57%); and North America: 4 weeks (18%) and 6 weeks (75%) (p < 0.00001).

CONCLUSIONS

This survey highlights international variations in practice in the management of chylothorax, particularly with respect to treatment duration and dietary fat restriction. Future research should include a multi-centre randomised controlled trial to inform evidence-based practice and reduce morbidity, particularly poor growth.

Pediatric chylothorax-lymphatic imaging enables targeted surgical treatment

Chylothorax-the collection of lymphatic fluid in the pleural space-is a rare finding in otherwise healthy adolescents. Initially, clinical signs and symptoms are often non-specific and a wide range of underlying causes necessitates extensive diagnostic workup. Treatment options include dietary measures, medical treatment, and various surgical procedures. We report about a 12-year-old boy with accidental diagnosis of chylothorax. Lymphatic imaging led to visualization of a leakage of an accessory left-sided thoracic duct and thoracoscopic clipping was successfully performed. Lymphatic imaging procedures depict underlying causes of chylothorax allowing targeted therapeutic management.