Author: Kanwarpal S. Bakshi, MD – Children’s Hospital Los Angeles
A 3-year-old child with hypoplastic left heart syndrome (HLHS) develops a persistent high-output chylothorax several weeks after extra-cardiac non-fenestrated (ECNF) Fontan completion. Despite aggressive medical therapy, the effusions persist. Dynamic contrast MR lymphangiography shows abnormal and diffuse lymphatic congestion around the lung parenchyma without a focal duct leak, while cardiac catheterization shows markedly elevated Fontan pressures. Which surgical intervention is MOST APPROPRIATE to treat the refractory chylothorax in this setting?
EXPLANATION
In the Fontan circulation, systemic venous return flows mostly “passively” into the pulmonary arteries without a subpulmonic ventricle, leading to chronically elevated central venous pressure (CVP). Sustained elevation of CVP increases hepatic lymphatic production while simultaneously obstructing forward lymphatic drainage into the venous system. This combination produces lymphatic hypertension, thoracic duct dilation, and formation of extensive collateral lymphatic channels.¹ As a result, Fontan patients may develop post-operative chylothorax, plastic bronchitis (PB), protein-losing enteropathy (PLE), and ascites as manifestations of lymphatic failure.¹,²
Chylothorax develops when chyle accumulates in the pleural cavity because the thoracic duct cannot effectively empty into the high-pressure Fontan system. Medical management includes pleural drainage, diuresis, dietary fat restriction or medium-chain triglyceride diets, and octreotide. When effusions continue to persist, advanced imaging, such as intranodal lymphangiography and dynamic contrast-enhanced MR lymphangiography, can define the underlying mechanism and help guide management.² Etiologies include traumatic thoracic duct branch leaks, pulmonary lymphatic perfusion syndrome (PLPS), and central lymphatic flow disorder (CLFD).¹-³ PLPS occurs when lymphatic flow is redirected retrograde into abnormal lymphatic networks in the chest.³ CLFD occurs when the thoracic duct is obstructed, dysplastic or absent, leading to abnormal lymphatic flow, multicompartmental effusions, and the presence of dermal backflow through lymphatic collaterals in the abdominal wall.¹,³
When imaging demonstrates a discrete lymphatic leak or PLPS, percutaneous interventions such as selective lymphatic duct (SLDE) or thoracic duct embolization (TDE) can be effective; however, many Fontan patients exhibit diffuse lymphatic hypertension or CLFD.³ Because thoracic duct occlusion in the setting of elevated Fontan pressures may further obstruct central lymphatic drainage and worsen complications such as PLE or ascites, catheter-based therapies can have limited efficacy in these hemodynamically driven lymphatic disorders.² These limitations underscore that in many Fontan patients, the underlying problem is global lymphatic failure caused by elevated venous pressure, rather than an isolated leak.
The innominate vein turndown procedure (answer choice C) directly addresses this core pathophysiology by creating a drainage pathway from the systemic venous circulation into the lower-pressure atrium. By diverting the left innominate vein to the atrium, the thoracic duct is decompressed into a circuit with significantly lower pressure than the cavopulmonary Fontan pathway. This functional “diastolic suctioning” increases thoracic duct transport capacity and improves lymphatic outflow, effectively relieving lymphatic hypertension, while increasing systemic preload in the Fontan circuit.4 This maneuver can also be useful in preventing and abating other lymphatic associated sequelae seen after the Fontan completion, including PB and PLE.
Hemodynamically, this maneuver introduces a controlled right-to-left shunt, reducing pulmonary blood flow (Qp) relative to systemic flow (Qs) and lowering the Qp/Qs ratio, akin to a fenestration, but with a potentially more significant decrease in thoracic duct pressure. While the trade-off is mild systemic desaturation, the overall benefit is relief of debilitating lymphatic complications, especially when prior catheter-based lymphatic techniques have failed. Postoperatively, if the patient is more than mildly desaturated, a band can be placed on the left internal jugular vein above the thoracic duct to limit the right-to-left shunt. 4
Surgical thoracic duct ligation (answer choice A), while useful for isolated traumatic thoracic duct injuries, does not address the elevated Fontan pressure that drives excessive lymphatic flow and impaired drainage. Pleurodesis (answer choice B) only prevents effusion reaccumulation but again does not correct the underlying lymphatic hypertension.
REFERENCES
1. Itkin M, Pizarro C, Radtke W, Spurrier E, Rabinowitz DA. Lymphatic Management in Single-Ventricle Patients. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2020;23:41-47. doi:10.1053/j.pcsu.2020.03.001
2. Bauer C, Scala M, Rome JJ, Tulzer G, Dori Y. Lymphatic Imaging and Intervention in Congenital Heart Disease. J Soc Cardiovasc Angiogr Interv. 2023;3(1):101174. Published 2023 Sep 27. doi:10.1016/j.jscai.2023.101174
3. Savla JJ, Itkin M, Rossano JW, Dori Y. Post-Operative Chylothorax in Patients With Congenital Heart Disease. J Am Coll Cardiol. 2017;69(19):2410-2422. doi:10.1016/j.jacc.2017.03.021
4. Hraska V, Hjortdal VE, Dori Y, Kreutzer C. Innominate vein turn-down procedure: Killing two birds with one stone. JTCVS Tech. 2021;7:253-260. Published 2021 Mar 18. doi:10.1016/j.xjtc.2021.01.045
5. Sinha P. Commentary: Innominate turndown-a better insurance for the Fontan circulation?. JTCVS Tech. 2021;7:261-262. Published 2021 Feb 8. doi:10.1016/j.xjtc.2021.02.011