Page 27 - Journal of Structural Heart Disease Volume 3, Issue 2

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Case Report
are acquired rather than congenital. The three most common etiologies are thrombosis surrounding a port or central line, external compression from tumors or other mass e ect, and surgical complications includ- ing direct injury of the thoracic duct or postoperative stenosis of the SVC or innominate vein [4, 7, 8, 9, 10].
Congenital—rather than acquired—SVC stenosis as presented in our case is exceedingly rare and thus far has only been reported in the presence of other signi - cant cardiac anomalies. For our patient, the absence of upper body edema or plethora, along with highly de- veloped collateral ow, indicates that this lesion had likely been present since birth. Although the causes of chylothorax are varied, the workup and management are similar across all etiologies. The diagnosis of chylot- horax is made based on pleural uid analysis contain- ing a triglyceride concentration greater than 110 mg/ dl, whereas it is excluded by a concentration less than 50 mg/dl. Intermediate values between 50 and 110 mg/dl can be further diagnosed by lipoprotein electro- phoresis of the uid to detect chylomicrons. Alterna- tively, a ratio of cholesterol-to-triglycerides in pleural uid of less than 1 is also diagnostic [11]. Chylothorax without a clear underlying cause (e.g., trauma, obstruc- tion, or post-surgical damage) accounts for 5–10% of cases and is typically diagnosed on lymphangiography or lymphoscintigraphy [12].
After initial invasive drainage of the effusion, if indicated for therapeutic or diagnostic purposes, the goal of therapy is to minimize production of chyle medically while treating the offending clot or obstruction, if possible. Medical treatment typ- ically involves a fat-restricted diet supplemented with medium-chain triglycerides, followed by oct- reotide (0.3–10 mcg/kg/hour titrated to response, with a median dose of 2.8 mcg/kg/hour) and then gut rest and TPN if other measures are unsuccessful. Approximately 80% of pediatric patients respond to medical therapy, although octreotide therapy and TPN carry their own risks [1, 13]. Recommen- dations vary regarding indications and timing for surgical management with thoracic duct ligation or pleurodesis, but cases are generally considered refractory when effusion persists for more than 2 weeks despite conservative management [14]. Overall, these surgical interventions have a high success rate, and the main risk factor for death or
chylothorax recurrence after surgery is thrombosis of the upper body venous vessels [15], thus con- firming the importance of relieving such an occlu- sion whenever possible.
There is only one previous report of isolated con- genital SVC stenosis leading to chylous e usion and respiratory failure; in that case, the patient present- ed in the immediate neonatal period with severe hy- drops and upper body edema consistent with SVC syndrome [16]. Here, we report the rst case without an obvious acquired etiology presenting outside the immediate perinatal period. Notably, the patient did not present with obvious clinical ndings of SVC syndrome and had developed signi cant venous collateralization, suggesting that the chronicity of his obstruction likely began during fetal life. Ulti- mately, his upper body central venous pressure was only mildly to moderately elevated due to collateral decompression, which likely allowed for a relatively slow accumulation of chyle in the pleural space until respiratory decompensation.
Furthermore, our patient’s hospital course con- rms the importance of understanding the various potential underlying causes of chylothorax and early intervention via relief of venous obstruction when possible. Our patient experienced a delay in treat- ment (i.e., abnormal echocardiogram on day 2, cardi- ology consulted on day 10, and the procedure itself performed on day 14) due to the standard of care of 2 weeks of medical therapy before declaring a chy- lothorax refractory and proceeding with an invasive means of treatment. An argument can be made that if a chylothorax is due to a known venous obstruc- tion, intervention could be performed immediately to relieve this obstruction in lieu of medical manage- ment. As such, it is essential to perform the necessary imaging studies to evaluate for venous anomalies, thrombosis, or intrathoracic mass a ecting both the innominate vein and/or the SVC.
Our patient’s presentation and rapid recovery following acute decompression of the upper body central veins with effective intravascular stent im- plantation demonstrates that significant chylous effusion can occur from severe congenital vascu- lar obstruction alone, in the absence of surgical complications or other factors. When chylothorax is caused by vascular obstruction, this phenom-
Harrison, D. J. et al.
Intravascular Stent Implantation for Chylothorax