Chylopericardial tamponade has rarely been described after heart surgery. Review of the literature indicates that it is more common after surgery for congenital heart disease. The typical appearance of the pericardial aspirate is milky although that is not the case always, particularly in the first few days after cardiothoracic surgery. The diagnosis can be easily missed if the atypical fluid is not sent to the laboratory for analysis, including triglyceride level measurement. Whether secondary to interruption of the thoracic lymphatic channels or obstruction of the thoracic duct, it requires catheter drainage and institution of parenteral nutrition and/or medium-chain triglycerides (MCTs) diet to reduce the production of lymph while assuring adequate nutrition. In case of failure of conservative therapy, surgical ligation of the thoracic duct becomes necessary and usually succeeds in controlling and ultimately resolving the problem.
A relatively healthy but obese (260 lbs) man developed shortness of breath and chest pain after a laparoscopic cholecystectomy done elsewhere in December 2008. Subsequently, he sustained a nontransmural myocardial infarction. Cardiac catheterization then showed a dilated aortic root and diseased left anterior descending and obtuse marginal branch of the circumflex coronary artery (OM), both of which were stented. He was started on Plavix (Clopidogrel bisulfate; Bristol-Myers Squibb/Sanofi Pharmaceuticals) and did well until February 8, 2009, when he was admitted to our institution with increased shortness of breath and was found to have severe aortic insufficiency. Repeat cardiac catheterization confirmed a 5.8-cm diffuse aortic root aneurysm, 4+ aortic insufficiency, and in-stent stenosis of the OM.
On February 13, he underwent a Bentall procedure using a 25-mm ATS (ATS Medical Inc., Minneapolis, MN USA) prosthetic valve sutured to a 28-mm Hemashield (Boston Scientific, Natick, MA USA) graft. Buttons of coronary ostia were reimplanted on the graft, and the left mammary artery was implanted on the OM. The right coronary artery was found to be dissected throughout its entire course. The pleural cavities were not entered during the procedure. Two mediastinal drains were left in place. The pathology report indicated myxoid changes with chronic inflammation of the aortic wall and dystrophic calcifications with myxoid changes of the aortic valve. He required reexploration for diffuse bleeding 8 hours after the initial surgery.
On February 15, oral anticoagulation with Coumadin (warfarin sodium; Bristol-Myers Squibb Co.) was started along with a low-salt heart-healthy diet. Two days later, his chest tubes and temporary pacing wires were removed after the chest drainage had tapered to <100 mL over a period of 12 hours. He was then transferred to the step-down unit.
On February 18, he was noted to have left upper extremity edema, and a Doppler ultrasound study confirmed thrombosis of the left internal jugular and subclavian veins as well as an axillary vein thrombus. By then, he was fully anticoagulated with international normalized ratio (INR) 2.57. The indwelling left subclavian central venous line was removed.
On February 19, he experienced a sudden onset of chest pain, agitation, and hemodynamic deterioration (blood pressure, 69/40 mm Hg). Chest x-ray revealed marked cardiomegaly, and a transesophageal echocardiogram (TEE) confirmed pericardial tamponade. He was returned to surgery for reexploration. Immediately upon opening the lower corner of the sternotomy incision, 1800 mL of dark brownish and cloudy fluid under tension were evacuated with rapid return of good hemodynamics. The pericardial cavity was explored with a rigid mediastinoscope without encountering any source of active bleeding or organized clots. The wound was thus closed after leaving three new drains in the pericardial cavity. His immediate recovery was excellent, and his appetite improved slowly. On February 22, the chest tubes drainage was scant, and the drains were removed.
On February 23, he became suddenly diaphoretic and hypotensive and experienced increased shortness of breath. Repeat bedside echocardiogram showed reaccumulation of a significant pericardial effusion with tamponade. Bedside pericardiocentesis yielded 600 mL of milky fluid resulting in instantaneous resolution of symptoms. An indwelling pigtail drain was left in the pericardium. Fluid analysis showed the presence of chylomicrons, with white blood cell count of 1860, red blood cell 45,100, mononuclear cells 64, polymorphonuclear cells 36, and lactate dehydrogenase level of 287 mg/dL and triglycerides level of 587 mg/dL. Fluid cultures were negative. He was started on an MCT diet supplemented with parenteral nutrition.
On February 26 and while pericardial drainage had been, respectively, 1650 and 1750 mL in the previous 2 days, the pericardial drain was accidentally dislodged. Repeat cardiac echo 6 hours later revealed buildup of a significant pericardial effusion without tamponade.
On February 27, in the face of recurrent accumulation of the chylous pericardial effusion, we decided to proceed with thoracic duct ligation without undue delay. The patient was given heavy cream laced with methylene blue before surgery in an attempt to identify the site of lymphatic drainage. A left-sided video-assisted thoracoscopic surgery was unsuccessful in identifying any lymph leakage. Because of his obesity, the thoracic duct was then ligated en masse through a small right thoracotomy, again without identifying any leaking site. A large right pericardial defect was created and bilateral chest tubes were left in place. The following morning, he was restarted on the MCT diet along with total parenteral nutrition (TPN), which was discontinued when his oral intake was satisfactory. The chest tubes drainage tapered down progressively. Repeat venous Doppler ultrasound showed recanalization of the left subclavian vein, but the internal jugular and axillary veins remained thrombosed. On March 8, talcum pleurodesis was performed empirically in each pleural cavity. Thereafter, daily chest tubes drainage tapered from 1400 mL initially to only scant amounts. On March 11, the chest tubes were removed after they stopped draining completely. Serial cardiac echos failed to reveal significant reaccumulation of a pericardial effusion. However, a computed tomography (CT) scan of the chest performed because of persistent retrosternal discomfort revealed the presence of a residual retrosternal 7.3 × 3.9 cm fluid collection communicating with a small 1.8 cm posterior pericardial effusion (Figs. 1, 2). A CT-guided 6.3-Fr pigtail drain was placed within the collection (250 mL of chylous fluid) and connected to a Jackson-Pratt (General Medical Inc., Raleigh, NC USA) reservoir. The drainage eventually became scant, and the drains were discontinued on March 20.
The next day, the patient was discharged home. He was followed up as an outpatient with repeat echos. He returned to a normal diet a month later and remains asymptomatic and free of recurrence10 months later.
While chylothorax is common and has been known to occur after almost every known surgical procedure performed in the neck or chest,1 chylopericardium—and particularly chylopericardial tamponade—remains to be a rare complication of cardiac surgery.2 It has been described in the following conditions: patients undergoing hemodialysis through a central venous catheter,3 after acute pancreatitis, in Gorham syndrome4,5 and other severe lymphatic malformations,6–8 in ruptured mediastinal cystic teratoma,9,10 in several malignancies,11 after trauma, in Behcet disease12 and filariasis, after radiation, after the entire spectrum of cardiac,13–16 thoracic and esophageal surgeries,17 and in patients with indwelling central lines with subclavian or jugular vein thrombosis.18 In its idiopathic form, it affects primarily children and newborns and appears to be the result of congenital malformation of the thoracic duct and its tributaries.19
Patients with chylopericardium may present with shortness of breath, typical cardiac tamponade20–22 with hemodynamic deterioration, or be essentially asymptomatic. Most often, the diagnosis is made clinically on the basis of a simple echocardiography or CT of the chest and fluid aspiration, although, more sophisticated tests such as direct lymphangiography7 and Technetium-labeled lymphoscintigraphy, both of which may identify the site of chylous leakage, have been advocated. The aspirated fluid usually has a characteristic milky appearance, and chemical analysis indicates high triglyceride content, typically in excess of 500 mg/dL, or the presence of chylomicrons.23 Fluid cultures are usually negative, and the cell count is predominantly lymphocytic. In our patient, the fluid content obtained during the first reexploration was mostly bloody and mistaken for a lysed hemothorax. It was not sent for chemical analysis, thus delaying the diagnosis and appropriate treatment initiation.
Anatomically, the largest lymphatic ducts are the right lymphatic duct, which drains the right upper body, and the thoracic duct, which drains the rest of the body. All lymph drainage leads to the right and left subclavian veins where blood and lymph mingle. Multiple anatomic variations of this junction exist.24 Obstruction of the thoracic duct or an injury along its course or along the course of any major lymphatic chain in the chest can cause the reflux or the leakage of chyle back into the pleura or pericardium. In our patient, the cause of the pericardial tamponade could have been due to (a) thrombosis of the left internal jugular and subclavian veins confluent with reflux of chyle back in the pericardium. However, venous thrombosis at the site of a central line is not that uncommon while chylopericardium is rare, thus the relationship is not clearly elucidated. (b) A continuous leak of lymphatic fluid from the divided edges of a generous thymic remnant at the time of the initial surgery13,25 or (c) a localized injury to the thoracic duct during left internal mammary artery harvest.16,20 Despite administering heavy cream mixed with methylene blue before attempting to suture ligate the thoracic duct, no lymphatic extravasation could be identified with this approach in either chest cavity. The delayed finding of a residual retrosternal collection of lymph communicating with the posterior pericardium on CT scan may well indicate that the divided thymic tissue was the culprit, although in the absence of reexploration of the sternotomy incision, we are unable to corroborate this theory.13
While most nutrients absorbed by the small intestine are passed on to the portal venous system and the liver for processing, fats are passed on to the lymphatic system and transported as chyle to the blood circulation at the rate of 125 mL/h. Thus, the mainstay of modern medical management of a chylous effusion, besides its adequate drainage, is the reduction of chyle production while maintaining adequate nutrition. This is accomplished by administering a parenteral nutrition supplemented by a “fat free” enteral diet. The latter diet consists of medium-chain fatty acid esters of glycerol (MCT) with 6 to 12 carbons that diffuse directly and passively from the gastrointestinal tract to the portal system, while the longer fatty acids, which constitute chyle, are absorbed directly into the lymphatic system. Prevention of septic complications is also paramount in these nutritionally depleted patients.
Conservative treatment of chylopericardium is carried on as long as the patient remains hemodynamically stable and shows no evidence of malnutrition, fluid and electrolytes imbalance or sepsis, and as long as the chest tubes drainage tapers down progressively. Early surgical ligation of the thoracic duct near the diaphragm, along with creation of a generous pericardial window, is justified when there are recurrent episodes of life-threatening tamponade—as in our patient, mechanical problems with chest tubes drainage, or continued significant leak of chyle beyond 2 weeks at most.26 Following this procedure, sufficient collaterals generally develop between the lymphatic and the venous circulations. Alternatively, although very rarely, interventional radiologists have been able to access the cysterna chyli and embolize the thoracic duct.27 Some have even attempted to repair the thoracic duct.28 Although considered generally safe and effective, thoracic duct ligation can rarely result in chylous ascites which itself may require a peritoneovenous shunt.29 Careful suture ligation of the divided thymic remnants, especially when generous, rather than division by electrocautery may also prevent leakage of chyle as may have occurred in our patient. Similarly, early removal of central venous catheters before they result in venous thrombosis, or early intervention by thrombolysis or stenting when obstruction does occur, may well prevent thoracic duct occlusion with resulting chylopericardium.
Despite its rarity after cardiac surgery, chylopericardial tamponade is usually easy to diagnose when the pericardial aspirate is milky in appearance. However, as demonstrated in this case report, the gross appearance of the aspirate alone is not a sensitive diagnostic criterion for chylous effusion and may lead to overlooking the diagnosis. Thus, all pericardial—and pleural—aspirates, irrespective of their appearance, need to be sent for chemical analysis, looking for chylomicrons and measuring triglycerides. However, and particularly in fasting and early postoperative patients, the traditional cutoff values for triglycerides (110 mg/dL) may not be present, thus missing the diagnosis entirely. When recognized, the treatment of chylopericardial tamponade includes tube drainage of the effusion and institution of a specific MCT diet supplemented with parenteral nutrition. When these conservative measures fail after a reasonable time, surgical ligation of the thoracic duct becomes necessary.
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Keywords:© 2011 Lippincott Williams & Wilkins, Inc.
Chylopericardium; Chylopericardial tamponade; Jugular vein thrombosis; Subclavian vein thrombosis; Thoracic duct surgery; Medium-chain triglycerides diet; Chylothorax