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Case Reports

Cardiac Tamponade: Chylopericardium Presenting 2 Weeks After Mechanical Aortic Valve Replacement Through a Median Sternotomy

South West Cardiothoracic Centre, Derriford Hospital, Plymouth, United Kingdom

Accepted for publication July 21, 2009.

^_* Address correspondence to Dr Nwaejike, South West Cardiothoracic Centre, Derriford Hospital, Plymouth, PL6 8DH, United Kingdom (Email: justnnamdi{at}aol.com).

	Abstract

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Chylopericardium is a rare disorder that can be secondary to thoracic duct injury. Consequences include nutritional, metabolic, and immunologic abnormalities, as well as cardiac complications, such as pericarditis and cardiac tamponade. We present a case of chylopericardium presenting as cardiac tamponade after a median sternotomy for mechanical aortic valve replacement.

	Introduction

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Chylopericardium is a rare disorder that can be secondary to thoracic duct injury. Consequences include nutritional, metabolic, and immunologic abnormalities, as well as cardiac complications, such as pericarditis and cardiac tamponade.

A 46-year-old woman was admitted with two syncope episodes after a mechanical AVR (21-mm St. Jude mechanical regent valve; St. Jude Medical, St. Paul, MN). She had two syncopal episodes, with one that occurred while lying in bed that morning causing her to feel very light-headed, hot and sweaty, and nauseous. She did not complain of chest pain, vomiting, or loss of consciousness. She had noticed herself to be increasingly short of breath on exertion for a week leading up to these two episodes of syncope. Thus, she was admitted to the emergency room after having arrived by ambulance. She was on warfarin after her mechanical atrial valve replacement and her past medical history included asthma and an appendicectomy as a child. She lived with her husband and daughter and she was a nonsmoker.

On presentation, she was tachycardic and tachypnoeic with a temperature of 37.8°C. She was hypotensive with a systolic blood pressure of 90 mm Hg, but with an infusion of 500 mL NaCl her blood pressure improved to 135 mm Hg. On examination, her lung fields were clear to auscultation, she had muffled mechanical aortic valve sounds, and the jugulo-venous pressure (JVP) was normal, with no ankle edema. Blood tests results: hemoglobin (10.9g/dL), leucocytes (20.4 g/dL), platelets (918 g/dL), sodium (137 g/dL), potassium (4.5 g/dL), creatine (79 mg/L), C-reactive protein (21 mg/L), alanine aminotransferase (273 U/L), and international normalized ratio (7.0).

A chest roentgenogram showed a large cardiac shadow (Fig 1) that was compared with her presternotomy (Fig 2), and roentgenogram taken on postoperative day 4 (Fig 3). A transthoracic echocardiography (Fig 4) showed a large global pericardial effusion up to 5 cm in depth with inspiratory variation and right ventricular collapse.

View larger version (131K): [in this window] [in a new window]   Fig 1. Chest roentgenogram on presentation showing a large cardiac shadow in keeping with a pericardial effusion with no obvious pleural effusions.

View larger version (161K): [in this window] [in a new window]   Fig 2. Presternotomy chest roentgenogram.

View larger version (136K): [in this window] [in a new window]   Fig 3. Chest roentgenogram on postoperative day 4.

View larger version (89K): [in this window] [in a new window]   Fig 4. Transthoracic echocardiogram showing pericardial effusion.

She had been placed on intravenous floxacillin (500 mg four times a day) and benzylpenicillin (1.2 g three times a day), which were both discontinued after the microbiology results were obtained.

She was initially placed on a fat-free diet, and the pericardial drain was removed a week later when the drainage had stopped. She was discharged home. On review at 6 weeks, she was seen in the outpatient clinic with no recurrence of her symptoms, and she was in good health.

	Comment

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This is an unusual presentation of a chylopericardium 2 weeks after a median sternotomy. Pediatric cardiac operations through median sternotomies are more commonly associated with chylothorax and chylopericardium; these include ligation of patent ductus arteriosus, coarctation with double aortic arch repairs, complex intracardiac repairs, and systemic-to-pulmonary shunts. However, chylothorax after these procedures is much more common than chylopericardium by a ratio of 22:3 [2].

We have found no previous published reports of a chylopericardium after aortic valve replacement.

Chylopericardium is a rare disorder that may be primary (idiopathic) or secondary to injury of the thoracic duct. In addition to the nutritional, metabolic, and immunologic abnormalities, cardiac complications can include pericarditis and cardiac tamponade [3].

Analysis of the aspirated fluid helps to make the diagnosis of chyle. A cholesterol level greater than 110 mg/dL reflects a 99% chance that the fluid is chyle, and a ratio of cholesterol to triglyceride of less than 1 is also diagnostic [1]. If the mediastinal pleura is intact, several days may elapse before chyle fills the mediastinum and ruptures into the pleural space, usually on the right side at the base of the pulmonary ligament [4]. The patient presented late with cardiac tamponade 2 weeks after a median sternotomy. Chest drainage immediately post-sternotomy did not show any evidence of chyle and was removed on postoperative day 2. Her presentation with pyrexia and raised inflammatory markers were probably indicative of a pericarditis, as chyle is known to be an irritant. Microscopy and cultures of the pleural fluid did not grow any organisms; therefore the antibiotics were discontinued.

The thoracic duct carries chyle from the intestinal tract to the bloodstream and usually extends from the cisterna chyli, which lies just anterior to the first or second lumbar vertebra and passes through the aortic hiatus of the diaphragm. The thoracic duct continues cephalad in the right thorax between the aorta and the azygos vein until the fifth thoracic vertebra where it crosses over the vertebral column behind the esophagus and continuing into the left posterior mediastinum. The thoracic duct passes behind the aortic arch, along the left border of the esophagus, and behind the left subclavian artery over which it arches in the anterolateral aspect of the superior mediastinum. Then it descends to empty into the junction of the left jugular and left subclavian vein [5].

It is very unusual to injure the thoracic duct during an aortic valve replacement through a median sternotomy, because the course of the thoracic duct is never directly within the operative field. Possible mechanisms of injury could occur during manipulation of the heart and aorta, causing a traction injury, and when cross clamping the aorta. Normally the thoracic duct at approximately level T4 to T5 is posterior to the descending aorta and ascends between the esophagus and the descending aorta [5]; of course, this is outside the operative field, and therefore it would be unusual for the surgeon to come in direct contact with it.

The most likely mechanism of injury to the thoracic duct in this case was believed to be a traction injury in which indirect forces were transmitted that tore the thoracic duct during manipulation of the heart and aorta during the operation. The mechanical aortic valve replacement was straightforward with no unforeseen events. Bypass was undertaken with standard aortic cannulation and a two-stage right atrial cannulation for return with intermittent antegrade cold blood cardioplegia. The patient was cooled to 32°C for the procedure with a cross-clamp time of 68 minutes and a bypass time of 82 minutes. The aortotomy was closed with continuous 3-0 Prolene sutures (Ethicon, Somerville, NJ). At no time was there excessive manipulation of the heart or the need to dissect around the aortic valve any more than would be necessary to position the aortic cross clamp.

In some individuals, two thoracic ducts exist within the mediastinum, or occasionally, a single thoracic duct drains into a right-sided great vein [5]. The known variation in the anatomy of the thoracic duct might suggest that duplication or multiplication of the mediastinal portion of the thoracic duct might have placed the thoracic duct (or a part of it) close to a point of contact with the aortic cross clamp. This was alluded to by Wurnig and colleagues [6] who pointed out that the relatively high incidence (39%) of duplication or multiplication of the mediastinal portion of the thoracic duct has important implications for successful duct ligation [6].

In conclusion, this is an interesting differential diagnosis of cardiac tamponade after a median sternotomy. The diagnosis confirmed by analysis of the pericardial fluid was clear, even though the mechanism of injury was not clear. Chylopericardium can be treated conservatively with a satisfactory outcome.

	References

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1. Pendharkar S, Tremblay A. Guidance on how to identify the cause—a diagnostic approach to pleural effusion J Respir Dis 2007;28:565-582.
2. Nguyen DM, Shum-Tim D, Dobell AR, Tchervenkov CI. The management of chylothorax/chylopericardium following pediatric cardiac surgery: a 10-year experience J Card Surg 1995;10(4 Pt 1):302-308.[Medline]
3. Brawley RK, Vasko JS, Morrow AG. Cholesterol pericarditis. Considerations of its pathogenesis and treatment. Am J Med 1966;41:235-248.[Medline]
4. Sahn SA. State of the art: the pleura Am Rev Respir Dis 1988;138:184-234.[Medline]
5. Valentine VG, Raffin TA. The management of chylothorax Chest 1992;102:586-591.[Free Full Text]
6. Wurnig PN, Hollaus PH, Ohtsuka T, Flege JB, Wolf RK. Thoracoscopic direct clipping of the thoracic duct for chylopericardium and chylothorax Ann Thorac Surg 2000;70:1662-1665.[Abstract/Free Full Text]

This article has been cited by other articles:

				N. Nwaejike, W. El-Amin, and J. Kuo Reply. Ann. Thorac. Surg., July 1, 2010; 90(1): 361 - 362. [Full Text] [PDF]

				B. C. Karabay, M. Ugurlucan, S. Ziyade, and O. Isik Is the Thoracic Duct Injury the Cause of Chylopericardium After Cardiac Surgery Performed Through Median Sternotomy? Ann. Thorac. Surg., July 1, 2010; 90(1): 360 - 361. [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Nnamdi Nwaejike Wail O. El-Amin James Kuo Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Nwaejike, N. Articles by Kuo, J. Search for Related Content PubMed PubMed Citation Articles by Nwaejike, N. Articles by Kuo, J. Related Collections Pericardium Valve disease