Learning Outcomes

Through this lecture, the practitioner

• Shall be able to expand his/her current indications for pericardectomy
• Understand the pros and cons of the thoracoscopic approach
• Get an overview of the different thoracoscopic approaches

The aim of the creation of a window in the pericardium or the performance of subtotal pericardectomy is to establish permanent drainage for patients with pericardial effusion. Pericardectomy is considered to be the definitive treatment for recurrent benign or idiopathic pericardial effusion and constrictive pericarditis. This procedure is advocated as a palliative treatment for malignant pericardial effusion. Pericardectomy was also recently recommended as an additional surgical procedure for the treatment of chylothorax in both dogs and cats. In a previous study of dogs with ultrasonographically detected pericardial effusion without cardiac masses, the median survival time was 1218 days among dogs that underwent pericardectomy and 532 days among dogs that underwent conservative management. Another study of dogs with heart-base tumors found a prolonged median survival time of 730 days among dogs that underwent pericardectomy and only 42 days among dogs that did not undergo pericardectomy.

The first publication on thoracoscopic pericardectomy in the field of veterinary medicine appeared in 1999. In early studies, thoracoscopic pericardectomy was associated with less postoperative pain and lower morbidity than traditional open thoracotomy and had the additional benefit of offering better visualization secondary to improved illumination and magnification of previously inaccessible areas. More recently, pericardectomy has also been performed thoracoscopically in association with concurrent right atrial tumor removal and thoracoscopic management of chylothorax.

Thoracoscopic creation of a 4- to 5-cm-diameter pericardial window has been recommended to palliate the clinical signs associated with pericardial effusion in dogs. In the study upon which this recommendation is based, all dogs exhibited immediate resolution of cardiac tamponade following thoracoscopic partial pericardectomy. However, 77% of dogs had neoplastic pericardial effusion, and long-term follow-up was available for only two dogs with idiopathic pericardial effusion. Consequently, no conclusions could be made regarding the long-term outcome of dogs with idiopathic pericardial effusion that underwent the pericardial window procedure. Whether a 4- to 5-cm pericardial window is large enough for long-term palliation of the clinical signs in dogs is unknown. Creation of a larger pericardial window or the performance of subtotal pericardectomy when performing thoracoscopic pericardectomy may be advisable. In one study, dogs with idiopathic pericardial effusion treated by thoracoscopic creation of a pericardial window had significantly shorter disease-free intervals and median survival times than did dogs treated by subtotal pericardectomy via thoracotomy (p<0.05). However, no significant differences were found between the two groups for dogs presented with neoplastic pericardial effusion. The authors suspected that this difference in the outcome may have been related to inaccuracy of the initial diagnosis {the excised pericardium was too small for accurate histopathologic diagnosis) or the inability of the pericardial window to palliate the signs of idiopathic pericardial effusion in the long term.

Three approaches to thoracoscopic pericardectomy have been described depending on whether the patient is in lateral, dorsal, or sternal recumbency (when combined with thoracic duct surgery). Given the short operative duration and sterile surgical environment, intraoperative broad-spectrum antibiotics are sufficient; postoperative antibiotic therapy is usually unnecessary.

The patient and port positions depend mainly on the surgeon's preference and patient's disease. Dorsal recumbency is generally preferred in most patients. Although lateral recumbency is most often preferred in patients with heart-base tumors, some authors reportedly select dorsal recumbency for such patients.

Thoracoscopy in dorsal recumbency avoids the need for selective intubation, maintains bilateral lung function, and is not technically demanding. With the patient in this position, the first trocar camera can be entered either between the last ribs at the sternocostal junction or in a paraxiphoid or subxiphoid location (between the xiphoid process and the last sternocostal junction or just caudal and dorsal to the xiphoid process). In the two latter cases, the scope is entered transdiaphragmatically.

With the patient in lateral recumbency, an intrathoracic view is best gained by pulmonary exclusion or limited pneumothorax. Several portal placements have been suggested in this approach. We recommend placement of the working channels at a sufficient distance from the heart to ensure adequate working space. The scope is placed in the middle or ventral third of the 10th intercostal space, just cranial to the diaphragm. The 5-mm instrument ports can then be placed cranial to the scope in the dorsal and ventral thirds of the sixth to eighth intercostal spaces depending on the patient's conformation. Dissection and resection can be accomplished with these two portals. Should another instrument be necessary (e.g., to move the cranial lung lobe aside), it could be placed in the ventral third of the third intercostal space.

Theoretically, subphrenic pericardectomy is optimal in cases of constrictive pericarditis and pericardial infection or neoplasia, while the pericardial window can be used in cases of neoplastic effusions, hemorrhage from neoplastic masses, inflammatory disease, and idiopathic effusions. The pericardial window procedure was evaluated in a more recent study. This procedure was associated with an acceptable complication rate (approximately 25%), low mortality rate (7%), rapid operative duration (<1 hour), and relatively short hospitalization time (1 day). In that study, of seven dogs with idiopathic pulmonary effusion, three died of uninvestigated lethargy and two were euthanized 638 and 1165 days after surgery, respectively, because of dyspnea secondary to persistent pleural effusion. These findings and those obtained by Case et al. again raise the question of the value of a simple pericardial window with respect to the long-term prognosis. Our recommendation is to remove as much pericardium as possible while avoiding any risk of phrenic nerve transection.

In one pericardioscopic study of cadaver, subphrenic pericardectomy allowed for better viewing of most intrapericardial structures than did the creation of an apical pericardial window. Greater than 50% visibility of the right atrium, right auricle, and left auricle was possible. Subphrenic pericardectomy improved observation of the aortic root and pulmonary artery, which is important in cases of mesothelioma or chemodectoma. Although subphrenic pericardectomy may not be necessary in all dogs with pericardial effusion, it may improve diagnostic accuracy during pericardioscopy.

References

1.  Atencia S, Doyle RS, Whitley NT. Thoracoscopic pericardial window for management of pericardial effusion in 15 dogs. Journal of Small Animal Practice. 2013;54:564–569.

2.  Case JB, Maxwell M, Aman A, et al. Outcome evaluation of a thoracoscopic pericardial window procedure or subtotal pericardectomy via thoracotomy for the treatment of pericardial effusion in dogs. Journal of the American Veterinary Medical Association. 2013;242:493–498.

3.  Dupré G, Corlouer J-P, Bouvy B. Thoracoscopic pericardectomy performed without pulmonary exclusion in 9 dogs. Veterinary Surgery. 2001;30:21–27.

4.  Dupré G. Thoracoscopic pericardial window and subtotal pericardectomy in dogs and cats. In: Boel A. Fransson and Philipp D. Mayhew, eds. Small Animal Laparoscopy and Thoracoscopy. First edition. John Wiley& Sons, Inc.;2015:294–301.

5.  Dunning D, Monnet E, Orton EC, et al. Analysis of prognostic indicators for dogs with pericardial effusion: 46 cases (1985–1996). Journal of the American Veterinary Medical Association. 1998;212:1276–1280.

6.  Ehrhart N, Ehrhart EJ, Willis J, et al. Analysis of factors affecting survival in dogs with aortic body tumors. Veterinary Surgery. 2002;31:44–48.

7.  Haimel G, Liehmann L, Dupré G. Thoracoscopic en bloc thoracic duct sealing and partial pericardectomy for the treatment of chylothorax in two cats. Journal of Feline Medicine and Surgery. 2012;14:928–931.

8.  Jackson J, Richter KP, Launer DP. Thoracoscopic partial pericardiectomy in 13 dogs. Journal of Veterinary Internal Medicine. 1999;13:529–533.

9.  Mayhew PD, Culp WT, Mayhew KN, et al. Minimally invasive treatment of idiopathic chylothorax in dogs by thoracoscopic thoracic duct ligation and subphrenic pericardiectomy: 6 cases (2007–2010). Journal of the American Veterinary Medical Association. 2012;241:904–909.

10.  Ployart S, Libermann S, Doran I, et al. Thoracoscopic resection of right auricular masses in dogs: 9 cases (2003–2011). Journal of the American Veterinary Medical Association. 2013;242:237–241.

11.  Skinner OT, Case JB, Ellison GW, et al. Pericardioscopic imaging findings in cadaveric dogs: comparison of an apical pericardial window and sub-phrenic pericardectomy. Veterinary Surgery. 2013;43:45–51.