The pericardium envelops the heart and portions of the great vessels as a protective capsule. When incised longitudinally and transversely along the diaphragm it can be suspended to present the heart for surgical procedures. The surgical importance of the pericardium stems from its involvement in alterations of cardiac filling. When the limited space between the noncompliant pericardium and heart acutely fills with fluid, cardiac compression and tamponade may ensue. Constrictive disorders arise when inflammation and scarring cause the pericardium to shrink and densely adhere to the surface of the heart. This chapter discusses pericardial anatomy and function and describes the conditions that commonly give rise to the surgical problems of pericardial constriction and tamponade. The chapter also describes the diagnosis and therapy of these entities, the management of effusions and tamponade early and late after cardiac surgery, and the rationale for and against pericardial closure at the time of cardiac surgery.
The pericardium serves two major functions. It maintains the position of the heart within the mediastinum and prevents cardiac distention by sudden volume overload. The pericardium attaches to the ascending aorta just inferior to the innominate vein and the superior vena cava (SVC) several centimeters above the sinoatrial node. The pericardial reflection encompasses the superior and inferior pulmonary veins and encircles the inferior vena cava (IVC), thereby making it possible for the surgeon to control the IVC from within the pericardium. The pericardial reflection attaches to the left atrium near the entrances of the pulmonary veins just below the atrioventricular groove (Fig. 57-1). The pericardiophrenic arteries that travel with the phrenic nerves as well as the branches of the internal mammary arteries and feeder branches directly from the aorta perfuse the pericardium. It is innervated by vagal fibers from the esophageal plexus, and the phrenic nerves course within it.
Pericardial attachments, reflections, and sinuses. Ao, aorta; IVC, inferior vena cava; LPA, left pulmonary artery; PA, pulmonary artery; PV, pulmonary vein; RPA, right pulmonary artery; SVC, superior vena cava.
The pericardium is a conical fibroserous sac made up of two intimately connected layers. The inner layer (serous pericardium) is a transparent monolayer of mesothelial cells. The visceral portion of the serous pericardium, or epicardium, and the parietal portion, which lines the fibrous pericardial sac, are continuous. The oblique sinus lies within the venous confluence and the transverse sinus lies between the arterial (aorta and pulmonary artery) and venous reflections (dome of left atrium and SVC). Such potential spaces allow the pericardium to expand and accommodate a limited amount of fluid. Normal pericardial fluid volume is approximately 10 to 20 mL. The pericardial mesothelial cells contain dense microvilli, which are 1 μm wide and 3 μm high, and facilitate fluid and ion exchange.1 Visceral pericardial lymphatic drainage occurs ...