Pericardial effusions that compress the cardiac chambers can cause cardiac tamponade.
Cardiac tamponade requires thorough clinical and echocardiographic imaging to determine whether emergency pericardiocentesis is needed.
Echocardiographic guidance of pericardiocentesis has increased the safety margin by indirect confirmation of needle placement and fluid drainage.
The pericardium is a protective double-lined sac that surrounds the heart. The function of the pericardium is to reduce the friction between the heart and surrounding mediastinal structures and also to provide a barrier against spread of infection and malignancies to the heart. Though most cardiac conditions affect the 4 chambers of the heart, its blood supply and/or the conduction system, the surrounding pericardium plays an important role in normal cardiac physiology and disease.
Under certain pathologic conditions, pericardial disease can lead to palpitations, hypotension, and acute cardiac decompensation.1 Patients presenting with pericardial tamponade accompanied by impending hemodynamic collapse require emergency pericardiocentesis. (An excellent video presentation by Fitch et al in the N Engl J Med. should be viewed in conjunction with this review.)2
NORMAL ANATOMY AND FUNCTION
The normal pericardium is a double-layered membrane that encases the heart and the origin of the great cardiac vessels. The outer fibrous layer (the parietal pericardium) is attached to the surrounding mediastinal structures: the diaphragm, sternum, and costal cartilages; while the inner serous layer (the visceral pericardium) lies on the surface of the heart and is contiguous with the epicardium.3 The pericardial lining secretes 15 to 35 mL of serous pericardial fluid (an ultrafiltrate of plasma that contains proteins, electrolytes, and phospholipids) that lubricates the surfaces of the heart to minimize the friction for the contracting heart, and drains through the mediastinal and tracheobronchial lymph nodes.2 Posteriorly, the pericardium stops at the base of the left atrium so that the posterior wall of the left atrium is not covered by the pericardial space.
With chronic pericardial fluid that accumulates gradually, pericardial compliance is able to increase to accommodate the slowly accumulating larger volumes. However, because the pericardium is a relatively stiff structure, intrapericardial pressure rises rapidly as intrapericardial volume becomes too large or the volume increases acutely, compressing the cardiac chambers, which could lead to pericardial tamponade.4
In suspected pericardial disease, transthoracic echocardiography (TTE) (including 2-dimensional (2D) TTE, M-mode echocardiography, pulse-wave Doppler, and inferior vena cava imaging, collectively 2D TTE) is the first-line imaging technique. 2D TTE can image the size, location, and relative pericardial volume and serve as a guide to therapeutic intervention (pericardiocentesis) (Figure 106–1).4,5
Small pericardial effusion: parasternal long-axis view, transthoracic echocardiogram; long-axis view of small pericardial effusion. LV, left ventricle; PERI, pericardial effusion; PLEURAL, pleural effusion; RV, right ventricle.