INTRODUCTION AND EPIDEMIOLOGY
Cardiac tamponade is a relatively rare condition. If a pericardial effusion compromises hemodynamics, pericardiocentesis can be lifesaving. The cause of cardiac tamponade may be determined by fluid analysis after pericardiocentesis (Table 34-1).1,2,3,4
TABLE 34-1Causes of Pericardial Effusions ||Download (.pdf) TABLE 34-1 Causes of Pericardial Effusions
|Cause ||Sagrista-Sauleda et al1 (n = 322) (%) ||Corey et al2 (n = 75) (%) ||Levy et al3 (n = 204) (%) ||Kil et al4 (n = 116) (%) |
|Acute idiopathic ||20 ||7 ||48 ||— |
|Idiopathic ||16 ||7 ||— ||4 |
|Malignancy ||13 ||23 ||15 ||52 |
|Chronic ||9 ||— ||— ||— |
|Post–myocardial infarction ||8 ||— ||— ||— |
|Uremia ||6 ||12 ||2 ||7 |
|Autoimmune ||5 ||12 ||10 ||5 |
|Radiation ||— ||14 ||— ||— |
|Infection ||— ||27 ||16 ||4 |
|Hypothyroidism ||— ||— ||10 ||3 |
|Tuberculosis ||— ||— ||— ||14 |
In a small study of medical cardiac tamponade, the mean volume drained was 593 ± 313 mL. When the primary cause was malignancy, the 1-year mortality was almost 80%.5 In Africa, up to 70% of pericardial effusions in patients with human immunodeficiency virus are caused by tuberculosis.6
Maintain a high degree of suspicion of cardiac tamponade for oncology patients who fit the clinical signs and symptoms of tamponade.
Blunt cardiac rupture is rare, occurring approximately in 1 in 2400 blunt trauma patients. Of this subgroup, 89% arrive alive to the ED.7 Those who arrive alive may benefit from a bedside US examination to detect a traumatic effusion. Tamponade, as a result of trauma, may require a temporizing pericardiocentesis while the patient is prepared for definitive surgical repair.
In a South African study, the mortality rates from gunshot wounds and stab wounds were 81% and 15.6%, respectively.8 This comparison underlines the probability that patients with stab wounds to the heart are more likely to survive to the ED and may benefit from pericardiocentesis.
The pericardium is a fibrocollagenous sac covering the heart that contains a small amount of physiologic serous fluid. The fibrocollagenous pericardium has elastic properties and will stretch in response to increases in intrapericardial fluid. Accumulation of fluid that exceeds the stretch capacity of the pericardium precipitates hemodynamic compromise and results in pericardial tamponade.
The initial portion of the pericardial volume–pressure curve is flat, so early on, relatively large increases in volume result in comparatively small changes in intrapericardial pressure. The pericardium becomes less elastic as the slope of the curve marches upward. As fluid continues to accumulate, intrapericardial pressure rises to a level greater than that of the filling pressures of the right atrium and ventricle. When this occurs, ventricular filling is restricted and results in cardiac tamponade.9