extension from an adjacent pneumonitis; the common causes of bacteremias - staphylococci, meningococci and H. influenzae - are more likely to reach the pericardium through the blood-stream. A pre-existing, noninfectious pericarditis, as is seen with uremia or following cardiac surgery, may increase susceptibility to hematogenous bacterial pericarditis. Acute serofibrinous pericarditis. The viruses typically causing this disease produce a relatively mild inflammatory reaction that is associated with focal damage to the adjacent myocardium. The response varies from a small amount of serous fluid with mononuclear cells and fibrinogen to a large, neutrophil-rich, bloody effusion. The tissue damage is the result of: 1. Direct cellular damage by the infecting virus 2. Destruction of viral-infected cells by sensitized T-lymphocytes 3. Antibody-dependent, cell-mediated cytotoxicity (null cell-dependent). Mild fibrosis and occasional adhesions between visceral and parietal surfaces may mark the healing of viral pericarditis. However, such a fibrotic reaction rarely gives rise to a constrictive pericarditis. The disease is self limiting and rarely fatal. Acute purulent pericarditis. The bacteria typically causing this disease produce a relatively strong rapidly progressing purulent reaction. The purulent material contains large numbers of polymorphonuclear leukocytes in a large volume of effusion. The tissue damage is the result of: 1. Toxin and enzyme production by the bacteria 2. Myocardial damage 3. Rapidly progressing cardiac tamponade Healing is associated with extensive fibrosis that may progress to a chronic, constrictive pericarditis. The mortality rate exceeds 50%.
CLINICAL SYMPTOMS AND SIGNS: Acute serofibrinous pericarditis gives rise to: a. Chest pain - rapid in onset, persistent for several hours to days. It is worse during inspiration and recumbency but improves with leaning forward. The pain is usually in the upper abdominal region overlying the stomach and may be sharp, dull, constricting and/or crushing making clinical differentiation from myocardial infarction difficult. Radiation of pain to the left trapezius ridge is particularly characteristic. b. Fever - not prominent c. Malaise d. Pericardial friction rub - this is usually a triphasic sound that resembles scratching or the crunch of footsteps on cold snow.