Diagnosis

Precordial chest pain, exercise intolerance, and fever are the major manifestations along with irritability and a grunting expiratory sound as they splint the thoracic cage (12,13). Pain is felt over the precordium, to the left over the trapezius ridge, and over the scapula; and it sometimes radiates down the arm and can become worse upon movement. Pain also can be referred toward the diaphragm (13). Pain is more common in acute pericarditis than in the indolent forms.

Cardiac examination shows muffled heart sounds, and increasing tachycardia as the effusion reduces the volume of the chambers. A pericardial friction rub may be heard. The rub is most audible during deep inspiration and with the patient kneeling, in the knee-chest position or when leaning forward. Tamponade is manifest by tachycardia, peripheral vasoconstriction, reduced arterial pulse pressure, and pulsus paradoxus.

Diagnosis of pericarditis is based on history, physical examination, and imaging tests. The etiology is best determined by examination of pericardial fluid for cell count and morphology, glucose, and protein concentrations. Serosanguinous or hemorrhagic fluid is often found in trauma, tumor, toxoplasmosis, tuberculosis, and streptococcal infection.

Radiological studies typically shows an increase in the size of the cardiac shadow, mostly in the absence of pulmonary congestion (13). The electrocardiogram usually manifests generalized ST-segment elevations without reciprocal ST-segment depression, except in leads Vi and aVR. Later this returns to baseline, and there is flattening or inversion of the T waves. Low-voltage QRS complexes can be seen without the pathologic Q waves of myocardial infarction. T-wave abnormalities can persist after recovery.

Ultrasound is the most valuable test when pericardial fluid is present, both M-mode and two-dimensional echocardiography illustrates a sonolucent space between the two layers of pericardium. Two-dimensional echocardiography can assist in direct catheter placement for drainage. Computed tomography can evaluate extracardiac masses and other causes of an enlarged cardiac silhouette: combined studies with flow imaging by magnetic resonance are helpful to define intracardiac masses.

Microbiological evaluation of pericardial fluid retrieved by pericardiocentesis is very important (14). Evaluation of the fluid should include Gram, acid-fast, and silver stains as well as culture for aerobic and anaerobic bacteria, viruses, mycobacteria, and fungi. Latex agglutination tests for bacterial antigens can facilitate diagnosis. Blood cultures should also be performed, as they can be positive in 40% to 70% of instances.

No differences were found in the clinical diagnostic features between cases of pericarditis due to anaerobic bacteria and those due to aerobic and facultative bacteria (9,10). The gramnegative anaerobic bacilli Prevotella and Fusobacterium spp. have increased their resistance to penicillins and other antimicrobials in the last decade. Complete identification and testing for antimicrobial susceptibility and beta-lactamase production are therefore essential for the management of infections caused by these bacteria.

Viral cultures from a site other than the pericardial fluid, such as the stool or throat, can be used to diagnose the likely cause of concomitant pericarditis. A rise in antibodies to that virus can confirm the infection. Serology is also helpful for the diagnosis of rickettsiae and mycoplasma.

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