How is Acute Pericarditis Diagnosed and Treated?

Laboratory data. A complete blood count, metabolic panel, and cardiac enzymes should be checked in all patients with suspected acute pericarditis. Troponin values are elevated in up to one-third of patients, indicating cardiac muscle injury or myopericarditis, but have not been shown to adversely impact hospital length of stay, readmission, or complication rates.^5,10 Markers of inflammation (e.g. erythrocyte sedimentation rate or C-reactive protein) are frequently elevated but do not point to a specific underlying etiology. Routine viral cultures and antibody titers are not useful.¹¹

Most cases of pericarditis are presumed idiopathic (viral); however, finding a specific etiology should be considered in patients who do not respond after one week of therapy. Anti-nuclear antibody, complement levels, and rheumatoid factor can serve as screening tests for autoimmune disease. Purified protein derivative or quantiferon testing and HIV testing might be indicated in patients with appropriate risk factors. In cases of suspected tuberculous or neoplastic pericarditis, pericardial fluid analysis and biopsy could be warranted.

Electrocardiography. The EKG is the most useful test in diagnosing acute pericarditis. EKG changes in acute pericarditis can progress over four stages:

• Stage 1: diffuse ST elevations with or without PR depressions, initially;
• Stage 2: normalization of ST and PR segments, typically after several days;
• Stage 3: diffuse T-wave inversions; and
• Stage 4: normalization of T-waves, typically after weeks or months.

While all four stages are unlikely to be present in a given case, 80% of patients with pericarditis will demonstrate diffuse ST-segment elevations and PR-segment depression (see Figure 2, above).¹²

Table 3 lists EKG features helpful in differentiating acute pericarditis from acute myocardial infarction.

Chest radiography. Because a pericardial effusion often accompanies pericarditis, a chest radiograph (CXR) should be performed in all suspected cases. The CXR might show enlargement of the cardiac silhouette if more than 250 ml of pericardial fluid is present.³ A CXR also is helpful to diagnose concomitant pulmonary infection, pleural effusion, or mediastinal mass—all findings that could point to an underlying specific etiology of pericarditis and/or pericardial effusion.

Echocardiography. An echocardiogram should be performed in all patients with suspected pericarditis to detect effusion, associated myocardial, or paracardial disease.¹³ The echocardiogram frequently is normal but could show an effusion in 60%, and tamponade (see Figure 1, p. 15) in 5%, of cases.⁴

Computed tomography (CT) and cardiac magnetic resonance imaging (CMR).CT or CMR are the imaging modalities of choice when an echocardiogram is inconclusive or in cases of pericarditis complicated by a hemorrhagic or localized effusion, pericardial thickening, or pericardial mass.14 They also help in precise imaging of neighboring structures, such as lungs or mediastinum.

Pericardial fluid analysis and pericardial biopsy. In cases of refractory pericarditis with effusion, pericardial fluid analysis might provide clues to the underlying etiology. Routine chemistry, cell count, gram and acid fast staining, culture, and cytology should be sent. In addition, acid-fast bacillus staining and culture, adenosine deaminase, and interferon-gamma testing should be ordered when tuberculous pericarditis is suspected. A pericardial biopsy may show granulomas or neoplastic cells. Overall, pericardial fluid analysis and biopsy reveal a diagnosis in roughly 20% of cases.¹¹

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Table 2. Specific causes of acute pericarditis

How is acute pericarditis treated?

Most cases of uncomplicated acute pericarditis are viral and respond well to NSAID plus colchicine therapy.^2,4 Failure to respond to NSAIDs plus colchicine—evidenced by persistent fever, pericardial chest pain, new pericardial effusion, or worsening of general illness—within a week of treatment should prompt a search for an underlying systemic illness. If found, treatment should be aimed at the causative illness.