Pericardial effusions are common sequelae of acute pericarditis. The presence of systemic arterial hypotension, tachycardia, elevated jugular venous pressure, and/or pulsus paradoxus (a decrease in systolic arterial pressure of more than 10 mm Hg with inspiration) suggests the development of a pericardial effusion and cardiac tamponade. In cardiac tamponade, the accumulation of pericardial fluid increases the intrapericardial pressure and leads to impaired diastolic cardiac filling, which results in collapse of the right atrium and ventricle during their diastolic periods and diminished cardiac output.
Any of the examination findings above that do not have an alternate explanation should prompt immediate echocardiographic evaluation, including pulsed-wave Doppler analysis. A body temperature > 100.4°F (38°C) is uncommon and may indicate purulent pericarditis; this finding should also prompt echocardiography and, possibly, pericardiocentesis.
Diagnostic testing in patients with suspected pericarditis should include ECG, chest radiography, and echocardiography. The 12-lead ECG in patients with acute pericarditis classically shows widespread, concave-upward ST-segment elevation associated with PR-segment depression and PR-segment elevation in lead aVR.
The ECG abnormalities may evolve through four phases:
Stage I: diffuse ST-segment elevation and PR-segment depression
Stage II: normalization of the ST and PR segments, with flattening of the T wave
Stage III: widespread T-wave inversions
Stage IV: normalization of the T waves
Prompt institution of therapy may prevent the appearance of all four stages. Nonetheless, the changes in stage I are observed in 60%-80% of patients with pericarditis.
ST-segment elevation may occur with many other diseases, most notably myocardial infarction; however, several echocardiographic features may help to distinguish these two entities. In myocardial infarction, the ST-segment elevations are often convex (dome-shaped) rather than concave, and they are often associated with Q-wave formation and the loss of R-wave voltage. PR-segment depression is uncommon, and atrioventricular block or ventricular arrhythmia is usually seen.
The most reliable distinguishing feature may be the ratio of ST-segment elevation (in mm) to T-wave amplitude (height in mm) in lead V6. When this ratio exceeds 0.24, acute pericarditis is almost always present.
The findings on chest radiography are usually normal, but they may reveal cardiomegaly when there is a large pericardial effusion. Most important, radiography may help to provide diagnostic information regarding the likelihood of other conditions, such as pneumothorax, pneumomediastinum, pneumonia, or aortic dissection.
The white blood cell count, erythrocyte sedimentation rate (ESR), and serum C-reactive protein (CRP) concentration are usually all elevated in patients with acute pericarditis; however, they are of little use in determining the etiology of the disease. Antinuclear and rheumatoid factor antibodies are seen in 10%-15% of cases. Viral cultures and antibody titers are not clinically useful. Plasma troponin concentrations are elevated in 35%-50% of patients with pericarditis; this finding is thought to be caused by epicardial inflammation rather than myocyte necrosis, although the long-term risk for troponin elevation in acute pericarditis is not clear. The concentration usually returns to normal within 1-2 weeks after the diagnosis. Serum creatine kinase and MB fractions are less often elevated than is the troponin value.
Transthoracic echocardiography is recommended in all patients with suspected pericarditis because the presence of an effusion helps to confirm the diagnosis, and clinical or echocardiographic evidence of tamponade indicates the need for therapeutic pericardiocentesis. Pericardiocentesis is indicated in patients with pericardial tamponade and in those with known or suspected purulent or neoplastic pericarditis. When pericardiocentesis is performed, the fluid should be analyzed for red and white blood cell counts, cytologic evidence of cancer, and triglycerides (which are elevated in patients with chylous effusion). The fluid should be cultured as well as examined microscopically.
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Cite this: Cardiology Case Challenge: Worsening Chest Pain After a Respiratory Infection in a Man With Hypertension - Medscape - Mar 24, 2022.