Acute Pericarditis - Diagnosis

Diagnosis

Inflammatory markers. A CBC may show an elevated white count and a serum C-reactive protein may be elevated.

Molecular markers. Acute pericarditis is associated with a modest increase in serum creatine kinase MB (CK-MB) and cardiac troponin I (cTnI), both of which are also markers for myocardial injury. Therefore, it is imperative to also rule out acute myocardial infarction in the face of these biomarkers. The elevation of these substances is related to inflammation of the myocardium. Also, ST elevation on EKG (see below) is more common in those patients with a cTnI > 1.5 µg/L. Coronary angiography in those patients should indicate normal vascular perfusion. The elevation of these biomarkers are typically transient and should return to normal within a week. Persistence may indicated myopericarditis. Troponin levels increase in 35 - 50% of people with pericarditis.

Electrocardiogram (EKG). EKG changes in acute pericarditis mainly indicates inflammation of the epicardium (the layer directly surrounding the heart), since the fibrous pericardium is electrically inert. For example, in uremia, there is no inflammation in the epicardium, only fibrin deposition, and therefore the EKG in uremic pericarditis will be normal. Typical EKG changes in acute pericarditis includes

• stage 1 -- diffuse, positive, ST elevations with reciprocal ST depression in aVR and V1. Elevation of PR segment in aVR and depression of PR in other leads especially left heart V5, V6 leads indicates atrial injury.
• stage 2 -- normalization of ST and PR deviations
• stage 3 -- diffuse T wave inversions (may not be present in all patients)
• stage 4 -- EKG becomes normal OR T waves may be indefinitely inverted

Because the most common cause of ST elevation is an acute myocardial infarction, and since acute pericarditis can also be a short term complication after an acute myocardial infarction, steps must be taken to differentiate the two EKG readings.

Rarely, electrical alternans may be seen, depending on the size of the effusion.

Chest X-ray. Usually normal in acute pericarditis, but can reveal cardiomegaly (enlarged heart) if the pericardial effusion is more than 200 mL. Conversely, patients with unexplained new onset cardiomegaly should always be worked up for acute pericarditis.

Echocardiogram. Usually normal in acute pericarditis but can reveal pericardial effusion, the presence of which supports the diagnosis, although its absence does not exclude the diagnosis.