Investigations
To help establish the diagnosis and look for high risk features a number of simple investigations should be performed within the ED.
Electrocardiography (ECG)
As well as looking for the characteristic features of pericarditis on the ECG it will also help to distinguish other potential causes of chest pain.
There are a number of ECG features which are characteristic of acute pericarditis (Fig 1).
Classically the evolution in pericarditis occurs in 4 stages:
- Stage 1 (acute phase within hours to few days) is characterised by diffuse ST elevation (typically concave up) and depression of the PR segment;
- Stage 2, typically seen in the first week, is characterised by normalisation of the ST and PR segments;
- Stage 3 is characterised by the development of diffuse T wave inversions, after the ST segments have become isoelectric;
- Stage 4 is represented by normalisation of the ECG or indefinite persistence of T wave inversions [6].
Typical ECG changes however have been reported to occur in only 60% of cases [12].
Fig 1 demonstrates the acute phase and demonstrates the ECG findings likely to be seen in the ED.
The above ECG changes are seen in the acute phase of pericarditis and are likely to be seen within the ED. As the disease progresses so may the ECG: there may be notched T waves, biphasic T waves or T wave inversion. These T wave changes may last for weeks or months but are of no clinical significance if the patient has recovered clinically.
Dysrhythmias are uncommon in pericarditis and if present may indicate myocardial involvement (myopericarditis).
The ECG changes seen in pericarditis can be confused with benign early repolarisation (BER). The most reliable ECG distinguishing feature is seen in lead V6. Specifically, when the ST elevation (mm) to T wave height (mm) ratio is greater than 0.25 acute pericarditis is more likely than BER (Figs 1 and 2) [7].
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| Fig 2: Benign early repolarisation | Fig 3: Pericarditis |
Learning bite
ST:T wave ratio in V6 can be used to help discriminate between BER and Acute Pericarditis [7].
Troponin
Troponin levels may be measured and are raised in 30-70% of patients with acute pericarditis. This does not offer any prognostic information [8]. A troponin rise is partially related to the extent of coexisting myocardial inflammation but, unlike in acute coronary syndromes, elevation in troponin is not associated with adverse outcome in pericarditis [13]. HoweverIf the troponin is raised the patient should be considered to have myopericarditis and as this is a feature of poor prognosis further inpatient workup should be considered.
Haematology
A full blood count should be performed looking for an increase in the white cell count (WCC). A mild lymphocytosis is common. Significantly raised WCC is an indicator of poor prognosis and will therefore make inpatient management more likely.
Echocardiography (ECHO)
The use of Echocardiography is important to help aid diagnosis and to consider the presence of large pericardial effusion or cardiac tamponade which are poor prognostic factors potentially requiring further management. Studies have demonstrated that Up to 60% of patients may have a mild-moderate pericardial effusion, whilst around 5% were shown to have cardiac tamponade [12].
Chest x-ray (CXR)
CXR is generally performed to look for alternative causes of chest pain. There may be radiological features of pneumonia if bacterial pericarditis is suspected or mass lesions indicative of neoplastic disease.
Computerised tomography of the chest (CT)
CT of the chest may be performed to look for alternative diagnoses such as acute aortic dissection or pulmonary embolism.
Other investigations
C-reactive protein
Elevated C-reactive protein is consistent with an inflammatory state [15].
Serial measurements may be helpful for monitoring disease activity and response to therapy [9].
Serum urea and electrolytes
Elevated levels of urea (particularly >21.4 mmol/L [>60 mg/dL]) suggest a uraemic cause [15].