Acute pericarditis - Disorders of the pericardium

Disorders of the pericardium

Acute pericarditis

Definition

Acute pericarditis is an acute inflammation of the pericardial sac.

Aetiology

Multiple aetiologies but common causes are as follows:

·        Myocardial infarction: 20% of patients develop acute pericarditis in the first few days following an infarction, although it is often asymptomatic and therefore goes undetected. Dressler’s syndrome is an immune-mediated pericarditis occurring between 1 month and 1 year in <1% of patients following myocardial infarction and is associated with a high ESR.

·        Viruses: The specific agent is often unidentified but may include coxsackie B, influenza, measles, mumps, varicella and HIV.

·        Other causes include uraemia, connective tissue disorders, trauma, rheumatic fever, tuberculosis and malignant infiltration. Acute bacterial pericarditis is unusual.

Pathophysiology

During acute pericarditis the pericardium is inflamed and covered in fibrin causing a loss of smoothness and an audible friction rub on auscultation.

Clinical features

Sharp substernal pain with radiation to the neck and shoulders and sometimes the back. Characteristically the pain is relieved by sitting forward and made worse by lying down, movement or deep inspiration. A pericardial friction rub is pathognomonic but may be transient, best heard at the left sternal edge accentuated by leaning forward and held expiration.

Complications

Pericarditis is often complicated by pericardial effusion and occasionally tamponade. Where there is an associated myocarditis, features of heart failure may be present.

Macroscopy/microscopy

An acute inflammatory reaction with both pericardial surfaces coated in a fibrinrich exudate.

Investigations

ECG usually shows widespread ST elevation, concave upwards (as opposed to the convex upward configuration of a myocardial infarction).

Other investigations are required to help identify an underlying cause, e.g. FBC (infection), U&Es (renal failure), ESR and cardiac enzymes (to exclude myocardial infarction).

Chest X-ray may suggest a pericaridal effusion (globular looking heart with increased size of the cardiac shadow).

Other investigations may be indicated, including echocardiogram, viral titres and blood cultures.

Pericardial aspiration may be used to obtain fluid for diagnosis, but is only considered where there is either a significant fluid collection or an undetermined aetiology.

Management

Analgesia and anti-inflammatory treatment with aspirin or NSAIDs is usually effective. A small percentage of patients may have a later relapse when steroids may be required. Drainage is necessary for cardiac tamponade.

Prognosis

Most cases of acute pericarditis, particularly of viral origin, run a benign and self-limiting course.