Anatomy

The pericardium is composed of an outer fibrous layer (parietal pericardium) and an inner serous membrane (visceral pericardium), with approximately 50 mL of plasma ultrafiltrate between.^[1]

It promotes cardiac efficiency by limiting dilation, maintaining ventricular compliance with preservation of the Starling curve,^[2] and distributing hydrostatic forces. It aids atrial filling by creating a closed chamber, reduces external friction, and acts as a barrier against infection and extension of malignancy. Finally, it anatomically fixes the heart to the sternum, diaphragm, and costal cartilages.

Pathogenesis

In most cases the pericardium becomes acutely inflamed, with pericardial vascularisation and infiltration with polymorphonuclear leukocytes. A fibrinous reaction frequently results in exudate and adhesions within the pericardial sac and a serous or haemorrhagic effusion may develop. In some conditions eg tuberculosis, sarcoidosis, fungal infections and rheumatoid arthritis, a granulomatous pericarditis develops.^[3]

Prevalence

Epidemiological data are sparse, but it is generally thought to account for 1 in 1,000 admissions.^[1] It is more common in men than in women, and is seen more frequently in adults than in children.

Presentation

Symptoms^[3][4]

Chest pain is the cardinal symptom. The pain may be:

• Dull, sharp, burning or pressing.
• Either barely perceptible or up to a severe level.
• Felt in the substernal or precordial region.
• Radiating to the neck, trapezius ridge (especially the left) or shoulders.
• Aggravated by inspiration, swallowing, coughing and lying flat.
• Relieved by sitting up and leaning forward.

Other symptoms can include a nonproductive cough, chills and weakness.

Signs

A pericardial friction rub is present on auscultation in 60-85% of cases. Clinically, the presence of a pericardial friction rub is pathognomonic - often a rub can be heard even when a pericardial effusion is present.^[1] It is often intermittent and evanescent, so frequent examination should take place if it is absent, but clinical suspicion is high.^[3]

• It has been described as a scratchy superficial sound, heard most strongly in the midline and lower left parasternal edge.
• It varies in strength with respiratory movements and is usually louder in inspiration.
• More than 50% of friction rubs have presystolic, systolic and diastolic components.
• 24% of patients with rubs are biphasic. This happens in tachycardia, when an early diastolic rub merges with the atrial component.
• Rarely, a monophasic rub can occur, particularly in patients with atrial fibrillation. It is sometimes mistaken for a murmur.

Other signs can include tachypnoea, tachycardia, and fever.

• Dyspnoea and orthopnoea are particularly noticeable when cardiac tamponade develops (haemodynamic changes resulting from restriction to the movement of heart muscle, secondary to pericardial effusion).
• Patients with tamponade may exhibit the Beck triad (hypotension, elevated systemic venous pressure often with jugular venous distention, and muffled heart sounds).
• Slowly developing tamponade may also result in pulsus paradoxus (defined as a 10 mm Hg decrease in arterial systolic pressure with inspiration).^[5]

Abdominal pain occurs occasionally in children.

Differential diagnosis

Other causes of chest pain - in particular:

• Myocardial infarction (MI) or ischaemia.
• Pleuritic pain.
• Pulmonary infarction.
• Peptic ulcer disease or oesophagitis.

Investigations

ECG

Serial ECGs are sometimes helpful in detecting these changes, in cases of diagnostic difficulty or in monitoring the development of cardiac tamponade.^[4]

When tamponade complicates acute pericarditis, electrical alternans may involve the P, QRS, or T complexes. Most often, only the QRS is involved; the QRS amplitude increases and decreases on alternate beats. In some cases of tamponade, electrical alternans is associated with variation in cardiac position (swinging heart). Electrical alternans is not seen in most cases of cardiac tamponade.^[4]

CXR

An enlarged 'flask-shaped' cardiac silhouette may be the first sign of a large pericardial effusion. This may not be evident in patients with small effusions (less than a few hundred millilitres) and may present with a normal silhouette.

Blood tests

• FBC with differential (may show leukocytosis).
• Erythrocyte sedimentation rate (ECR) and C-reactive protein (CRP) levels (usually raised).
• U&E levels (uraemia).
• Cardiac enzymes (associated myocarditis or MI).

In one study, an elevated troponin I level was found in 32% of patients with viral or idiopathic pericarditis. The troponin I level was related to the extent of myocardial inflammation but was not a negative prognostic marker.^[7]

NB: resolving acute pericarditis (one week or less) may need no further investigations. However, if symptoms persist (and before labelling the condition 'idiopathic'), the following may be indicated:^[8]

• Blood cultures.
• Tuberculin testing with sputum for acid-fast bacilli.
• Antistreptolysin titre.
• Rheumatoid factor, antinuclear antibody, and anti-DNA values.
• Thyroid function (if significant pericardial effusion is present).
• Antibodies for HIV, Coxsackie virus, influenza virus and echovirus.
• Examination of pericardial fluid or pericardial biopsy specimens for fungi and malignant cells.
• Pericardial biopsy for culture and microscopic examination in cases of recurrent or persistent effusion.

Echocardiography

This is appropriate if pericardial effusion or tamponade is suspected. M-mode demonstrates persistence of the echo-free space between the parietal pericardium and the epicardium during the cardiac cycle. Fluid adjacent to the right atrium is an early indicator of an effusion. Other causes of echo-free space that must be considered include pericardial masses, pleural effusion and epicardial fat.

CT or MRI scanning

This is helpful in cases of diagnostic doubt. A pericardial thickening >5 mm may be seen. When pericardial thickening or fluid cannot be demonstrated, the diagnosis of restrictive cardiomyopathy should be considered.

Pulse oximetry waveform

This is a non-invasive method of diagnosing pulsus paradoxicus, which is particularly useful in paediatric patients.^[9][10]

Surgical procedures

Pericardiocentesis under echocardiographic monitoring is occasionally used in cases of diagnostic difficulty, especially in cases of impending tamponade. This would be recommended if there were echocardiographic evidence of right atrial or ventricular diastolic collapse, irrespective of whether clinical signs of tamponade were present.^[11]

If tamponade recurs, a pericardial biopsy should be performed with histological and bacteriological examination. Endomyocardial biopsy and cardiac catheterisation may also be indicated in cases of diagnostic difficulty.

Management

Immediate management

Patients with suspected pericarditis should be admitted to hospital:

• To exclude other life-threatening causes of chest pain.
• To be assessed for evidence of haemodynamic instability.
• To be monitored for the onset of complications, eg tamponade.
• To be assessed and monitored for the development of adverse prognostic factors.

Adverse factors include:^[12]

• Fever of more than 38°C.
• Trauma.
• Anticoagulation therapy.
• Myopericarditis.
• Subacute onset.
• Immunosuppression.
• Severe effusion with tamponade.

In their absence, patients can be followed up on an outpatient basis.^[13]

Outpatient/community management

Treatment should be provided for the underlying cause.

• For viral or idiopathic cases the following have been shown to be effective:
  • Non-steroidal anti-inflammatory drugs (NSAIDs) - egindometacin 50 mg 8-hourly.^[14]
  • Colchicine - there is evidence that this reduces the incidence of recurrence, and may be ultimately considered first-line in patients with idiopathic pericarditis.^[15]
• Cessation of possible causative drugs, eg phenytoin.
• Anticoagulants should be avoided unless the pericarditis is secondary to acute MI, as they can cause intrapericardial bleeding and possibly fatal tamponade.^[4]
• Bacterial or mycotic infections should be treated with appropriate antimicrobials.
• Uraemic pericarditis may respond to increased frequency of dialysis, systemic or local steroid therapy, and aspiration therapy. Intrapericardial triamcinolone may be useful.

Management of complications

• Immediate pericardiocentesis may be required when cardiac tamponade develops rapidly with falling blood pressure, and shock developing. This may be done without echocardiographic guidance in an emergency, but open thoracotomy is safer.
• Symptomatic constrictive chronic pericarditis usually requires pericardial resection.
• Recurrent or persistent symptomatic effusive pericarditis may be treated with balloon pericardiotomy, a surgical pericardial window, or sclerosis with tetracycline.
• Recurrent pericarditis - idiopathic pericarditis or pericarditis due to cardiac surgery, MI, or trauma, may recur. Colchicine, 1 mg a day, may be helpful, in addition to NSAIDs.^[14] The role of steroids is controversial.^[15] Uncommonly, pericardial resection is required.

Prognosis

This will depend on the aetiology. Most viral and idiopathic cases follow a self-limiting course within one to three weeks. Pericarditis associated with neoplasm, purulent effusion or tuberculosis has a complicated course and worse outcome. The mortality rate approaches 85% for untreated tuberculous pericarditis.