Pericarditis: Causes and Anatomy

• Pericarditis involves inflammation of the pericardium, the heart's fibrous sac.
• It is most commonly seen in young adult men.
• Pericarditis accounts for 0.1% of all hospital admissions and 5% of emergency department admissions for chest pain.
• In most cases, the cause of acute pericarditis is unknown (idiopathic).

Anatomy of the Pericardium

• The pericardium has two parts: an outer fibrous pericardium and an inner serous pericardium.
• The fibrous pericardium surrounds the heart with connective tissue without attaching to it.
• The serous pericardium has a parietal layer (sticks to the fibrous pericardium) and a visceral layer (attaches to the heart as the epicardium).
• A small space, the pericardial cavity, exists between the parietal and visceral layers containing fluid that reduces friction during heart movement.

Causes

• Most cases are idiopathic.
• Infections from viruses (e.g., coxsackievirus, HIV), bacteria (e.g., staphylococcus, Mycobacterium tuberculosis), and fungi (e.g., histoplasmosis)
• Acute myocardial infarction 1-3 days post-infarction, involving the full thickness of the ventricular wall (transmural).
• Dressler’s syndrome is an autoimmune response weeks to months after myocardial infarction.
• Cancer, either primary (e.g., mesotheliomas) or metastatic (e.g., breast or lung cancers).
• Autoimmune disorders like rheumatoid arthritis.
• Drug-induced causes include hydralazine.
• Uraemic causes are due to toxic metabolite accumulation from end-stage renal disease.

Risk Factors

• Age: Average age of acute pericarditis patients is 41-60 years; advanced age increases risk for bacterial pericarditis.
• Sex: Males have a higher risk of acute pericarditis.
• Seasons: Idiopathic pericarditis is more common in the spring and fall.
• Steroids: Recurrent pericarditis occurs more often in patients being treated with steroids.
• Additional risk factors for bacterial pericarditis: Diabetes, extensive burn injuries, systemic infections, immunosuppression, heart surgery, chest trauma, pre-existing pericardial effusion.

Clinical features

• Chest Pain (>90%): Typically retrosternal, can radiate to the neck, shoulders, and arms (trapezius ridge radiation is classic).
• Chest pain is exacerbated by deep inspiration (pleuritic) and lying down; relieved by sitting or leaning forward.
• Dyspnoea is a common symptom
• Systems review: Identifies clues related to the causative diagnoses such as recent infective symptoms or a known autoimmune disorder
• Drug history (e.g. chemotherapy drugs) can be a contributing factor.
• Travel history: May reveal recent travel to countries endemic for certain infectious diseases

Clinical Examination

• Pericardial rub: Friction between pericardial layers, loudest at the left lower sternal border, heard best when the patient leans forward.
• Soft/distant heart sounds may indicate Pericardial effusion.
• Beck’s triad (hypotension, muffled heart sounds, raised JVP) indicates Cardiac tamponade.

Cardiac Tamponade

• Presents with signs of decreased cardiac output and shock (hypotension, tachycardia, tachypnoea, cool peripheries, diaphoresis, peripheral cyanosis).
• The y descent of the JVP is usually absent.
• Pulsus paradoxus (≥10mmHg drop in systolic pressure during inspiration) may be present.

Differential Diagnoses

• Acute coronary syndrome
• Pneumonia with pleurisy
• Pulmonary embolism
• Gastro-oesophageal reflux disease
• Costochondritis
• Aortic dissection
• Intra-abdominal pathology
• Pneumothorax
• Decompensated heart failure

Bedside Investigations

• Basic observations (vital signs): to check for signs of shock.
• 12-lead ECG: Look for widespread ‘concave/saddle shaped’ ST-elevation, except in aVR and often V1, and PR segment depression.
• Low voltage QRS complexes/‘electrical alternans’ indicates significant pericardial effusion.

Laboratory Investigations

• No single diagnostic test exists for acute pericarditis.
• Full blood count: Raised white blood cell count is a common finding.
• Inflammatory markers: Raised CRP/ESR are common findings.
• Troponin: May be elevated if there is co-existent myocarditis.

Imaging

• Chest X-ray: Often normal; cardiothoracic ratio raised with effusions >300ml, globular cardiac silhouette might be seen.
• Transthoracic echocardiography: Checks for effusion and signs of haemodynamic compromise.
• Cardiac CT or MRI: May be performed in atypical presentations to look for pericardial thickening and inflammation.

Management

• Treatment aims to alleviate symptoms, as acute idiopathic pericarditis is typically self-limiting in 70-90% of patients.
• Treat underlying condition if identified.
• Restrict physical activity until symptoms resolve.
• Athletes should return to sports after three months with full symptom resolution and normalised investigation findings.
• Safety netting for symptoms of deterioration is important.

Symptomatic Management

• Non-steroidal anti-inflammatories (e.g., ibuprofen) are first-line, with gastroprotection (PPI).
• Colchicine as an adjunct reduces recurrences by approximately 50% during follow-up.
• Corticosteroids are second-line, with colchicine concurrently.

Predictors of Poor Prognosis

• Fever >38oC
• Subacute onset
• Large pericardial effusion
• Cardiac tamponade
• Failure of response to NSAIDs after a week of therapy

Complications

• Pericardial effusion fluid accumulation due to reduced reabsorption because of a rise in systemic venous pressure from heart failure or pulmonary hypertension (transudate)
• Cardiac tamponade: Pericardial pressure builds up and impedes right heart filling, leading to underfilling of the left heart.
• Approximately 15-30% of patients develop a recurrence of symptoms.
• Novel treatment options now exist for refractory recurrent pericarditis, including immunosuppressants (such as azathioprine), intravenous immunoglobulins and IL-1 antagonists (such as anakinra).
• A potential alternative to giving further medical treatment is pericardiectomy (surgically removing part or all of the pericardium).
• Constrictive pericarditis: Inflammation leads to fibrosis, calcification, and adhesions, hindering diastolic filling.
• Pericardiectomy (resection of the pericardium) is the definitive treatment for chronic constrictive pericarditis.