16.9: Pericarditis I: Introduction

Pericarditis is defined as the inflammation of the pericardium, the thin, sac-like membrane surrounding the heart. This condition can cause significant chest pain and other symptoms, often necessitating medical intervention. The pericardium has two layers: the inner visceral layer and the outer parietal layer, separated by a small amount of fluid that reduces friction during heartbeats.

Types of Pericarditis

Pericarditis can be classified into several types based on the duration and nature of the inflammation:

• Acute Pericarditis: This type lasts less than six weeks and is the most common form. It often presents with a sudden onset of symptoms.
• Chronic Pericarditis: It lasts longer than three months; chronic pericarditis can develop gradually and often leads to more severe complications.
• Recurrent Pericarditis: After an initial episode of acute pericarditis, some patients may experience a recurrence, often within weeks or months.
• Constrictive Pericarditis: In this severe form, the pericardium thickens and scars, restricting the heart's ability to function properly.
• Effusive-Constrictive Pericarditis: This is a combination of fluid accumulation (effusion) and constriction, presenting a more complex clinical scenario.

Causes of Pericarditis

The causes of pericarditis vary and can be categorized as either infectious or non-infectious:

Infectious Causes

• Viral Infections: The most common cause, often including viruses such as Coxsackievirus, Echovirus, and others.
• Bacterial Infections: Less common but can be severe, including tuberculosis and bacterial pneumonia.
• Fungal Infections: Rare, typically occurring in immunocompromised individuals.
• Parasitic Infections: Also rare but possible in certain geographical regions.

Non-Infectious Causes

• Autoimmune Diseases: Conditions like Systemic lupus erythematosus (SLE), rheumatoid arthritis, and scleroderma can trigger pericarditis.
• Trauma or Injury: Physical injury to the chest, including surgery and accidents, can lead to pericarditis.
• Post-Myocardial Infarction: Inflammation that occurs after a heart attack.
• Cancer: Metastasis to the pericardium from other cancers, such as lung or breast cancer.
• Medications: Certain drugs, including some chemotherapeutic agents, can induce pericarditis.
• Uremia: Increased urea levels and other waste products in the blood, typically due to kidney failure.

Pathophysiology of Pericarditis

The pathophysiology of pericarditis involves a complex interplay of inflammatory processes. When the pericardium becomes inflamed, it undergoes several changes:

• Inflammation: Inflammatory cells, including neutrophils, lymphocytes, and macrophages, infiltrate the pericardium and release inflammatory mediators such as cytokines and chemokines.
• Vascular Permeability: Increased permeability of pericardial blood vessels allows proteins and cells to leak into the pericardial space, accumulating fluid known as pericardial effusion.
• Fibrin Deposition: In some cases, fibrin, a protein involved in blood clotting, is deposited on the pericardium, leading to a rough and thickened pericardial surface.
• Fibrosis and Scarring: Chronic inflammation can lead to fibrosis, where the pericardium thickens and scars. In constrictive pericarditis, this fibrosis restricts the normal movement of the heart, impeding its function.
• Pressure Changes: The accumulation of fluid or the development of fibrotic tissue can increase pressure within the pericardial sac, affecting the heart's ability to fill and pump blood efficiently.

Conclusion

Pericarditis is a multifaceted condition with various types, causes, and underlying pathophysiological mechanisms. Understanding these aspects is crucial for effective diagnosis and management.