What is the pathophysiology of pericarditis?

Pathophysiology of Pericarditis

Pericarditis represents an inflammatory response of the pericardium triggered by diverse stimuli—infectious, chemical, physical, or ischemic—with the NLRP3 inflammasome and interleukin-1 (IL-1) pathway serving as the central pathophysiological mechanism driving both acute inflammation and recurrent disease.

Core Inflammatory Mechanism

The pathophysiology centers on a stereotypical inflammatory cascade initiated when the mesothelial cells of the pericardial layers sustain acute damage 1, 2:

• Initial trigger: Pathogens, irritants, or tissue injury interact with toll-like receptors (TLRs) on pericardial mesothelial cells, initiating the inflammatory response 1
• NLRP3 inflammasome activation: This macromolecular structure acts as a damage sensor, assembling in response to the initial insult and releasing pro-inflammatory cytokines, particularly IL-1β 2
• Auto-amplification loop: IL-1β stimulates the IL-1 receptor, which increases transcription of additional pro-inflammatory genes required for further NLRP3 inflammasome assembly, creating a self-perpetuating autoinflammatory cycle 1, 2
• Clinical validation: This pathway is confirmed by the therapeutic efficacy of colchicine (an indirect NLRP3 inflammasome inhibitor) and direct IL-1 blockers like anakinra and rilonacept in preventing recurrences 2, 3

Etiological Framework

The inflammatory response varies based on the underlying trigger 4:

Infectious Causes

• Viral infections: The most common etiology in developed countries, with cardiotropic viruses causing inflammation through direct cytolytic effects and subsequent immune-mediated mechanisms 4
• Tuberculosis: The predominant cause globally and in endemic regions, particularly sub-Saharan Africa where it frequently coexists with HIV infection 4
• Bacterial infections: Less common but associated with higher risk of progression to constrictive pericarditis (20-30% risk) 4

Non-Infectious Causes

• Autoimmune disorders: Including systemic lupus erythematosus, rheumatoid arthritis, and systemic vasculitides, where self-antigens on mesothelial cells or microbial peptides may stimulate autoreactive T cells and B cells producing anti-heart antibodies 4, 1
• Post-injury syndromes: Delayed inflammatory responses following myocardial infarction, cardiac surgery, or iatrogenic trauma (percutaneous interventions, pacemaker insertion, ablation procedures) 4
• Neoplastic: Secondary metastatic tumors (lung, breast cancer, lymphoma) or rare primary pericardial mesothelioma 4
• Metabolic: Uremia, myxedema, and other metabolic derangements 4
• Drug-induced: Lupus-like syndromes from procainamide, hydralazine, or hypersensitivity reactions to various medications 4

Pathophysiological Complications

Recurrent Pericarditis

• Affects approximately 30% of patients within 18 months after initial episode 4
• Driven by persistent NLRP3 inflammasome activation and IL-1β auto-induction, creating an autoinflammatory disease pattern 1, 2
• Risk factors include inadequate initial anti-inflammatory therapy, early corticosteroid use, and elevated high-sensitivity C-reactive protein 5

Cardiac Tamponade

• Results from pan-cyclic compression of cardiac chambers by increased pericardial fluid 6
• Primary abnormality involves competition among cardiac chambers for fixed intrapericardial volume 6
• Features include transmission of thoracic pressure through pericardium and heightened ventricular interdependence 6
• Occurs in less than 3% of acute pericarditis cases but represents a life-threatening complication 3

Constrictive Pericarditis

• Develops from chronic inflammatory process leading to pericardial fibrosis and calcification 4, 7
• Pericardium limits diastolic filling, causing dissociation of intracardiac and intrathoracic pressures 6
• Risk varies by etiology: <1% in viral/idiopathic, 2-5% in immune-mediated, 20-30% in bacterial pericarditis 4
• Results in diastolic dysfunction, elevated venous pressures, respiratory variation in ventricular filling, and reduced cardiac output 6

Clinical Implications

Common pitfall: Early high-dose corticosteroid use is associated with increased risk of complicated pericarditis and should be avoided as first-line therapy 5. The pathophysiology supports NSAIDs plus colchicine as initial treatment, directly targeting the inflammasome pathway while avoiding the complications associated with premature immunosuppression 2, 3.

The understanding that pericarditis represents an inflammasome-driven autoinflammatory condition rather than a simple infectious or autoimmune process has fundamentally shifted treatment approaches, with IL-1 blockers emerging as steroid-sparing alternatives for refractory recurrent cases 2, 3, 5.