Pericarditis: A High-Yield USMLE Review

Pericarditis is inflammation of the pericardium presenting with pleuritic chest pain and a characteristic ECG of diffuse ST elevation without reciprocal changes. It is a key STEMI mimic on the exam, and recognizing its distinguishing features prevents unnecessary emergent catheterization. Post-MI forms (early pericarditis and Dressler syndrome) are frequently tested associations.

Presentation

• Sharp, stabbing pleuritic chest pain that worsens with breathing or movement
• Pain relieved by leaning forward; patients are often observed sitting up and leaning forward
• Pericardial friction rub on auscultation
• Persistent pain lasting hours to days — unlike the more transient or exertional/paroxysmal pain of ACS or PE, this persistence is a key distinguishing feature
• In post-MI settings (Dressler syndrome), fever and pleuritic chest pain with a pericardial effusion

Diagnosis

• ECG shows diffuse ST elevation with PR depression and no reciprocal ST changes, distinguishing it from STEMI
• Physical exam reveals a pericardial friction rub and pain relieved by leaning forward
• If a pericardial effusion develops, watch for elevated JVP and pulsus paradoxus (drop in systolic BP >10 mmHg during inspiration), which raise concern for tamponade

Management

• Acute idiopathic/viral pericarditis is treated with high-dose NSAIDs plus colchicine
• In the post-MI setting (early post-infarct pericarditis and Dressler syndrome), high-dose aspirin plus colchicine is preferred; other NSAIDs (e.g., ibuprofen, indomethacin) are avoided because they may impair infarct healing and increase remodeling risk
• Avoid anticoagulation when a pericardial effusion is present due to bleeding/tamponade risk
• Early post-infarct pericarditis is usually self-limited

High-yield

• Diffuse ST elevation with PR depression and NO reciprocal changes is the classic pericarditis ECG
• Pain is sharp/pleuritic, worse with breathing, relieved by leaning forward, and characteristically persistent (hours to days)
• Dressler syndrome: autoimmune pericarditis 2–10 weeks post-MI with fever, pleuritic chest pain, and effusion — treat with aspirin plus colchicine, not NSAIDs
• Cardiac tamponade: Beck's triad is hypotension, elevated JVP/jugular venous distention, and muffled heart sounds; pulsus paradoxus is a classic accompanying finding but is NOT part of Beck's triad
• Constrictive pericarditis: elevated JVP with Kussmaul's sign (JVP rises with inspiration) and pericardial knock; pulsus paradoxus is typically absent — this is the key contrast with tamponade
• Uremic pericarditis is an indication for urgent dialysis in chronic kidney disease

Pitfalls

• Mistaking pericarditis for STEMI — remember the diffuse ST elevation lacks reciprocal changes; comparing to prior ECGs and recognizing mimics avoids unnecessary cath lab activation
• Giving anticoagulation in Dressler syndrome when a pericardial effusion is present, risking hemorrhagic tamponade
• Attributing pulsus paradoxus to constrictive pericarditis — it is the classic finding of tamponade; constriction is distinguished by Kussmaul's sign
• Overlooking pulsus paradoxus and elevated JVP that signal progression to tamponade
• Confusing the pleuritic, sharp, persistent quality of pericarditis with the pressure/squeezing pain of ACS
• Reaching for ibuprofen or indomethacin in post-MI pericarditis — use aspirin plus colchicine instead to avoid impairing infarct healing