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Pericarditis and Myocarditis for USMLE Step 1 & COMLEX-USA Level 1

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Pericarditis
  • Etiology:
    • Infectious: Viral (Coxsackievirus B, echovirus), bacterial (tuberculosis, staphylococcal), fungal.
    • Non-infectious:
    • Post-MI (acute pericarditis and Dressler syndrome).
    • Autoimmune conditions (systemic lupus erythematosus, rheumatoid arthritis).
    • Uremia, malignancy, radiation exposure, trauma.
  • Pathophysiology:
    • Inflammation of the pericardial sac disrupts normal lubrication, causing friction and potential fluid accumulation (pericardial effusion).
    • If effusion impairs ventricular filling, it can lead to cardiac tamponade.
  • Clinical Presentation:
    • Chest pain: Sharp, worsens with inspiration, relieved by leaning forward.
    • Pericardial friction rub: Scratchy sound heard best at the left lower sternal border.
    • Fever: Especially with infectious causes or post-MI pericarditis.
  • Diagnosis:
    • ECG:
    • Diffuse ST-segment elevation with PR-segment depression (early).
    • T-wave inversion and normalization in later stages.
    • Echocardiography: Detects pericardial effusion or signs of tamponade.
    • Lab findings: Elevated ESR, CRP, leukocytosis in some cases.
  • Complications:
    • Cardiac tamponade: Beck’s triad (hypotension, distant heart sounds, elevated jugular venous pressure).
    • Constrictive pericarditis: Chronic fibrosis leading to impaired ventricular filling and heart failure.
  • Treatment:
    • NSAIDs and colchicine: First-line therapy to reduce inflammation and recurrence risk.
    • Glucocorticoids: For autoimmune-related or refractory pericarditis.
    • Pericardiocentesis: For tamponade or large effusions.
    • --
Myocarditis
  • Etiology:
    • Infectious: Viral (Coxsackievirus B, adenovirus, parvovirus B19), bacterial (Lyme disease, Chagas disease), parasitic (Trypanosoma cruzi).
    • Non-infectious:
    • Autoimmune diseases (sarcoidosis, lupus).
    • Drug-induced myocarditis (e.g., chemotherapy, clozapine).
  • Pathophysiology:
    • Inflammation of the myocardium causes myocyte injury and impaired contractility.
    • Chronic inflammation can lead to ventricular dilation and dilated cardiomyopathy.
  • Clinical Presentation:
    • Chest pain: May mimic acute coronary syndrome.
    • Heart failure symptoms: Dyspnea, orthopnea, edema, and fatigue.
    • Palpitations and syncope: Reflecting arrhythmias like ventricular tachycardia or heart block.
    • Systemic symptoms: Fever, malaise, and myalgias suggest viral etiology.
  • Diagnosis:
    • ECG: Nonspecific ST/T wave changes, ventricular arrhythmias, heart block.
    • Echocardiography: Shows reduced ejection fraction and ventricular dilation.
    • Cardiac MRI: Demonstrates myocardial edema and late gadolinium enhancement.
    • Endomyocardial biopsy: Confirms diagnosis in severe or refractory cases.
    • Lab tests: Elevated troponin, BNP, and inflammatory markers.
  • Complications:
    • Heart failure: Acute or chronic.
    • Arrhythmias: Ventricular fibrillation or complete heart block.
    • Dilated cardiomyopathy: From chronic myocardial damage.
    • Sudden cardiac death: Due to severe ventricular arrhythmias.
  • Treatment:
    • Supportive care: Oxygen, diuretics, ACE inhibitors, and beta-blockers for heart failure.
    • Antiarrhythmic medications: For ventricular arrhythmias.
    • Immunosuppressive therapy: Used in autoimmune myocarditis.
    • Mechanical support: ECMO or ventricular assist devices in severe heart failure.
    • --
Differences Between Pericarditis and Myocarditis
  • Pathophysiology:
    • Pericarditis involves inflammation of the pericardium, while myocarditis affects the myocardium.
    • Myocarditis can impair cardiac contractility, leading to heart failure and arrhythmias.
  • ECG Findings:
    • Pericarditis: Diffuse ST elevation and PR depression.
    • Myocarditis: Nonspecific ST/T wave changes, ventricular arrhythmias, heart block.
  • Complications:
    • Pericarditis: Tamponade, constrictive pericarditis.
    • Myocarditis: Heart failure, arrhythmias, sudden death.
    • --
Key PointsPericarditis and Myocarditis
  • Pericarditis presents with pleuritic chest pain, pericardial rub, and diffuse ST elevation. It can lead to cardiac tamponade and requires NSAIDs and colchicine for management.
  • Myocarditis can mimic acute coronary syndrome and lead to heart failure, arrhythmias, and dilated cardiomyopathy. Diagnostic tools include cardiac MRI and biopsy.
  • ECG: Pericarditis shows diffuse ST elevation, while myocarditis presents with arrhythmias and nonspecific ST/T wave changes.
  • Complications: Pericarditis can cause tamponade, while myocarditis may result in sudden death from ventricular arrhythmias.