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Pericarditis and Myocarditis for the American Board of Internal Medicine (ABIM) Exam

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Pericarditis and Myocarditis
  • Pericarditis and myocarditis are distinct inflammatory conditions affecting the heart. Pericarditis involves inflammation of the pericardial sac, while myocarditis targets the myocardium (heart muscle). Both conditions are clinically relevant for internal medicine due to their diagnostic overlap and management challenges.
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Pericarditis
  • Etiology:
    • Infectious causes: Viral infections (Coxsackievirus, echovirus, influenza), bacterial (tuberculosis, staphylococcal), and fungal pathogens.
    • Non-infectious causes:
    • Autoimmune (systemic lupus erythematosus, rheumatoid arthritis).
    • Post-myocardial infarction syndromes (Dressler's syndrome).
    • Uremia, malignancy, radiation therapy, and trauma.
  • Clinical Presentation:
    • Chest pain: Sharp, pleuritic, and often relieved by sitting upright and leaning forward.
    • Pericardial friction rub: High-pitched scratching sound heard on auscultation.
    • Dyspnea: From cardiac tamponade or pericardial effusion.
    • Fever: May indicate infectious or autoimmune etiology.
  • Diagnosis:
    • ECG findings:
    • Diffuse ST-segment elevation with PR-segment depression (early stages).
    • ST normalization followed by T-wave inversion in later stages.
    • Echocardiography: Detects pericardial effusion and assesses for signs of tamponade.
    • Blood tests: Elevated inflammatory markers (ESR, CRP), leukocytosis.
    • Pericardiocentesis: Fluid analysis in suspected infectious or malignant pericarditis.
  • Complications:
    • Cardiac tamponade: Life-threatening condition caused by accumulation of fluid in the pericardium, impairing ventricular filling.
    • Constrictive pericarditis: Chronic thickening and fibrosis of the pericardium, leading to heart failure.
  • Management:
    • NSAIDs (e.g., ibuprofen) for pain and inflammation.
    • Colchicine: Reduces recurrence.
    • Glucocorticoids: For refractory or autoimmune-related pericarditis.
    • Pericardiocentesis: For tamponade or large effusions.
    • Antibiotics: For bacterial pericarditis.
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Myocarditis
  • Etiology:
    • Infectious causes: Viruses (Coxsackievirus, adenovirus, parvovirus B19), bacteria (Lyme disease, Chagas disease), fungi, and parasites.
    • Non-infectious causes:
    • Autoimmune conditions (sarcoidosis, giant cell myocarditis).
    • Toxic causes (e.g., alcohol, anthracyclines).
    • Hypersensitivity reactions (e.g., drug-induced myocarditis).
  • Clinical Presentation:
    • Chest pain: Can mimic acute coronary syndrome.
    • Dyspnea and signs of heart failure: Due to reduced ventricular function.
    • Palpitations: May reflect arrhythmias, including ventricular tachycardia.
    • Systemic symptoms: Fever, myalgia, and fatigue are common in viral myocarditis.
  • Diagnosis:
    • ECG findings: Nonspecific ST/T wave changes, heart block, or arrhythmias.
    • Echocardiography: Demonstrates reduced ejection fraction or ventricular dysfunction.
    • Cardiac MRI: Identifies myocardial inflammation and edema (T2-weighted images).
    • Endomyocardial biopsy: Gold standard for diagnosis, used when specific histologic or infectious confirmation is needed.
    • Blood tests: Elevated troponin and BNP levels indicate myocardial injury.
  • Complications:
    • Heart failure: Acute or chronic deterioration in left or right ventricular function.
    • Arrhythmias: Ventricular arrhythmias and atrioventricular block.
    • Dilated cardiomyopathy: Result of chronic myocarditis.
    • Sudden cardiac death: From ventricular arrhythmias.
  • Management:
    • Supportive care: Oxygen, diuretics, ACE inhibitors, and beta-blockers for heart failure.
    • Antiviral therapy: Limited role but considered in specific infections.
    • Immunosuppressive therapy: For autoimmune myocarditis (e.g., corticosteroids, azathioprine).
    • Antiarrhythmic therapy: For ventricular arrhythmias.
    • Mechanical support: In severe cases, intra-aortic balloon pump or extracorporeal membrane oxygenation (ECMO).
    • Heart transplantation: In end-stage heart failure.
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Differences Between Pericarditis and Myocarditis
  • Pathophysiology:
    • Pericarditis involves inflammation of the pericardial sac.
    • Myocarditis is an inflammatory process within the myocardium, often leading to myocardial dysfunction.
  • ECG Findings:
    • Pericarditis: Diffuse ST-segment elevation and PR-segment depression.
    • Myocarditis: Nonspecific ST/T wave changes, heart block, or ventricular arrhythmias.
  • Complications:
    • Pericarditis: Risk of cardiac tamponade and constrictive pericarditis.
    • Myocarditis: Heart failure, arrhythmias, and dilated cardiomyopathy.
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Key Points
  • Pericarditis presents with sharp chest pain relieved by leaning forward, pericardial friction rub, and diffuse ST-segment elevation on ECG.
  • Myocarditis often mimics acute coronary syndrome (ACS) with chest pain, arrhythmias, and signs of heart failure. ACS shows specific regional ECG changes, whereas myocarditis typically shows diffuse nonspecific changes.
  • Cardiac MRI and endomyocardial biopsy are essential tools for myocarditis diagnosis, especially when autoimmune or infectious etiologies are suspected.
  • NSAIDs and colchicine are first-line treatments for pericarditis, while immunosuppressants and heart failure therapies are critical for managing myocarditis.
  • Pericarditis can lead to cardiac tamponade and constrictive pericarditis, while myocarditis may progress to heart failure and dilated cardiomyopathy.