Acute Myocarditis

Related Subjects: |Assessing Breathlessness |Chronic Heart Failure |Acute Heart Failure and Pulmonary Oedema |Loop Diuretics |Chest X Ray Interpretation

Inflammation of the myocardium (acute or chronic) resulting in a variety of presentations, including an incidental ECG finding to fulminant cardiac failure, arrhythmias and sudden cardiac death. Most commonly caused by viral infection but may also be bacterial, protozoal (Chagas), fungal, autoimmune or due to toxic exposure.

📖 About

• ❤️ Acute myocarditis = inflammation of the heart muscle → risk of fatal arrhythmias & acute HF.
• 👶👩‍🦳 Affects any age; triggered by infections (viral 🦠, bacterial 🧫, parasitic 🪱) or non-infectious causes (autoimmune ♻️, toxins ☠️, drugs 💊).
• ⚡ Presentation: acute, subacute, or chronic. Severe cases → cardiogenic shock.
• 🫀 Long-term risk = dilated cardiomyopathy → chronic HF.

🧬 Aetiology & Pathology

• Inflammation → dilated, poorly functioning LV with ↑ troponins 📈.
• Types:
  • Lymphocytic → viral/drugs.
  • Eosinophilic → parasites/hypersensitivity.
  • Giant-cell → fulminant, autoimmune, poor prognosis.
  • Granulomatous → sarcoidosis, arrhythmias.

🦠 Causes

🩺 Clinical Presentation

• Viral prodrome: fever 🤒, myalgia, malaise.
• Chest pain ❤️🔥 (often pericarditic).
• Fatigue, SOB 🫁, palpitations ⚡.
• Syncope → malignant arrhythmias.
• Signs: murmurs (MR), S3/S4, rub, tachyarrhythmias, cardiogenic shock 🫀.

🧪 Investigations

• Bloods: ↑ CRP/ESR, ↑↑ troponin/BNP 📈, ± autoantibodies.
• ECG: AF, VT, LBBB, ST/T changes ⚡.
• CXR: cardiomegaly, pulmonary edema.
• Echo: LV dysfunction, effusion.Echocardiogram, rule out regional wall abnormalities, dilated cardiomyopathies and valvular dysfunction
• Cardiac MRI 🖼️: oedema, fibrosis (Lake Louise criteria). Look for evidence of myocardial inflammation/oedema and fibrosis (late gadolinium enhancement)
• Endomyocardial Biopsy (gold standard 🏆): When diagnosis uncertain. Look for lymphocytic infiltrates, necrosis.

🚑 Management

• ABC, oxygen, correct electrolytes.
• CCU monitoring 📡 with telemetry. Treat arrhythmias and Heart failure
• Bed rest 🛌, avoid exercise and exertion until recovery
• HF therapy: ACEi/ARB, β-blocker, diuretics.
• Anticoagulate if AF or mural thrombus risk.
• Cardiopulmonary assist devices if haemodynamically unstable
• Advanced support: IABP, ECMO, transplant for refractory cases.
• Specific therapy: antivirals (rare), immunosuppression for giant-cell/sarcoid, antiparasitic for Chagas.

⚠️ Complications

• Dilated cardiomyopathy → chronic HF.
• 25% progress to acute ventricular dysfunction
• Arrhythmias (VT, VF) → sudden death ⚡.
• Thromboembolism 🩸 (systemic or pulmonary).
• Heart block → pacemaker.

📚 References

• Kindermann I. et al. (2012) JACC
• Cooper LT et al. (2007) Circulation – Biopsy role
• Yu DQ et al. (2014) Exp Ther Med – IVIG in fulminant myocarditis

🧑‍⚕️ Case Examples — Acute Myocarditis

• Case 1 (Viral myocarditis): 🦠 A 22-year-old man develops chest pain and palpitations 1 week after a flu-like illness. ECG shows ST elevation in several leads, but troponin rise is modest compared to STEMI. Echo reveals mildly impaired LV function. Analysis: Viral infection (e.g., Coxsackie, adenovirus) is the commonest cause. Presents like ACS but with disproportionate troponin rise and systemic prodrome. Diagnosis: Acute viral myocarditis. Management: Supportive (rest, avoid strenuous activity for 6 months, beta-blockers/ACEi if LV dysfunction). No role for routine antivirals.
• Case 2 (Autoimmune/immune-mediated myocarditis): 🧬 A 30-year-old woman with systemic lupus erythematosus (SLE) presents with acute shortness of breath, chest pain, and tachycardia. Troponin is elevated, echo shows reduced EF and global hypokinesia. Analysis: Myocardial inflammation as part of autoimmune disease flare. Often indistinguishable from viral causes without biopsy. Diagnosis: Autoimmune myocarditis. Management: Treat with corticosteroids/immunosuppression under specialist guidance, plus supportive heart failure therapy.
• Case 3 (Fulminant myocarditis): 🚨 A 40-year-old man presents with fever, syncope, and cardiogenic shock after a recent viral illness. BP 75/45, tachycardic, CXR shows pulmonary oedema. Echo: severely reduced LV function. Analysis: Life-threatening fulminant myocarditis with rapid progression to cardiogenic shock. Diagnosis: Fulminant myocarditis. Management: ICU admission, inotropes/vasopressors, mechanical circulatory support (IABP/ECMO) if refractory, consider urgent transplant.