Acute Myocarditis ✅

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

⚡ Myocarditis = inflammation of the myocardium, acute or chronic, presenting anywhere from incidental ECG changes to fulminant heart failure, arrhythmias, or sudden cardiac death. 🦠 Causes: viral (most common), bacterial, protozoal (Chagas), fungal, autoimmune, toxins, or drugs.

📖 About

• ❤️ Acute myocarditis → risk of fatal arrhythmias & acute HF.
• 👶👩‍🦳 Can affect all ages; triggers include viral infections, bacteria, parasites, autoimmune conditions, toxins, and drugs.
• ⚡ Presentation: acute, subacute, or chronic. Severe → cardiogenic shock.
• 🫀 Long-term: dilated cardiomyopathy → chronic HF.
• 🧬 Histology:
  • Lymphocytic → viral/drug-related
  • Eosinophilic → hypersensitivity or parasitic
  • Giant-cell → autoimmune/fulminant, poor prognosis
  • Granulomatous → sarcoidosis, arrhythmias

🦠 Myocarditis Causes – Detailed Investigations & NICE‑Aligned Management

🩺 Clinical Features

• Prodrome: fever, myalgia, malaise.
• Chest pain (often pericarditic), palpitations, fatigue, dyspnoea.
• Syncope → may indicate malignant arrhythmia.
• Signs: murmurs (MR), S3/S4, pericardial rub, tachyarrhythmias, cardiogenic shock.

🧪 Investigations

• Bloods: ↑ CRP/ESR, ↑ troponin/BNP, ± autoantibodies.
• ECG: AF, VT, LBBB, ST/T changes.
• CXR: cardiomegaly, pulmonary oedema.
• Echocardiogram: LV dysfunction, effusion, regional wall abnormalities, valvular assessment.
• Cardiac MRI: myocardial oedema, late gadolinium enhancement for fibrosis (Lake Louise criteria).
• Endomyocardial biopsy (gold standard): lymphocytic infiltrates, necrosis; indicated if diagnosis uncertain.
• Other: Holter monitoring, exercise testing for arrhythmia risk once stable.

⚡ Myocarditis Treatment (NICE-compliant) — Detailed Overview

1️⃣ Supportive & Initial Care

• ABC approach: secure airway, support breathing, maintain circulation
• Continuous telemetry in CCU/ward with cardiac monitoring
• Frequent vital signs: HR, BP, SpO₂, RR
• Strict fluid balance; avoid fluid overload in LV dysfunction
• Bed rest; restrict strenuous activity until recovery

2️⃣ Heart Failure Management

• ACE inhibitors / ARBs: Start low and titrate (Lisinopril, Ramipril, Losartan, Candesartan)
• β-blockers: Bisoprolol or Carvedilol once haemodynamically stable
• Diuretics: Furosemide ± metolazone for congestion; monitor renal function and electrolytes
• Mineralocorticoid receptor antagonists: Spironolactone for persistent LV dysfunction
• Follow NICE CG108 principles for acute and chronic HF therapy

3️⃣ Arrhythmia Management

• Supraventricular: AF/flutter rate control, anticoagulate as indicated
• Ventricular: VT/VF — ACLS protocol, amiodarone; lidocaine/mexiletine if refractory
• Bradyarrhythmias: Temporary pacing if high-grade AV block; permanent pacemaker if persistent

4️⃣ Immunomodulatory Therapy

• Corticosteroids: Autoimmune myocarditis only; e.g., Prednisolone 1 mg/kg/day
• Immunosuppressants: Methotrexate, azathioprine, mycophenolate for specialist-selected cases
• IVIG: Consider in fulminant viral or paediatric myocarditis
• Plasmapheresis: Rare, for refractory immune-mediated cases
• Routine immunosuppression not recommended for typical viral myocarditis

5️⃣ Advanced Circulatory & Respiratory Support

• Inotropes: Dobutamine for low-output; Noradrenaline for hypotension/shock
• Mechanical support: IABP, VA-ECMO, LVAD/BiVAD as bridge or transplant
• Mechanical ventilation if pulmonary oedema or ARDS
• Transplantation for refractory end-stage myocarditis

6️⃣ Anticoagulation

• Indications: AF, intracardiac thrombus, EF <35%
• Drugs: DOACs (Apixaban, Rivaroxaban) or Warfarin
• Monitor bleeding risk and renal function

7️⃣ Activity & Rehabilitation

• Restrict strenuous exercise 3–6 months
• Gradual return guided by echo/MRI and exercise testing
• Long-term supervised cardiac rehab if chronic or recurrent disease

8️⃣ Follow-Up Monitoring

• 1–2 weeks: clinical review + ECG
• 6–12 weeks: echocardiography to assess LV function
• 3–6 months: cardiac MRI to document resolution
• Monitor troponin/NT-proBNP trend and arrhythmia symptoms

📊 NICE & UK Guidance Highlights

• Heart failure: use evidence-based HF therapy as tolerated
• Arrhythmias: treat per ACLS and HF risk; avoid pro-arrhythmic drugs
• Immunosuppression: specialist-led only, not routine
• Monitoring: telemetry and repeated imaging for instability/arrhythmia risk
• Exercise: avoid competitive sport until resolution confirmed
• Biomarkers: serial troponin/NT-proBNP guide severity and response

📌 High-Yield Exam Pearls

• β-blockers and ACEi foundational once stable
• Corticosteroids only in immune-mediated or giant-cell myocarditis
• IVIG for fulminant myocarditis, not routine viral cases
• Anticoagulate only if AF, thrombus, or LV dysfunction
• Avoid strenuous exercise until normal LV function and biomarkers documented

⚠️ Complications

• Dilated cardiomyopathy → chronic HF.
• Acute ventricular dysfunction (≈25%).
• Arrhythmias (VT/VF) → sudden death.
• Thromboembolism (systemic or pulmonary).
• Heart block → may require pacemaker.

🧑‍⚕️ Case Examples

• 22-year-old man, chest pain & palpitations 1 week after flu-like illness.
• ECG: ST elevation; troponin rise modest; echo: mild LV dysfunction.
• Management: supportive care, avoid strenuous activity 6 months, HF therapy if needed.

• 30-year-old woman with SLE, SOB, chest pain, tachycardia, elevated troponin, reduced EF.
• Management: corticosteroids/immunosuppression + supportive HF therapy.

• 40-year-old man, fever, syncope, cardiogenic shock post-viral illness. Echo: severely reduced LV function.
• Management: ICU admission, inotropes/vasopressors, ECMO/IABP if refractory, consider urgent transplant.

📚 References

• Kindermann I. et al. (2012) JACC
• Cooper LT et al. (2007) Circulation – Role of biopsy
• Yu DQ et al. (2014) Exp Ther Med – IVIG in fulminant myocarditis
• NICE CG108: Acute Heart Failure (2018)