Table of Contents
Overview – Myocarditis
Myocarditis refers to inflammation of the heart muscle (myocardium), often accompanied by myocyte necrosis. It may present subtly or cause sudden cardiac death, particularly in younger individuals. Myocarditis can result from viral infections or exposure to cardiotoxic substances, leading to acute or chronic heart failure, arrhythmias, or pericarditis. Timely diagnosis and supportive management are critical to prevent complications.
Definition
Myocarditis is inflammation of the heart muscle, often accompanied by myocyte necrosis and variable degrees of myocardial dysfunction. It is commonly identified by elevated cardiac enzymes such as troponin I (positive in ~35% of cases).
Aetiology
Viral Myocarditis
- Causative viruses:
- Coxsackievirus
- Rhinovirus
- Influenza
- Parvovirus B19
- Coronavirus
- Mechanism:
- Direct myocardial invasion
- OR secondary autoimmune response → myocardial inflammation
- Result: Ventricular thickening and systolic dysfunction
Toxic Myocarditis
- Causative agents:
- Mechanisms:
- Hypersensitivity drug reactions
- Direct myocardial toxicity
Clinical Features
- Often asymptomatic or mild in early stages
- Systemic symptoms:
- Fever
- Fatigue
- Malaise
- Cardiac symptoms:
- Dyspnoea, orthopnoea, paroxysmal nocturnal dyspnoea
- Cough (due to pulmonary congestion)
- Chest pain (± associated pericarditis)
- Palpitations and arrhythmias
Complications
- Dilated cardiomyopathy → congestive heart failure
- Arrhythmias → risk of sudden cardiac death
- Pericarditis → pericardial effusion
Investigations
- ECG + continuous telemetry (to detect arrhythmias)
- Serial troponin I or T:
- At baseline, 6 hours, and 24 hours
- Bloods:
- FBC (↑WCC)
- CRP & ESR (elevated inflammatory markers)
- CXR:
- Cardiomegaly
- Echocardiography:
- Dilated cardiac chambers
- Reduced ventricular function
Management
- Bed rest during the acute phase
- Congestive heart failure (CCF) therapy:
- ACE inhibitors or angiotensin receptor blockers (e.g. Perindopril/Candesartan)
- Beta-blockers (e.g. Carvedilol)
- Diuretics (e.g. Frusemide)
- Warfarin (to prevent thromboembolism)
- Supportive therapy:
- Fluids
- Analgesia
- Treat the underlying cause:
- Antivirals if appropriate
- Discontinue offending drugs or toxins
Summary – Myocarditis
Myocarditis is inflammation of the heart muscle, often caused by viral infections or toxic agents. It can present with chest pain, dyspnoea, fatigue, or palpitations, and can lead to heart failure, arrhythmias, or pericardial complications. Diagnosis involves cardiac enzymes, ECG, and imaging. Management includes supportive care, heart failure therapy, and treatment of the underlying cause. For a broader context, see our Cardiovascular Overview page.