Myocarditis

Question 1

What is myocarditis?

Answer 1

Acute inflammation and necrosis of myocardium in the absence of ischaemia (characteristic of coronary artery disease).

Question 2

What is the aetiology/risk factors of myocarditis? (x12)

Answer 2

• Viruses such as Coxsackie B, echovirus, EBV, CMV, HIV, adenovirus, influenza
• Bacteria such as post-streptococcal, TB, diphtheria and Lyme disease
• Fungal such as candidiasis
• Protozoal such as trypanosomiasis (Chagas disease)
• Helminths such as trichinosis
• Non-infective: systemic and autoimmune disorders (SLE, sarcoidosis, IBD)
• Hypersensitivity myocarditis such as antibiotic sulphonamides
• Chemotherapy agents
• Cocaine abuse
• Heavy metals
• Radiation
• Peripartum and postnatal women

Question 3

What is the pathophysiology of myocarditis?

Answer 3

Unclear. However, in viral-mediated myocarditis, there are three mechanisms: (1) infectious organism invades myocardium, (2) local and systemic immunological activation, (3) cellular CD4+ (cellular) and B-cell clonal expansion (humoral) occurs causing worsening inflammation, anti-heart antibody production and further myonecrosis.

Question 4

What is the epidemiology of myocarditis: Two areas – common aetiology?

Answer 4

Coxsackie B virus is a common cause in Europe and USA. Chagas disease is a common cause in S America.

Question 5

What are the symptoms of myocarditis? (x4)

Answer 5

• Prodromal (between appearance of initial symptoms and development of the full disease) flu-like illness – fever, malaise, fatigue and lethargy
• Breathlessness (from pericardial effusion or myocardial dysfunction)
• Palpitations
• Sharp chest pain (suggesting associated pericarditis)

Question 6

What are the signs of myocarditis? (x2)

Answer 6

Signs of concurrent pericarditis OR signs of complications such as heart failure or arrythmias.

Question 7

What are the blood investigations for myocarditis? (x4)

Answer 7

• FBC show increased WCC (infective cause)
• Raised ESR/CRP
• Cardiac enzymes may be increased – notably creatinine kinase and troponin, but this is not common as disease is non-ischaemic
• Serology: viral or bacterial to identify the cause e.g., Antistreptolysin O titre against streptolysin O, and ANA

Question 8

What are the other investigations for myocarditis?

Answer 8

• ECG
• CXR may show cardiomegaly with or without pulmonary oedema due to chronic heart failure
• Pericardial fluid drainage: measure glucose, protein, cytology, culture and sensitivity
• Echocardiography: assess systolic/diastolic function, wall motion abnormalities, pericardial effusion

Question 9

What does ECG show in myocarditis?

Answer 9

Non-specific ST segment and T-wave abnormalities (and saddle-shaped ST elevation if pericarditis is concurrent).