myocarditis

Question 1

definition

Answer 1

Acute inflammation and necrosis of cardiac muscle (myocardium).

Question 2

aetiology

Answer 2

Usually unknown (idiopathic).

Infection:

• Viruses: e.g. Coxsackie B, echovirus, EBV, CMV, adenovirus, influenza. Bacterial: e.g. post-streptococcal, tuberculosis, diphtheria, Lyme disease. Fungal: e.g. candidiasis.
• Protozoal: e.g. trypanosomiasis (Chagas disease).
• Helminths: e.g. trichinosis.

Non-infective: Systemic disorders (e.g. SLE, sarcoidosis, polymyositis), hypersensitivity myocarditis (e.g. sulphonamides).

Drugs: Chemotherapy agents (e.g. doxorubicin, streptomycin) Others: Cocaine abuse, heavy metals, radiation.

Question 3

symptoms

Answer 3

Prodromal ‘flu-like’ illness, fever, malaise, fatigue, lethargy. Breathlessness (pericardial effusion/myocardial dysfunction). Palpitations.
Sharp chest pain (suggesting associated pericarditis).

Question 4

signs/examinations

Answer 4

signs of concurrent pericarditis or other complications: heart failure, arrhythmia

Question 5

investigations

Answer 5

Blood: FBC (raised WCC in infective causes), U&E, raised ESR or CRP, cardiac enzymes (may be raised). To identify the cause (viral or bacterial serology, antistreptolysin O titre, ANA, serum ACE, TFT).

ECG: Non-specific T wave and ST changes, widespread saddle-shaped ST elevation in pericarditis.

CXR: May be normal or show cardiomegaly with or without pulmonary oedema

Pericardial fluid drainage: Measure glucose, protein, cytology, culture and sensitivity.

Echocardiography: Assesses systolic/diastolic function, wall motion abnormalities, pericardial effusion.

Myocardial biopsy: Rarely required (result does not influence management).

1st investigations to order:

• 12 lead ECG
• serum trops
• serum CK
• serum CK-MB
• serum BNP
• 2D echocardiogram

Question 6

treatment

Answer 6

haemodynamically stable:
1. ACEi (ramipril) or ARB (irbesartan) – to dilate arteries, improve cardiac output
+ treat underlying cause
++ beta blockers (bisoprolol)
++ oral vasodilators/nitrates (hydralazine + isosorbide dinitrate)
++ diuretics (furosemide/bumetanide)
++ aldosterone antagonists (spironolactone)
++ long term anticoagulants (warfarin)

haemodynamically unstable
1. intravenous arterial vasodilator + invasive haemodynamic monitoring (nitroprusside)
+ treat underlying cause
++ IV glyceryl trinitrate – for patients with elevated pulmonary vasculature and cardiac filling pressures, pulmonary oedema, and respiratory distress
++ IV inotropes or vasopressors (dobutamine or phenylephrine) – to up the BP

refractory cardiogenic shock:
1. intra aortic balloon pump (IABP)
++ left ventricular assist device (LVAD)

Question 7

complications

Answer 7

Severe cases can lead to chronic inflammation, cardiac failure. Resolution of inflammation with different degrees of residual dilated cardiomyopathy, arrhythmias and death.

Question 8

prognosis

Answer 8

Usually mild and self-limiting. Recovery is variable in patients with severe acute myocarditis.