Myocarditis

Question 1

Define myocarditis.

Answer 1

Inflammation of the myocardium in the absence of the predominant acute or chronic ischaemia as in CAD

Question 2

Who is most affected by myocarditis?

Answer 2

• Very variable presentation so difficult to estimate true incidence and prevalence
• ?M>F

Question 3

What are the risk factors for myocarditis?

Answer 3

• Infection e.g. HIV; most common cause of myocarditis worldwide is Trypanosoma cruzi with an estimated 18 million people infected
• Smallpox vaccination
• AI/immune-mediated diseases - SLE, scleroderma etc
• Women in peripartum and postnatal periods
• Drugs and toxins*

*anthracyclines, arsenic, carbon monoxide, ethanol, iron, interleukin-2, cocaine, smallpox vaccination, SARS-CoV-2 vaccination, catecholamines, cyclophosphamide, heavy metals (copper, iron, lead), antibiotics (penicillins, cephalosporins, sulfonamides, amphotericin B), thiazide diuretics, antiepileptics (carbamazepine, phenytoin, phenobarbital), digoxin, lithium, amitriptyline, dobutamine, and snake bites.

Question 4

What is the aetiology of myocarditis?

Answer 4

Infectious:

• Viral e.g. influenza A and B, adenovirus, coxsackie B virus
• Bacterial e.g. myobacterial, streptococcal, mycoplasma
• Spirochetal e.g. Lyme disease, syphilis, leptospirosis
• Mycotic e.g. aspergillus, candida, histoplasma
• Protozoal e.g. toxoplasmosis, malaria
• Rickettsial e.g. Q fever

Non-infectious:

• Toxins/drug relates - arsenic, ethanol, CO, cocaine, heavy metals
• Hypersensitivity - antibiotics, thiazide diuretics, antiepileptics, lithium, digoxin
• Systemic disorders - sarcoidosis, thyrotoxicosis, IBD

Question 5

How does myocarditis present?

Answer 5

• Flu-like prodrome - 2-3 weeks before, with fever, malaise, lethargy, fatigue
• Positional chest pain (worse when lying down)
• Dyspnoea/orthopnoea - new onset CHF
• SOB
• Palpitations
• Elevated neck veins
• S3 and S4 gallop
• Pericardial friction rub
• Arrhythmias e.g. sustained VT
• Peripheral hypoperfusion - can present as left ventricular systolic dysfunction

Question 6

How do you diagnose myocarditis?

Answer 6

Investigations:

• ECG: non-specific ST changes (elevation and depression common), T-wave abnormalities
• CXR - pulmonary infiltrates in the setting of myocarditis-induced CHF
• CK, troponins - mildly elevated - not present in pericarditis.
• BNP - may be elevated if CHF
• TTE echo - may show ventricular motion abnormalities

Other:

• Endomyocardial biopsy (diagnostic but not routinely performed) - done in patients with persistent symptoms who do not respond to treatment
• Coronary angio - exclude MI
• Cardiac MRI
• Viral PCR

Question 7

What is the most common cause of heart failure worldwide?

Answer 7

Trypanosoma cruzi related myocarditis = Chagas heart disease

Question 8

What is the management of haemodynamically stable myocarditis?

Answer 8

In ventricular dysfunction:

• ACEi/ARB/valsartan - improve survival in CHF
• Diuretic - improves patient comfort
• Vasodilator or ionotropes - decrease pulmonary and LV filling pressures
• Beta-blockers - start once acute treatment given
• Aldosterone - given in NYHA stage II-IV heart failure

Anticoagulation - prevent LV thrombus formation

+/- corticosteroids - treat underlying autoimmune condition

+/- permanent pacemaker - often required in Chagas’ disease due to conduction abnormalities and ventricular arrhythmias

Question 9

What is the management of haemodynamically unstable myocarditis?

Answer 9

Some develop fulminant HF or cardiogenic shock and require…

• Pulmonary artery catheter - monitoring cardiac filling and response to therapy
• Vasodilator - sodium nitroprusside
• Vasopressors - noradrenaline
• Positive inotropes - dobutamine
• Intra-aortic balloon pump or LV assist device (LVAD) - bridge to recovery or heart transplant

Question 10

What are the complications of myocarditis?

Answer 10

• AF
• VTs
• Dilated cardiomyopathy
• Sudden cardiac death
• Multisystem organ failure

Question 11

What is the prognosis of myocarditis?

Answer 11

• Varies
• Severity of illness at presentation correlates with long-term outcomes
• Myocardial oedema without fibrosis is also associated with a positive prognosis