- This is acute or chronic inflammation of the myocardium – and may present similarly to MI.
Epidemiology
- More freq in children & young adults. Post-mortem studies suggest it is a major cause of sudden unexpected death in adults, implicated in ~20% of those aged <40 years.
Causes
Infection – lots of candidates all rare except for viral
- Viral:
- Coxsackievirus, enteroviruses, adenovirus, HIV, EBV, CMV, Hep A&C, influenza, HSV, RSV, measles, mumps, rubella and parvoviruses, vaccinia, Herpes/varicella zoster…
- Bacterial:
- Brucella, gonococcus and meningococcus, H influenzae, mycobacterium, Strep. spp, salmonella, Staph. spp, Mycoplasma, Trep. pallidum, C. diphtheria and V. cholerae.
- Spirochetal:
- e.g. Lyme disease (borrelia) and leptospira
- Fungal:
- e.g. Actinomyces, aspergillus, candida, cryptococcus, histoplasma.
- Protozoal:
- e.g. Toxoplasma gondii and Trypanosoma cruzi
- Parasitic:
- e.g. Ascaris, schistosoma
- Rickettsial:
- e.g. Q fever (Coxiella burnetti)
Immune Mediated
- Autoantigens:
- Chagas’ Disease (most common worldwide), Sarcoidosis, SLE, Rh F., **Scleroderma, Chlamydia pneumoniae, Churg-Strauss syndrome, Giant-cell myocarditis, IBD, IDDM, Kawasaki’s, Myasthenia gravis, polymyositis, thyrotoxicosis, Wegener’s granulomatosis.
- Allergens:
- Drugs (acetazolamide, amitriptyline, cefaclor, colchicine, frusemide, isoniazid, lidocaine, methyldopa, penicillin, phenytoin, tetracycline, thiazides and tetanus toxoid).
- Alloantigens:
- Heart-transplant rejection
Toxic Myocarditis
- Drugs:
- Ethanol, cytotoxic antibiotics (anthracyclines, e.g. doxorubicin), amphetamines, cocaine, cyclophosphamide, fluorouracil, lithium, interlukin-2 and trastuzumab.
- Heavy metal poisoning:
- lead, copper, iron
- Physical agents:
- Electric shock, hyperpyrexia, radiation
- Others:
- arsenic, insect stings and bites, phosphorus, carbon monoxide and inhalants
Symptoms and signs:
- From asymptomatic with ECG abnormalities to severe heart failure. Patients commonly complain of flu-like prodrome, fever, fatigue, dyspnoea, chest pain and palpitations. There may be a tachycardia, soft S1, S4 gallop, and signs of heart failure.
Investigations
- ECG:
- ↑HR, ↑ or ↓ST, ↓T waves, atrial arrhythmias, transient AV block.
- CXR.
- Cardiomegaly common. Echo. For cardiac fn.
- Bloods:
- FBC, U&E, CK, Trop, ESR or CRP, LFT, serology, autoantibodies. Myocardial biopsy:_ limited sensitivity <70%.
- Antimyosin scintigraphy
Management:
- Treat underlying cause. Pharm. support. Mechanical support (ECMO, ventricular assist devices). Steroids/immunodepressants Rx for autoimmune causes. Ongoing trials on antiviral agents/viral vaccines. Cardiac monitoring. CCU/ICU. May need transplantation.
Prognosis:
- Most mort in first 72-96hrs. 95% survival if mech. support not reqd for first 72hrs. Commonly progresses to chronic HF or dilated cardiomyopathy. Better prognosis in children.