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Related Subjects: |Assessing Breathlessness |Chronic Heart Failure |Acute Heart Failure and Pulmonary Oedema |Loop Diuretics |Chest X Ray Interpretation

About

• Serious disease of the myocardium: can result in fatal arrhythmias and heart failure.
• It can occur at all ages. There are both infectious and non-infectious triggers.
• Presentation may be acute, subacute or chronic, but often rapid onset with acute heart failure or cardiogenic shock
• It may result in dilated cardiomyopathy

Aetiology

• Inflamed myocardium. Dilated poorly functioning heart. Elevated troponin.
• Can result in end-stage cardiac failure, thromboembolism and arrhythmias.

Causes

• Idiopathic: all investigations negative; 50% presumably viral but unproven.
• Viral infection: parvovirus B19 and HHV6, Coxsackie A (mild), Coxsackie B (severe) and influenza; echovirus; adenovirus; HIV; CMV.
• Non-viral infection: Chagas disease (Trypanosoma cruzi), toxoplasmosis. Rickettsial: Scrub typhus, Rocky Mountain spotted fever, Q fever, Lyme disease causes temporary conduction block.
• Bacterial: leptospirosis, diphtheria, Clostridia, TB, brucella.
• Drugs and toxins: doxorubicin, Herceptin, cyclophosphamide, penicillin, phenytoin, methyldopa, cocaine abuse.
• Fungal: with malignancy and/ or immunosuppressive therapy; aspergillosis (not uncommon in generalized infection), mucormycosis (about 20% in patients with disseminated form; invasion of arteries causes infarction), candidiasis (endocarditis most common), cryptococcosis (HIV)
• Heavy metals: arsenic, cobalt, mercury exposure.
• Miscellaneous: radiation, peripartum cardiomyopathy, post-cardiac transplant rejection.
• Inflammatory: sarcoidosis, Kawasaki disease, SLE, Wegener's granulomatosis, thyrotoxicosis, rheumatoid arthritis, rheumatic fever. Giant cell myocarditis: rare usually fatal form of myocarditis.

Pathology

• Myocarditis is characterised by an inflammatory cellular infiltrate (which may be focal or diffuse) in the presence or absence of cardiac myocyte injury
• Lymphocytic myocarditis – associated with a range of pathogens (predominantly viruses), drugs, radiation exposure and autoimmune disorders.
• Eosinophilic myocarditis – a relatively uncommon form associated with parasitic infections, hypersensitivity reactions to various agents, eosinophilic inflammatory disorders and rarely a neoplastic process.
• Giant-cell myocarditis – idiopathic in most cases but can also be associated with certain autoimmune disorders including autoimmune thyroid disease and inflammatory bowel diseases.
• Granulomatous myocarditis – associated with sarcoidosis

Clinical Symptoms

• Viral type illness, fever and muscle aches
• Increasing fatigue and dyspnoea over days and weeks
• Patient may be young with no background of cardiac disease
• Chest pain - pericarditis, syncope, presyncope, malaise, viral type of illness
• Sudden death due to VF or pump failure

Clinical Signs

• Murmur of MR, S3, S4, pericardial rub
• Severe forms have ventricular arrhythmias and severe cardiac failure
• LVF, AF, VT or sudden cardiac death

Investigations

• Bloods: FBC: Elevated WCC, Elevated CRP/ESR. Others: check ANA, dsDNA, ASO titres, TFTs. HIV test.
• ECG: AF, ST/ T wave changes even mimicking STEMI/NSTEMI; those with Q waves or LBBB are a poor prognostic group; ectopic, VT, VF, heart block.
• CXR: may show cardiomegaly and pulmonary oedema.
• Cardiac biomarkers: CK and CKMB may be elevated, elevated troponin in proportion to damage.
• BNP: would be expected to be elevated
• Echocardiogram: this is a key test to assess LV and RV dysfunction, enlarged chambers, thrombus, pericardial effusion, and valve regurgitation. However, there are no specific echocardiographic features of myocarditis.
• Coronary Angiography: may be done to exclude coronary artery disease as the cause. Normal coronaries.
• Cardiac MRI: non-invasive and valuable clinical tool for the diagnosis of myocarditis. Initial changes in myocardial tissue and oedema can be seen on T2-weighted oedema imaging.
• Transvenous endomyocardial biopsy: rarely done but is the gold standard for diagnosis. It may show lymphocytic infiltration and myocyte necrosis. Giant cells in Giant cell myocarditis.
• Serology and PCR: influenza or Coxsackie serology and parvovirus.

Differential

• Silent myocardial infarction and ischaemic cardiomyopathy
• Dilated cardiomyopathy

Management: Urgent Echocardiogram is key

• ABC if in extremis. Manage pulmonary oedema. Correct electrolytes. Manage arrhythmias. Admit CCU/HDU.
• Supportive: bed-rest and avoid overexertion, treat heart failure and arrhythmias as usual.
• Usually in CCU with telemetry depending on presentation and severity. Ensure access to early defibrillation.
• Standard heart failure regime including beta-blockers, diuretics, ACE inhibitors or angiotensin-II receptor blockers (ARBs) should be initiated.
• Intra-aortic balloon pumping may be considered to augment cardiac output whilst awaiting improvement, treatment or transplant.
• VTE prophylaxis and full anticoagulation, especially if AF or LA / LV thrombus.
• Steroids have no evidence base. IV immunoglobulin (400 mg/kg per day) for 5 days may help preserve LVEF in adult acute fulminant myocarditis. Others: immunosuppression for giant cell myocarditis.
• Antiprotozoal therapy for Chagas disease. Withdrawal of toxic medications. Avoid exercise during the acute period and convalescence. Heart transplant in those with dilated CMP, giant cell myocarditis, end-stage cardiac failure. Cardiogenic shock and heart failure

Algorithm

References

• Update on Myocarditis Ingrid Kindermann, Christine Barth, Felix Mahfoud, Christian Ukena, Matthias Lenski, Ali Yilmaz, Karin Klingel, Reinhard Kandolf, Udo Sechtem, Leslie T. Cooper and Michael Bhm
• Kinderman et al. (2012) Update on myocarditis. J Am Coll Cardiol, 59:779. Dan-Qing Yu et al. (2014) IVIG in the therapy of adult acute fulminant myocarditis:
• A retrospective study. Exp Ther Med, 7:97. Complications: some develop a dilated cardiomyopathy and end-stage heart failure which may improve. V T / VF. Heart block needing pacing. Sudden cardiac death, thromboembolism.