Makindo Medical Notes

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

About

• Acute myocarditis is a serious inflammatory disease of the myocardium that can lead to fatal arrhythmias and heart failure.
• It can occur at any age and is triggered by both infectious (viral, bacterial, parasitic) and non-infectious causes (autoimmune, toxic).
• The presentation can be acute, subacute, or chronic, but often includes rapid onset of symptoms such as acute heart failure or cardiogenic shock.
• Long-term consequences can include dilated cardiomyopathy, which may result in chronic heart failure.

Aetiology

• The myocardium becomes inflamed, leading to a dilated, poorly functioning heart and elevated cardiac biomarkers like troponin.
• Severe cases may progress to end-stage cardiac failure, thromboembolism, and life-threatening arrhythmias.

Causes

Pathology

• Myocarditis is characterized by an inflammatory infiltrate in the myocardium, which may be focal or diffuse, with or without cardiac myocyte injury.
• Lymphocytic myocarditis: Commonly associated with viral infections, drugs, radiation, and autoimmune disorders.
• Eosinophilic myocarditis: Associated with parasitic infections, hypersensitivity reactions, and rarely neoplastic processes.
• Giant-cell myocarditis: Idiopathic in many cases but can be associated with autoimmune diseases like autoimmune thyroiditis or inflammatory bowel diseases.
• Granulomatous myocarditis: Associated with sarcoidosis, which may cause arrhythmias and conduction abnormalities.

Clinical Symptoms

• Viral-type illness, with fever, muscle aches, and flu-like symptoms.
• Progressive fatigue, shortness of breath, and symptoms of heart failure over days to weeks.
• Chest pain, resembling pericarditis, syncope, presyncope, and general malaise.
• Sudden cardiac death can occur due to ventricular fibrillation or severe pump failure.

Clinical Signs

• Heart murmurs (e.g., mitral regurgitation), S3 or S4 gallop, and pericardial rub.
• Severe cases may present with ventricular arrhythmias and significant cardiac failure.
• Signs of left ventricular failure (LVF), atrial fibrillation, or ventricular tachycardia (VT).

Investigations

• Blood tests: Elevated WCC, CRP, ESR. Consider ANA, dsDNA, ASO titers, and HIV testing.
• ECG: May show atrial fibrillation, ST/T wave changes, Q waves, LBBB, or ventricular arrhythmias.
• CXR: May reveal cardiomegaly or pulmonary edema.
• Cardiac biomarkers: Elevated troponin, CK, and CKMB.
• BNP: Typically elevated, indicating heart failure.
• Echocardiogram: Assesses left and right ventricular function, chamber size, and pericardial effusion.
• Cardiac MRI: Key non-invasive tool for detecting myocardial inflammation and edema.
• Endomyocardial biopsy: Gold standard but rarely performed; may show lymphocytic infiltration and myocyte necrosis.
• Viral serology and PCR: For identification of causative viruses like influenza or Coxsackie.

Management: Urgent Echocardiogram is Key

• Initial Management: ABC approach with oxygen if hypoxic, diuretics for pulmonary edema, and electrolyte correction.
• Supportive Care: Bed rest and avoidance of exertion; treat heart failure and arrhythmias as usual.
• CCU Monitoring: Telemetry for continuous monitoring and access to defibrillation.
• Heart Failure Management: Standard regimen including ACE inhibitors, beta-blockers, and diuretics.
• Advanced Support: Intra-aortic balloon pumping may be considered for cardiogenic shock while awaiting improvement or heart transplant.
• Anticoagulation: Prophylaxis for VTE, especially in atrial fibrillation or presence of thrombus.
• Immunotherapy: IV immunoglobulin (IVIG) in cases of fulminant myocarditis; consider immunosuppressive therapy for giant cell myocarditis.
• Specific Treatments: Antiparasitic drugs for Chagas disease; cessation of toxic medications; heart transplant in end-stage heart failure.

Complications

• Development of dilated cardiomyopathy leading to chronic heart failure.
• Arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF), leading to sudden cardiac death.
• Thromboembolism due to impaired cardiac function and blood stasis.
• Heart block, potentially requiring pacemaker implantation.

Algorithm

References

• Update on Myocarditis by Ingrid Kindermann et al. (2012). 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.
• Cooper LT et al. (2007). "The Role of Endomyocardial Biopsy in the Management of Cardiomyopathies." Circulation, 116:2216-2233.