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giant cell myocarditis

Epidemiology: - rare - annual incidence 0.13/100,000 persons - tends to occur in younger adults & middle-aged persons - 4th or 5th decade of life [2] - case of 22 year old [3] - affects men & women equally Pathology: - T-cell mediated autoimmune process - myocarditis - widespread inflammatory infiltrates - multinucleated giant cells, eosinophils, & lymphocytes causing myocardial necrosis - myocardial fibrosis, scarring - with or without noncaseating granulomas [2] Clinical manifestations: - presentation with palpitations, dizziness, & chest pain - often quickly progressive - median survival of 6 months after symptom onset [2] - hypoxia, hypotension - congestive heart failure - heart block (5%) [2] - ventricular arrhythmias - palpitations - sustained ventricular tachycardia (50%) - less commonly, it can mimic an acute myocardial infarction - syncope - no lymphadenopathy or rash Laboratory: - complete blood count - eosinophils in blood may show eosinophilia - cardiac troponin T in serum is elevated Special laboratory: - electrocardiogram - low voltage - ventricular arrhythmia - heart block - bifascicular block or left bundle-branch block [2] - endomyocardial biopsy is needed to establish a diagnosis - myocardial involvement typically patchy - a negative biopsy does not rule out giant cell myocarditis - sensitivity of endomyocardial biopsy is 69% - repeat biopsy can increase yield to 80-93% Radiology: - myocardial perfusion imaging - no coronary artery obstruction - cardiac magnetic resonance imaging (MRI) - subendocardial involvement in giant-cell myocarditis - right ventricular side of basal interventricular septum is involved in cardiac sarcoidosis [2] Complications: - sometimes fatal; death or heart transplantation 89% [2] - sudden cardiac death uncommon - other autoimmune diseases, including myasthenia gravis, inflammatory bowel disease & thyroiditis are common Differential diagnosis: - cardiac sarcoidosis - usually occurs in the setting of systemic sarcoidosis - HFrEF Management: - combination immunosuppression: - 2-3 drugs including cyclosporine, prednisone, azathioprine, mycophenolate mofetil, or muromonab - presence of eosinophils in diseased myocardium may be associated with greater responsiveness to immunosuppressive therapy - may increase long-term survival [2] - implantable cardioverter-defibrillator (ICD) - even when left ventricular systolic dysfunction is mild - cardiac transplantation - inotropic agents & mechanical support as a bridge to cardiac transplantation - acute rejection is higher with giant-cell myocarditis than with dilated cardiomyopathy (16% vs 5%) [2] - 5-year survival rate of 71% [1] - 1, 5, & 10 years after transplantation are 94%, 82%, & 68%, respectively [2] - recurrence of giant-cell myocarditis in cardiac-transplant recipients occurs in 20-25%, but may respond to an increase in immunosuppression

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myocarditis

References

  1. Jani SM, Nallamothu BK, Cooper LT, Smith A, Fazel R. Beating, Fast and Slow. N Engl J Med 2017; 377:72-78. July 6, 2017 PMID: 28679100 http://www.nejm.org/doi/full/10.1056/NEJMcps1608688
  2. Rothaus C A Man with Cardiomyopathy and Ventricular Tachycardia. NEJM REsident 360. April 25, 2018 https://resident360.nejm.org/content_items/a-man-with-cardiomyopathy
  3. Medical Knowledge Self Assessment Program (MKSAP) 20 American College of Physicians, Philadelphia 2025
  4. Bang V, Ganatra S, Shah SP, et al. Management of patients with giant cell myocarditis: JACC Review Topic of the Week. J Am Coll Cardiol. 2021;77:1122-1134. PMID: 33632487