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
• 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

Clinical manifestations

• often quickly progressive
  • median survival of 6 months after symptom onset
• congestive heart failure
• heart block (5%)
• ventricular arrhythmias
  • palpitations
  • sustained ventricular tachycardia (50%)
• less commonly, it can mimic an acute myocardial infarction
• syncope

Laboratory

• complete blood count
  • eosinophils in blood may show eosinophilia

Diagnostic procedures

• electrocardiogram
  • low voltage
  • ventricular arrhythmia
  • heart block
    • bifascicular block or left bundle-branch block
• 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

Complications

• sometimes fatal; death or heart transplantation 89%
• sudden cardiac death uncommon
• other autoimmune diseases, including myasthenia gravis, inflammatory bowel disease & thyroiditis are common

Differential diagnosis

• cardiac sarcoidosis

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
• 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%)
  • 5-year survival rate of 71%
    • 1, 5, & 10 years after transplantation are 94%, 82%, & 68%, respectively
  • recurrence of giant-cell myocarditis in cardiac-transplant recipients occurs in 20-25%, but may respond to an increase in immunosuppression

More general terms

• myocarditis