Clinical Pearls & Morning Reports
Giant-cell myocarditis is rare, with an annual incidence estimated at 0.13 cases per 100,000 persons. Nevertheless, it is important to consider this diagnosis in the relevant clinical context, because it is often quickly progressive and sometimes fatal. Read the latest Clinical Problem-Solving article.
Q. What causes giant-cell myocarditis?
A. The pathophysiology of giant-cell myocarditis is not well understood, but it is thought to be a T-cell–mediated autoimmune process. It tends to occur in younger and middle-aged persons and affects men and women equally.
Q. What are the typical manifestations of giant-cell myocarditis?
A. Giant-cell myocarditis typically manifests with symptoms and signs of congestive heart failure, heart block, or ventricular arrhythmias. Less commonly, it can mimic an acute myocardial infarction or cause sudden cardiac death. Sustained ventricular tachycardia occurs in nearly half the patients with giant-cell myocarditis.
Figure 4. (10.1056/NEJMcps1608688/F4) Photomicrograph of an Endomyocardial-Biopsy Specimen.
A: Endomyocardial biopsy is needed to establish a diagnosis of giant-cell myocarditis. Because myocardial involvement in giant-cell myocarditis is typically patchy, a negative biopsy does not rule out the disease. In one case series, the sensitivity of endomyocardial biopsy for the diagnosis of giant-cell myocarditis was 68%. Repeating the biopsy can substantially increase the yield, up to 80 to 93%, and should be considered when clinical suspicion for giant-cell myocarditis is high. In patients with giant-cell myocarditis, the affected myocardium shows widespread inflammatory infiltrates, with multinucleated giant cells, eosinophils, and lymphocytes causing myocyte necrosis. Multinucleated giant cells are not exclusive to giant-cell myocarditis and are also present in cardiac sarcoidosis; some cases cannot be categorized with certainty owing to this histologic overlap. Granulomas and fibrosis tend to be more prominent in cardiac sarcoidosis, whereas necrosis and eosinophils are predominant in giant-cell myocarditis.
A: In a case series of patients with giant-cell myocarditis, the rate of death or cardiac transplantation at 1 year without immunosuppressive therapy was 100%, with a median transplant-free survival of less than 3 months after symptom onset. Data from more recent case series and one prospective study indicate that, with the use of combination immunosuppression (generally involving two or three drugs including cyclosporine, prednisone, azathioprine, mycophenolate mofetil, or muromonab [an anti–T-lymphocyte antibody]), the prognosis for patients with giant-cell myocarditis has improved considerably, with transplant-free survival rates of approximately 69% at 1 year and 58% at 5 years. Although the most effective immunosuppressive strategy is not known, long-term immunosuppression is generally recommended, because recurrence of giant-cell myocarditis has been reported with cessation of immunosuppression as late as 8 years after the initial diagnosis. Cardiac transplantation for giant-cell myocarditis is associated with a 5-year survival rate of 71%, which is similar to post-transplantation survival rates among patients with other conditions. Recurrence of giant-cell myocarditis occurs in up to 20 to 25% of cardiac-transplant recipients, but cases of recurrence may respond to an increase in the immunosuppression regimen.