Clinical Pearls & Morning Reports
Published April 25, 2018
For many years, giant-cell myocarditis and cardiac sarcoidosis were considered to be essentially the same disease, characterized by myocarditis and the presence of multinucleated giant cells with or without granulomas. They are now recognized as two pathologically distinct entities, but distinguishing them clinically has remained a challenge. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: What are some of the features of giant-cell myocarditis?
A: Giant-cell myocarditis is aggressive and often fatal, with a rate of death or heart transplantation of 89% and a median survival of only 6 months after symptom onset. Patients typically present in the fourth or fifth decade; the clinical presentation can include congestive heart failure or new-onset cardiomyopathy (in 75% of patients), syncope, palpitations or sudden death due to ventricular tachycardia (in 15%), and heart block (in 5%). An initial electrocardiogram frequently shows evidence of bifascicular block or left bundle-branch block. Endomyocardial biopsy is essential for establishing the correct diagnosis. The characteristic pathological features of giant-cell myocarditis include multinucleated giant cells and myocyte necrosis. The pathological features of cardiac sarcoidosis also include multinucleated giant cells, but the hallmark features of noncaseating granulomas, fibrosis, and scarring are typically more prominent.
Q: Are there any imaging findings that may help distinguish between giant-cell myocarditis and cardiac sarcoidosis?
A: Several subtle findings on MRI may be helpful in distinguishing cardiac sarcoidosis from giant-cell myocarditis. Involvement of the right ventricular side of the basal interventricular septum is specific for cardiac sarcoidosis, whereas subendocardial involvement is specific for giant-cell myocarditis.
A: Immunosuppression with glucocorticoids alone does not appear to increase survival or decrease the likelihood that heart transplantation will be performed, although combined treatment with glucocorticoids and agents such as azathioprine, calcineurin inhibitors, antithymocyte globulin, mycophenolate mofetil, or methotrexate may increase long-term survival. Ventricular tachycardia commonly occurs in patients who do not undergo heart transplantation, and therefore, it is appropriate to consider implantable cardioverter–defibrillator (ICD) implantation even when left ventricular dysfunction is only mild to moderate. Unfortunately, given the aggressive nature of the inflammatory process, many patients will have rapid progression to hemodynamic collapse. Mechanical circulatory support is often necessary during early treatment and in patients for whom heart transplantation is indicated.
A: For patients who do not have a response to immunosuppressive therapy and receive mechanical circulatory support, heart transplantation is the best long-term therapeutic option. The risk of acute rejection is higher with giant-cell myocarditis than with dilated cardiomyopathy (16% vs. 5%), but no substantial difference in survival has been reported. Cumulative survival rates among patients with giant-cell myocarditis at 1, 5, and 10 years after transplantation are 94%, 82%, and 68%, respectively; these rates are similar to outcomes associated with other forms of end-stage cardiomyopathy.