Key result
Reclassification to cardiac sarcoidosis linked to ~63% lower risk of death or transplant vs GCM.
Why the study?
Differentiating cardiac sarcoidosis from giant cell myocarditis is difficult and prone to confusion, and whether they represent different phenotypes of a single disease has been debated.
Does cardiac sarcoidosis have a different prognosis compared to true giant cell myocarditis in patients initially diagnosed with GCM?
Cohort (n=73)
Yes
Does cardiac sarcoidosis have a different prognosis compared to true giant cell myocarditis in patients initially diagnosed with GCM?
A substantial proportion of patients historically diagnosed with giant cell myocarditis actually have cardiac sarcoidosis, which is associated with a significantly more favorable transplant-free survival.
AIMS: Cardiac sarcoidosis (CS) and giant cell myocarditis (GCM) are inflammatory cardiomyopathies sharing histopathological and clinical features. Their differentiation is difficult and susceptible of confusion and apparent mistakes. The possibility that they represent different phenotypes of a single disease has been debated. METHODS AND RESULTS: We made a retrospective audit of 73 cases of GCM diagnosed in Finland since the late 1980s. All available histological material was reanalyzed as were other examinations pertinent to the distinction between GCM and CS. Finding granulomas in or outside the heart was considered diagnostic of CS and exclusive of GCM. Altogether 45 of the 73 cases of GCM (62%) were reclassified as CS. In all except one case, this was based on finding sarcoid granulomas that either had been originally missed (n = 29) or misinterpreted (n = 11) or were found in additional posttransplant myocardial specimens (n = 3) or samples of extracardiac tissue (n = 1) accrued over the disease course. Supporting the reclassification, patients relocated to the CS group had less heart failure at presentation (prevalence 20% vs. 46%, P = 0.017) and better 1 year transplant-free survival (82% vs. 45%, P = 0.011) than patients considered to represent true GCM. CONCLUSIONS: Recognizing granulomas in or outside the heart remains a challenge for the pathologist. Given that CS and GCM are considered distinct diseases and granulomas exclusive of GCM, many cases of GCM, if thoroughly scrutinized, may need reclassification as CS. However, whether CS and GCM are truly different entities or parts of a one-disease continuum has not yet been conclusively settled.
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Ekström et al. (2020) conducted a cohort in Idiopathic Giant Cell Myocarditis (GCM) and Cardiac Sarcoidosis (CS) (n=73). Cardiac sarcoidosis (reclassified) vs. True giant cell myocarditis was evaluated on Composite of death from any cause or cardiac transplantation (HR 0.370, 95% CI 0.169-0.809, p=0.013). Patients reclassified as having cardiac sarcoidosis had significantly better transplant-free survival compared to those maintaining a true giant cell myocarditis diagnosis (HR 0.370, p=0.013).
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