Cardiac magnetic resonance in giant cell myocarditis: a matched comparison with cardiac sarcoidosis

Aims Giant cell myocarditis (GCM) is an inflammatory cardiomyopathy akin to cardiac sarcoidosis (CS). We decided to study the findings of GCM on cardiac magnetic resonance (CMR) imaging and to compare GCM with CS. Methods and results CMR studies of 18 GCM patients were analyzed and compared with 18 CS controls matched for age, sex, left ventricular (LV) ejection fraction and presenting cardiac manifestations. The analysts were blinded to clinical data. On admission, the duration of symptoms (median) was 0.2 months in GCM vs. 2.4 months in CS (P = 0.002), cardiac troponin T was elevated (>50 ng/L) in 16/17 patients with GCM and in 2/16 with CS (P < 0.001), their respective median plasma B-type natriuretic propeptides measuring 4488 ng/L and 1223 ng/L (P = 0.011). On CMR imaging, LV diastolic volume was smaller in GCM (177 +/- 32 mL vs. 211 +/- 58 mL, P = 0.014) without other volumetric or wall thickness measurements differing between the groups. Every GCM patient had multifocal late gadolinium enhancement (LGE) in a distribution indistinguishable from CS both longitudinally, circumferentially, and radially across the LV segments. LGE mass averaged 17.4 +/- 6.3% of LV mass in GCM vs 25.0 +/- 13.4% in CS (P = 0.037). Involvement of insertion points extending across the septum into the right ventricular wall, the hook sign of CS, was present in 53% of GCM and 50% of CS. Conclusion In GCM, CMR findings are qualitatively indistinguishable from CS despite myocardial inflammation being clinically more acute and injurious. When matched for LV dysfunction and presenting features, LV size and LGE mass are smaller in GCM.

Automated summary

This study compared the characteristics of giant cell myocarditis (GCM) and cardiac sarcoidosis (CS) on cardiac magnetic resonance (CMR) imaging. The results showed that GCM patients had smaller LV diastolic volume and significant differences in myocardial injury markers compared to CS patients. In addition, there were almost no differences between GCM and CS patients in terms of CMR, with both showing multifocal late gadolinium enhancement. It is suggested that CMR be used for the diagnosis and clinical management of GCM.