Evaluation and treatment of cardiac sarcoidosis (CS) suffer from lack of sensitive and easily repeatable markers of disease activity. We studied measurements of high-sensitivity cardiac troponin T or troponin I (hs-cTnT/I) taken at presentation and during treatment in 62 patients with new-onset CS (48 women, mean age 49 years). Hs-cTnT was measured in 50 patients and was elevated (>13 ng/L) at presentation in 26 of them (52%). Hs-cTnI was measured in the remaining 12 patients and was elevated (>0.04 ng/mL) in 7 of them (58%). Left ventricular ejection fraction averaged 43 +/- 14% in association with elevated hs-cTnT/I (n = 33) versus 53 +/- 10% with normal hs-cTnT/I (n = 29; p = 0.001). Hs-cTnT/I was remeasured after 4 weeks of steroid therapy in 38 patients and was normalized in 16 of the 24 (67%) with an elevated pretreatment concentration and remained normal in the rest of the 14 patients (p <0.001). During follow-up (median, 17 months), cardiac death (n = 2); aborted sudden death (n = 5), sustained ventricular tachycardia (n = 8), or new complete atrioventricular block (n = 1) was recorded in 11 of 33 patients with elevated hs-cTnT/I versus in 5 of 29 with normal hs-cTnT/I (log-rank p = 0.068). Two-year event-free Kaplan-Meier cardiac survival estimate (95% confidence interval) was 67% (48% to 81%) with elevated hs-cTnT/I versus 93% (76% to 99%) with normal hs-cTnT/I. In CS, circulating hs-cTnT/I may help clinicians evaluate disease activity and treatment response. Their prognostic value remains tentative pending more follow-up data. (C) 2015 Elsevier Inc. All rights reserved.