To study the association of serum cardiac troponin T (cTnT) and cardiac troponin I (cTnI) with creatine kinase (CK) in patients with idiopathic inflammatory myopathies (IIM).

We performed a retrospective study on patients with IIM followed by the rheumatology service of a county hospital from 2004 to 2008. Patients with myocardial ischemia and/or with renal failure were excluded. Clinical data including electromyogram, muscle biopsy, and CK, cTnT and cTnI were recorded. Patients who had simultaneous analysis of CK and cardiac troponin (cTnT or cTnI) levels were studied. CK levels were correlated with cTnT and cTnI by chi-square test and Spearman correlation.

We identified 49 patients with IIM (69 observations) who satisfied our inclusion criteria. The primary diagnosis was polymyositis in 23, dermatomyositis in 16, and myositis associated with connective tissue disease in 10 patients. There were 33/49 women with average age 45.8 years. Twenty-eight patients with IIM had simultaneous CK and cTnT values assayed. Of those patients, 18/23 with elevated CK also had elevated cTnT, and 5/5 patients with normal CK levels had normal cTnT levels (p = 0.005). In 41 patients with IIM who had simultaneous CK and cTnI levels assayed, only 1/29 with elevated CK had elevated cTnI, and 12/12 patients with normal CK had normal cTnI (p = 0.5). CK correlated strongly with the cTnT (r = 0.62, p = 0.001) but did not correlate with cTnI.

Elevated cTnT, but not cTnI, was highly associated with CK in patients with IIM despite the absence of myocardial ischemia.