Creatine kinase isoforms as circulating markers of deterioration in idiopathic dilated cardiomyopathy

Background: A proportion of patients with dilated cardiomyopathy (DCM) may have ongoing myocardial damage secondary to viral or immune mediated myocardial inflammation. Hypothesis: The prognostic determinants identify patients with decreased survival but do not provide a measure of myocardial damage. To obtain an objective assessment of myocardial damage in DCM, we measured plasma levels of creatine kinase (CK), its isoenzymes (CK‐MM and CK‐MB), and separated the isoforms of CK‐MM and CK‐MB. Methods: The cohort consisted of 77 consecutive patients (61 men, 16 women) with DCM (World Health Organization criteria), aged 49 ± 14 years (range 19–60). Patients had been symptomatic for 29 ± 38 months (range 0.5–200 months) with 48 in New York Heart Association class I/II and 29 in class III/IV at the time of diagnosis. During median follow‐up of 27 months from diagnosis (range 0.6–165), 50 patients remained clinically stable and 27 had deteriorated. Results: A significantly higher proportion of patients with DCM had abnormal MB2/MB1 ratio compared with normal volunteers (11,14% vs. 1, 1%, p = 0.003). Patients who deteriorated had higher MB2/MB1 ratio, (1.22 ± 0.62 vs. 0.85 ± 0.56;p = 0.01), and more frequently had abnormal MB2/ MB1 ratio (8,30% vs. 3,6%;p=0.004) and CK and CK‐MM activities (5, 19% vs. 2, 4%;p = 0.03) than those who remained stable. Patients with DCM with high CK‐MB activity had 3.13‐fold increased odds of sudden death or need for cardiac transplantation (95% confidence interval 1.53–6.40, p = 0.008). Thus, CK measurements, in particular CK‐MB isoforms, are markers of myocardial damage in a subset of patients with DCM and could be useful in investigating the possibility of persistent myocardial damage in these patients.