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.