Background: Serum cardiac troponin T (cTnT) levels are elevated in a high percentage of hemodialysis (HD) patients and as a result, they have been considered low specificity for ischemic heart disease (IHD). Recently, several authors have indicated the value of cTnT as a marker of IHD and left ventricular hypertrophy (LVH), as well as a mortality predictor. We try to establish the value of cTnT as an IHD marker and a mortality predictor in our patients on HD.
Subjects and methods: Fifty-eight HD patients were prospectively studied from October 2000 to April 2002. Clinical and laboratory evaluations, including cTnT, C-reactive protein (CRP) and N terminal fragment of brain natriuretic peptide (pro-BNP) levels, were performed at the beginning of the study and at 6 and 18 months. HD patients with two or more cTnT measurements were classified in four groups: group I with all levels <0.04 ng/mL; group II with all levels between 0.04 and 0.1 ng/mL; group III with all levels >/=0.1 ng/mL; and group IV including those patients in whom cTnT levels increased during follow-up, switching from one group to another (from <0.04 to 0.04-0.1 or from 0.4-0.1 to >0.1 ng/mL).
Results: Mean and median cTnT levels were 0.07 +/- 0.09 and 0.04 ng/mL, respectively. Of clinically stable dialysis patients 15.5% had cTnT levels >0.1 ng/mL. In the stepwise multiple regression analysis, the subset of variables best explaining cTnT levels were pro-BNP levels, history of IHD and residual diuresis volume (r2=0.45). The analysis of variance (ANOVA linear regression analysis for repeated measures) showed an increase in cTnT and pro-BNP levels (significantly from 18 months). cTnT and CPR levels were the only variables predicting mortality (Cox's proportional hazards model). When patients were analyzed according to cTnT groups during the follow-up, no patient in group I (n=23) and only one patient in group II (n=11) experienced IHD; three patients in group III (n=12) had been diagnosed with IHD at the start of the study, and five patients in group IV (n=16) developed de novo IHD.
Conclusions: Of patients on HD 15.5% had cTnT levels >0.1 ng/mL. The main variables associated with cTnT levels were IHD, pro-BNP levels and residual diuresis. cTnT and pro-BNP levels tended to increase with time on dialysis. cTnT together with CRP levels were the best mortality predictors in our HD patients. The stability over time of cTnT levels within normal ranges (<0.1 ng/mL) suggests a very low risk of subsequent IHD development, while a progressive and sustained increase in cTnT levels suggests a high risk of IHD development.