Background: The prevalence and significance of higher than normal cardiac troponin I (cTnI) levels in asymptomatic chronic hemodialysis (HD) patients remains a source of discussion. The aim of the present study was to evaluate the prevalence of higher than normal cTnI levels in asymptomatic HD patients, as determined by the last generation of immunoassay, and to perform further cardiological investigations in those patients with persistently elevated cTnI levels.
Methods: All chronic HD patients in our center who had exhibited no symptoms of coronary artery disease (CAD) during the previous four weeks were screened. cTnI levels were determined before dialysis in all patients using the last generation AccuTnI assay (UniCel DxI 800, Beckman Coulter). The cTnI levels of those patients with elevated cTnI at the screening evaluation were then measured monthly for six months. We were thus able to identify a group of patients with persistently elevated cTnI levels (> 3 consecutive months) who subsequently underwent cardiac echography and dipyridamole-exercise (D-E) thallium testing. If stress myocardial ischemia was detected, a coronary angiography was then performed.
Results: Fifty patients (32 males) were included: mean age 62.8 +/- 13.6 years, 20 (40%) with a history of CAD, and 21 (42%) diabetic. At the initial screening, the mean cTnI concentration was 0.05 +/- 0.06 microg/L and the cTnI levels were higher than normal (> 0.09 microg/L) in six patients (12%). In the follow-up, the cTnI normalized immediately in two patients but remained persistently elevated (range, 0.10-0.48 microg/L) in four (8%). These four patients (all males, one diabetic) had a mean age of 70.2 +/- 6.6 years, and all had heart failure with a history of severe CAD with previous myocardial infarction (n = 4), coronary stenting (n = 3), and/or bypass (n = 2). D-E thallium imaging showed reversible myocardial ischemia in all. The stress ischemia involved one to four cardiac segments and was slight to moderate in three patients and severe in the diabetic patient. A coronary angiogram was performed in all patients, and showed lesions of variable severity: severe three-vessel CAD with severe systolic dysfunction in two patients (including the diabetic), and non-critical/peripheral coronary stenosis in the other two.
Conclusions: Among the asymptomatic HD patients in our center, we identified four (8%) with persistently elevated cTnI levels, as determined using the last generation AccuTnI assay. All of them had a history of severe CAD with heart failure and exhibited reversible myocardial ischemia upon D-E thallium imaging; coronary angiography revealed coronary lesions of variable severity. Overall, our data indicate that persistent low-grade cTnI elevation occurs in HD patients having longstanding severe cardiac disease, but, from our data, it is difficult to reach a conclusion as to the best clinical approach for this group of patients.