[Cardiovascular risk markers in hemodialysis].

PURPOSE

Although maintenance dialysis prevents death from uremia, patient survival remains an important issue. Cardiovascular (CV) events have been considered the main cause of death in hemodialysis (HD) patients. Some authors demonstrated an expected remaining life span of < or =2 yrs in HD patients who had a myocardial infarction. Therefore, it is very important to appraise risk factors and to adopt the correct diagnostic approach to match therapy. Nevertheless, acute myocardial infarction can be misdiagnosed in uremic patients, because typical markers have high false positivity rates. It has been estimated, for example, that 29% of HD patients have elevated serum troponin T concentrations, but do not have evidence of myocardial injury. Troponin T is more frequently elevated than troponin I among asymptomatic patients with renal insufficiency and this could be due to the relatively higher levels of an unbound cytosolic pool of troponin T and its higher molecular weight. Neither the common cardiac markers (LDH, LDH 1, CPK, CK-MB) are sensitive or specific as in the general population, but a recent 2-yr observational study showed that pre-dialytic high serum concentrations of troponin T and CK-MB mass were associated with complete mortality, cardiac mortality, myocardial infarction and unstable angina (MACEs). In our study, we evaluated how dialysis influenced serum troponin I and CK-MB mass, and then we assessed serum homocysteine (Hcy), an additional CV risk factor in uremic patients.

METHODS

We studied 17 uremic patients (13 males, four females) on standard HD and six patients (four males, two females) on on-line hemodiafiltration (HDF), who were taking folic acid for at least 3 months. Patients who suffered from acute or chronic cardiac ischemic disease were excluded. We performed arterial gas-analysis, Na+, K+, Ca++, Mg++, Cl-, P, serum albumin, creatinine (Cr), urea, total homocysteine (tHcy), red blood count (RBC), troponin I and CK-MB mass, both pre and post-dialysis. We assessed urea reduction rate percentage (URR%), Kt/V, Hcy percentage reduction ratio (ORR%), and anthropometric parameters.

RESULTS

Anthropometric parameters, pre- and post-dialytic pH, HCO3 and electrolytes did not differ between the two groups, Kt/V and URR%. Even in on-line HDF, ORR% directly correlated with KtV and URR% (r=0.79, p<0.04; r=0.76, p<0.05, respectively). Troponin I and CK-MB mass were not significantly different in pre- vs post-dialysis, both on standard HD and on-line HDF. Nevertheless, in standard HD, post-dialytic troponin I correlated with serum sodium concentration (r=0.93, p<0.000), potassium (r=0.67, p<0.004) and serum chlorine (r=0.92, p<0.92, p<0.000). CK-MB mass showed a correlation with serum chlorine (r=0.49, p<0.05). Post-dialytic CK-MB mass correlated with serum potassium for on-line HDF (r=0.83, p<0.03).

CONCLUSIONS

Our study suggests the probability that dialytic adequacy improves CV outcome causing a reduction in the concentration of homocysteinemia and it demonstrates that convective treatments (on-line HDF) are best in reaching this end-point. Our data suggests that hemodialytic treatments, both standard HD and on-line HDF did not modify serum troponin I and CK-MB mass. We can use these parameters as a diagnostic approach in acute or chronic cardiac ischemic disease in HD patients, because they are not influenced by the hemodialytic procedure. This allows the selection of high risk patients, and offers them on-line treatment as the best suitable therapeutic option.