Routinely measured cardiac troponin I and N-termina pro-B-type natriuretic peptide as predictors of mortality in haemodialysis patients

Aims Cardiac troponin (cTn) and B-type natriuretic peptide (BNP) are elevated in haemodialysis (HD) patients, and this elevation is associated with HD-induced myocardial stunning/myocardial strain. However, studies using data from the international Dialysis Outcomes and Practice Patterns Study (DOPPS) have shown that these cardiac biomarkers are measured in <2% of HD patients in real-world practice. This study aimed to examine whether routinely measured N-terminal pro-BNP (NT-proBNP) and cTnI (contemporary assay) are more appropriate than clinical models for reclassifying the risk of HD patients who have the highest risk of death. Methods and results Pre-dialysis levels of cTnI and NT-proBNP at study enrolment were measured in 1152 HO patients (Japan DOPPS Phase 5). The patients were prospectively followed for 3 years. Cox regression was used to test the associations of cardiac biomarkers with all-cause mortality, adjusting for potential confounders. Subgroup analyses were performed to assess potential effect modification of clinical characteristics, such as age, systolic blood pressure, HD vintage, diabetes mellitus, coronary artery disease, and a history of congestive heart failure. At baseline, 337 (29%) patients had elevated cTnI (99th percentile of a healthy population: >0.04 ng/mL) with a median (inter-quartile range) level of 0.020 (0.005-0.041) ng/mL, and 1140 (99%) patients had elevated NT-proBNP (cut-off for heart failure: >125 pg/mL) with a median level of 3658 (1689-9356) pg/mL. There were 167 deaths during a median follow-up of 2.8 (2.2-2.8) years. Higher levels of both cardiac biomarkers were incrementally associated with mortality after adjustment for potential confounders. Even after adjustment for alternative cardiac biomarkers, the overall P value for the association was <0.01 for both biomarkers. However, the prognostic significance of NT-proBNP was moderately diminished when cTnI was added to the model. The hazard ratios of mortality for cTnI > 0.04 ng/ml. (vs. cTnI < 0.006 ng/mL) and NT-proBNP > 8000 pg/mL (vs. NT-proBNP < 2000 pg/mL) were 2.56 (95% confidence interval: 1.37-4.81) and 1.90 (95% confidence interval: 0.95-3.79), respectively. Subgroup analyses showed that the associations of both cardiac biomarkers with mortality were generally consistent between stratified groups. Conclusions Routinely measured NT-proBNP and cTnI levels are strongly associated with mortality among prevalent HD patients. These associations remain robust, even after adjustment for alternative biomarkers, suggesting that cTnI and NT-proBNP have identical prognostic significance and may reflect different pathological aspects of cardiac abnormalities.