Impact of hemoglobin variability on cardiovascular mortality in maintenance hemodialysis patients

Purpose Although the association between anemia and cardiovascular mortality in hemodialysis patients is well established, whether hemoglobin variability (Hgb-Var) affects the prognosis remains unclear. We aimed to evaluate the association between Hgb-Var and cardiovascular mortality in Chinese hemodialysis patients. Methods This retrospective study included 252 patients starting hemodialysis in Xin Hua Hospital between January 2009 and December 2015. Patients were divided into three tertiles based on Hgb-Var, as reflected by SD Hgb(mean), SD Hgb(range), and Hgb(deflection) during a 12-month evaluation period after hemodialysis initiation. Left ventricular ejection fraction (EF) and left ventricular mass index (LVMI) were evaluated by echocardiography. Information on cardiovascular deaths occurred by December 2017 was collected. Multivariate Cox regression models were constructed to evaluate the association between Hgb-Var and cardiovascular mortality. Results A total of 75 deaths and 52 cardiovascular deaths occurred during the 47-month follow-up (range 29.5-70). Under multivariate regression, the subgroup with the highest Hgb-Var had a higher risk of cardiovascular mortality after adjusting for relevant factors (HR vs. lowest SD Hgb(mean): 9.15, 95% CI 2.82, 29.693, P < 0.0001; HR vs. lowest SD Hgb(range): 3.81, 95% CI 1.40, 10.38, P = 0.005). Per 1 SD of Hgb(mean) and Hgb(range) elevations were both related to a 10% increase in the cardiovascular mortality risk. Baseline EF% and LVMI did not differ across the Hgb-Var subgroups. EF% upon the last patient visit to the clinic was lower in the subgroup with the highest SD Hgb(mean) (P = 0.02). Conclusions High Hgb-Var is an independent risk factor for cardiovascular mortality in hemodialysis patients and might influence the cardiac function.