Mild and moderate to severe early acute kidney injury following cardiac surgery among patients with heart failure and preserved vs. mid-range vs. reduced ejection fraction A retrospective cohort study

BACKGROUND Patients with heart failure who undergo cardiac surgery have increased long-term mortality in which acute kidney injury (AKI) plays a role. However, little is known about whether the incidence of AKI differs according to stratified left ventricular ejection fraction (LVEF). OBJECTIVES To assess the risks of mild AKI and moderate to severe AKI postcardiac surgery among patients with heart failure. DESIGN Retrospective cohort analysis of patient data. Ejection fractions were categorised as LVEF less than 40%, heart failure with reduced ejection fraction (HFrEF); LVEF 40 to 49%, heart failure with mid-range ejection fraction (HFmrEF); and LVEF at least 50%, heart failure with preserved ejection fraction (HFpEF). PATIENTS AND SETTINGS Patients who underwent cardiac surgery from 2012 to 2019 in Fuwai Hospital, Beijing, China, were consecutively enrolled. MAIN OUTCOME MEASURES The primary endpoint was postoperative AKI staged either as mild AKI or moderate to severe AKI. The secondary outcome was the peri-operative composite adverse event of dialysis support, tracheotomy, intrasurgical and postsurgical mechanical cardiac support and in-hospital mortality. This study also assessed chronic renal dysfunction at follow-up. RESULTS Of the 54 696 included patients, 18.9% presented with heart failure. Among these with HFpEF, HFmrEF and HFrEF, the incidence of postoperative mild AKI was 37.0, 33.4 and 37.6%, respectively. Patients with HFpEF and HFmrEF were characterised by numerically greater prevalence of moderate to severe AKI than HFrEF (8.5 vs. 9.1 vs. 5.8%). HFrEF and HFmrEF patients had comparable risks for mild AKI relative to HFpEF patients, odds ratio (OR) 0.885; 95% confidence interval CI 0.763 to 1.027 for HFmrEF vs. HFpEF; OR 1.083; 95% CI 0.933 to 1.256 for HFrEF vs. HFpEF. Patients with HFmrEF were more at risk for moderate to severe AKI than patients with HFpEF (OR, 1.368; 95% CI 1.066 to 1.742), but HFrEF and HFpEF did not differ significantly (OR 1.012; 95% CI 0.752 to 1.346). An increasing number of noncardiac comorbidities led to a higher risk of mild AKI and moderate to severe AKI in patients with heart failure; and its effect on AKI was almost equal among the three heart failure strata. The incidence of postoperative composite adverse outcome increased in a graded manner from HFpEF to HFmrEF to HFrEF. Information on the creatine concentrations at 3 months postoperatively and longer were retained for 5200 out of 10 347 (50.6%) heart failure patients in our charts. The AKI severity and the presence of HFmrEF contributed substantially to the development of renal dysfunction over a median [IQR] follow-up of 10 months [4.0 to 21.0]. CONCLUSIONS Initiative programmes aimed at patients with HFrEF to prevent moderate to severe AKI and chronic kidney dysfunction should also include patients with HFmrEF.