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

Abstract

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.