The Survival Benefit of "Fistula First, Catheter Last" in Hemodialysis Is Primarily Due to Patient Factors

Abstract

Patients needing hemodialysis are advised to have arteriovenous fistulas rather than catheters because of significantly lower mortality rates. However, disparities in fistula placement raise the possibility that patient factors have a role in this apparent mortality benefit. We derived a cohort of 115,425 patients on incident hemodialysis ≥67 years old from the US Renal Data System with linked Medicare claims to identify the first predialysis vascular access placed. We compared mortality outcomes in patients initiating hemodialysis with a fistula placed first, a catheter after a fistula placed first failed, or a catheter placed first (n=90,517; reference group). Of 21,436 patients with a fistula placed first, 9794 initiated hemodialysis with that fistula, and 8230 initiated dialysis with a catheter after failed fistula placement. The fistula group had the lowest mortality over 58 months (hazard ratio, 0.50; 95% confidence interval, 0.48 to 0.52; P<0.001), with mortality rates at 6, 12, and 24 months after initiation of 9%, 17%, and 31%, respectively, compared with 32%, 46%, and 62%, respectively, in the catheter group. However, the group initiating hemodialysis with a catheter after failed fistula placement also had significantly lower mortality rates than the catheter group had over 58 months (hazard ratio, 0.66; 95% confidence interval, 0.64 to 0.68; P<0.001), with mortality rates of 15%, 25%, and 42% at 6, 12, and 24 months, respectively. Thus, patient factors affecting fistula placement, even when patients are hemodialyzed with a catheter instead, may explain at least two thirds of the mortality benefit observed in patients with a fistula.

Keywords: access; arteriovenous fistula; dialysis; hemodialysis access; mortality; mortality risk.

Figure 1.

Kaplan–Meier survival curves over 58 months after initiating hemodialysis (HD) by vascular access groups. The AVF group (line I) had an AVF placed first and initiated HD with the AVF, the AVF-CVC group (line II) had an AVF placed first but initiated HD with a catheter, and the CVC group (line III) had a catheter placed first and initiated HD with the catheter.

Figure 2.

Proportional hazard analysis of mortality for vascular access subgroups on the basis of age, sex, race, and comorbidities, with the CVC group as reference. The AVF access group (diamonds) consists of those patients who had an AVF placed first and initiated hemodialysis with the AVF. The AVF-CVC access group (squares) had an AVF placed first but initiated hemodialysis with a catheter. The CVC access group (vertical bold line indicates HR, 1.0) had a catheter placed first and initiated hemodialysis with the catheter. Bars denote 95% CIs. The results shown were derived from 40 separate Cox proportion hazard models, each adjusted for the following covariates: age at ESRD onset, race, sex, body mass index, primary cause of ESRD, duration of pre–ESRD nephrology care, and comorbidity index. In subgroup analyses by comorbidities, the corresponding comorbidity was removed from the comorbidity index calculation to avoid potential collinearity (e.g., in subgroup analysis of diabetes, diabetes was not included in the comorbidity index calculation). Numerical values for the HRs are shown in Supplemental Table 2. COPD, chronic obstructive pulmonary disease.