The Effect of Predialysis Fistula Attempt on Risk of All-Cause and Access-Related Death

Abstract

Whether the lower risk of mortality associated with arteriovenous fistula use in hemodialysis patients is due to the avoidance of catheters or if healthier patients are simply more likely to have fistulas placed is unknown. To provide clarification, we determined the proportion of access-related deaths in a retrospective cohort study of patients aged ≥18 years who initiated hemodialysis between 2004 and 2012 at five Canadian dialysis programs. A total of 3168 patients initiated dialysis at the participating centers; 2300 met our inclusion criteria. Two investigators independently adjudicated cause of death using explicit criteria and determined whether a death was access-related. We observed significantly lower mortality in individuals who underwent a predialysis fistula attempt than in those without a predialysis fistula attempt in patients aged <65 years (hazard ratio [HR], 0.49; 95% confidence interval [95% CI], 0.29 to 0.82) and in the first 2 years of follow-up in those aged ≥65 years (HR_{0-24 months}, 0.60; 95% CI, 0.43 to 0.84; HR_{24+ months}, 1.83; 95% CI, 1.25 to 2.67). Sudden deaths that occurred out of hospital accounted for most of the deaths, followed by deaths due to cardiovascular disease and infectious complications. We found only 2.3% of deaths to be access-related. In conclusion, predialysis fistula attempt may associate with a lower risk of mortality. However, the excess mortality observed in patients treated with catheters does not appear to be due to direct, access-related complications but is likely the result of residual confounding, unmeasured comorbidity, or treatment selection bias.

Keywords: arteriovenous fistula; hemodialysis; hemodialysis access.

Figure 1.

Fistula attempts and independent fistula use in cohort of incident HD patients. A total of 2300 patients met our inclusion criteria and 21% received a predialysis fistula attempt. The majority started dialysis with an independently functioning fistula and 82% used the fistula independently throughout follow-up. In those who did not attempt a fistula prior to the start of dialysis, 33% attempted fistula creation during follow-up and 15% used them independently. Independent fistula use was defined as catheter-free fistula use.

Figure 2.

Forest plot for all-cause mortality according to whether patient received a predialysis fistula attempt, by age group and time from dialysis initiation. We identified a significant interaction between age and fistula attempt when modeling the outcome of mortality. Accordingly, Cox models were stratified by age (<65 years and ≥65 years) and adjusted for important baseline variables. Predialysis fistula attempt was associated with lower mortality in younger patients and in the first 24 months of therapy among those ≥65 years. After 24 months, the risk of mortality was significantly higher in those who had attempted a fistula prior to the start of dialysis. *Adjusted for sex, BMI, at least 4 months or predialysis care, inpatient start, cancer, cerebrovascular disease, congestive heart failure, coronary artery disease, diabetes, gastrointestinal bleeding, peripheral vascular disease, polycystic kidney disease, albumin, hemoglobin, and eGFR.

Figure 3.

Death rates, per 1000 person-years, by cause of death and according to whether patient received a predialysis fistula attempt. The rate of death was higher in those who underwent a predialysis fistula attempt, for all categories of cause of death examined. Patients with a limited life expectancy due to malignancy or other chronic diseases were excluded from the analysis. Total follow-up time in the no attempt group was 2515 person-years and 1029 person-years in the attempt group.

Figure 4.

Rates of access-related and nonaccess related death per 1000 person-years of follow-up, by age, and according to whether patient received a predialysis fistula attempt. Although the rates of death were highest in older patients and in those who had not undergone a predialysis fistula attempt, the rates of access-related death were low in all groups, regardless of age. In patients aged <65 years, the rates of death per 1000 person-years of follow-up were 4.4 (95% CI, 1.8 to 10.7; total 1126 person-years follow-up) in those who did not attempt a fistula predialysis compared with 2.3 (95% CI, 0.3 to 16.0; 443 person-years follow-up) in those who did. In patients aged ≥65 years, rates of death per 1000 person-years of follow-up were 3.6 (95% CI, 1.5 to 8.6; 1389 person-years follow-up) in those who did not attempt a fistula predialysis compared with 5.1 (95% CI, 1.7 to 15.9; 586 person-years follow-up) in those who did. AVF, arteriovenous fistula.