Use of aspirin associates with longer primary patency of hemodialysis grafts

Abstract

Extended-release dipyridamole plus low-dose aspirin (ERDP/ASA) prolongs primary unassisted graft patency of newly created hemodialysis arteriovenous grafts, but the individual contributions of each component are unknown. Here, we analyzed whether use of aspirin at baseline associated with primary unassisted graft patency among participants in a randomized trial that compared ERDP/ASA and placebo in newly created grafts. We used Cox proportional hazards regression, adjusting for prespecified baseline comorbidities and covariates. Of all participants, 43% reported use of aspirin at baseline; of these, 82% remained on nonstudy aspirin (i.e., excluding ERDP/ASA) at 1 year. After 1 year of follow-up, the incidence of primary unassisted patency among participants using aspirin at baseline was 30% (95% CI: 24 to 35%) and among those not using aspirin was 23% (95% CI: 18 to 27%). Use of aspirin at baseline associated with a dose-dependent prolongation of primary unassisted graft patency that approached statistical significance (adjusted HR, 0.83; 95% CI: 0.68 to 1.01; P=0.06). Use of aspirin at baseline did not associate with prolongation of cumulative graft patency or participant survival. In conclusion, use of aspirin associates with a trend toward longer primary unassisted patency of newly placed hemodialysis grafts similar to that observed for ERDP/ASA.

Figure 1.

Primary unassisted patency is prolonged in patients on aspirin at baseline. Cumulative incidence of loss of primary unassisted graft patency for baseline aspirin users (dashed line) and nonusers (solid line). The median patency in the baseline aspirin users and nonusers was 5.8 (95% CI, 4.8 to 7.4) and 4.1 months (95% CI, 3.5 to 5.3; P = 0.13), respectively.

Figure 2.

Primary unassisted graft patency is prolonged for all groups exposed to aspirin. Primary unassisted graft patency and 95% confidence intervals at 1 year are shown for the four groups of aspirin exposure: patients randomized to either ERDP/ASA or placebo and patients who were users or nonusers of aspirin at baseline.

Figure 3.

Prolongation of primary unassisted graft patency is associated with a higher baseline dose of aspirin. Cumulative incidence of loss of primary unassisted graft patency in patients stratified into three levels of self-reported baseline aspirin use: no aspirin use (solid line) or 12 to 81 mg/d (dashed line) or ≥325 mg/d (dotted line) of aspirin. Patients using 12 to 81 mg/d and ≥ 325 mg/d of aspirin at baseline had an 11 (HR = 0.89, 95% CI = 0.70 to 1.12, P = 0.30) and 24% (HR = 0.76, 95% CI = 0.59 to 0.99, P = 0.04) reduction in loss of primary unassisted patency compared with participants on no aspirin at baseline, respectively.

Figure 4.

Cumulative graft patency is not prolonged by baseline aspirin use. Cumulative incidence of loss of cumulative graft patency in baseline aspirin users (dashed line) and nonusers (solid line).