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Anti-platelet therapy in graft thrombosis: results of a prospective, randomized, double-blind study
R Sreedhara1, J Himmelfarb, J M Lazarus
1Vanderbilt University Medical Center, Nashville, Tennessee.
Insights
Dipyridamole significantly reduced thrombosis in new expanded polytetrafluoroethylene (ePTFE) grafts for hemodialysis patients. Aspirin did not improve outcomes, and neither drug helped patients with previously thrombosed grafts.
Area of Science:
- Nephrology
- Vascular Surgery
- Pharmacology
Background:
- Vascular access thrombosis is a significant complication for hemodialysis patients.
- Expanded polytetrafluoroethylene (ePTFE) grafts are commonly used for hemodialysis access.
- Thrombosis of ePTFE grafts leads to substantial morbidity and healthcare utilization.
Purpose of the Study:
- To evaluate the efficacy of dipyridamole and aspirin in preventing thrombosis of ePTFE grafts in hemodialysis patients.
- To compare the effects of dipyridamole alone, aspirin alone, and their combination against placebo.
- To assess outcomes in patients with new grafts versus those with previously thrombosed grafts.
Main Methods:
- Prospective, randomized, double-blind, placebo-controlled, parallel group study.
- 107 hemodialysis patients with ePTFE grafts were followed for 18 months.
- Patients were divided into two groups: new grafts (Type I) and revised/previously thrombosed grafts (Type II).
Main Results:
- In Type I patients, dipyridamole alone showed a significantly lower thrombosis rate (21%) compared to placebo (42%) (P=0.02).
- Dipyridamole and aspirin combination (25%) and aspirin alone (80%) did not show significant benefit over placebo.
- In Type II patients, thrombosis rates were high across all groups (78%), precluding further analysis.
Conclusions:
- Dipyridamole is effective in reducing thrombosis in new ePTFE grafts for hemodialysis.
- Aspirin does not offer a significant benefit in preventing ePTFE graft thrombosis.
- Neither dipyridamole nor aspirin demonstrated efficacy in patients with a history of ePTFE graft thrombosis.
Abstract:
Hemodialysis (HD) vascular access thrombosis remains a major cause of morbidity, accounting for 17.4% of all HD patient hospital admissions in 1986. We initiated this prospective, randomized, double-blind, placebo-controlled, parallel group study to examine if dipyridamole and/or aspirin decreased the rate of thrombosis of expanded polytetrafluoroethylene (ePTFE) grafts in HD patients. Two patient groups were studied: Type I--with a new ePTFE graft; and Type II--with thrombectomy and/or revision of a previously placed ePTFE graft. One hundred and seven patients were followed for 18 months or until the first thrombotic episode. Actuarial analysis of Type I patients showed cumulative thrombosis rates (mean +/- SEM) of 21 +/- 9% on dipyridamole alone, compared with 25 +/- 11% on dipyridamole and aspirin combination, 42 +/- 13% on placebo, and 80 +/- 12% on aspirin alone. The relative risk of thrombosis with dipyridamole was 0.35 (P = 0.02) and that for aspirin was 1.99 (P = 0.18). In Type II patients, the rate of thrombosis was high in all study drug and placebo groups (overall 78% thrombosis) and actuarial analysis was not carried out because of the small number of patients enrolled. We conclude that dipyridamole is beneficial in patients with new ePTFE grafts and that aspirin does not improve the risk of thrombosis in ePTFE grafts. Neither dipyridamole nor aspirin has any beneficial effect in patients with prior thrombosis of ePTFE grafts.