The Influence of Platelet Inhibition on the Patency of Femoro-Popliteal Dacron Bypass Grafts

Abstract

Neointimal hyperplasia and thrombosis initiated by platelet activity may contribute to the failure of femoropopliteal Dacron bypass grafts. We have therefore undertaken a randomised prospective double blind trial comparing the efficacy of a combination of acetyl salicylic acid (ASA) 330 mg and dipyrida mole (DPM) 75 mg three times daily, with placebo in maintaining the patency of femoropopliteal Dacron bypass grafts implanted to relieve disabling claudica tion. Patients received either ASA/DPM or placebo commencing pre-opera tively and continuing for 12 months. Seventy-three double velour (Microvel) grafts in 65 patients were studied, 38 grafts in the placebo group and 35 grafts in the active group. The following were measured pre-operatively and at 3, 6, 9 and 12 months postoperatively: maximum walking distance (MWD); ankle/bra chial systolic pressure index (ABSPI); graft patency; platelet adhesion and ag gregation; template bleeding time; ASA and DPM levels. After 1 year, 10 patients had been withdrawn (9 ASA/DPM: 1 placebo) and 4 out of 26 grafts in the active group and 15 out of 37 in the placebo group had occluded ( P < 0.05 Chi square test). We conclude that inhibition of platelet function by the use of a combination of ASA and DPM improved the patency rate of femoropopliteal Dacron bypass grafts.

Reduction of indium-111 platelet deposition on Dacron vascular grafts in humans by aspirin plus dipyridamole.

“…Although the mechanisms of occlusion are multifactorial,' many studies in animals and in humans suggest that platelet accumulation may play a prominent role, either directly by the formation of occlusive thrombus or indirectly by stimulation of intimal hyperplasia. Studies of indium-i 1 1 ("'In)-labeled platelets have documented that platelet deposition is greatest early after arterial graft placement.2' 3 Although deposition decreases in the subsequent 6 months, platelet accumulation remains readily detectable for periods of up to 10 years.4 5 Aspirin plus dipyridamole, used early postoperatively when deposition is maximal, reduces "'In-labeled platelet uptake on Dacron or polytetrafluoroethylene arterial grafts in humans6' 7 and has been associated with improved short-term patency compared with placebo ther-6, [8][9][10] apy.Whether aspirin plus dipyridamole reduces platelet uptake on older grafts that have a lesser rate of platelet deposition, but a continued risk of occlusion, remains unclear. Prior studies have documented that other platelet inhibitory agents, including ticlopidine," suloctidil,'2 and sulfinpyrazone'3 do not reduce platelet accumulation on grafts greater than 9 months old.…”

“…2' 3 Although deposition decreases in the subsequent 6 months, platelet accumulation remains readily detectable for periods of up to 10 years. 4 5 Aspirin plus dipyridamole, used early postoperatively when deposition is maximal, reduces "'In-labeled platelet uptake on Dacron or polytetrafluoroethylene arterial grafts in humans6' 7 and has been associated with improved short-term patency compared with placebo ther-6, [8][9][10] apy.…”

A Critical Analysis on the Impact of Antiplatelet Therapy in the Patency of Infrainguinal Bypass Grafts

“…The first meta-analysis published in 1994, [8] included 11 studies [9][10][11][12][13][14][15][16][17][18][19]. In these studies, allocation to antiplatelet therapy compared to placebo was associated with a proportional reduction of 38% (± 9%) in graft occlusion, which was highly significant [8].…”

Indications of combined vitamin K antagonists and aspirin therapy

“…The Antiplatelet Trialists' Collaboration showed a beneficial effect of aspirin therapy with no clear differences between types of arterial disease. The efficacy of long-term treatment with aspirin in patient's who undergo infrainguinal bypass surgery, however, has been studied in only a few randomised trials [58][59][60][61][62]. The BOA (The Dutch Bypass Oral Anticoagulants or Aspirin) trial showed that VKAs were better for the prevention of infra-inguinal-vein-graft and for lowering the rate of ischemic events.…”