21 Oct

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Additional information

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Additional informationAdditional information regarding the effect of antiplatelet therapy on graft patency has been derived from the VA Cooperative Study. Postoperative angiograms were obtained within 60 days of surgery (level I study).49A The drug regimens employed included: (1) aspirin 325 mg/day; (2) aspirin 975 mg/day; (3) aspirin 975 mg/day combined with dipyridamole 225 mg/day; and (4) sulfinpyrazone 800 mg/day. Aspirin was begun 12 h before surgery. Other drugs (dipyridamole and sulfinpyrazone) were begun 2 days before surgery. Among 555 patients (1,781 grafts) there was greater graft patency (92-94%) with drug regimens that included aspirin than placebo (85% patency) (p<.05). A disadvantage, however, was a greater rate of reoperation (6.5%) among treatment groups that included aspirin compared with treatment groups that consisted of either sulfinpyrazone or placebo (1.7%, p<.01). itat on

Aspirin, given in combination with dipyridamole, has shown inconsistent results in a number of level I and II studies (Table 8). Most investigators administered aspirin in a dose of approximately 1 g/day in combination with dipyridamole 225 mg/day, although one group administered aspirin 1,300 mg/day and dipyridamole 100 mg/day. A greater incidence of saphenous vein bypass graft patency was found by some at 3-6 months (92% vs 77%) (p<.02) and 92% vs 75% (pC.Ol). One group reported improved graft patency in patients at 1 month (97% vs 90% patency) and again at 1 year (89% vs 75% patency). Some studies, however, failed to show beneficial results of aspirin given in combination with dipyridamole. In investigations that showed no beneficial effect, antiplatelet therapy was begun 2-5 days after operation, whereas the studies that showed a beneficial effect employed antiplatelet therapy within 1 day of operation (Table 8).
In a randomized level I study sulfinpyrazone has been reported to be associated with greater graft patency at 1-2 weeks after bypass among treated patients, 96% graft patency (204 of 212) vs 91% graft patency (199 of 219) (p<.025). This was not confirmed, however, in the VA Cooperative Study. On the other hand, ticlopidine (a new antiplatelet agent) has been shown to increase graft patency (level I study).

Categories: Antithrombotic Therapy
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