Does platelet-suppressant therapy (dipyridamole-aspirin or pentoxifylline-aspirin) prevent prosthetic heart valve thromboembolism compared to warfarin in patients with prosthetic heart valves?
Warfarin is superior to antiplatelet regimens (dipyridamole-aspirin or pentoxifylline-aspirin) for the prevention of thromboembolism in patients with prosthetic heart valves, particularly those with isolated mitral valve replacement.
In a prospective, randomized, parallel study, two regimens of platelet-suppressant therapy (PST)--dipyridamole-aspirin and pentoxifylline-aspirin--were compared with standard oral anticoagulation with warfarin in the prevention of prosthetic heart valve thromboembolism. In the entire group of 254 patients followed for 395.6 patient-years, the thromboembolic rate was significantly less in the warfarin group (warfarin vs dipyridamole-aspirin, p less than .005; warfarin vs pentoxifylline-aspirin, p less than .05). Subgroup analysis disclosed that, in patients with isolated mitral valve replacement, warfarin was superior to both of the PSTs with respect to the prevention of thromboembolism (warfarin vs dipyridamole-aspirin, p = .005; warfarin vs pentoxifylline-aspirin, p less than .05). Furthermore, a significant number of our patients could not tolerate the antiplatelet agents. However, in the rare situation in which repeated significant bleeding occurs despite careful adjustment of the dosage of warfarin, PST may be an acceptable alternate method of thromboembolism prophylaxis.
Mok et al. (1985) studied this question.