Therapy and Prevention Prosthetic Valve Thrombosis

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 < .005; warfarin vs pentoxifyllineaspirin, p < .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 < .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. Circulation 72, No. 5, 1059-1063, 1985. WHEN THE EFFECT of anticoagulant is maintained within a therapeutic range it significantly reduces, but does not eliminate, the risk of thromboembolism in patients with prosthetic heart valves. ' However, adequate anticoagulation at all times is difficult to achieve,2 and it carries a definite risk of its own.3 In clinical practice, whenever the use of oral anticoagulation is complicated, e.g., in children with prosthetic heart valves or when adequate facilities for careful anticoagulation are not available, antiplatelet agents have been used as the alternatives.4 It would be advantageous to patients with prosthetic heart valves if platelet-suppressant therapy (PST) could be used in place of oral anticoagulation. We undertook a prospective, randomized, parallel study to evaluate the efficacy of PST for the prevention of thromboembolism in patients with mechanical prosthetic heart valves. AntiFrom the Departments of Surgery and Medicine, University of Hong Kong, Grantham Hospital, Hong Kong. Supported by grants from the Hong Kong Heart Foundation Ltd., Hong Kong, and Boehringer Ingelheim and Hoechst, West Germany. Address for correspondence: C. K. Mok, Grantham Hospital, 125 Wong Chuk Hang Road, Hong Kong. Received Nov. 26, 1984; revision accepted June 27, 1985. *Present address: 1 A Jalan Ilmu, Singapore 1129. Vol. 72, No. 5, November 1985 coagulation with warfarin was used as the control. The regimens of antiplatelet agents used in the present study were derived from our previous study on platelet survival among patients with mechanical prosthetic heart valves.6 The present report is an analysis of the relevant data from the prospective trial.