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(Circulation. 1996;94:2055-2056.)
© 1996 American Heart Association, Inc.

Articles

Optimal Antithrombotic Therapy for Mechanical Prosthetic Heart Valves

James H. Chesebro, MD; Valentin Fuster, MD, PhD

Key Words: anticoagulants • thrombosis • prosthesis • valves • Editorials

	Introduction

 
Thromboembolism and bleeding during therapeutic anticoagulation are the major chronic risks for patients after mechanical prosthetic heart valve replacement. Prophylaxis for thromboembolism based on pathogenesis and risk and the involvement of both fibrin and platelets has led to permanent long-term oral anticoagulant therapy for consistent protection.^{1 2 3} The incidence of thromboembolic events is related to the type of valve and its location; the incidence after aortic valve replacement is lower than after mitral valve replacement.^{2 3} The peak incidence of thromboembolism is during the first 3 months after surgery, probably reflecting the lack of endothelialization of the newly implanted prosthetic materials and delay in achieving therapeutic anticoagulation in the early days after operation.^{4 5} The Dacron sewing ring is common to all prosthetic heart valves and forms a substrate for platelet deposition as soon as blood flows across the valve.² Current recommendations are levels of oral anticoagulation that prolong the prothrombin time ratio to an international normalized ratio (INR) of 2.5 to 3.5 for tilting-disk and bileaflet valves and probably for caged-ball valves.³

The study reported in this issue of Circulation by Acar et al and the AREVA Group⁶ is well designed, well conducted, and focused on lower-risk patients. It addresses the optimal target level for anticoagulation. They compared a target INR of 2.0 to 3.0 with 3.0 to 4.5 in a randomized trial after a single mechanical prosthetic valve replacement with either of two bileaflet mechanical prostheses (St Jude valve in 81% and Omnicarbon valve in 19% of the 433 patients) placed . . . [Full Text of this Article]