15 Oct

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Incidence of thromboembolism

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Incidence of thromboembolismThe incidence of thromboembolism in patients with ball valve prostheses who were taking full doses of anticoagulants (warfarin or dicumarol) ranged between 1 and 21/100 patient years. Fewer throm-boemboli seemed to occur with the cloth-covered Starr-Edwards valves than with the Starr-Edwards valves that had exposed metal struts. Also, valves in which the cloth margin extended to the inlet surface had fewer thromboemboli. in detail

Thromboembolic events in patients with prosthetic ball valves who were considered to be inadequately anticoagulated were in general more frequent than in adequately anticoagulated patients. In these level III studies, the incidence of thromboembolism in the former patients was at least twice that of fully anticoagulated patients, but nearly half that in untreated patients. An exception to this was a retrospective analysis of a subgroup of patients with prosthetic ball valves in the mitral position, which showed no difference in the incidence of thromboembolism dependent on whether anticoagulation was or was not in their defined therapeutic range. On the other hand, one retrospective analysis showed the most disadvantageous effects of inadequate anticoagulants in patients with valves in the mitral position; inadequate anticoagulant therapy with valves in the aortic position resulted in statistically insignificantly greater occurrences of thromboemboli. Also, some authors found no thromboemboli with valves in the aortic position, irrespective of whether anticoagulants were used. Some of these investigators defined anticoagulant therapy to be adequate if all prothrombin times were ^1.5 X control. Others defined anticoagulation as being adequate when PTs were 2-2.5 times control. Some considered anticoagulation to be adequate when the PT was 25-30 s. All of these investigators used rabbit brain thromboplastin in the performance of PTs.

Categories: Antithrombotic Therapy
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