17 Oct

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Occurrence of thromboemboli

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Occurrence of thromboemboliThe occurrence of thromboemboli in patients with Medronic-Hall valves parallels the experience with other disc-occluder valves. Among 379 patients in whom the PT was maintained at 2-2.5 times control (presumably using North American thromboplastin), thromboembolic events occurred at a rate of 2.3/100 patient years after mitral valve replacement and at 2.1/100 patient years after aortic valve replacement (level V study). Problems related to anticoagulation occurred with an incidence of 1.2/100 patient years.
Regarding the St. Jude valve, excellent results have been reported in patients treated with anticoagulants (Table 4A). A prospective nonrandomized experience (level III) among 136 patients, when treated with Coumadin (PT 1.3-1.8 x control) showed thromboembolic complications at a rate of 1.7/100 patients/year among those with valves in the aortic position and 4.2/ 100 patients/year among patients with valves in the mitral position. A retrospective case series evaluation (level V) showed an incidence of thromboembolism of 0.7/100 patients/year with valves in the aortic position and 0.9/100 patients/year with valves in the mitral position. (A “therapeutic range” of anticoagulation was present in less than 50% of patients.) comments

Another retrospective case series without controls showed “late” thromboemboli at a rate of 0.6/100 patients/year in the aortic position and 3.9/100 patients/year in the mitral position among patients treated with acenocoumarol. Others, depending on valve position and the number of valves, showed an incidence of thromboembolism of 1.3/100 patients/ year to 3.7/100 patients/year in patients treated with anticoagulants. Most thromboembolic events in patients with valves in the mitral position occurred in patients with AF. Those with preoperative fibrillation were 1.8 times more likely to suffer a thromboembolic event. Small numbers of untreated patients showed a high incidence of thromboemboli.
Table 4A— Thromboemboli with St. Jude Valves

Treatment No. of Patients ValvePosition ProthrombinTime Thromboembolic Episodes/100 pts/yr EvidenceLevel Reference
Warfarin 93 Ao 1.3-1.8 X 1.7 III Nair et al, 1988“®
61 M 1.3-1.8 x 4.2
12 Ao + M 1.8-2 x 0
Warfarin 147 Ao _ 0.7 V Horstkotte, Korter, 1983*
167 M 0.9
Acenocoumerol 269 Ao 0.6 V LeCler et al, 198325
244 M 3.9
98 Ao + M 4.4
Warfarin 73 Ao _ 1.3 V Chaux et al, 198426
90 M 2.3
35 Ao + M 3.7
ASA 325 mg or dipyridimole 225 mg or both 42 Ao 3.2 III Hartz et al, 1986378
ASA 900 mg+ 13 Ao V McGrath et al, 198737C
dipyridamole 150 mg 9 M (24% in 9 mo)
7 Other
ASA 300 mg + dipyridimole 75-225 mg 52 Ao 2.1 V Ribeiro et al, 198637A
ASA 300 mg + dipyridimole 75-225 mg 15 Ao + M (some M bioprosthetic) 10.0
ASA (dose?) 26(children) AoM (12.5% in 4 yr) V Borkon et al, 1986370

Categories: Antithrombotic Therapy
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