19 Oct

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Valves in the mitral position

Antithrombotic Therapy in Mechanical and Biological Prosthetic Heart Valves and Saphenous Vein Bypass Grafts: Valves in the mitral positionThromboemboli occurred more frequently in patients with valves in the mitral position than in those with valves in the aortic position, and more often in patients with multiple bioprosthetic valves than in those with a single bioprosthetic valve. The higher incidence of emboli from the mitral valve, however, may reflect the more frequent occurrence of atrial fibrillation in such patients.
A high frequency of thromboembolic episodes within the first three months after insertion has been observed by some, and, for this reason, anticoagulants were administered 6-12 weeks after insertion by most groups, even though anticoagulants were subsequently discontinued (Table 5). A recent retrospective study, however, showed that the frequency of thromboemboli was linear, and not restricted primarily to the first 3 months after operation (Table 5). Most reports of early thromboembolic events were of patients with valves in the mitral position. Early thromboembolism has also been reported in patients with valves in the aortic position, however. More info

A less intense regimen of warfarin INR 2.0-3.0, PT 1.3-1.5 using North American thromboplastin has been demonstrated to be as effective as the more intense regimen of warfarin, but has fewer bleeding complications (level I).
Among patients with bioprosthetic valves in normal sinus rhythm who were treated with anticoagulants, thromboembolic complications were extremely rare (Tables 6, 7). In a retrospective review of patients with bioprosthetic valves in the mitral position who had an increased risk of thromboembolism due to AF, clots in the left atrium, an enlarged left atrium, or a preoperative embolism, the incidence of thromboembolism was found to be lower in those with bovine pericardial valves than in those with porcine bioprosthetic valves. Fewer thromboemboli occurred with bovine pericardial valves, even though the patients were treated with warfarin for only 6 weeks, whereas those with porcine valves received warfarin an average of 6 months (Table 5).
Table 5—Early Thromboemboli with Bioprosthetic Valves

Greater Risk First 3 Mo Thromboemboli Occurring During First 3 Mo, % ValveR)sition Anticoagulants in Patients with Thromboemboli, % EvidenceLevel Reference
Yes 71 (5 of 7) Ao, M 75 untreated V Oyer et al, 1977s*
Yes 67 (16 of 24) M 86 untreated V Ionescu et al, 198238
Yes 80 (8 of 10) M 90 treated V Hetzer et al, 198234
No Linear development Ao, M Variable V Magilligan et al, 1985*

Table 6—Thromboemboli with Rioprosthetic Valves Patients in Sinus Rhythm

Treatment ValveType No.Valves ValvePosition Prothrombin Time (% of control) Thromboemboli Episodes/ 100 pts/yr Thromboemboli,% EvidenceLevel Reference
None (after 6-12 wk warfarin) Porcine 83 Ao, M, ?Ao + M 10 at 36 mo IV Williams et al, 198038
None (after 6 wk warfarin) Porcine 546 Ao 1.89 ~4 at 36 mo 12 at 108 mo IV Cohn et al, 198433
WarfarinAspirin Porcine 124 Ao, M, Ao + M 20-30 0 at 23 mo* IV Nunez et al, 198238
1 g/day Porcine 260 Ao, M, Ao + M 0 at 23 mo* IV Nufiez et al, 198236
1 g/day or 0.5 g qod Porcine 185 M, Ao+M 0 at 32 mo* IV Nufiez et al, 198444

Table 7—Thromboemboli with Bioprosthetic Valves in Patients with Atrial Fibrillation or Atrial Thrombus

Treatment ValveType No.Valves ValvePosition Prothrombin Time (% of control) ThromboemboliEpisodes/lOOpts/yr Incidence of Thromboemboli EvidenceLevel Reference
None Porcine 11 Ao, M, ?Ao + M 16% at 36 mo IV Williams et al, 1980“
(after
6-12 wk
warfarin)
None Porcine 105 M 15-25 16.2% at 31 mo* IV Conzalez-Lavin et al, 198443
(after
24 wk
warfarin)
None Bovine peri 275 M, M ±Ao±TV 0.6 V Ionescu et al, 198238
(after Bovine peri 209 M 1% at 46 mo* IV Gonzalez-Lavin et al, 198443
6 wk
warfarin)
Warfarin Porcine 147 M 15-25 2.3 V Hetzer et al, 198234
Porcine 151 M 20-30 4.6% at 23 mo* IV Nufiez et al, 198236
51 M + Ao 5.9% at 23 mo*
Aspirin
1 g/day Porcine 135 M 1.3 4.4% at 32 mo* IV Nufiez et al, 19823*
(also Nufiez et al, 198444)
Aspirin
500 mg Porcine 219 M 0.3 0.5% at 32 mo* IV Nufiez et al, 198444
qod 143 M + Ao 0.5 0.7% at 32 mo*

Categories: Antithrombotic Therapy
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