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*All study results of warfarin vs. control are based on intention-to-treat analysis and include ischemic stroke and systemic thromboembolism, excluding hemorrhage and transient ischemic attacks. Myocardial Infarction: WARIS (The Warfarin Re-Infarction Study) was a double-blind, randomized study of 1214 patients 2 to 4 weeks post-infarction treated with warfarin to a target INR of 2.8 to 4.8. [But note that a lower INR was achieved and increased bleeding was associated with INR's above 4.0; (see DOSAGE AND ADMINISTRATION)]. The primary endpoint was a combination of total mortality and recurrent infarction. A secondary endpoint of cere-brovascular events was assessed. Mean follow-up of the patients was 37 months. The results for each endpoint separately, including an analysis of vascular death, are provided in the following table: Text Continues Below
TABLE 2
% Risk Event Warfarin Placebo Reduction
(N= 607) (N= 607) RR (95% CI) (p-value)
Total Patient Years 2018 1944 of Follow-up
Total Mortality 94 (4.7/ 100 py) 123 (6.3/ 100 py) 0.76 (0.60, 0.97) 24 (p= 0.030) Vascular Death 82 (4.1/ 100 py) 105 (5.4/ 100 py) 0.78 (0.60, 1.02) 22 (p= 0.068)
Recurrent MI 82 (4.1/ 100 py) 124 (6.4/ 100 py) 0.66 (0.51, 0.85) 34 (p= 0.001)
Cerebrovascular 20 (1.0/ 100 py) 44 (2.3/ 100 py) 0.46 (0.28, 0.75) 54 (p= 0.002) Event
RR= Relative risk; Risk reduction=( I -RR); CI= Confidence interval; MI= Myocardial infarction; py= patient years Mechanical and Bioprosthetic Heart Valves: In a prospective, randomized, open label, positive-controlled study (Mok et al, 1985) in 254 patients, the thromboembolic-free interval was found to be significantly greater in patients with mechanical prosthetic heart valves treated with warfarin alone compared with dipyridamole-aspirin (p< 0.005) and pentoxifylline-aspirin (p< 0.05) treated patients. Rates of thromboembolic events in these groups were 2.2, 8.6, and 7.9/ 100 patient years, respectively. Major bleeding rates were 2.5, 0.0, and 0.9/ 100 patient years, respectively. In a prospective, open label, clinical trial (Saour et al, 1990) comparing moderate (INR 2.65) vs. high intensity (INR 9.0) warfarin therapies in 258 patients with mechanical prosthetic heart valves, thromboembolism occurred with similar frequency in the two groups (4.0 and 3.7 events/ 100 patient years, respectively). Major bleeding was more common in the high intensity group (2.1 events/ 100 patient years) vs. 0.95 events/ 100 patient years in the moder-ate intensity group. In a randomized trial (Turpie et al, 1988) in 210 patients comparing two intensities of warfarin therapy (INR 2.0-2.25 vs. INR 2.5-4.0) for a three-month period following tissue heart valve replacement, thromboembolism occurred with similar frequency in the two groups (major embolic events 2.0% vs. 1.9%, respectively and minor embolic events 10.8% vs. 10.2%, respectively). Major bleeding complications were more frequent with the higher intensity (major hemorrhages 4.6%) vs. none in the lower intensity. Page: << Prev | 1 | 2 | 3 | 4 | 5
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