Warfarin Sodium (Page 7 of 9)

14.3 Myocardial Infarction

WARIS (The Warfarin Re-Infarction Study) was a doubleblind, randomized study of 1214 patients 2 to 4 weeks post-infarction treated with warfarin to a target INR of 2.8 to 4.8. The primary endpoint was a composite of total mortality and recurrent infarction. A secondary endpoint of cerebrovascular 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 Table 7:

Table 7WARIS – Endpoint Analysis of Separate Events

RR=Relative risk; Risk reduction=(1 — RR); CI=Confidence interval; MI=Myocardial infarction; py=patient years

Event Warfarin ( N = 607 ) Placebo ( N = 607 ) RR ( 95 % CI ) % Risk Reduction ( p value )
Total Patient Years of Follow-up 2018 1944
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 Event 20 (1/100 py) 44 (2.3/100 py) 0.46 (0.28, 0.75) 54 (p=0.002)

WARIS II (The Warfarin, Aspirin, Re-Infarction Study) was an open-label, randomized study of 3630 patients hospitalized for acute myocardial infarction treated with warfarin to a target INR 2.8 to 4.2, aspirin 160 mg per day, or warfarin to a target INR 2 to 2.5 plus aspirin 75 mg per day prior to hospital discharge. The primary endpoint was a composite of death, nonfatal reinfarction, or thromboembolic stroke. The mean duration of observation was approximately 4 years. The results for WARIS II are provided in the Table 8.

Table 8WARIS II – Distribution of Events According to Treatment Group

a Major bleeding episodes were defined as nonfatal cerebral hemorrhage or bleeding necessitating surgical intervention or blood transfusion.

b The rate ratio is for aspirin plus warfarin as compared with aspirin.

c The rate ratio is for warfarin as compared with aspirin.

d Minor bleeding episodes were defined as non-cerebral hemorrhage not necessitating surgical intervention or blood transfusion.

e Includes death, nonfatal reinfarction, and thromboembolic cerebral stroke.

CI=confidence interval

ND=not determined

Event Aspirin ( N = 1206 ) Warfarin ( N = 1216 ) Aspirin plus Warfarin ( N = 1208 ) Rate Ratio ( 95 % CI ) p value
No . of Events
Major Bleedinga 8 33 28 3.35b (ND) ND
4.00c (ND) ND
Minor Bleedingd 39 103 133 3.21b (ND) ND
2.55c (ND) ND
Composite Endpointse 241 203 181 0.81 (0.69-0.95)b 0.03
0.71 (0.60-0.83)c 0.001
Reinfarction 117 90 69 0.56 (0.41-0.78)b < 0.001
0.74 (0.55-0.98)c 0.03
Thromboembolic Stroke 32 17 17 0.52 (0.28-0.98)b 0.03
0.52 (0.28-0.97)c 0.03
Death 92 96 95 0.82

There were approximately four times as many major bleeding episodes in the two groups receiving warfarin than in the group receiving aspirin alone. Major bleeding episodes were not more frequent among patients receiving aspirin plus warfarin than among those receiving warfarin alone, but the incidence of minor bleeding episodes was higher in the combined therapy group.

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