Warfarin in atrial fibrillation: DISCUSSION(1)

This study assessed the cost-effectiveness ofwarfarin intervention versus placebo from society’s perspective. Clearly, this analysis shows a protective effect with warfarin (66% reduction in embolic events) compared with no antithrombotic therapy. The data from these clinical trials, when combined, provide physicians with strong evidence to use warfarin routinely for those who qualify. A simiiar reduction in embolic events was also found (64% reduction) by investigators using the total Swedish population.

Frequently, warfarin may not be prescribed due to an increased risk of bleeding. This increased risk is underscored in the Stroke Prevention in Atrial Fibrillation (spinaf) study which resulted in 121 (n=260) bleeding events, compared with 21 (n=335), 40 (n=212), 41 (n=212) and seven (n=210) in the other four clinical trials (Table 2). It should be noted, however, that this group reported bleeding events which occurred more than once in the same person, which may have not been reflected in the other studies. It is also interesting to note that the spinaf group was the only trial not to have any fatal bleeds (Table 7). buy ampicillin


Bleeding complications

Group Study (reference)/n Fatal Major Minor INR*
Warfarin AFASAK (4)/335 1 1 20 42
BAATAF (5)/212 1 2 38 83
CAFA (6)/187 1 4 37 43
SPAF (7)/210 1 3 4 71
SPINAF (8)/260 0 6 115* 56
No AFASAK (4)/336 0 0 0
antithrombotictherapy BAATAF (5)/208 1 1 21
CAFA (6)/191 0 2 28
SPAF (7)/211 1 3 1
SPINAF (8)/265 0 4 Щ 96*

*Average percentage of time patients were in the International Normalized Ratio (INR) range when tested; fIn 64 people; *In 46 people. AFASAK Copenhagen Atrial Fibrillation trial; BAATAF Boston Area Anticoagulation Trial for Atrial Fibrillation; CAFA Canadian Atrial Fibrillation Anticoagulation study; SPAF Stroke Prevention in Atrial Fibrillation study; SPINAF Stroke Prevention In Nonrheumatic Atrial Fibrillation study.

The high bleeding rates in the past may have been due to lack of standardization of thromboplastin reagent (ie, some throm boplastin is more reactive), resulting in an in creased dose. This problem has been resolved, with a standardization of prothrombin time, using the World Health Organization reference, which is inr, resulting in a downward dose for most indications.


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