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Major Bleeding Events Lead to Under Use of Anticoagulation in Atrial Fibrillation, but Ischemic Strokes do not Alter Prescribing Practices

Henry I. Bussey, Pharm.D., FCCP, FAHA
February, 2006

Review: Choudhry NK, Anderson GM, Laupacis A, Ross-Degnan D, Normand SL, Soumerai SB. Impact of adverse events on prescribing warfarin in patients with atrial fibrillation: matched pair analysis. BMJ. 2006 Jan 21;332(7534):141-5. Epub 2006 Jan 10.

Canadian investigators examined data for 116,200 patients with non-valvular atrial fibrillation. Hospital admission for gastrointestinal hemorrhage or intracranial hemorrhage occurred in 3,921 patients (3.4% of the entire group). The 530 physicians who were managing these patients exhibited a 21% reduction in the use of warfarin in their atrial fibrillation patients following the major bleed in the index case. This reduced use of warfarin persisted for at least one year following the event. Hospital admission for an ischemic stroke in patients not receiving warfarin occurred in 8,720 patients (7.5% of the entire group). The 704 physicians who were managing these patients did not exhibit a change in warfarin use following the ischemic event. It would appear that a major bleed while on warfarin leads to reduced use of warfarin for other patients of that physician, but the development of an ischemic stroke in a patient not being anticoagulated did not influence prescribing practices. Some have suggested that the mindset behind these apparent paradoxical responses to patient events is that a hemorrhage while on warfarin is viewed by the physician as an event that he/she caused by prescribing warfarin. An ischemic stroke, however, is often viewed as an act of God that is due to the disease and, therefore, the physician either is not responsible or is somehow less responsible for the ischemic stroke, which might have been prevented with appropriate therapy.

Numerous studies have reported that only approximately 50% of patients with atrial fibrillation who should receive anticoagulation actually do receive such therapy. Based on the review from the American College of Chest Physicians Consensus Conference on Antithrombotic Therapy, there are approximately 2.5 million patients with atrial fibrillation in the U.S. with an average annualized stroke risk of about 4.5% per year.1 If only one-half of these individuals are receiving anticoagulation, then that means that 1.25 million patients who should be anticoagulated are not being treated appropriately. At an average annualized risk of stroke of about 4.5% per year, that means that approximately 56,000 of these patients are having a stroke every year. On-treatment analysis of available studies indicate that warfarin therapy can produce more than an 80% reduction in this stroke rate thereby preventing more than 44,000 strokes.2 At an average cost of almost $100,000 per stroke, that equates to an additional $4 billion annually in healthcare costs.3

By contrast, in the first five trials of primary prevention in atrial fibrillation, the annualized risk of major hemorrhage was less than 1% and the risk of intracranial hemorrhage less than 0.2%. 1 For the majority of patients, therefore, the ischemic stroke risk reduction with warfarin therapy far outweighs the bleeding risk associated with well-managed warfarin. It therefore seems unfortunate that the Canadian investigators found that a hemorrhage while on warfarin was associated with an additional 21% reduction in the use of warfarin in atrial fibrillation patients, but an ischemic stroke was not associated with an increase in the use of anticoagulation in patients with atrial fibrillation.

References

  1. Singer DE, Albers GW, Dalen JE, Go AS, Halperin JL, Manning WJ. Antithrombotic Therapy in Atrial Fibrillation. Chest 2004; 126:429s-456s.

  2. Atwood JE. Albers GW. Anticoagulation and atrial fibrillation. Herz. 1993; 18(1):27-38.

  3. Heart Disease and Stroke Statistics--2006 Update. A Report From the American Heart Association Statistics Committee and Stroke Statistics Subcommittee, http://circ.ahajournals.org/cgi/reprint/
    CIRCULATIONAHA.105.171600v1
    . accessed Jan. 29, 2006
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