Tuesday, August 21, 2012

Going to ground: risk of falls and oral anticoagulation


In The House of God, a 1970s novel detailing his experience as a first-year medical resident, Samuel Shem (a pseudonym for Stephen Bergman, MD), cites the above axiom as one of the Laws of the House of God taught to him by a senior resident known only as The Fat Man.  The rule itself refers to the propensity of elderly patients to fall or fall from their hospital beds, and like many concepts from the novel that have made their way into the medical vernacular, an assessment of fall risk remains an important evaluation in both hospitalized and ambulatory patients and often significantly impacts the strategies of care offered or delivered to them.

One of the most common scenarios during which a discussion of fall risk occurs is when determining the appropriate antithrombotic strategy for an elderly patient with atrial fibrillation (assuming their annual risk of stroke warrants oral anticoagulation, as determined by the CHADS2 and/or CHA2DS2-VASc score).  The risk of major hemorrhage associated with a traumatic fall is often cited as a reason not to provide full anticoagulation, but evidence from the literature indicates these risks are often overestimated; more importantly, the preference for aspirin in many of these patients is unlikely to ameliorate these risks.

For example, in the Birmingham Atrial Fibrillation Treatment of the Aged Study (BAFTA) [1], patients over the age of 75 years (mean 81.5 years) with atrial fibrillation were randomized to aspirin 75 mg daily or adjusted-dose warfarin (INR goal 2-3); after a mean follow-up period of nearly 3 years, adjusted-dose warfarin was associated with a reduction in the number of total strokes compared to aspirin (3.4% versus 1.6%, respectively, p = 0.003), a difference that was largely driven by a difference in ischemic strokes (2.5% versus 0.8%, p = 0.0004).  More importantly, the benefits observed with warfarin were not accompanied by an increase in major hemorrhage or hemorrhagic stroke. In another analysis [2], the risk of falls among elderly patients with atrial fibrillation was not found to be a major contributor to the hemorrhagic events associated with warfarin -- in fact, a patient would need to fall nearly 300 times in a single year for the risks to outweigh the potential benefits.

Given the alternatives now afforded by the new oral anticoagulants apixaban, dabigatran, and rivaroxaban -- which are arguably safer than warfarin in appropriately selected patients -- the benefits associated with full anticoagulation are even more likely to outweigh the hemorrhagic risks commonly attributed to falls. In fact, when it comes to intrancranial hemorrhage, the most devastating complication of a traumatic fall, each of the new oral anticoagulants is associated with a markedly lower risk compared to warfarin -- a difference in absolute risk per year of 0.24%, 0.44%, and 0.20% with apixaban, dabigatran, and rivaroxaban, respectively [3-5].

Thus, as the population continues to age and the incidence of atrial fibrillation grows, it is likely that discussions involving the appropriate antithrombotic strategy in elderly patients with this condition will only become more frequent as time goes on. While every patient should be evaluated for their individual risk of stroke and hemorrhage, we should be cautious not to potentially deny them the benefits of oral anticoagulation in favor of an antithrombotic strategy (i.e., aspirin) that is definitively less effective but also unlikely to ameliorate the risk of hemorrhage associated with a traumatic fall.

  1. Mant J, Hobbs FD, Murray E; for the BAFTA investigators; Midland Research Practices Network (MidReC). Warfarin versus aspirin for stroke prevention in an elderly community population with atrial fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial. Lancet. 2007 Aug 11;370(9586):493-503.
  2. Man-Son-Hing M, Nichol G, Lau A, Laupacis A. Choosing antithrombotic therapy for elderly patients with atrial fibrillation who are at risk for falls. Arch Intern Med. 1999 Apr 12;159(7):677-85.
  3. Granger CB, Alexander JH, Wallentin L, et al; for the ARISTOTLE Committees and Investigators. Apixaban versus warfarin in patients with atrial fibrillation. N Engl J Med. 2011 Sep 15;365(11):981-92.
  4. Connolly SJ, Ezekowitz MD, Wallentin L, et al; RE-LY Steering Committee and Investigators. Dabigatran versus warfarin in patients with atrial fibrillation. N Engl J Med. 2009 Sep 17;361(12):1139-51.
  5. Patel MR, Mahaffey KW, Califf RM, et al; for the ROCKET AF Investigators. Rivaroxaban versus warfarin in nonvalvular atrial fibrillation. N Engl J Med. 2011 Sep 8;365(10):883-91.

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