Anticoagulant Use in Patients with Risk of Falling
to the editor: The article on acute management of atrial fibrillation by Dr. King and colleagues in American Family Physician1 states that “patients with a significant risk of falling … should not receive long-term anticoagulation therapy.” I reviewed the pertinent references2,3 and found statements advising caution in the use of anticoagulation therapy in patients who fall; however, no data supported not using this therapy at all in these patients.
Many falls lead to minor or no injuries, but the risk of subdural hematomas can be life-threatening. One study4 analyzed the risk of bleeding from falls in elderly patients (at least 65 years of age) who are anticoagulated for atrial fibrillation. The study found that a person taking warfarin must fall about 295 times in one year for warfarin not to be considered the optimal therapy.4 The investigators concluded that falls are not as important a factor in deciding on treatment for atrial fibrillation as previously thought. Another study5 used the same numbers to recommend warfarin therapy.
I often see patients who are admitted to our nursing homes after sustaining an embolic stroke because of atrial fibrillation who were not given anticoagulation therapy because of a risk of falling. Physicians are obligated to inform our patients of the risks and benefits of anticoagulation, and they need to use the current data to most accurately describe these risks and benefits. In the case of patients with atrial fibrillation who fall, the benefit is on the side of anticoagulation.
in reply: Dr. Hamrick raises some interesting and important points regarding the risk of anticoagulation and the risk of falls in patients with chronic atrial fibrillation. Dr. Hamrick correctly points out that warfarin (Coumadin) therapy provides an important advantage of stroke prevention. However, the main evidence cited in Hamrick's letter regarding the risk attributable to falls is a decision analysis,1 not a primary evidence study or meta-analysis. Another important consideration is the assumptions that went into the decision analysis. The risk of stroke was estimated to be 6 percent, while the risk of subdural hematoma was estimated at 0.00023 per year, or a 1.4 relative risk from falling. These numbers appear to be at the extremes of possible estimates. Furthermore, the risk of falls was computed using elderly patients in community dwelling settings who were at no particular increased risk of falls. Finally, the article1 did not consider any serious bleeding consequences except subdural bleeding, such as intracerebral hemorrhage or hip fracture bleeding.
A more recent analysis2 of anticoagulation in patients with atrial fibrillation quoted a risk of stroke of 2.4 to 4.5 events per 100 patient-years for patients receiving anticoagulants, and 2.2 events per 100 patient-years for major bleeding events for patients receiving warfarin. This resulted in the conclusion that using war-farin rather than aspirin in 1,000 patients for one year would prevent 23 ischemic strokes while causing nine additional major bleeds.
Physicians must analyze the benefit-to-risk ratio for each patient, as we advised in our article.3,4 Dr. Hamrick's letter is a good reminder that a patient's age should not be used as the sole criterion for risk of falling, because patients over 65 years of age are most likely to receive the benefit from using anticoagulants. In patients with atrial fibrillation who have additional risk factors for falling, those whose chance of a significant fall can reach 78 percent (i.e., sedative use, cognitive impairment, disability of the lower extremity, palmomental reflex, gait disturbance, or foot abnormalities5), and especially those with multiple risk factors, we would still advise extreme caution in prescribing anticoagulation, especially with warfarin.