Fall risk and anticoagulation for atrial fibrillation in the elderly: A delicate balance

Stroke risk

The CHADS₂ score was, until recently, the most widely used method for assessing stroke risk in patients with nonvalvular atrial fibrillation. CHADS₂ assigns 1 point each for congestive heart failure, hypertension, age ≥ 75, and diabetes, and 2 points for prior stroke or transient ischemic attack (range 0–6 points). Annual stroke risk based on the CHADS₂ score ranges from about 2% to about 18% (Table 1).¹¹

The CHA₂DS₂-VASc score,¹² a modification of CHADS2, appears to assess the risk of stroke more accurately, especially at the lower end of the scale, and recent guidelines for managing atrial fibrillation recommend using the CHA₂DS₂-VASc algorithm¹³. CHA₂DS₂-VASc is similar to CHADS₂, except that it assigns 1 point for ages 65 to 74, 2 points for ages 75 and older, 1 point for vascular disease (coronary artery disease, peripheral arterial disease, aortic aneurysm), and 1 point for female sex (Table 1).^11,12

For both CHADS₂ and CHA₂DS₂-VASc, systemic anticoagulation is recommended for patients who have a score of 2 or higher. Our patient’s CHADS₂ score is 2, and her CHA₂DS₂-VASc score is 4, corresponding to an annual estimated stroke risk of 4% with both scores (Table 1). Note, however, that the CHA₂DS₂-VASc score provides more information at the lower end of the spectrum.

Bleeding risk

Several scoring systems for assessing bleeding risk have also been developed (Table 2).^14–16 Of these, the HAS-BLED score has come to be used more widely in recent years.

Perhaps not surprisingly, some of the same factors associated with risk of stroke also predict increased risk of bleeding (eg, older age, hypertension, prior stroke).14 Note, however, that history of falling or high risk of falling is only included in one of the bleeding risk models (HEMORR₂HAGES).¹⁵

These tools are somewhat limited by their lack of consideration of concomitant antiplatelet therapy (only included in HAS-BLED) or history of bleeding (only ATRIA¹⁶ considers major and minor bleeding, HEM-ORR₂HAGES does not specify bleeding severity, and HAS-BLED only considers major bleeding). The models also fail to include medications such as antibiotics or antiarrhythmic agents, which are commonly used by older patients with atrial fibrillation and may increase bleeding risk. In addition, all bleeding risk scores were developed for warfarin, and their applicability to patients treated with the newer oral anticoagulants has not been established.

At the time of presentation, our patient has a HAS-BLED score of 2 (1 point each for age and hypertension), placing her at intermediate risk of bleeding.¹⁴

Fear the clot, not the bleed

So how does one balance the risk of stroke vs the risk of bleeding? An adage from the early days of thrombolytic therapy for acute myocardial infarction was “fear the clot, not the bleed.” In other words, in the present context the consequences of a thrombus embolizing from the heart to the brain are likely to be more devastating and more permanent than the consequences of anticoagulation-associated hemorrhage.

Support for this view is underscored by a 2015 study by Lip et al,¹⁷ who examined stroke and bleeding risks and outcomes in a large real-world population of patients age 75 and older. The analysis included 819 patients ages 85 to 89 and 386 patients age 90 and older. The key finding was that the oldest patients derived the greatest net benefit from anticoagulation.

Moreover, the Canadian stroke registry of 3,197 patients, mean age 79, showed that advanced age was a more potent risk factor for ischemic stroke than it was for hemorrhagic stroke.¹⁸

Thus, the benefit from anticoagulation in patients with atrial fibrillation does not appear to have an upper age limit.

A shared decision

But that is not the end of the story. Since there is tension between benefits and risks with either approach (ie, anticoagulation or no anticoagulation), it is important to discuss the issues and options with the patient and relevant caregivers. Most older adults have witnessed the ravages of stroke in a friend or relative, and a recent study showed that most would be willing to accept a modest risk of bleeding to prevent a stroke.²³

However, this is ultimately a personal decision for each patient, and in accordance with the principle of patient autonomy, the patient’s expressed wishes should be honored by using a process of shared decision-making.

Which anticoagulant?

Finally, what about the choice of anticoagulation? The complexities of using warfarin, including its narrow therapeutic range and myriad interactions with other medications and foods, can make it a less appealing option for both patient and provider.

We recommend a novel oral anticoagulant as first-line therapy in the absence of contraindications such as severe renal insufficiency, and prefer apixaban because it is the only agent shown to be superior to warfarin with respect to both stroke prevention and bleeding risk.²⁴

Important disadvantages of the novel oral anticoagulants include their higher cost and lack of an effective antidote in the event of clinically significant bleeding (with the exception of idarucizumab, which was recently approved for reversal of serious bleeding associated with dabigatran), issues that may be of particular concern to older adults. While there is no therapeutic range to monitor for the newer agents, more frequent monitoring for occult anemia may be needed.

Thus, selection of an anticoagulant should also be individualized through shared decision-making.

Is aspirin alone an alternative?

And what if the patient chooses to forgo anticoagulation? In that case, aspirin 75 to 325 mg/day may seem reasonable, but there is scant evidence that aspirin is beneficial for stroke prevention in patients with atrial fibrillation in this age group, and aspirin, too, is associated with an increased risk of bleeding.²⁵

As a result, current US and European guidelines recommend a very limited role for aspirin as a single agent in the management of atrial fibrillation.²⁶ The joint 2014 guidelines of the American Heart Association, American College of Cardiology, and Heart Rhythm Society give aspirin a class IIB recommendation (ie, it “may” be considered), level of evidence C (ie, very limited) for use as an alternative to no antithrombotic therapy or systemic anticoagulation only in patients with a CHA₂DS₂-VASc score of 1, thereby excluding all patients age 75 and older.¹³

In most cases, aspirin as sole prophylaxis against stroke in atrial fibrillation should be avoided in the absence of another indication for its use, such as coexisting coronary artery disease or peripheral arterial disease.