Managing atrial fibrillation in elderly people

Chronic atrial fibrillation is the commonest arrhythmia seen in clinical practice. Not only does it cause increased morbidity and mortality among affected individuals; it also adds a significant burden to healthcare costs. The prevalence of atrial fibrillation increases steadily with age (from 0.5% of those aged 50-59 years to 8.8% of those aged 80-89 years), as do the associated risks.¹ Even in the absence of rheumatic heart disease, there is a sixfold increase in thromboembolic phenomena, and atrial fibrillation accounts for up to 36% of all strokes in elderly people.² It is the commonest arrhythmia requiring admission to hospital and is the primary diagnosis in 20% of all new outpatient cardiology appointments. As the population ages so these effects will be exacerbated.

Patients who develop atrial fibrillation are likely to present to their general practitioner with palpitations, shortness of breath, and fatigue. The loss of atrial systolic function can reduce cardiac output by up to 50%, especially in those with coincident ventricular impairment.³ Older patients, who are particularly vulnerable to these effects, may develop exercise intolerance, which is reversible when sinus rhythm is re-established,⁴ or may decompensate and develop frank heart failure.

The most effective way of minimising the increased thromboembolic risk and treating symptoms is to return the heart rhythm to sustained sinus rhythm by electrical or chemical cardioversion. Cardioversion is safe, with an estimated risk of thromboembolism of <1%, even among those at highest risk,⁵ which compares favourably with that seen in chronic atrial fibrillation. Cardioversion is most effective when delivered soon after the onset of atrial fibrillation because of structural changes in the atria which perpetuate the arrhythmia.⁶,⁷ Moreover, when the arrhythmia has been present for less than 48 hours cardioversion is safe without prior anticoagulation.⁸ Early diagnosis and treatment are therefore important, but how can they be achieved? Once the condition has been identified in the community, assessment in hospital is essential since cardioversion remains a secondary care service.

Large series have shown initial success rates for cardioversion of around 75%-91% in patients of all ages. Factors shown to reduce the likelihood of successful cardioversion include increased duration of arrhythmia (over 12 months), increased left atrial diameter (>45 mm), and heart failure of New York Heart Association class II or greater. Most studies found that increased age itself had no independent effect on the success of cardioversion.⁹ Restoration and maintenance of sinus rhythm after successful cardioversion may be enhanced by the use of antiarrhythmic therapy,¹⁰ though optimal drug therapy has yet to be determined.

Failing conversion to sustained sinus rhythm, antithrombotic treatment with warfarin reduces the risk of stroke in patients with atrial fibrillation by about 70%.¹¹ Many physicians do not use anticoagulation in elderly people, perceiving the risk:benefit ratio to be too high, and continue to prescribe aspirin instead,¹² despite its lack of efficacy in this age group.¹¹ Although anticoagulation in those aged over 75 is associated with greater risk when the international normalised ratio (INR) is maintained at 2.0-4.5, both the BAATAF and SPAF III trials showed that anticoagulation to a lower INR of 1.5-3.0 is both safe and effective in reducing the risk of stroke in this age group.¹¹ Starting warfarin therapy in the community is logistically difficult, requiring daily visits for blood sampling, frequent communication, and dose adjustments by patients, all of which are more difficult in elderly people. New low dose starting regimens for the outpatient initiation of warfarin, particularly in elderly patients with atrial fibrillation, should help facilitate its more widespread use.¹³

Wide variations exist in the current management of elderly patients with atrial fibrillation.¹² Surveys of use of anticoagulation show consistently that elderly people are less likely to receive anticoagulants than younger ones on the grounds of age alone, even when the risk:benefit profile seems favourable.¹⁴ Atrial fibrillation in an elderly patient seems to be accepted by many clinicians as a norm and is not treated aggressively. The ideal management of atrial fibrillation is cardioversion to sustained sinus rhythm, which both abolishes the increased thromboembolic risk and obviates the need for anticoagulation, or, failing this, adequate long term anticoagulation, which should be carefully considered in all patients regardless of age. In practice, even though the ideal may be unachievable, many elderly patients with atrial fibrillation remain suboptimally treated.