The rising rate of AF
A decade ago, atrial fibrillation was considered an emerging epidemic – has it now reached its peak? Kate Woods looks at the rise and rise of AF.
TEN years ago, GPs were managing atrial fibrillation (AF) at a rate of 0.6 per 100 encounters, or about 578,000 times a year,1 but when it came to hospital admissions, heart failure was more often the culprit.
But the tables have now turned.
GPs are managing the condition at a rate of 1.3 per 100 encounters, or about 1.5 million times a year.1
And when it comes to hospital admissions, they are 200% higher than they were 17 years ago and they are exceeding those for heart failure.2
The annual cost of AF to the Australian economy is about $5200 per person per year, more than double that of obesity and higher than the per-person cost of cardiovascular disease and osteoarthritis.3
It has been estimated that about 2% of the general population and 5% of the population older than 65 years have AF. But as cardiologist Professor Ben Freedman warns, this doesn’t take into account those people with asymptomatic AF and consequently, we may actually be underestimating the problem.
“AF is now a very common condition – I think the lifetime risk is about one in four – so it affects many people,” says the University of Sydney and Concord Hospital professor.
“Unfortunately, the community is completely unaware of the condition, so we have a lot of work ahead of us.” AF is the most common arrhythmia and is associated with significant morbidity and mortality.
This includes a four- to five-fold increased risk for stroke, a doubling of the risk for dementia, a tripling of the risk for heart failure and a 40-90% increase in the risk for overall mortality.4
Many causes of the condition are well known and include long-standing high blood pressure; coronary, valvular and congenital heart disease; excess-ive alcohol consumption; and hyperthyroidism.
More recently, however, AF has been linked to medical conditions often associated with poor lifestyle and behavioural habits such as obesity.
“We know AF is a disease of the elderly, we know we have an ageing population, and we know therefore that we should be seeing more of it,” Professor Freedman says. “But as well as the elderly, we are seeing an increase in incidence rates in the younger age groups, and we believe the reasons for this are the rising levels of obesity, diabetes, lack of exercise and sleep apnoea.
“It’s a big concern.”
RATE VERSUS RHYTHM
Currently, there are two broad strategies used to manage AF: rate control, when AF is allowed to continue and medication is given to control ventricular rate; and rhythm control, when treatment is directed towards restoring and maintaining sinus rhythm.
“There is controversial data to suggest one strategy may be superior to the other, but the bottom line is none of us really know,” says Professor Prash Sanders, director of cardiac electrophysiology at the Royal Adelaide Hospital and chair of cardiology research at the University of Adelaide.
“Certainly from a patient perspective, being in normal rhythm... is better... it’s just more efficient.”
Along with cardioversion, antiarrhythmic agents are often used to keep patients in normal rhythm. But as most of the antiarrhythmic agents have toxic side-effects, including sudden cardiac death, Professor Sanders says many doctors are “nervous about using them”.
In those patients whose AF recurs despite cardioversion and ongoing antiarrhythmic medication, interventional treatment is the alternative.
“Ablation is an invasive procedure that is costly, but it does have good results and has been proven to improve quality of life,” Professor Sanders says.
“There is also some data to suggest it will also reduce risk of stroke and some data to suggest it improves survival, but in both cases that data is not definitive.”
The other treatment often prescribed to patients with AF is anticoagulant therapy, particularly warfarin. In fact, warfarin was the most commonly prescribed medication for AF in 2008-09, used at a rate of 50 per 100 AF problems managed.1
“I think anticoagulation is a most important treatment, but it does come down to a question of whether the risk of stroke outweighs the risk of actually using warfarin, which in itself can cause stroke in about 0.5% of people per year,” Professor Sanders says.
“But there are some new drugs coming out that may eventually replace warfarin, and new technology that may become more widely used in the future.
“This new technology – recently introduced in Australia – involves blocking off the atrial appendage in a bid to reduce stroke risk. One study has shown it may actually be equivalent to warfarin in a subgroup of patients.”
RISK FACTOR APPROACH
When it comes to treatment and the future, however, Professor Freedman believes we may need to focus our attention on risk factors, rather than existing therapies, to curtail the problem.
“I don’t think that electrical operations will be the answer for AF in the elderly in the future. There will be too much of it, and I don’t think it will be that amenable.
This means “we will be still faced with drug therapy, which is not completely satisfactory and will never be completely free of side-effects.
“Instead, I think we will have to place a lot more attention and focus on the things that predict the onset of AF and how we can prevent onset rather than waiting until it happens.”
Perth cardiologist Dr Michael Davis agrees a change in focus is needed to ensure incidence rates are brought under control, but remains pessimistic control will occur.
“Quite a few studies have shown other therapies such as statins, ACE inhibitors and angio-tension receptor blockers, even fish oil, can have an impact,” he says.
“And some research from Adelaide [shows] that we might be able to reduce incidence by helping people drastically modify their lifestyle: lose weight, eat healthier, drink less alcohol, exercise more and so on.”
But, Dr Davis, who is the director of cardiology at Perth’s Hollywood Private Hospital and a member of the Atrial Fibrillation Association’s medical advisory committee, says there is never going to be a magic bullet.
“And I am, unfortunately, somewhat pessimistic. I actually believe that despite all our efforts, we are going to see the incidence of atrial fibrillation continue to rise well into the future.”
1. Australian Family Physician 2010;39(7):461
2. The University of Adelaide (30 August 2010) “Heart disorder hits national epidemic proportions”. Press release. Retrieved 4th September 2010. www.adelaide.edu.au/news/print41021.html
3. PricewaterhouseCoopers (2010) The Economic Costs of Atrial Fibrillation in Australia. www.strokefoundation.com.au
4. Circulation 2009;119:606-618