Boston conference offers hope for ‘A-fib epidemic’
The U.S. is facing “an epidemic of atrial fibrillation,” according to Peter Friedman MD, PhD, FACC, FHRS, a Cape Cod Healthcare cardiac electrophysiologist who recently attended the 28th Annual International AF Symposium in Boston. “There may be five million new patients identified in this country every year.”
In a normal heart rhythm, all of the cells in the two upper chambers, the two atria, are activated simultaneously, he said. The atria contract together as a unit, and that forces blood down into the lower chambers, the ventricles.
With atrial fibrillation – often referred to as “A-fib” – the electrical impulse in the upper chambers is disorganized. “Instead of all the cells working in unison, each cell is firing independently of every other cell,” he said. “If you actually look at the atria in an animal or an open chest human model, with normal rhythm you can see the atria contracting. When you're in atrial fibrillation, you look at the atria and it looks like a bag of worms. They're just quivering. There’s no organized contraction.”
The result is that the heart is less efficient leading to shortness of breath, inability to exercise and retention of fluids.
“Patients also may feel palpitations,” he said. “They can feel their heart beating fast and irregularly.”
A-fib also can cause blood to stagnate in the heart. “Then when the rhythm goes back to normal, or even if it doesn't go back to normal, those blood clots can break loose and cause a stroke,” he said. “If you look at all patients with what we call ischemic stroke, that is stroke due to loss of blood supply to one area of the brain, probably 40 percent or so of those patients have their stroke as a result of atrial fibrillation. That's the reason why anticoagulant therapy is so important to prevent stroke.”
Aging Population and Obesity
The increasing prevalence of A-fib is partly due to an aging population, said Dr. Friedman, but there are other factors.
“Morbid obesity certainly increases the risk of developing AF, and we have an obese population,” he said.
Sleep apnea, excess alcohol use and inadequate treatment of hypertension also play a role in why the arrhythmia is increasing in frequency.
“If you modify those risk factors, theoretically it should help. Has it been shown statistically? Actually not, but we still encourage people to lose weight,” Dr. Friedman said. “We still try to identify sleep apnea and treat that if it’s identified. Aggressive management of hypertension. Reduction of alcohol consumption. All those things are theoretically advisable and worth pursuing, but you can’t really say in a given patient, if you stop drinking, your AF’s going to go away. It’s not a one-to-one relationship.”
Encouraging News
There was some encouraging news at the Boston conference, he said.
“It is exciting that nationally and internationally, there’s so much interest in improving techniques and not just standing pat on what we have.”
One area of ongoing research is an attempt to improve ablations, which are small burns or freezes that cause some scarring on the inside of the heart to help break up the electrical signals that cause irregular heartbeats.
“The goal is to selectively destroy those cells that are firing rapidly and drive the heart into AF,” he said. “Radiofrequency ablation and cryoablation are reasonably effective, but they have limitations. If you burn or freeze too much, you can cause damage to other structures.”
A new technology called pulsed field ablation involves delivery of very brief, but high-energy voltage across the cell that causes the death of those cells.
“The interesting thing is that myocardium, the heart muscle cells, are much more prone to pulsed field ablation than other cells like neurons, skeletal muscle, GI tract,” Dr. Friedman said. “You can apply pulsed field ablation to the heart and damage the target cells with much less risk of collateral damage to distant tissues."
“Clinical trials for pulsed field ablation are underway in the U.S. and Europe, but I think it’ll be at least another year or two before it’s approved for use. That’s clearly the wave of the future. It will be at least as effective as the methods we use now, and probably safer.”
Blood Thinner Alternatives
Another topic of great interest at the Boston meeting, he said, was an alternative to blood thinners to prevent stroke.
“If patients are on a blood thinner and they have bleeding, there's an alternative called “left atrium appendage closure.” The left atrium appendage is like a little windsock that's attached to the left atrium, but it's really out of the mainstream of the circulation in that chamber. In patients who develop AF, the blood that stagnates tends to stagnate most strikingly in the appendage because it's out of the way of the main flow of blood. It's been estimated that among folks who develop a blood clot and a stroke from AF, 90 percent of those clots come from the atrial appendage.
“There are now devices that can be implanted through a catheter into the appendage, which prevent blood from getting into the appendage. One is a device called the Watchman, which is like a little umbrella that sits in the appendage. The other one is called the amulet, which is a different design, but also apparently just as effective. Not every patient is suitable for one or the other. It depends on the anatomy of the appendage. But there was a lot of interest in reviewing the results of these appendage-closure devices in terms of their reduction in stroke risk.”
