Medical Minute 8-22: Freezing Atrial Fibrillation

By: Vanessa Welch Email
By: Vanessa Welch Email

Michael Young has lived with atrial fibrillation since the nineties. His racing, irregularly-beating heart would come and go.

"Sometimes, it was when I was exercising. Sometimes, it's late at night," said Michael Young, Has Atrial Fibrillation.

It would leave him dizzy and short of breath, but that wasn't what bothered him most.

"For me, the worst thing has been this kind of psychological thing."

The fact that atrial fibrillation increases the risk of stroke kept Michael up at night. Mayo Doctor Doug Packer says medications can help, but they often stop working or have side effects. Patients need more options.

"If a patient's heart is beating rapidly and irregularly, it is incredibly obnoxious. It is, in fact, a real hit on their quality of life," said Douglas Packer, M.D., Cardiac Electrophysiologist at Mayo Clinic in Rochester, MN.

He's now using a new technique to fix the problem. First, a catheter is threaded up to veins in the heart, and a balloon is inflated. That balloon is cooled rapidly, which creates a freezing zone around the opening of the vein.

"If we can block off the electrical conduction from inside the vein to the rest of the heart, we can be successful in eliminating atrial fibrillation."

Study results show a 70-percent success rate.

"It's the first time that this kind of an approach has been used to eliminate atrial fibrillation. If they are in the 70 percent where it works, the results are dramatic."

Michael was in that 70-percent.

"A month now after the procedure, things are pretty quiet down there."

Now, he can focus on his work and stop worrying about his heart.

For more information on other series produced by Ivanhoe Broadcast News contact John Cherry at (407) 691-1500,


BACKGROUND: Atrial fibrillation (AF) is an irregular and often rapid heart rate that usually causes poor blood flow to the body. During atrial fibrillation, the heart's two upper chambers, the atria, beat chaotically and irregularly out of coordination with the two lower chambers, the ventricles, of the heart. Symptoms include heart palpitations, shortness of breath and weakness. Episodes of atrial fibrillation can come and go, or a patient may have chronic atrial fibrillation. Although atrial fibrillation itself usually isn't life-threatening, it is a serious medical condition that sometimes requires emergency treatment. (SOURCE:

TREATMENTS: Treatment for atrial fibrillation depends on how often the person has symptoms, how severe they are, and whether they already have heart disease. General treatment options include medicines, medical procedures, and lifestyle changes. One goal of treating AF is preventing blood clots from forming, which will lower the risk of stroke. Another goal is controlling how many times a minute the ventricles contract; this is called rate control. It’s important because it allows the ventricles enough time to completely fill with blood. Also, another goal is restoring a normal heart rhythm, which is called rhythm control. Rhythm control allows the atria and ventricles to work together to efficiently pump blood to the body. (SOURCE:

NEW TREATMENT: A new, minimally invasive procedure for patients living with atrial fibrillation has been approved by the FDA. During this procedure, called cryoablation, doctors insert a balloon catheter into a blood vessel in the upper leg and snake it through the circulatory system until it reaches the heart. Once in place, the cryoballoon is inflated, and extremely cold energy flows through the catheter, freezing the heart tissue that is causing the irregular heartbeat. This new freezing system is a more straightforward way to treat atrial fibrillation. By using the freezing ablation on very specific areas, doctors can get the blood to flow and stop the electrical signals that cause the arrhythmia. (SOURCE:

Dana Wirth Sparks
Mayo Clinic Department of Public Affairs
Rochester, MN


Douglas Packer, MD, a cardiac electrophysiologist from the Mayo Clinic in Rochester, MN, talks about a new treatment for atrial fibrillation.
What is atrial fibrillation?
Doug Packer: Atrial fibrillation is the very most common rhythm abnormality that we deal with. It’s the one where the upper chambers may be beating at three to four hundred times per minute. The good news is, is that the lower chambers will only beat at one hundred to say a hundred and eighty, two hundred beats per minute. So one of our jobs is in dealing with patients who have atrial fibrillation is to deal with fast heart rates. In other patients we’re actually trying to eliminate the abnormal heart rhythm altogether.
When you said three hundred to four hundred beats per minute what’s the normal range?
Doug Packer: Normal for the upper and lower chambers would be someplace between sixty and a hundred beats per minute. As long as that’s the heart rate then patients do very well. If the heart rate goes up to a hundred and fifty, or two hundred or two hundred and fifty beats per minute patients can feel palpitations or fluttering, they can feel chest tightness, they can feel very short of breath.
What is the danger with that, what can that lead to?
Doug Packer: The risk with atrial fibrillation is if the upper chambers are beating very, very rapidly, they don’t contract very well and if they don’t contract very well blood clot can form on the inner surface. The first risk is stroke risk. If the upper chambers are beating chaotically and if in fact the muscle is quivering blood clot can form. So if patients have high blood pressure or diabetes or they have underlying heart disease they can actually have that kind of blood clot that can pass to brain and create a stroke. So one of the foundations of treatment is some kind of blood thinner to prevent the stroke.

But you’re studying a different type why isn’t that always used? I’m assuming Coumadin, a drug like that.
Doug Packer: In most cases in patients who are over the age of say sixty five treating them with some kind of a blood thinner is very, very important to reduce the stroke risk. The other part of all of this though is symptoms, quality of life. If a patient’s heart is beating rapidly and irregularly it is incredibly obnoxious. Other than the stroke risk may not be particularly dangerous but it is in fact very symptomatic, it is in fact a real hit as it were on their quality of life.
Is there anything right now to treat the irregular heartbeat?
Doug Packer: There are a couple of different ways that we can treat this abnormal heartbeat. One of the ways that we treat is with a drug to keep the heart from going too rapidly. That affects a certain junction box in the middle of the heart, it keeps this upper chamber rate from passing down in to the lower chamber. Another approach which seems to work better for most patients is something to keep the heart in normal rhythm.
Which would be what?
Doug Packer: To keep the heart in normal rhythm we can use drugs that prevent this chaotic beating in the first place. Or if the heart does go into the chaotic beating pattern then these medications will get it back in to normal rhythm. There are drugs like flecainide or sotalol or dofetilide. Many patients are treated with amiodarone. But again the real reason for using these is to get the heart back in to normal rhythm so the patients don’t have the symptoms.
If medications are out there why would ablation be needed, why try ablation?
Doug Packer: The problem with drug therapy is it frequently doesn’t work. If you look at patients who have atrial fibrillation it can be a very difficult disease because the drugs only work in twenty to say forty percent of patients who have the rhythm problem. So over time we’ve developed something else, something else that will restore normal rhythm and keep it there. That’s ablation.
Tell me about this technique you’re using with the freezing and how does that work?
Doug Packer: For years we’ve used catheter approaches, where we thread a catheter up from the leg, across in to the left side of the heart which is really where this atrial fibrillation comes from. We’ve used heat from the tip of the catheter delivered to the tissue that creates a little scar that blocks the electrical impulses. What we’re doing now with the cold technique is to actually use a balloon catheter. Now that catheter is also threaded in to the heart, a balloon is inflated and then it’s positioned in to one of the veins around the heart which creates the atrial fibrillation. So if the balloon is positioned and then is cooled fairly rapidly it creates a freezing zone around the opening of that vein which is where these electrical impulses are coming from. So if we can block off the electrical conduction from inside the vein to the rest of the heart we can be successful in eliminating atrial fibrillation.
So by using cold or freezing the electrical impulse cannot travel through, it stops it from traveling through?
Doug Packer: It’s exactly right to think of this as blocking off electrical conduction. In a way it’s an insulator, an electrical insulator. And so using a balloon approach to do this creates that kind of ring where electrical impulses can’t travel and it does it with one delivery instead of having to move the catheter from one point to the next point to the next point to the next.
So is that how the heat is used, by moving the catheter around or is heat a different technique all together?
Doug Packer: The way that we do heating at this point is moving the catheter from one point to the next, to the next, to the next. There are a of couple of balloon systems that are being developed that would do the same one shot approach but they will be some time in development and in testing.
In research has the freezing produced similar results as the heat and it’s just a different way of doing it or is the freezing better?
Doug Packer: These different approaches haven’t really been compared head to head yet. So they’ve been looked at in single trials that only test the effect of say a balloon ablation versus drug therapy. Those are the ways that those studies are designed, in part because of an FDA mandate. So we have to compare one study with another as opposed to getting information within one single study. A recent large clinical trial demonstrated that the success rate for eliminating atrial fibrillation using this balloon approach was about sixty nine point nine percent. Now some of those patients needed to have a second procedure and some of those patients needed to be on other drug therapy. But the bottom line was about a seventy percent success rate, I think that that’s comparable with other approaches. The ease of doing this though with a single delivery makes this a nice option.
Is it the balloon or is it the freezing or are both new?
Doug Packer: The balloon approach has been tested using a variety of different models over the last ten years. This is the first time though that a balloon has been tested in large clinical trials in the US. It’s the first time that this kind of an approach has been used to eliminate atrial fibrillation. I’m sure that there will be other approaches that will be similar that will come along over time. But at present this is the one that has the capability and has the track record from the standpoint of a large clinical trial.
When you freeze it will this last or can the area that you froze somehow break down?
Doug Packer: One of the problems with any ablation is its effect can be temporary. Now if the freezing or the heating goes all the way through the tissue then it actually destroys some of those cells that are conducting the electricity. Now if it turns out that they heal and that’s something that can happen in maybe seventeen to thirty percent then you can have the same problem back. The other thing is that these large clinical trials follow patients only for a period of one year so we don’t know yet what’s going to happen after that time frame.
What does this treatment offer to patients, what is their life like before and what does this offer them?
Doug Packer: There are a lot of patients who have atrial fibrillation that can’t even feel it. They don’t even know it’s there even though the upper chambers are beating totally chaotically. Unfortunately there are many, many patients who have atrial fibrillation who feel every beat. And we’re talking about a hundred and sixty thousand new cases of atrial fibrillation each year in the United States and about two point five million patients that have this overall. So you’re looking at a large number of very symptomatic patients. Some of them simply feel fast heart beating, some of them feel a sensation almost like a panic attack, some get short of breath and some have chest tightness. But the ones that are symptomatic can be very symptomatic. So what’s the goal, eliminate the symptoms improve the quality of life.
What are you hearing from patients after they get this done?
Doug Packer: Regardless of the approach that we use, whether it’s a freezing technique or whether it’s a heating technique if they’re in the seventy percent where it works the results are dramatic from the standpoint of how they feel. So really the reason why we do an ablation is quality of life. We want to prevent strokes but they may still need a blood thinner to do that. But as far as quality of life goes the results can be very impressive. I have to admit that there are twenty to thirty percent where it doesn’t work and we have to do it a second time. This also works better in patients who have atrial fibrillation that comes and goes and comes and goes. This balloon approach has only been used in those patients not in patient who have a lot of underlying heart disease. So those are additional studies that need to be done over time.
Is there anyone with atrial fibrillation who is not a candidate for this?
Doug Packer: In making a decision about whom to treat one needs to know the kind of atrial fibrillation, whether it comes and goes, or whether it’s there and permanent and what the underlying disease is. The studies that have been done so far with balloon therapies are in patients who have paroxysmal atrial fibrillation that comes and goes and comes and goes without a lot of underlying heart disease. If patients have persistent atrial fibrillation and that persistent atrial fibrillation is in the setting of underlying disease, cardiac enlargement, past heart attack, heart failure and those sorts of things that takes a much more extensive procedure. And right now we’re using heat in a number of different locations to do that.
So there’s treatment for them this just isn’t the right treatment for them?
Doug Packer: This balloon approach hasn’t been used on patients that have extensive underlying disease. So this is one place like most of medicine where you need to stick with the data. You do a clinical trial, you find out if a device or a drug works and you go with your best results in appropriate patients.

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