Tuesday, March 07, 2006

Alternatives to warfarin for atrial fibrillation.

This post was inspired by a query provided at Dr Helen.

Marc who is 66 yrs old asks

I have atrial fibrillation but I don't want to be on warfarin the rest of my life. Discuss ablation or any new procedures and their likelihood of success. I did not respond to cardioversion at age 63.

We note that Marc is 66 years old and there is an obvious danger of coronary artery disease. This does make a slight difference in management. Let us assume that his atrial fibrillation is not CAD related, nor metabolic disease related, like thyrotoxicosis.

It's understandable that he may not wish to be on warfarin. The latest clinical trails show that there are two strategies to managing atrial fibrillation, rhythm control (trying to get them to go back to sinus rhythm with drugs and cardioversion) and rate control with warfarin to prevent strokes. On a very personal note, any 66 year old patient I have with atrial fibrillation will be advised rate control and warfarin. I am not a believer in rhythm control.

Having said that, what about catheter ablation? We must note that this method gained much popularity after Tony Blair underwent it sometimes in 2004. However, it is still largely experimental and has yet to reach mainstream cardiology as the method is undergoing evolution.

In understanding ablation you will need to understand that atrial fibrillation is essentially chaotic atrial rhythm, the sources of the atrial ectopics, running about 300-500 rate, may arise from varied foci, though the paroyxsmal ones tend to come from around the pulmonary vein. It is true that no matter how chaotic the atrium may beat, all the atrial impiluses have to pass through the AV node, which acts as a gatekeeper for impulses coming into the ventricle, so that the ventricle never beat 500/min. The AV node filters out the excesses so that the ventricle beats at maybe 100/min. We have quite a variety of ablation technique to choose from.

The easiest one, is to ablate the AV node and implant a pacemaker so that the ventricular rate can be controlled at 60-70/min with rate reflex control. We can even implant a DDIR pacer for better quality of life. However, these patients may still require warfarin.

The French at Bordeaux pioneered the pulmonary vein isolation technique sometime in 1994. This is one of the better technique, with a success rate of 85% almost. It does require some skill to do, meaning the success rates cannot be transfered easily to a US or Malaysian center, where the procedure is not performed as often. The other center doing this often is in Taiwan. Isolating the pulmonary vein does reuire special imaging techniques and has it's own set of risk, including strokes, the usual catheterisation complications, and also pulmonary vein stenosis causing pulmonary edema.

The Italians at Milan are using a technique called anatomically based circumferential pulmonary vein ablation. This is essentially what the Bordeaux experts are doing except with a wider pulmonary ablation circle so as to lessen the risk of pulmonary vein stenosis. The success figures are not as good.

Of course there is always the surgical "maze" operations, that can be done. Much more invasive and may not be as good.

That's how the matter currently stands. Looking at the overall picture, in 2006, rate control with a safe dose of warfarin, may be your best option, unless you have bleeding risks. In that case it may be best to link up with Bordeaux or Taiwan to have this done.

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2 comments:

Jan said...

When you state that you opt for rate rather than rhythm control is this for all patients or do you take into account symptoms?
I have had patients who, despite being rate controlled, still felt fatigue, DOE and/or had reduced exercise capacity while in afib. And they did better once undergoing cardioversion.

Are any of the thrombin inhibitors available in Malaysia? We are getting ready to start a clinical trial on dabigatran. Curious if you have any clinical experience with this class of drugs.
Thanks.

Dr Ng Swee Choon said...

http://hmatter.blogspot.com/2006/03/rate-control-vs-rhythm-control.html