Devices & Diagnostics

Atrial fibrillation registry, new trial will test old vs. new ablation methods

I guess I’ve now become an “old dog” in medicine.  The residents look younger, the fellows, sharp and trim, and some of my contemporary physicians, like well-worn time-pieces, are beginning to complain of sore knees, backs, and declining vision.  And then there’s the nocturia…   Ugh. But for those of us who’ve been around the block […]

I guess I’ve now become an “old dog” in medicine.  The residents look younger, the fellows, sharp and trim, and some of my contemporary physicians, like well-worn time-pieces, are beginning to complain of sore knees, backs, and declining vision.  And then there’s the nocturia…   Ugh.

But for those of us who’ve been around the block a bit, there remains the constant desire to remain up-to-date, novel, even original.  So we try new new things.  Sometimes they work for us, sometimes they don’t.  One thing’s for certain, however, it’s much harder for salespeople to sway us old dogs, because by now, many of our habits are based on past experiences, not press releases.

Take for instance, three-dimensional mapping in the EP lab.  It’s cool stuff: electrodes or magnets are arranged around the patient to create an X, Y, Z coordinate system of sorts, and a catheter is moved about inside the coordinate system to locate structures, map arrhythmias, and to facilitate movements of catheters without x-ray guidance.   The pictures are multicolor and stunning.  They are also typically studded with little circular dots placed in locations chosen by a technician to look stunning.  Sometimes, this technology makes a critical difference in the outcome of a case.  Other times, it’s probably a waste of money, since some arrhythmias are defined by very well-defined anatomic locales whose need for precisely localized ablation lesions are simply not necessary.

So I was surprised to hear one industry rep remark that “every” new fellow uses 3-D mapping systems these days to ablate anything.  Maybe he was selling his system, maybe not.  But I wondered:  Really?  Even for something as straightforward as a typical atrial flutter ablation?  “Yeah,” he said.  “They don’t know how to map the old-fashioned way like you (older) guys do.”

Maybe that’s a good thing. Maybe not.  There’s much more to successful ablation than locating a catheter in three-dimensional space or placing a dot on an artificially-created geometric surface.  Yet these days, I rarely hear people speak about catheter stability, injury current, unipolar electrograms, or polarity reversal any more.  Instead, when using these 3-D mapping systems, catheter ablation it sounds more like a game of connect-the-dots: “You’ve got a gap over there.”

So too, with our ablation technology.

This week I finally broke down and tried irrigated ablation catheters for ablation and my experience?  Underwhelming.  There was extra tubing, a stiff catheter, fluid burdens I never had to think about before, and an inability to have any surrogate for catheter contact (such as tip temperature).  In return, I received only a promise of larger lesions, simpler ablation before the case started yet found myself struggling to complete a relatively simple procedure.  Certainly there was plenty that was new and unfamiliar: new catheters, new technology, new anecdotes to remember.  But at the end of both cases I performed, I found myself moving back to a conventional non-irrigated ablation catheter to achieve success.  Needless to say, this ol’ dog wasn’t impressed.

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Now I know there are irrigated ablation catheter proponents out there.  They sing its praises and wouldn’t perform catheter ablation with anything but this technology.  But I wonder how many of them ever looked at the physiology of what they’re doing.  Years ago, I performed sinus node ablation in dogs with 50 watts of power using an 8mm tip conventional radiofrequency ablation catheter equipped with temperature feedback.  I saw what that much energy did to the dog’s heart… and surrounding lungs.  I will never forget that finding.   My practice in man was forever changed as a result of that opportunity.  I find it hard to believe we need more energy than that if there is good catheter contact.

And yet, I now see FDA-approved 100-watt RF generators now and irrigated-tip ablation catheters capable of creating steam pops deep in tissue while having nice cool endocardial tip temperatures displayed that provide an artificial level of reassurance to our younger operators.  I know there’s a reason these technologies were developed: influential doctors in our EP community demanded they be developed and industry responded.  Skill levels of operators are different. It was new and innovative.  It promised better outcomes while being acceptably safe, yet without so much as a lick of real-life multi-center case-based post-market proof.

So when I see the relatively high complication risks of atrial fibrillation reported recently, I wonder if some of those complications were from this push to higher power, irrigated-tip ablation catheters capable of making ridiculously larger, deeper ablation lesions in our rush to expedite the procedure couched on the unproven hope that with larger lesions, the need for repeat ablation would be reduced.  Is it?  Are we creating more problems than those we are hoping to solve?  Truth is: we don’t know.

Which is exactly why we need an atrial fibrillation registry.  It’s also why we need studies like the prospective, randomized atrial fibrillation ablation trial like the CABANA (Catheter Ablation versus Antiarrhythmic Drug Therapy for Atrial Fibrillation) trial to begin to answer such complicated questions.  Whether there will be enough data for subgroup analysis of irrigated tip ablation catheter from non-irrigated ablation technologies in CABANA remains to be seen.  But at least the CABANA investigators didn’t require a particular form of energy delivery for the ablation arm of the study.  Will there be value in such a subgroup analysis?  It will depend on the numbers.

At least this old dog remains happy he can contribute to this arm of the ablation trial and hopefully remain innovative and creative in the years ahead while still practicing on the basis of my experience.

And who knows, maybe one day, we’ll make catheter ablation safer for our patients as a result – you know: the old fashioned way.

Westby G. Fisher, MD, FACC is a board certified internist, cardiologist, and cardiac electrophysiologist (doctor specializing in heart rhythm disorders) practicing at NorthShore University HealthSystem in Evanston, IL, USA and is a Clinical Associate Professor of Medicine at University of Chicago's Pritzker School of Medicine. He entered the blog-o-sphere in November, 2005. He writes regularly at Dr. Wes. DISCLAIMER: The opinions expressed in this blog are strictly the those of the author(s) and should not be construed as the opinion(s) or policy(ies) of NorthShore University HealthSystem, nor recommendations for your care or anyone else's. Please seek professional guidance instead.

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