EP Lab Digest - February 2008 - (Page 29)

FEBRUARY 2008 CRYOTHERAPY UPDATE 29 would agree that CryoCath’s Freezor catheter, which has a 4mm electrode, produces a very small lesion.We have not had much luck getting this to work at least in adults, although George I understand you still do use it some in children. GEORGE F. VAN HARE, MD: Yes, for sure. PETER J. WELLS, MD: The 6mm catheter generates a lesion that is maybe not quite as big as a 4mm RF lesion, but pretty similar in size and depth.The 8mm catheter almost certainly generates a lesion that is approximately the size achieved with an irrigated RF catheter, which is quite a bit bigger — that is something that is important to remember as far as lesion size.The next thing that is very important is time to effect. Cryo is a very precise technology, so you really want the catheter to be right on top of the target in order to have it work. So if the target arrhythmia disappears before -30 degrees — we’ll discuss examples of cryomapping in a few minutes — that is considered excellent, because you are in very close proximity to the arrhythmia target. If it doesn’t go away until you’re down to -70 degrees having been on for about 20 seconds, that is still okay, but once we get past 20 or 30 seconds, it means that it’s really kind of a marginal position, and the catheter should be repositioned and tried again. GEORGE F.VAN HARE, MD: I think also what people have found is that even when the lesion is acutely successful with time to effect beyond 20 or 30 seconds, that pathway is coming back. RAJJIT ABROL, MD: It’s not unlike RF, though. We also look at RF and the time that it takes for RF to work with eliminating accessory pathways.Very often if it takes more than 5 to 8 seconds for RF to work, then the chances are that pathway may recur as well. PETER J.WELLS, MD: Right.We have an example of this phenomenon. One of the two cases we did here in preparation for this is this concealed accessory pathway.The cryo is already on, and there is a white hash across the bottom third of the screen; we’ve just induced SVT, which is going down the AV node and up this left lateral pathway. Now we’re out to 30 seconds, then 40 seconds, and we didn’t really have an effect. So that is something that needs to be noted. GEORGE F. VAN HARE, MD: The key point to keep in mind is that when you’re at a spot and you’re not getting success within 20 or 30 seconds, you don’t need to go the full four minutes. In fact, you should come off, reposition your catheter and try again. RAJJIT ABROL, MD: Here is the important thing to note between the 4mm and 6mm catheters: if you’re doing pediatric EP, you have the mapping option available with the 4mm catheter where the temperature will go to -30 degrees; stay there, you can see time to effect, and if you’re in a good spot, then put in a full lesion, which is what I’m sure you do with your kids.As opposed to using the 6 or the 8, as we’ve described, by doing 20- or 30second cycles, finding an endpoint, and targeting that endpoint. If you find that endpoint in the first 30 seconds, then continue with the full four-minute lesion, and thaw and refreeze at the same spot. PETER J. WELLS, MD: Right. We should also mention the importance of single versus double freeze cycles, either for lesion depth or lesion diameter. If the time is short, then refreezing does significantly increase the lesion size, whereas if time is long, there tends to be a slight increase in lesion volume, but not dramatic. One important thing to note, which Raj discovered here at Baylor, was that if you’re in the same place, the refreeze time to nadir temperature is much faster than on the initial freeze.We think that this initially tells you that you’re at the same site, which is absolutely where you want to be. RAJJIT ABROL, MD: George, how long do you wait between freezes and refreezes as many people have different timeframes? GEORGE F.VAN HARE, MD: Thirty seconds. See ROUNDTABLE page 30 http://www.ascenths.com/cardiology http://www.ascenths.com http://www.ascenths.com

Table of Contents Feed for the Digital Edition of EP Lab Digest - February 2008

EP Lab Digest - February 2008 Creating the U-M Center for Arrhythmia Research: Interview with José Jalife, MD Texas Cardiac Arrhythmia Institute and St. David’s Medical Center Launch State-of-the-Art Training Center Contents Letter from the Editor Spotlight Interview: Caritas St. Elizabeth’s Medical Center 10-Minute Interview: Sue Deck, BS, RN, RCES Keeping Pace With a Blog Roundtable Discussion on Cryoablation Procedures Email Discussion Group: February 2008 Events Calendar Industry News and Products Classifieds Advertisers Index

EP Lab Digest - February 2008

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