Study reports advance in ablation technique

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Quote

....New research is aimed at localizing the tissue source of the disorganized electrical impulses that generate AF. Our understanding of AF is evolving, and the source of AF is proving to be more focal than had been previously believed, lending itself to more precise physiological (as opposed to anatomical) mapping and consequent targeted ablation procedures.1

Researchers collaborating at the University of California-Los Angeles and the University of Indiana have studied the use of conventional ablation techniques either with or without focal impulse and rotor modulation (FIRM).1 FIRM is a guidance technique that utilizes physiological mapping to identify the location of spiral waves (rotors) and focal impulses that are responsible for generating the aberrant rhythm of AF.1 Once mapped, areas containing pathological focal impulses and rotors can be targeted precisely using conventional ablative techniques.

Preceding the ablative procedure with physiological mapping allowed the investigators to shorten the length of the procedure; while AF ablation can typically take hours, AF ablation utilizing the FIRM technique takes only minutes (average time, 2.5 minutes).1 Additionally, the precision afforded by FIRM mapping resulted in a significant decrease in the area and the volume of tissue destroyed by the ablation catheter's radiofrequency heat waves.

In terms of outcomes, the FIRM-guided procedures demonstrated an impressive increase in the 2-year success rate of the ablation. Research comparing FIRM to non-FIRM ablation revealed that 82.4% of those undergoing FIRM-guided ablation remained AF-free, while about 55% of those undergoing ablation without FIRM guidance reverted back to AF within 2 years of the research protocol.1 Overall, preceding conventional ablation with FIRM mapping appears to confer an 86% improvement in patient outcomes over non-FIRM-guided ablation.....

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Lone paroxysmal vagal atrial fibrillation. Age 62, female, no risk factors. Autonomic instability since severe Paxil withdrawal in 2004, including extreme sensitivity to neuro-active drugs, supplements, foods. Monthly tachycardia started 1/11, happened only at night, during sleep, or when waking, bouts of 5-15 hours. Changed to afib about a year ago, same pattern. Frequency increased over last 6 months, apparently with sensitivity to more triggers. Ablation 6/27/13 by Steven Hao.

Thanks for the report Iatrogenia, but be aware that this not recent news and is still far from proven,

This report is nearly two years old now, and the excitement over FIRM has muted considerably. It is a modest resolution system at this point and the jury is still out whether it may or may not add any real value over careful 3d EAM mapping in experienced hands. This hype of a 2.5 minute ablation as an 'average' is nonsense. This is without isolating any PVs and only addressing one rotor on occasion to get an immediate termination of AF from said rotor, which says little about how lasting that is.

One of the big question marks with the Topera mapping system is their resolution with less sensors at 64 compared to the higher resolution of say Cardio-Insight vest non-invasive map giving 252 sensors and a whole heart view. With FIRM they claim to find such a large percentage of stable rotors, however the higher resolution the phase-mapping system is capable of imaging, the less the number of truly stable rotors you find. And the more which appeared stable on lower resolution imaging systems like Topera, the greater the number of those that appeared to be stable are found to wander and/or be transitory in a more detailed view and analysis! So which is it?? There are still many holes to fill and Topera let the initial hype game run far ahead of their reality, whatever their eventual real world contribution turns out to be.

One researcher thought, "well maybe the FIRM system is on to something by using lower resolution and maybe we only muddy the water by trying to view this signals with finer resolution, so he tested that hypothesis and conclusively showed that was not true and that there was no advantage and only a drawback to using lower resolution phase map imaging compared to higher resolutions systems.

Dr. Jose Jalife has probably the highest resolution system there is which uses multiple color optical cameras all focused at the heart in his rotor and AFIB very interesting research at University of Michigan and can image this rotor singularity points to sub-micron scale and he has found a wide array of occasional stable rotors and very many highly transitory rotors often lasting less than half a cycle length and/or meandering all over the left or right atrium and bouncing off ridges, orifice openings, scars, valve or vein ostiums etc etc.

So which do you ablate?? The is truly no consensus at all about that and very strong debate whether this will turn out to be much more than another way to look at a generally similar phenomena as views via a different mechanism as CAFEs. After all, so far the one consistent thing found with rotor research is that they do play a role in AFIB mechanism and that we have very much to learn before these systems are ready for front line EPs to include them in their EP labs.

The bottom line is those stats in that report are highly misleading and they include a good PVI ablation in addition a firm hunt for non-PV sources with FIRM tracking down the most prominent focal trigger it can find and then ablating that compared to ONLY a rather amateur level PVI with the terrible success rates they quote for the PVI only control group.

If FIRM people want to talk turkey, compare their PVI and FIRM paroxysmal ablation to say a Natale, Bordeaux or University of Penn to name but a few quality approaches to ablation, that does a professional PVAI or PVI PLUS tracking down extra-PV signals as well and compare those results over two years with independent review. Then at least you are comparing more apples to apples and not some deliberately skewed example like the one quoted in that article that only seems to give a compelling story to report.

Ive no doubt that using FIRM too along with a quality PVAI ablation may well help improve outcomes, but the very low 55% success rate from a PVI-ony paroxysmal AF ablation that they were touting in that study must have been achieved by recruiting some trainee EPs in their first three weeks on the ablation job to get comparative results that poor and its not even comparing a comparable procedure. Both of them are doing a PVI and only the FIRM goes beyond that to address at least one prominent Non-PV trigger, which everyone knows is the best way to improve outcomes over a simple PVI alone anyway, regardless of the mapping method used to ferret out which non-PV triggers to zap.

The truth is too that all of these phase-mapping systems have discovered that the vast majority of these 'rotors' are found to congregate in several predictable regions of high activation which include ... no surprise to anyone who follows the ablation field ... the PV antrum area, the posterior LA wall and the Left Atrial Appendage ...

The inside of the left atrium is really tiny. about the size of the inside of a tennis ball for the whole thing! Now you divide that up into three prime areas where most of these triggers are found and it doesn't take much creativity to be right most of the time when you know the very small regions you need to address to begin with.

Now whether there is some incremental advantage in using the better of these new phase-mapping systems to help pin point just which trigger sources to ablate over and above the very good guidance and results top EPs already achieve using 3D electro-anatomical voltage mapping along with ICE to detect remains to be seen.

Perhaps they will prove a very useful adjunct to the tool kit of EPs everywhere over time, and I really hope they do. I expect the more promising systems will help like the Cardio-Insight system which could also prove very useful for ablation follow up screening to help decide with a touch up might be needed etc and zero in on the area before hand, or to test various new drugs on a patient and see which ones quiet down the triggers the best etc etc.

But right now it is very much a work in progress and these breathless jump the gun announcements from the FIRM group has lost most all of its steam by over promising and under-delivering so far.

In addition to possible insights from phase-mapping research there are a number of other exciting potentially ablation enhancing technologies on the near horizon as well such as Contact Force catheters, Advanced Cardiac Therapuetics 'Tempasure' catheter system that incorporated microwave radiometry in the ablation tip to measure real time temp deeper below the surface of the atrium to determine when a transmural burn has happened, and Acutus Medicals new imaging system capable of generating very high resolution surface reconstruction maps of the entire heart or chamber very quickly from beat to beat and display it in dynamic or static view..

In other words, there is a lot of progress being made, yet some of these systems and companies will fail, and a couple will really pan out and lead to improvements all through the process.

Topera's system may even pan out in the end and offer some real merit once it all shakes out, but at this point, we mostly only hear from people there with a strong financial interest in the company, and so far, their promotional efforts have been more aggressive and overly-optimistic than their results support at this time. That is why its always good to first wait until a broad group of the top docs in this field adopt a new tech before getting too excited about any such reports from mostly company generated studys.

Shannon



Edited 1 time(s). Last edit at 02/20/2014 04:23PM by Shannon.

Regarding the resolution issue. An insitu basket sensor is probably as high if not higher in resolution than the 256 sensor exterior vest. Because of the distance and body geometry, vest sensors have to go through math processing steps called spatial deconvolution and even then, there will be noise from refractions and reflections. The basket sensor is almost a direct measurement because it is so close to the source. I wonder if that is why some of the vest investigators are seeing spatial drift of the "rotors" and FIRM guys are not. Also the fact that Jais hasn't said anything negative maybe an indication that Cardioinsight has the processing figured out better than the newer guys jumping on the bus. The article is old and I look forward to seeing newer reports where they have tracked patients for longer and also show that the "rotors" are spatially stable. It should be relatively easy to proof whether the rotors drift is real or not - use it on a right sided SVT where we know the rotor is not moving and show us what you've got using the sensors. Basket or vest.

Yes researcher the spatial differences with a 64 in a small area versus a 256 vest is a valid point as you note, but the Basket catheter often fails to make full contact inside the atrium which limits resolution utility . They are trying to address that limitation with a larger array basket catheter now. The real difference though is in the whole chamber image or even whole heart view with the CardioInsight, or even more with a system another researcher in Orlando presented that was much higher resolution yet still as well as the optical cameras if Jalife that are far higher resolution than any of the above, and at each step up in improved global resolution view of the whole atrium or preferably whole heart activation, you get more differentiation between seeing what looks like more stable rotors as in Topera versus the micron level Rez of the optical camera arrays used in fundamental rotor research that shows much more variability in rotor type.. ie transient unstable versus stable and realitve go mixed in a tight region which would seem to make better ablation candidates... Except Karl Heinz Kuck said the majority of time he would try to ablate the most beautiful stable seeming rotors, nothing happened most of the time!

The presentation at Orlando by that researcher ruled out the idea that maybe the FIRM system had a more accurate story than the progressively more resolving systems above. The functional resolution is comprised of both sensor quality, type and number as well as algorithm sophistication applied.

I thing Topera may well develope a useful product, but their jumping the gun as they did coupled with too much secrecy and unwillingness to fully demo a live FIRM process in front of independent peers at these top conferences so far had created more skepticism than confidence that they will be the real winners in this phase-mapping race. Time will tell, but a more cautious approach to claims early on would likely have worked better in their favor while they continue to iron out the bugs in their system like the limitations if the original basket catheter.

I hope all these systems work out eventually, but I have a hunch that the phase mapping approach of CardoInsight and two other similar concepts will become more practically useful in integration with 3D EAM systems too, which can add the very valuable tool of voltage mapping catheter location and easier integrating with CF catheters too .. A kind of hybrid view similar to what Bordeaux is aiming at developing, assuming the phase mapped approach really does add net value to the best of current cutting edge imaging and mapping tools which still remains to be seen.

Shannon



Edited 1 time(s). Last edit at 02/20/2014 08:30PM by Shannon.

I'm finding this discussion fascinating. Shannon and Researcher - you both know a lot more than I do about this procedure!

Hi researcher,

Regarding rotor stability comparing FIRM via a vis more advanced non-invasive phase-mapping systems like Jalifes color optical camera array and Dr Phillip Cuculich with his research with his ECGI (Electrocardiographic Imaging) developed by Dr Yoram Rudy at Washington University with their very similar system to CardioInsight except with 256 sensor in the form of strips lining the chest and back of a patient, where Cuculich then took the direct assumption that the Topera FIRM system with its lower overall system resolution showing less information might be telling the more realistically 'stable' story.

He set about thoroughly testing that hypothesis and showed that it was wrong. That using less information in the search for accurate detection and classification of rotors as either stable or transient and wandering was not an advantage and gave more of an averaged and basic view of the data that lacked the nuance and specificity of high resolution imaging systems. The system they are working with after registering the positions of sensor imaging to a 3D CT scan of the heart they can then take the electrical info from the body surface and move it down to the surface of the heart to be able to display that info in ways to understand the activation sequences and repolarizations of each heartbeat.

This results in a powerful system for analysis that compares closely to invasive mapping. Its hard to capture the entire activation sequence of an AFIB cycle with even a large internal catheter which has a relatively narrow localized view compared to the panoramic view of the whole heart from these non-invasive phase mapping efforts.. This can come in very handy when trying to 'reproducibly' capture an entire spatial activation sequence of an arrhythmia with aspects of instability like AFIB.

That's very hard to do with any loacalized catheter inside the atrium. So these are different tools taking differnt views of the situation.

He also highlighted the limitations of phase mapping and how critical it is to make sure that very tight correlation and confirmation between non-invasive phase mapping and direct mapping exists, otherwise you don't really know for sure what you are looking at.

He said that "phase-mapping is a way to depict spatial-temporal changes in activation during AFIB ( or any arrhythmia) but it's never yet been truly validated in cardiac electrogram analysis, even though it is being used now as if it has been so validated (ie jumping the gun and making big unvalidated assumptions while doing so). It is important work toward improve our understanding of AF on a deeper level but both Cuculich, Heinz-Kuck and Jose Jalife emphasized it was definitely not ready for prime time use in front line EP labs until the various unknowns and contridictions are better sorted out.

Like Heinz-Kuck said, " when he can ablate so many perfectly stable looking rotors that should be ideal candidates for ablation and then nothing happens most of the time, that is a big red flag that there are real holes in our theory". Heinz-Kuck and Jalife both acknowledged the real risk of potentially making some rotors fixed in place by ablating them which is the last thing you want to do, at least until they far better understand the core science and process here.

Its certainly an interesting area and sure to be a big focus in ongoing research.

Shannon



Edited 1 time(s). Last edit at 02/21/2014 11:30AM by Shannon.

Shannon, When FIRM first came out, I was confused (still confused) on why the method looked at phase instead of period (frequency). It made a lot of sense to take the whole image in time lapsed form rather than the point by point electrograms gathered by Carto and similar systems. I think that all the EPs mentioned above would agree that the holistic electrical image would be better. The proof will be that they can use their system and show that they can "see" (for example right atrail flutter) a right sided rotor that we know is not moving followed by successful CTI ablation. Conceptually, Topera and CardioInsight are on the right track and I hope they succeed. I don't blame them for keeping things close to the vest for now as that means the difference between a viable business or not. Optical imaging is too far out technically (physics and engineering challenges) for me to fathom.

Hi researcher

I too expect this whole area of research and development to pay real dividends as the years go by, and likely in ways not fully anticipated now. Although I expect a real boon will be in better diagnosing or arrhythmias and follow up after ablations and monitoring and adjusting drug therapy via the non-invasive vest-like systems will really help fine tune the diagnosis and could be used to better screen which patients are likely to do well with a more typical EP who has the simple anatomical PVAI down pat versus though with more obvious non-PV sources who need a more experienced operator doing the procedure.

I will be very pleasantly surprised if they are ever able to reduce advanced AFIB ablation down to a simple CTI flutter or SVT type deal like Narayan has postulated. That sounds like manna to all the less experienced EPs who dread having to spend years developing real EP interpretive skills and excellent manual dexterity with a catheter, but its unlikely to happen. AFIB is too multi-factorial and is more a consequence of many different more core etiologies that will be likely to have a simple 'one size fits all' simple procedure for reliably fixing it.

Its fine there are trying to get excellent results while fine tuning the procedure and minimizing the areas needed to ablate along the way for sure. But I can see some zealots are so married to this "less is more' mantra that they are in danger of missing the forest for the trees and thus trying so hard to fit a square peg in a round hole to make AFIB ablation conform to their idea of an SVT-like simple procedure, that they may well wind up going off course for a while at the expense of their patients in pursuits of and end point that really should not be an end point. The End point much be the get the most sustainable long term freedom from AFIb/Flutter/Tachy without drugs with acceptable safety.

Whatever reduction in procedure with advancing mapping, imagine and catheters that is realized is great, but doing also trying to do one burn less or do the fastest clock time on an ablation as target goals in and of themselves is misguided and even dangerous long term in my view. We don't want to put the donkey in front of the cart here.

It will be interesting to see how all this pans out too.


On another note that you will likely appreciate researcher,

I just found out this morning I am going to Austin next week to attend the EP-Live 2014 conference which should be very informative and interesting and will witness both live and recorded procedures with a number of other EPs in training, including live Fluroless Ablation by Rodney Horton, a live long standing persistent AF ablation by Andrea Natale, a live Cyro ablation by Javier Sanchez and Amin Al-Ahmad, recorded CAFE ablation with Moussa Mansour, Persisent AF ablation with Doug Packer from Mayo, recorded AF ablation using the Univ of Penn approach with Francis Marchlinski. Then a recorded AF albation with Gery Tomassoni using FIRM Rotor mapping along with a full PVAI. .. and that is just the first day! Also in the afternoon session some recorded cases of Vivek Ready, Connor Barrett., David Callans and Luigi DiBiase doing Post ablation right sided flutter ablations and Multi-electrode mapping ablation by DiBiase.

On day two will be several Interesting variations of VT ablations as well as AF ablations including David Burkhardt using the Stereotaxis magnetic guidance system, David Wilber, Henry Hsia and Kalyan Shivkumar.. Also a 'Non-invasive ablation' will be shown as well as an Ultrasound ablation by Vivek Reddy and the CardioFocus Heartlight laser balloon ablation by Sakis Themistoclakis,

Finally, several LAA closure device procedures including a live Lariat with DJ Lakkiready and Watchman too.

Should learn a lot and find out the various strengths and issues with the different approaches and systems that I can pass along here and in the AFIB Report in the coming months.

Shannon

Sounds like a great symposium. We are the nerds here right out of Big Bang Theory.

Interesting comments, thanks!

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Lone paroxysmal vagal atrial fibrillation. Age 62, female, no risk factors. Autonomic instability since severe Paxil withdrawal in 2004, including extreme sensitivity to neuro-active drugs, supplements, foods. Monthly tachycardia started 1/11, happened only at night, during sleep, or when waking, bouts of 5-15 hours. Changed to afib about a year ago, same pattern. Frequency increased over last 6 months, apparently with sensitivity to more triggers. Ablation 6/27/13 by Steven Hao.

Ha researcher, someone has to do it, right!
I figured you'd be familiar with most of those faculty at this conference. Should be interesting.

You're welcome Iatrogenia glad you find the technical side of this discussion worthwhile as well. Listening to the leaders in this field discuss and debate the path forward and once we start to digest what is going on at the forefront, it helps to put present options in a clearer perspective and get a better sense for the road ahead as well.

The more I and others here, like yourself with the keen interest you have shown in looking beneath the surface, can learn to better translate this stuff so its more accessible and understandable to everyone, I hope it will make it easier for all who are trying to sort this challenging condition out for themselves and to make the best decisions along the way.

Shannon



Edited 1 time(s). Last edit at 02/22/2014 09:17AM by Shannon.