After posting my article, Rotors! Rotors! Rotors! Good News for Patients with Persistent A-Fib (2016 AF Symposium), I was surprised when Patti said we didn’t have the term ‘rotors’ in our Glossary of A-Fib Terms. So we just added it:
Rotors: underlying drivers that sustain or propagate an A-Fib signal after it has been triggered (like an echo). Elimination of rotors by catheter ablation improves long-term freedom from A-Fib.
Why You Want a Doctor Who Understands the Significance of Rotors
The ability to diagnose rotors enables a more patient-specific treatment approach by focusing on just a few critical areas in each individual patient’s heart and results in fewer lesions (ablation scars).
Stay away from EPs who ablate only the pulmonary veins (PV).
This is important. You should stay away from EPs who ablate only the pulmonary veins (PV) and don’t check for non-PV triggers like rotors and focal points. That is a one-size-fits-all approach. (See my editorial: Huge Growth in Number of EPs Doing Catheter Ablations, But All EPs Are Not Equal)
A more reasonable approach tailors treatment to each individual’s specific physiology. This requires a more experienced EP and precise location identification using advanced mapping techniques (such as the FIRM Mapping and Ablation System by Topera/Abbott Laboratories or the ECGI/ECVUE system by CardioInsight Technologies/Medtronic).
What This Means to Patients
You want an experienced doctor (EP) who understands the significance of ‘rotors’; who will use advanced mapping techniques, when needed, to search for and isolate non-PV triggers.
You must do your due diligence to find the right EP. I know it’s a lot of effort. Don’t settle for an EP because their office is nearby. Be prepared to travel if that’s what it takes.
Remember: You must be your own best patient advocate.
How to Select Your Doctor
To learn more about how to select the right doctor for you and your treatment goals, see my article: Finding the Right Doctor for You and Your A-Fib.
AF Symposium 2015
The Changing Ablation World: Going Beyond PVI With ECGI Mapping and Ablation Techniques
By Steve S. Ryan, May 2015
ECGI is changing everything—not only the way mapping and ablations are done, but also our basic understanding of A-Fib. Instead of potentials and CFAEs, EPs will focus on ablating drivers (rotors and foci). Ablating the PVs will still be basic. But in more difficult cases, EPs must look for non-PV triggers or drivers.
Prof. Michel Haïssaguerre of the French Bordeaux group/LIRYC gave a presentation entitled “Beyond PVI—Mapping and Ablation Techniques for Elimination of Drivers in Persistent AF.” Non-Invasive Electrocardiographic Imaging, or ECGI (from CardioInsight) is a radically new and innovative mapping and ablation system.
The ECGI Vest-Like Device Innovative Mapping and Ablation System
The day before their ablation, the patient lies down on their back and a technician places a vest-like device with 256 electrodes over their chest and stomach. These electrodes combine with rapid CT (Computed Tomography) scans to produce a very detailed 3D color map of the heart.
The system automatically detects rotors and foci and computes them into a “Cumulative Map” or movie. These driver regions are ranked, based on statistical prevalence. They are displayed in statistical density maps which define the ablation roadmap.
The use of ECGI mapping results in a drastic decrease of RF burns needed
Ablation using ECGI results in a drastic decrease of RF burns needed to produce A-Fib termination.
In ECGI, Paroxysmal and Persistent A-Fib Ablation are Different
Paroxysmal: Using ECGI in 41 paroxysmal patients, Dr. Haïssaguerre found that the A-Fib drivers originated from the PV/post LA region. They consisted of PV discharges interacting with short-lived ostial rotors, which is in accordance with current knowledge and practice of A-Fib ablation. (A standard PVI ablation normally targets these areas.)
Persistent: But in 248 persistent A-Fib cases (54% with Structural Heart Disease), he found multiple interplaying A-Fib drivers coming from both atria but usually clustered in 4 regions. (The regions could vary from 1-7.) These drivers were short lived (3-4 reentries/firings) but periodically recurred in the same areas. As one would expect, the number of driver regions increased with the duration of persistent A-Fib. Long-Lasting persistent had 7 driver regions diffused throughout the atria. Cases with only 1 driver region were rare (9%).
Relationship of Drivers and CFAEs
These driver regions overlapped with areas of CFAEs (Complex Fractionated Atrial Electrograms). But whereas CFAEs were found in 49% of the total atrial surface, drivers were found only in 19%. Also, fractionated signals were more frequent and spanned a greater part of the A-Fib cycle length in driver regions than elsewhere (71% vs 47%). (This is good news for patients with persistent A-Fib. With ECGI, much less heart area needs to undergo ablation burns.)
Best Ablation Outcome is A-Fib Termination, But Not Always Possible with Persistent A-Fib
Dr. Haïssaguerre showed slides where he ablated driver regions which transformed rapid complex A-Fib signals into slower organized signals. He stated from his own experience and from several studies that the best outcome of ablation was A-Fib termination into sinus rhythm or tachycardia.
But this result was much harder to achieve in long-lasting persistent A-Fib. In cases where patients had only recently went into persistent A-Fib (1-3 months), 75% had A-Fib termination targeting driver regions. While in long-lasting persistent A-Fib, only 13% had A-Fib termination. Dr. Haïssaguerre’s hypothesis was that early persistent A-Fib is initially driver-dependent, while long-lasting persistent cases progress to widespread substrate disease.
In another study following 90 patients, 85% of patients with A-Fib termination were A-Fib free after 12 months (in the remaining 15%, 54% were paroxysmal). While patients who didn’t have their A-Fib terminated, only 63% were A-Fib free (all were persistent).
What EPs Do When AF Persists After ECGI Driver Ablation
• Check driver regions (including PVs) to ensure abolition of rapid-disorganized EGMs (electrogram signals).
• Body Surface Remapping—to look for new drivers appearing after the first ones are eliminated. Many have observed that this strategy often improves results in difficult cases of long-lasting A-Fib.
Right Atrium Ablation
Dr. Haïssaguerre recommended ablating the right atrium after the left. Right atrium drivers can disappear after left atrium ablation.
Dr. Haïssaguerre’s Conclusions
• Noninvasive mapping visualizes AF drivers which are Multiple, Meandering, ShortLasting and Associated with Complex EGMs (electrogram signals).
• Ablation targeting these AF critical regions allows high rate of AF termination with minimal RF delivery.
• 85% AF freedom at one year when procedural AF termination is achieved.
• Reproducibility in 8 centers in Germany, Belgium and France (AFACART) (Eight centers in Europe are now performing ECGI ablations with similar results.)
Non-PV Triggers: If your EP only ablates the PVs, you should look elsewhere. I just read an O.R. (Operating Report) where the EP only CryoBalloon ablated the PVs. Even though the patient was still in A-Fib after the PVs were ablated, the EP didn’t look for non-PV triggers. He simply shocked the patient back into sinus rhythm and put him on an antiarrhythmic drug. Chances are the patient’s A-Fib will return, since the non-PV triggers in his heart weren’t ablated.
Driver regions overlap with CFAEs—CFAEs can be ignored: In difficult cases of A-Fib, EPs used to spend a lot of time mapping and ablating CFAEs. Sometimes there were so many CFAEs that the EP wound up debulking much of the left atrium. In Dr. Haïssaguerre’s research, CFAEs could cover nearly half of the total atria surface. But with ECGI, only 19% of that area is ablated. ECGI makes the EP’s job simpler and causes less burns on the patient’s heart.
Try to Get Out of Persistent A-Fib: If you haven’t done so already, ask your EP to be Electrocardioverted in order to avoid long-lasting A-Fib which causes atrial remodeling that produces widespread fibrosis and diffuse driver regions.
You may want to try the newer antiarrhythmic drug Tikosyn (dofetilide) which works well in some cases of persistent A-Fib. (When starting Tikosyn, you will have to be hospitalized for three days to get the dosage right and to check for bad side effects.)
Currently some long-standing A-Fib can’t be cured: The best outcome of ablation is A-Fib termination. But some long-lasting persistent cases turn into widespread substrate disease where it’s not always possible to map and ablate drivers. Even the famed Bordeaux group hasn’t yet figured out a way to achieve 100% success when ablating all long-standing persistent A-Fib.
If you have long-standing persistent A-Fib, should you just throw in the towel and give up? No. In Dr. Haïssaguerre experience, 63% of persistent patients who didn’t have their A-Fib terminated were still A-Fib free. You could be in that 63%. Just be realistic and don’t expect miracles.
Last updated: Saturday, May 30, 2015
20th Annual AF Symposium
by Steve S. Ryan, PhD
This overview should give you a sense of the topics floating through the three days in Orlando and the over sixty presentations by fifty A-Fib experts and researchers. (Most recent brief reports listed first)
(Please be advised that the Symposium organizers go to great lengths not to identify or unfairly publicize one device over another. When writing these reports I often have to do a good deal of research to correctly identify and describe particular devices that are demonstrated, as a service to readers. But this in no way implies or suggests that one device is superior to another.)
Dr. Gerhard Hindricks of the University of Leipzig in Germany gave a dynamic presentation of a catheter ablation of a 46-year-old female with paroxysmal A-Fib using the Rhythmia 3-dimensional multipolar mapping system by Boston Scientific. Along with his colleagues Drs. Andreas Bollmann and Jedrzej Kosiuk, they used the Rhythmia special basket catheter to generate a 3-D map of electrogram voltages and activation times. To me it seemed amazingly fast. The eight-splined bidirectional catheter produced 1,000 data points per minute. In what seemed like only a few passes, they produced a 3-D color reconstruction of the patient’s left atrium.
The actual ablation was routine. They terminated the A-Fib into sinus rhythm without having to use Electrocardioversion. But they found that the PV isolation was incomplete. Using the same Rhythmia 3-D mapping catheter, they were easily and quickly able to locate the gap in the Left Superior PV and ablate it.
Dr. Vivek Reddy from Mount Sinai School of Medicine in New York City gave a very well referenced and persuasive presentation on the Watchman device which closes off the Left Atrial Appendage to prevent clots and strokes. The theory behind the Watchman device is that most A-Fib clots originate in the Left Atrial Appendage (LAA). The Watchman closes off the LAA where 90-95% of A-Fib strokes come from. It’s a very low risk procedure that takes as little as 20 minutes to install. Afterward, you would usually not need to be on blood thinners. (For more, see my article, The Watchman Device: The Alternative to Blood Thinners).
Dr. Reddy certainly persuaded me that the FDA should approve the Watchman device. Dr. Reddy, earlier in Washington, had made the same persuasive arguments before the FDA.
Dr. Andrew Farb from the FDA took the bull by the horns and gave his perspective on the various LAA Closure (Occlusion) Devices. But as one would expect, he didn’t indicate how the FDA would rule on the Watchman device, since deliberations were still ongoing.
After his presentation, I asked him several pointed questions about this, but he was, of course, careful not to comment about current FDA deliberations. My guess? If body language, momentum, mood of the presentations, and more importantly recent research indicate anything, the Watchman device probably will not be approved by the FDA.
There was a palpable sense of sadness at the end of these presentations. The attendees realized that the game may be over for the Watchman device. I hope I am wrong, since the Watchman device would be an important tool to help A-Fib patients. Once the FDA rules and the current clinical trials of the Watchman device end, you will probably have to go to Canada or overseas to get a Watchman device installed.
(Happily I was wrong on this prediction. Update: The U.S. Food and Drug Administration (FDA) approved Boston Scientific’s WATCHMAN™ LAA closure technology for use in the U.S. on March 13, 2015. It has been available internationally since 2009. The FDA approval of the WATCHMAN device is based on the clinical program which consists of numerous studies, with more than 2,400 patients and nearly 6,000 patient-years of follow-up. The Watchman device will be available first at U.S. centers where it has been used in clinical studies.)
Watchman May Win FDA Approval
In my earlier brief reports on the Orlando AF Symposium, based on the recent research and the FDA presentation, I said the Watchman device probably won’t be approved in the US. I’m happy to say that I am most likely wrong.
At the LAA Symposium 2015 in Marina del Rey, CA, it was suggested that the Watchman device may be approved by the middle of this year. One presenter described how the FDA chairman talked with several people who were going to Canada to have the Watchman device installed. He seemed embarrassed that the Watchman was available everywhere in the world but not in the US and said that it has to be approved.
Other doctors I talked with at the LAA Symposium were of the same opinion. Presenters described how clinical trials for other LAA closure devices were on hold so that they could get approved in comparison to the Watchman (Non-Inferiority Trials). Dr. Dhanunjaya Lakkireddy of the University of Kansas Medical Center said that we are at a “tipping point” for the (A-Fib) industry.
As everyone, including the FDA, is well aware, A-Fib innovations usually start in Europe where they are more easily approved. Then only later do they move to the US for FDA approval, since the FDA generally requires more data than European regulators.
Drs. Jun Dong and Andrew Farb from the FDA described the FDA’s ‘Easy Feasibility Study’ (EFS) program where medical device innovations could be evaluated in the US without having to go to Europe first. He encouraged researchers and attendees to take advantage of the new EFS program. This is major news and may make the development of A-Fib innovations much easier to accomplish in the US.
For further information, contact: Andrew Farb, Email: Andrew.email@example.com. 301-796-6317
Dr. Luigi Di Biase from the Albert Einstein College of Medicine in the Bronx, NY and Dr. Daniel Singer from Massachusetts General Hospital in Boston each described potentially great developments in reversal agents for apixaban (Eliquis) and rivaroxaban (Xarelto).
Dr. Di Biase described studies where leaving people on uninterrupted rivaroxaban and apixaban before, during and after an ablation dramatically reduced the amount of silent thromboembolic lesions and were as safe as warfarin with regards to stroke and TIAs. (This didn’t work with dabigatran [Pradaxa].) But if patients develop bleeding or effusion during the ablation, they are in trouble because there is no direct reversal agent as there is for warfarin. He has used Factor IV as an indirect reversal agent. Dr. Singer also described how Factor IV was used as a reversal agent for apixaban.
But there are new reversal agents for apixaban and rivaroxaban which promise to completely reverse the effects of these two drugs in less than four minutes. The FDA is speeding up studies on these reversal agents. But one never knows when or if the FDA will approve them.
Dr. John Day of the Intermountain Heart Institute in Murray, UT (and recently elected president of the Heart Rhythm Society) may be the first A-Fib leader to publicly question whether women should be given one point on the stroke risk CHA2DS2-VASc scale just because of their gender. Many doctors have said this in a circumspect way. Dr. Eric Prystowsky in a presentation at last year’s AHS meeting thought that most doctors would agree with Dr. Day, “as long as there wasn’t a camera focused on them.” He gave the example of a 45-year-old woman in good health and a 45-year-old man with hypertension who according to current guidelines should both be given one point on the stroke risk CHA2DS2-VASc score.
As readers of A-Fib.com, you know that’s been my opinion ever since the original European guidelines came out. Women in their child-bearing years are much less at risk of stroke because of the blood-thinning effect of losing blood each month. And even after menopause women have less risk of stroke. But eventually they do have more strokes. But not because of an innate inferiority, but because women live longer than men. Stroke is age related. An observational Danish registry study documents this.
For more, see The Denmark Study: Women in A-Fib Not at Greater Risk of Stroke Contrary to CHA2DS2-VASc Guidelines!) (Be advised that the original European guidelines were written by doctors with major conflicts of interest.) These guidelines may be a not so very subtle form of gender bias.
Living in A-Fib is more dangerous than having an ablation, according to Dr. Josef Kautzner from Prague, the Czech Republic. Studies have documented that the adverse effects of living in A-Fib, having to take A-Fib drugs and anticoagulants for life are both pragmatically and statistically worse than having an ablation. Dr. Kautzner discussed how A-Fib can cause or is associated with silent brain lesions and dementia. Any time you go into a hospital is a risk. And no one would say that a catheter ablation is a walk in the park. But an ablation is a low risk procedure, though not risk free. The risk is similar to having your tubes tied. The possible adverse effects of an ablation procedure (like bleeding at the groin) are generally temporary, unlike the lasting, permanent damage you can do to your heart, body and brain by living in A-Fib for years.
The most hotly discussed topic at this year’s symposium was rotors. The opinions expressed about rotors were at times very heated, more than I had ever seen at an AF Symposium. Dr. Shih-Ann Chen of Taipei, Taiwan disagreed with Dr. Sanjiv Narayan of Stanford, CA about the basic concepts of rotors and how they should be defined. Dr. Ravi Mandapati of UCLA and Loma Linda University disagreed with Dr. Narayan which was all the more striking in that he had worked with Dr. Narayan when he was at UCLA. Dr. Pierre Jais of Bordeaux, France said that the FIRM mapping system misses 40% of the atrium area.
Drs. Haissaguerre and Jais from Bordeaux and Dr. Sebastien Knecht of Brussels, Belgium gave presentations on how they were using the CardioInsight body surface mapping vest to perform ablations of “drivers” at many different centers, while Dr. Karl-Heinz Kuck from Hamburg, Germany using a different body surface mapping system said that he couldn’t ablate rotors. Dr. Narayan says the FIRM system finds a maximum of 2-3 rotors in the atria, while other systems find as many as seven. The FIRM system says rotors are usually relatively stable and can last as long as 30 seconds while others say they rotate in one fixed spot for only one or two rotations, that they tend to migrate within a certain area.
The presenters obviously didn’t share a consensus of basic concepts of what rotors are, how they work, their importance in A-Fib, how they should be correctly identified, used, and ablated. (It seems to me the Bordeaux group has the best understanding and pragmatic use of rotors. They refer to “rotors” and focal sources as “drivers.”) But the CardioInsight system Bordeaux uses isn’t currently available or isn’t being tested in the US.
Obesity was one of the most often discussed topics. There is a growing consensus among EPs that it isn’t enough to just give obese patients a catheter ablation while not dealing with their obesity. If the obesity isn’t dealt with, their A-Fib is very likely to re-occur. A-Fib will develop in other spots that haven’t been ablated. The condition (obesity) that triggered or caused the A-Fib will trigger or cause it again, if it isn’t taken care of.
Dr. Prashanthan Sanders of Adelaide, Australia described the great results he is getting in his clinic which includes a weight loss program and counseling. He convinces his overweight patients to buy into the program, lose weight, and keep it off. The program works so well that just by losing weight patients become A-Fib free. This program is a holistic approach to health and also is developed to work for diabetes, sleep apnea, hypertension, binge drinking and smoking.
Dr. Sanders foresees a world where some patients become A-Fib free simply by changing their life style, where they don’t have to have a catheter ablation to become A-Fib free.
Many other doctors commented that A-Fib treatment at many centers today includes or should include much more than A-Fib ablation and drugs. A-Fib centers should have nutritionists, exercise therapists, sleep apnea specialists, etc. as part of their A-Fib program.
Dr. John Day of the Intermountain Heart Institute in the Challenging Cases Discussion described his experience with the dreaded Atrial Esophageal Fistula. Though very rare, this is one of the few possible complications of a catheter ablation that can kill you. An ablation, if not done with caution, can irritate and damage the esophagus which often lies right next to the heart. Over 2-3 weeks stomach acid can eat through this damaged area to produce a hole or fistula from the esophagus into the heart.
As soon as Dr. Day saw this patient, he knew it was a fistula and immediately called surgeons and a GI doctor. All the surgeons were doing operations and didn’t want to do the surgery in the EP lab. Dr. Day described how he and his colleagues ran down the hospital hallway to the operating room while giving the patient a transfusion and at the same time pumping out the blood escaping from his heart.
The GI doctor got there first and put in a stent in the esophagus to plug the hole. There was lots of discussion as to whether this was the best approach, but it worked. The patient survived but had to spend a month in the hospital.
This cautionary and very dramatic tale certainly got the attention of all the attendees. No matter how rare a fistula is, every EP and A-Fib center must have an established protocol in place to deal with it. I remember Dr. Hugh Calkins in a previous Symposium advising, “There are only two kinds of EPs—those who have not had an Atrial Esophageal Fistula and those who have!” (Dr. Calkins’ patient with fistula also survived.)
Dr. Peter Kowey of Lankenau Hospital in Winnewood, PA described a case that illustrates the kind of dilemma both doctors and patients often have to face. A 92-year-old woman with paroxysmal A-Fib who had been treated for many years with warfarin had some bruising and nuisance bleeding, but never anything major.
Dr. Kowey thought that ethically he should tell her about the different new anticoagulants which may be superior to warfarin, then see if she wanted to change. She went with apixaban (Eliquis), then six months later had a stroke even though she was taking apixaban properly and conscientiously. Happily, she made an almost full recovery. She returned to warfarin which had worked for her in the past and which she was comfortable using.
One of the reasons Dr. Kowey discussed the new anticoagulants with his 92-year-old patient was because warfarin is considered more apt to cause bleeding in older patients. The newer anticoagulants in clinical trials caused less bleeding. But we don’t have much data from the clinical trials on people over 90 years old.
Can we say that apixaban didn’t work or was ineffective? No. Anticoagulants reduce but do not totally eliminate the risk of an A-Fib stroke. Just because she had a stroke doesn’t mean apixaban didn’t work.
Dr. Jeremy Ruskin pointed out that there has never been and probably never will be a head-to-head comparison of the three new anticoagulants. But in my opinion apixaban (Eliquis) appears to have tested better and is safer than the others
For more, see my 2013 BAFS articles, The New Anticoagulants (NOACs) and Warfarin vs. Pradaxa and the Other New Anticoagulants.
In the satellite case live presentations, Drs. Rodney Horton and Amin Al-Ahmad from the Texas Cardiac Arrhythmia Institute in Austin, TX surprised us by doing an ablation without wearing the standard lead aprons to prevent fluoroscopy exposure. Even more surprising was one of the lab assistants who was pregnant. She could work on the ablation because no fluoroscopy was used. The doctors did the whole ablation using ICE (Intracardiac Echo) and 3D mapping. They showed for example how ICE can be used to thread the catheter up into the heart and into the left atrium. Dr. Horton said that not having to wear those heavy lead aprons would probably add 5-10 years to his ablation career.
(They didn’t wear surgical masks during the ablation which was surprising to me. I will write them for an explanation.)
The live satellite case from Beijing, China was technically flawless and probably a first of its kind. But it wasn’t much of a learning experience for the attendees. The Chinese EPs only used one catheter and had to frequently pull out the mapping catheter and replace it with the ablation catheter, etc. When the expert panel asked them questions, the Chinese EPs either didn’t understand or simply didn’t answer them. They seemed very uncomfortable. It seemed like a throwback to ablation techniques of 20 years ago.
Drs. Claudio Tondo, Gaetano Fassini, Massimo Moltrasio, and Antonio Dello Russo from Milan, Italy showed how they do a catheter ablation for A-Fib and install the Watchman device in the same procedure, when it’s needed. They do the ablation procedure first. Then when the patient is in sinus rhythm, they install the Watchman device. (This can’t be done in the US, because the Watchman device hasn’t received FDA approval. In later discussions including representatives of the FDA, there was an all too real possibility that the Watchman will never receive FDA approval.)
Drs. Kevin Heist and Moussa Mansour from Massachusetts General in Boston showed in a live case how they used a Contact Force Sensing catheter combined with Jet Ventilation. (There are two Contact Force Sensing catheters approved by the FDA—the ThermoCool Smart Touch device by Biosense Webster (approved Feb. 24, 2014) and the TactiCath Quartz Contact Force Ablation Catheter by St. Jude Medical (approved Oct. 27, 2014). This live case used the TactiCath catheter but didn’t imply or suggest it is superior to the ThermoCool catheter. For a description of each, see my 2014 AF Symposium report The New Era of Catheter Ablation Technology: Force Sensing Catheters.
This combination of Force Sensing Catheter with Jet Ventilation for RF ablation probably represents the most advanced RF ablation strategy available today. Jet Ventilation doesn’t stop the heart from beating as in bypass surgery. But to this observer it seemed to put the heart in a type of slow motion with a lot less movement than when the heart is beating in normal sinus rhythm. You could really see a difference when they turned the Jet Ventilation off and on. Slowing down the heart like this helps the ablation doctor make lesions in hard-to-access areas and makes it easier to hold the catheter steady and apply the right contact pressure.
Drs. Michel Haissaguerre and Pierre Jais from Bordeaux/LYRIC gave presentations on the ECGI system. The day before their ablation, the patient lies down on his/her back and a technician places a vest-like device with 256 electrodes over his/her chest and stomach. These electrodes combine with rapid CT (Computed Tomography) scans to produce a very detailed 3D color map of the heart. (For a detailed description and discussion of the ECGI system, see 2013 BAFS: Non-Invasive Electrocardiographic Imaging [ECG]) The system automatically detects rotors and foci and computes them into a “Cumulative Map” or movie. These driver regions are ranked, based on statistical prevalence.
Then, Dr. Sebastien Knecht from CHU Brugmann, Brussels, Belgium, described the AFACART trial design and preliminary results using the CardioInsight ECGI system. Many centers in Europe including four in Germany are now using the CardioInsight. Requiring very little training, technicians and EPs using the CardioInsight system are getting similar great results like the Bordeaux group. Though these studies just started, it looks like the CardioInsight ECGI mapping and ablation system is poised to revolutionize the way EPs map and perform ablations.
Dr. Jose Jalife of the University of Michigan in Ann Arbor, MI, continued his exciting research on fibrosis and A-Fib. In previous Symposiums Dr. Jalife demonstrated how A-Fib produces fibrosis. When he paced sheep into A-Fib, their hearts became fibrotic within a very short time. The markers of fibrosis (collagen and scarring) increased progressively as the sheep went from paroxysmal to persistent A-Fib. (See A-Fib Produces Fibrosis—Experimental and Real-World Data.)
Fibrosis is tissue that has fiber-like characteristics which develop in place of the normal smooth walls of the heart. Fibrotic tissue is scarred, immobile, basically dead tissue with reduced or no blood flow and no transport function. It results in a loss of atrial muscle mass. Over time it makes the heart stiff, less flexible and weak, overworks the heart, reduces pumping efficiency and leads to other heart problems. Fibrosis, up to now, was considered permanent and irreversible. But Dr. Jalife gave his sheep a Gal-3 inhibitor GM-CT-01 that actually prevented and reduced fibrosis! (For his previous presentations, see 2014 BAFS: The Holy Grail: Preventing A-Fib by a GAL-3 Inhibitor.)
In his continuing studies of sheep, Dr. Jalife found that fibrosis predicts recurrence, and that fibrosis can not be reversed if it is well established, even with GAL-3 Inhibitors.
Last updated: Friday, November 18, 2016
ECGI vs. FIRM: Direct Comparison, Phase/Waveform Mapping
Report by Dr. Steve S. Ryan, PhD
In a further discussion of the ECGI mapping and ablation system, Dr. Phillip Cuculich of the Washington University School of Medicine in St. Louis, MO gave a presentation entitled “Advances in and Limitations of Noninvasive Mapping of AF.” (For a detailed description and discussion of the ECGI system, see 2013 BAFS: Non-Invasive Electrocardiographic Imaging ECG (ECG).
Background: ECGI stands for Non-Invasive Electrocardiographic Imaging used at Yoram Rudy’s lab at Washington University in St. Louis to understand the mechanisms of heart rhythm disease. A similar system called Electrocardiographic Mapping (ECM/ecVUE) uses similar technology, but has been developed and tested for clinical use in Europe (http://www.cardioinsight.com) and has different goals. Each group works independently and has different ways to seek solutions.
The software used by the ECGI system to produce data and images from the multi-channel ECG mapping and CT scan is called CADIS.
POTENTIAL BENEFITS OF ECGI
Dr. Cuculich began by describing the potential benefits of ECGI:
• Save time: Locate the arrhythmia in a single beat
• Better Preparation: Understand and plan for the arrhythmia before an ablation
• Avoid Frustration: Map and ablate unstable, transient or complex arrhythmias
• Research Platform for Discovery: Identify and describe the mechanisms of arrhythmias
A-FIB PATTERNS OR SIGNALS AS REVEALED BY ECGI
After imaging patients with ECGI, A-Fib patterns are a combination of mechanisms:
• In simple A-Fib, Dr. Cuculich showed movies of left pulmonary vein focal sites with 1 to 2 wavelets and a left-to-right activation pattern
• In complex (Long-standing Persistent) A-Fib, he showed movies of four or more simultaneous wavelets, a high degree of wavelet curvature, and frequent wave breaks (no focal sites). The patterns tend to repeat and follow a preferred path.
FIRM AND ECGI COMPARISON
|Inside the heart||Outside the heart (body surface mapping)|
|Up to 64 contact electrodes to produce up to 64 electrograms||1000 reconstructed electrodes|
|QRST subtracted||No signal subtraction|
|70% rotor, 30% focal||Multiple wave fronts (1-4), 15% rotor|
|Stable beat-to-beat||Transient focal activity, transient rotational circuits|
(In the ECGI imaging/mapping system the number of points on the heart is changeable. But they have found 1000 to be a good number for reliable, detailed analysis.)
Dr. Cuculich compared ECGI data to recent invasive epicardial (inside-the-heart) mapping and body surface mapping (called “Phase Lock”). The data showed significant agreement between the imaging systems. Also, ECGI compares favorably to surgical maze mapping data.1
But compared to FIRM, the most common patterns of A-Fib Dr. Cuculich found were multiple wavelets, with pulmonary vein and non-pulmonary vein focal sites. Rotor activity was seen rarely.2
NO STANDARD DEFINITION OF “ROTOR”
There is no standard definition of a rotor. In Dr. Cuculich’s studies he used 2 rotations at the same spot as a “rotor.” This is perhaps why he found less rotors than in the FIRM system and in the CardioInsight system as described by Dr. Jais where they found 80% rotors. See: BAFS 2014 Jais, ECGi & Circular Catheter
Another major difference in ECGI and FIRM is that ECGI uses wavelet analysis (activation of the wavefront), while FIRM and CardioInsight uses phase mapping to describe the behavior of the arrhythmia. The main point of Dr. Cuculich’s presentation is that one must be very careful when applying phase techniques, as it can introduce rotor behavior into the imaging map. Dr. Cuculich’s group is studying whether this rotor behavior may be a true cause for the maintenance of A-Fib or just an artifact.
ECGI—TOO MANY ELECTRODES?
In a conversation with the author, Dr. Cuculich brought up comments that perhaps ECGI/ECM uses too many electrodes to see stable rotors, that perhaps panoramic imaging with fewer electrodes could improve the identification of rotors. (ECGI has a much larger number of electrode points in the heart [usually 1000] compared to FIRM [64 max].) To test this hypothesis, he analyzed A-Fib using 64 spaced electrodes in each atrium vs. standard ECGI. It turned out that fewer electrodes did not help to visualize rotors.
PHASE MAPPING, WAVEFRONTS, WAVELET TRANSFORMATION, ACTIVATION PATTERNS
Dr. Cuculich introduced new concepts in the use of ECGI (at least to this author)—phase mapping and the importance of wavefronts or wavelet transformation in A-Fib signals. “ECGI uses wavelet transform looking at pure activation time.” He asked, “how does…phase mapping affect the result?” He related phase mapping to the CONFIRM concept of “phase lock” where a simple 12-lead ECG analysis can classify A-Fib mechanistically.3
Doctors (and we patients) are still struggling to understand what phase mapping and wavelet transformation actually mean. Dr. Cuculich’s studies of phase mapping techniques (Hilbert transform) in A-Fib show that phase mapping highlights and accentuates the curvature of a wavefront and thus indicates a rotor is present. According to Dr. Cuculich, phase mapping is highly dependent on the chosen cycle length. He concluded that “while published ECGI data used wavelet transform to identify activation patterns, phase mapping techniques (when performed carefully and correctly) may offer additive information.”
We’re grateful to Dr. Cuculich for his comparison of ECGI and FIRM which helps us understand both imaging system better. But it’s definitely disturbing that both systems vary so greatly. Why does the FIRM system find 70% rotors and ECGI only 15%? Why are FIRM’s A-Fib signals stable and ECGI’s transient? Why does the FIRM system not focus on wavefronts and wavelet transformation?
One way to resolve these discrepancies would be to use a standard Lasso mapping catheter to meticulously map every potential A-Fib-producing spot in an animal or human with Long-standing Persistent A-Fib (where one would expect to find multiple A-Fib producing spots in the heart). Then immediately use both the FIRM and ECGI system to map the same heart and compare the results.
Perhaps the single biggest new discovery in human A-Fib mapping is rotors. But there’s considerable debate about their definition and behavior. Dr. Cuculich found that rotors are relatively rare (15%), whereas the FIRM and CardioInsight studies indicate that 70-80% of A-Fib drivers are rotors.
Dr, Cuculich introduced new concepts, insights and vocabulary to our understanding of A-Fib, (some of which I’m still having trouble wrapping my head around). Are wavefronts and wavelet transformation important in themselves or are they part of the development of rotors? Phase mapping and wavelet transformation applied to A-Fib is a major innovation that may lead to a better understanding of how A-Fib signals activate in the heart. Besides making mapping and ablating A-Fib easier and more effective, ECGI with its detailed, high resolution capabilities may give us new insights into A-Fib.
- Lee, G. et al. Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity. European Heart Journal (2104) 35, 86-97. Last accessed May 13, 2013, URL:http://www.ncbi.nlm.nih.gov/pubmed/23935092 doi:10.1093/eurheartj/eht267↵
- Cuculich, PS et al. Noninvasive characterization of epicardial activation in humans with diverse atrial fibrillation patterns. Circulation. 2010 Oct 5; 122(14): 1365-72. Last accessed May 13, 2013, URL: http://tinyurl.com/okp4229↵
- Non-invasive identification of stable rotors and focal sources for human atrial fibrillation: mechanistic classification of atrial fibrillation from the electrocardiogram, Europace. February 28, 2013. Last accessed May 13, 2013, URL: http://tinyurl.com/njt9zd7; doi:10.1093/europace/eut038↵
FIRM (Focal Impulse and Rotor Modulation) for Catheter Ablation of A-Fib by Dr. Narayan of UC San Diego
by Steve S. Ryan, PhD
I have received several emails asking why I don’t write about Dr. Sanjiy M. Narayan’s studies. I must admit to not understanding some aspects of FIRM and was hoping further information would make things clearer.
Ablating focal beats and electrical rotors, or as Dr. Narayan describes them, “localized areas of electrical activity” is nothing new. (See 2011 Boston A-Fib Symposium, Using CFAEs in Ablating Persistent A-Fib, and 2009 Boston A-Fib Symposium, CFAEs vs. Dominant Frequency) Dr. Narayan’s FIRM procedure uses the largest 64-pole standard basket catheter to do the mapping and uses “monophasic action potentials” (MAPs) catheter mapping to physiologically identify the A-Fib generating spots in the heart.
Proprietary, Patented Algorithm
What is new is the proprietary, patented algorithm Dr. Narayan uses to display the optical images and movies of the activation. (A description of the signal processing Dr. Narayan uses is found in the article “Computational Mapping Identifies Localized Mechanisms for Ablation of Atrial Fibrillation.”) Topera Medical, which licensed this algorithmic-based mapping system, calls it RhythmView.
This author doesn’t understand how Dr. Narayan’s proprietary system differs from other non-proprietary systems using basket catheters to map focal beats and rotors, with the possible exception that he uses the largest basket catheter with a wide field of view to be able to map almost an entire atria at one time.
Targets Rotors and Focal Beats Before Any Other Ablation Sites
After ablating rotors and focal sources found by his FIRM mapping system, Dr. Narayan also ablates the pulmonary veins utilizing wide area circumferential ablation—similar to what is currently done in most A-Fib centers.
Dr. Narayan targets ablation at rotors and focal beats before any other ablation sites, including the pulmonary veins. “Ablation at only rotors and focal sources revealed by our mapping approach (without pulmonary vein isolation) terminated AF predominantly to sinus rhythm in seconds to minutes.”
According to Dr. Narayan, “patients undergoing this targeted ablation (FIRM) experienced a superior rate of AF elimination in the long-term compared to patients undergoing traditional ablation procedures focusing on trigger mechanisms near the pulmonary veins.” Yet, after ablating rotors and focal sources found by his FIRM mapping system, Dr. Narayan also ablates the pulmonary veins utilizing wide area circumferential ablation—similar to what is currently done in most A-Fib centers.
Others Start By Ablating the PVI First
Dr. Narayan’s approach differs from standard operating procedure in almost all centers which start with ablating or isolating the pulmonary vein openings first before moving to other areas.
To this author, Dr. Narayan’s approach doesn’t make intuitive sense. If the pulmonary veins are still firing when mapping is done of the rest of the atrium, wouldn’t these PV signals interfere with or confuse the mapping? In most paroxysmal A-Fib patients, isolating the pulmonary veins is often all that’s needed to eliminate A-Fib (these patients often don’t have any other sources of A-Fib signals outside of the pulmonary veins).
Dr. Narayan found that patients with persistent A-Fib had more sources than those with paroxysmal A-Fib, though these sources were few in number—only about 2 for both atria. This is in contrast to previous studies which have found a greater number of A-Fib producing spots, especially in persistent A-Fib patients.
Dr. Narayan found that almost one-quarter of A-Fib sources come from the right atrium.
Contrasts with Established Protocols
For persistent A-Fib patients Dr. Narayan makes a left atrial roof line ablation, and for those with typical atrial flutter he makes a cavotricuspid isthmus ablation. No other ablation is performed even for persistent A-Fib. This contrasts with established protocols for ablating persistent A-Fib. (See 2008 Boston A-Fib Symposium, Stepwise Approaches in Ablating Chronic A-Fib.)
PRECISE-PAF trial results of FIRM ablation for atrial fibrillation without pulmonary vein isolation (PVI). This was a multi-center trial performed at nine centers with 33 patients showed a 67% termination of A-Fib, with another 17% showing a greater than 10% slowing in their A-Fib.
This is a relatively few number of patients.
EDITOR’S COMMENTS: Perhaps the most important innovation of FIRM is the ability to map and ablate rotors and focal beats in “seconds to minutes.”
Right now doctors doing ablations on patients with persistent A-Fib spend a great deal of time and effort tracking down and ablating rotors and focal sources of A-Fib. If Dr. Narayan’s FIRM system makes this part of the ablation procedure easier, faster and more accurate, this would be a major medical breakthrough for A-Fib patients and doctors.
(The author admits to not understanding how the FIRM system works compared to other systems using basket mapping catheters.)
But one can question the validity and accuracy of the FIRM system, since it typically finds only about 2 A-Fib sources in each atria.
It’s hard to compare Dr. Narayan’s results or to say his approach is superior to standard Pulmonary Vein Isolation. Most experienced A-Fib centers achieve around a 67% success rate as Dr. Narayan does. Though Dr. Narayan first ablates rotors and focal sources in the left atrium, he does later ablate the Pulmonary Veins like almost all other centers.
(It probably makes more sense to first ablate the PVs, then use the FIRM system to track down any A-Fib
A second important innovation of Dr. Narayan’s FIRM mapping system is the finding that one-quarter of A-Fib signals come from the right atrium. If future trials confirm this finding, doctors might have to change their ablation procedures and direct more attention to the right atrium.
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Last updated: Wednesday, September 2, 2015