16th Annual Boston AF Symposium, January 13-15, 2011 “Atrial Fibrillation: Mechanisms and New Directions in Therapy.”
The overall mood of the 16th Boston A-Fib Symposium was certainly influenced by the winter blizzards which cancelled many flights into Boston (including the author’s). “Let’s make it work” seemed to be the mantra as the organizers moved presenters who did arrive to take the place of those who were delayed. Talks scheduled for Friday were moved to Thursday morning, while Friday’s sessions started a half hour early so that all speakers could give their talks. To the author, this Symposium’s signature or most prominent topics of interest were Recurrence/Reconduction/Durability of catheter ablations, and the identification and use of CFAEs in catheter ablations. Another important topic was dabigatran (recently approved by the FDA) and other blood thinners as alternatives to warfarin.
Recurrence/Reconduction/Durability of Catheter Ablations
Though Pulmonary Vein Ablation (Isolation) (and the Maze-type operations) are currently the only hope of a long lasting fix to make patients A-Fib free, there is increasing evidence that a successful PVA(I) isn’t always permanent. Dr. Karl-Heinz Kuck from St. George Hospital in Hamburg, Germany described early studies which showed recurrence/reconnection within the first years after an ablation, but no or little recurrence after that. However, at his facility he followed for five years 161 patients who were ablated in 2003-4 and found that there was a steady progressive recurrence rate over time which he hypothesized will continue after five years. He concluded that, “we may not (permanently) cure patients with A-Fib.” Of his patients fixed after a single ablation, 60% remained A-Fib free after five years. Dr. Kuck also cited a recent Bordeaux study of patients ablated in 2001-2. Of patients who had a single ablation, only 30% were A-Fib free after five years. Of those who had two ablations, 63% were A-Fib free after five years. But most patients had two ablations. There was an annual 8.9% recurrence rate over time.) [It should be noted that ablation techniques have changed and improved significantly since those early days of catheter ablation].)
Recurrence Due to Reconnected Pulmonary Veins
Dr. Francis Marchlinski of the Un. of Pennsylvania described how in his experience A-Fib recurrence after a PVI is often due to reconnected Pulmonary Veins. “Since PV reconnection is the rule, and not all patients even attempt repeat procedures, then we may be underestimating true efficacy.”
Editor’s Note: In private conversations and in the question and answer sessions, doctors were very concerned about the durability of RF catheter ablations. In a successful ablation doctors isolate the pulmonary veins and check for entrance and exit block—that no A-Fib signals are getting through the lesion lines that isolate the veins. But current ablation techniques all too often create lesions that don’t last.
Other Causes of Recurrence
Dr. David Wilber of Loyola, Chicago cited several studies which also found approximately a 7% yearly rate of late recurrence. But he suggested the causes may not be only PV reconnection, but also heart health factors such as hypertension, diabetes, large left atrium, obesity, smoking, etc. He pointed out that atrial deterioration and heart disease may progress even if a patient is in sinus rhythm due to factors such as atrial remodeling and fibrosis.
Editor’s comment: People in sinus rhythm certainly have improved heart health and quality of life than when they were in A-Fib. But being in sinus rhythm doesn’t mean one can ignore other health and heart factors.
It was recommended that patients A-Fib free after a catheter ablation be counseled and monitored closely for heart health factors, particularly high blood pressure. They should be warned about the possibility that their A-Fib could return if they don’t take care of their overall heart health.
Watershed Year for A-Fib Patients (and Doctors)—Dabigatran Approved
Dr. Daniel Singer of Massachusetts General and Dr. Jeffrey Weitz of McMaster University, Canada described the major improvements in stroke prevention now available to patients. Not only did the FDA approve the new anticoagulant dabigatran (Pradaxa), but other possible replacements for warfarin made major advances in the approval process—rivaroxaban, apixaban, and edoxaban. They described some of the advantages of dabigatran over warfarin:
- Warfarin requires crucial monitoring and requires on average 17 INR tests/year, while dabigatran only needs to be taken twice a day to be effective.
- Warfarin often interacts with and is affected by other meds and diet, while dabigatran doesn’t seem to have a great deal of interaction problems.
- It takes four days for warfarin to be effective or to be eliminated from the body, but dabigatran can be effective in 30 minutes to two hours.
- Warfarin can cause bleeding problems, but dabigatran in clinical trials produced a 60% reduction in intracranial bleeds compared to warfarin.
- Warfarin is affected by genetics. People starting warfarin need to be tested for variations in the CYP2C9 and VKORC1 genes, while this isn’t necessary when starting dabigatran.)
According to Dr. Singer, warfarin reverses the risk of stroke in A-Fib, but aspirin doesn’t. In three clinical trials using dosages of 75 mg (baby aspirin) and 325 mg, aspirin produced a Relative Risk Factor of 21% (0-38%), but had no significant impact on severe/fatal stroke.
Editor’s Note: People at low risk of an A-Fib stroke (CHADS2 score of 0-1) are often put on aspirin antiplatelet therapy. But we know that aspirin is not very effective in preventing an A-Fib stroke. Dabigatran, however, would give real protection from an A-Fib stroke. In the clinical trials dabigatran provided a 34% reduction in stroke compared to warfarin.1. The author predicts that dabigatran will replace aspirin for patients at low risk of an A-Fib stroke.
One of the highlights of the Boston A-Fib Symposium is always the Live Case Transmission of A-Fib procedures from around the world. This year six different cases were presented, four of them pre-taped. (Previous Symposiums only had two.) The first was from Milan, Italy. Dr. Claudio Tondo from Milan and Dr. Moussa Mansour from Massachusetts General demonstrated the Laser Balloon Catheter (not yet FDA approved in the US) in an ablation on a patient (CardioFocus, Inc., Marlborough, MA). By using a balloon laser delivery system, the variable size balloon can be positioned in a vein opening to encircle the vein. Two overlapping laser energy ablations can usually completely isolate the vein without any gaps. The catheter features direct visualization (endoscopic). The doctor sees directly through the catheter the area he/she is ablating. This is an example of what the doctor sees. “LSPV” is the Left Superior Pulmonary Vein, “LIPV” is the Left Inferior Pulmonary Vein. http://www.cardiofocus.com/pdf/Schmidt_CircEP_Laser.pdf Some doctors expressed reservations that the Laser (and the recently FDA approved Cryo) Balloon catheters might be penetrating the interior of the Pulmonary Veins possibly causing future stenosis (swelling). In the Laser Balloon Catheter trials there were cases of phrenic nerve paralysis. In a taped presentation Dr. Pierre Jaïs from the French Bordeaux group showed an ablation using 3D Rotational Angiography which produces a 3D real time X-Ray image of the heart (Philips Medical Systems). A 3-D reconstruction of a left atrium obtained by rotational angiography
- LOA indicates left anterior oblique
- RAO fight anterior oblique
- CRAN cranial
- CAUD caudal
Dr. Jaïs said the Bordeaux group routinely does Caviotricuspid Isthmus lesions (Flutter Ablation) in the right atrium during a Pulmonary Vein Ablation (Isolation) procedure. It only takes an extra ten minutes. They do it while waiting to check back on other lesions. They never completely isolate the Left Atrial Appendage which could possibly lead to clots forming in the LAA and A-Fib stroke. If they have to ablate deep inside the LAA, they are careful not to hit the Phrenic Nerve. Dr. Gerhard Hindricks from the Un. of Leipzig, Germany showed a pre-taped ablation featuring 3-D mapping and an electro-magnetic system which compensated for heart movement. Dr. Andrea Natale showed a pre-taped “Convergent” ablation featuring both a Surgeon and an EP working on the same patient. The surgeon used an Endoscopic Catheter which has a light delivery system so that the doctor has direct vision of where they are ablating, similar to the Laser Balloon Catheter above. The surgeon gained access to the outside of the heart through the diaphragm (unlike standard Mini-Maze operations which make traumatic holes between the chest ribs). He did not have to deflate the lungs to ablate the heart (which can be damaging, especially to older patients). After the Surgeon was finished, the EP went inside the heart to ablate areas not touched by the surgery. As explained by Dr. Natale, this Convergent Procedure is used primarily in difficult cases such as long standing Chronic A-Fib. The Surgeon makes basic ablation lines thereby allowing the EP more time to hunt for and ablate more elusive A-Fib sources within the heart.
Editor’s comment: Surgeons working with EPs to improve the results of Mini-Maze operations has the potential of improving the results of Mini-Maze surgeries for A-Fib patients. However, the convergent procedure had 2 deaths out of a very small number of patients…one atrioesophageal fistula and one death from a large stroke.
For most A-Fib patients, this “Convergent” operation seems overly invasive and risky, and so far has had poor results.
Dr. Natale mentioned that he never uses amiodarone during an ablation, because it can suppress A-Fib triggers and source areas in the heart. Dr. Moussa Mansour, live from Milan Italy, demonstrated another potentially important development in the catheter ablation field—the Contact Force Sensor Catheter (TactiCath, Endosense, SA). It uses three optical fibers to measure “microdeformation”—how much the catheter tip bends when pressed against heart tissue. The force applied changes the wavelength of light in the optical fibers. The force applied during an ablation shows up on a imaging/mapping system as either yellow, green or red. Doctors can see when they make an ablation how much force they applied to a particular spot. Dr. Vivek Reddy of Mount Sinai Medical Center, New York showed a pre-taped demonstration of a novel noose device that closes off the left Atrial Appendage (Lariat II, SentreHeart, Inc., Palo Alto, CA) in cases where the patient can not tolerate anticoagulants like Coumadin. (The Watchman device which closes off the Left Atrial Appendage requires a patient be on anticoagulants for a couple of months.) From the inside of the heart a balloon is placed inside the Left Atrial Appendage to expand it and make it accessible to the noose device which is inserted from the outside of the heart. The positioning balloon is withdrawn before the Lariat noose is closed around the base of the Left Atrial Appendage. The noose completely closes off the Left Atrial Appendage which dies and is no longer electrically active. The Lariat II snare device has already been approved by the FDA.
CFAEs are Complex Fractionated Atrial Electrograms (an electrogram is a picture of the electrical activity of the heart as sensed by a pacemnaker or catheter in the heart). They are low voltage electrical signals with very short cycle lengths used to identify areas in the heart that need to be ablated. Dr. Jose Jalife of the Un. of Michigan showed how CFAEs can have different forms of waveform propagation, such as Collision, Block, Pivot Point and Slow Conduction. Dr. Mauritz Allessie of Maastricht Un. in the Netherlands described his “double layer hypothesis”—that in cases of persistent A-Fib two layers of dissociated fibrillation waves mutually feed each other eternally. Editor’s Note: Dr. Allessie’s description of a new mechanism to explain how A-Fib works in persistent A-Fib patients is a potential game changer. Dr. Allessie had the following warning about using CFAEs, “If you see an area of continuous electrical activity, do not immediately jump to the conclusion that you have found an area of A-Fib nest or driver.” Dr. Sanjiv M. Narayan of the Un. of California, San Diego, working with the French Bordeaux group, described five different types of CFAEs. He hypothesized that Type I CFAEs (rapid localized activity with low amplitude, rapid rate, and narrow spectral organizational index) might indicate localized rapid reentry and be clear cases of “Focal” A-Fib that should be ablated. (MAP stands for Monophasic Action Potential catheter mapping.) Dr. Shin-Ann Chen of Taipei Veteran’s General Hospital, Taiwan, described how in cases of long standing Persistent A-Fib there are so many CFAEs that it is difficult to ablate them all (his facility has a guideline to limit CFAE ablations to only three sites). He proposes a “Similarity Index” or “New Regularity Index” to identify CFAE sites to ablate. Using non-linear analysis he identifies CFAE sites similar in consistency of interval, electrogram morphology, and voltage amplitude in a particular patient. Ablating these sites results in more successful termination of A-Fib than using other factors such as dominant frequency analysis, fractionated interval analysis, or harmonic index. Dr. David Wilber of Loyola Un., Chicago, explained how current observational systems of identifying CFAEs to ablate are subjective and non-reproducible. However, “automated electrogram analysis provides a rapid, objective, and systematic method of identifying sites with CAFEs” to be ablated. He discussed three different algorithms being tested:
1. Counting peak to peak intervals
2. Counting short coupling intervals between discrete & complex fractionated electrograms
3. Looking at continuous CAFEs
“But we are still searching for the optimal criteria to identify the most useful characteristics for successful ablation.” He also described how pharmaceutical intervention—using the antiarrhythmic drug ibutilide (Corvert) shrinks the number of CFAE sites by prolonging cycle length and decreasing some of the short cycle lengths. Dr. Moussa Mansour of Massachusetts General Hospital in Boston cited several studies indicating that ablating CAFEs is an effective strategy for treating persistent A-Fib. CFAEs may identify A-Fib drivers, may indicate a nearby autonomic ganglionated plexus, or may identify areas of slow conduction for a local reentrant circuit. But current definitions of CFAEs and procedural end points are not uniform. And CFAE areas may be extensive in persistent A-Fib, covering as much as 86% of left atrium sites and requiring extensive ablation. Dr. Mansour discussed several strategies to differentiate “Active” CFAEs from “Passive” (areas that don’t drive or trigger A-Fib).
- Pharmacologic intervention reduces the number of CFAE sites. But we don’t know if this affects only the “passive” CFAEs or the “active” CFAEs as well.
- Monophasic Action Potential catheters can identify “Far-field” signals which don’t affect A-Fib.
- Limiting ablation to Continuous Electrical Activity CFAEs. The Bordeaux group identifies areas with 90% fractionation which may indicate an A-Fib driver
- Using a multi-spine catheter for mapping, the Bordeaux group identifies passive activation where a wave simply passes through a field of mapping, whereas Centrifugal activation can represent a driver for A-Fib.
- Massachusetts General uses electrical anatomical mapping to identify activation patterns. They found three basic patterns: Colliding Waves (22%), Passive Activation (48%), and Pivot Points (30%). Pivot Points may indicate drivers for A-Fib.
Editor’s comment: The above studies may represent advances in both the understanding and use of CFAEs in ablating persistent A-Fib. Doctors are much closer to finding a definitive strategy for using CFAEs effectively.
Dr. Nassir Marrouche of the Un. of Utah described the data enhancement (also called “delayed-enhancement”) MRI process which uses a metallic Gadolinium contrast dye to see in 3D and identify collagen fibrotic areas in the heart. The Gadolinium contrast dye penetrates and stays longer in dead, hardened fibrotic tissue, then washes out later. MRI imaging does not expose patients to ionizing radiation. Dr. Marrouche uses MRI to “personalize A-Fib treatment.” He separates A-Fib patients by their degree of fibrosis into what he calls four “stages:”
- A “Utah 1” patient has little scarring or fibrosis.
- A “Utah 2” patient has 5% to 20% of scarring or fibrosis.
- A “Utah 3” patient has 20% to 35% scarring or fibrosis.
- A “Utah 4” patient has a lot of scarring or fibrosis, over 35%
When considering other factors such as the duration of A-Fib, size of the left atrium, how symptomatic a patient is, whether they are paroxysmal, persistent, long-standing persistent or permanent, what counts—what’s key for success, according to Dr. Marrouche, is the amount of fibrosis in the left atrium. The degree of fibrosis correlates with the danger of stroke. For example a 20%+ degree of fibrosis (stages Utah 3 and 4) indicates a threefold increased risk of stroke. These patients should be kept on Coumadin, Pradaxa, or protected by devices such as the Watchman. Utah Stages 1 and 2 usually only need a PVI to terminate A-Fib. While Utah Stage 3 requires more extensive ablation. Stage 4 is what Dr. Marrouche calls ‘the point of no return. Success rates for catheter ablation are only 3%-4% after one year at Dr. Marrouche’s facility.2 20-30 minutes after an ablation, Dr. Marrouche also uses MRI to check lesion accuracy and safety. If there are problems, the patient can be wheeled back into the EP lab to continue the ablation. Dr. Marrouche is starting the DECAAF trail (Determinant of Catheter Ablation of Atrial Fibrillation using Delayed-Enhancement MRI) at 24 centers around the world. Each patient will have an MRI and be separated into stages before an ablation, then 3 months later will get another MRI to look at the amount of lesions. It’s possible that someone in A-Fib for 6 months could have more scarring/fibrosis than someone in A-Fib for 6 years. In the question and answer session following Dr. Marrouche’s presentation, Dr. Vivek Reddy from Mount Sinai, NY made the following observation, “We should be cautious about equating scarring (fibrosis) with abnormal tissue that should be ablated. There is a discordance between voltage that correlates with scar tissue and CFAEs.” Dr. Pierre Jaïs from the French Bordeaux group, in a study that was developed in collaboration with Dr. Marrouche, addressed this same topic—how do MRI delayed-enhancements (fibrosis) correlate with electrogram characteristics of A-Fib? “We expected to see more fractionation in fibrotic areas, but found just the opposite.” He showed a slide of a patient in persistent A-Fib for 18 months. The patient’s posterior left atrium wall had large delayed-enhancement areas (fibrosis), but no complex fractionated potentials at all. He found this in the vast majority of patients. It was more frequent to find CFAEs in areas of no delayed-enhancement. There was only a 6% overlap of areas of delayed-enhancement and CFAEs, which was an inverse correlation.
Editor’s comments: It must be devastating to sit in Dr. Marrouche’s office and be told you are “past the point of no return,” you are doomed to life in A-Fib because you have too much fibrosis in your heart. What about all the Chronic A-Fib patients who have been made A-Fib free? Dr. Jaïs’ long-term persistent A-Fib patients, particularly those with underlying heart disease, have a lot of fibrosis but often are made A-Fib free. However, we don’t know if those Chronic patients had more than 35% fibrosis. But one would expect that many did.
A 3%-4% success rate in cases of over 35% fibrosis (Utah Stage 4) is dismal. Could it be that they are targeting for ablation fibrosis areas which research shows do not generate A-Fib signals? One wouldn’t normally expect to see a lot of electrical activity in fibrous tissue. Why not use established protocols for ablating Chronic A-Fib in Utah Stage 4 patients?
What then are the real benefits for patients in using MRI to determine levels of fibrosis? It certainly would be a help for doctors to learn before an ablation how difficult a case might be. But doctors currently get this information from such factors as the duration of A-Fib, size of the left atrium, how symptomatic a patient is, and whether they are paroxysmal, persistent, long-standing persistent or permanent.
Identifying and locating fibrosis areas in the heart doesn’t seem to be much of a help in the ablation procedure.
Level of fibrosis does correlate with the danger of stroke and could be a good tool to identify and treat patients with more risk of stroke.
An MRI might be useful in checking the quality of ablations, but it seems somewhat cumbersome to move a patient back and forth from the EP lab to the MRI room.
Added 4/24/11: In a further study, Stage IV patients were four times more likely to have a stroke than patients with a low level of atrial fibrosis. And the level of fibrosis didn’t always correlate with standard CHADS2 risk scores of stroke. 16.5% of patients with a CHADS2 score of 0 (low risk) and 18.5% with a score of 1 (intermediate risk) had Stage IV atrial fibrosis. Whether you were in paroxysmal or persistent A-Fib didn’t seem to have an impact on the likelihood of stroke rate. Women were three times more likely to have a stroke than men. The researchers hypothesized that, because men tend to get treatment for A-Fib sooner, women had more extensive remodeling and fibrosis than men, which led to a higher stroke risk.3 Editor’s comments: MRIs to measure fibrosis in the heart should become a routine diagnostic tool for anyone in A-Fib. According to this study, the CHADS2 method of evaluating risk of stroke doesn’t work in many cases. Should we retire the CHADS2 and replace it with a more empirical, scientific method such as fibrosis measurement? Some people have argued that there is less risk of stroke if one is in continuous A-Fib rather than paroxysmal (occasional), because one might be more at risk of a clot when the heart stops and starts beating normally. But this study indicates that whether one is paroxysmal or persistent doesn’t seem to influence the risk of stroke. The finding that women are three times more likely to have a stroke than men should be a wake-up call for doctors (and of course for women)! If women hear from their doctor “It’s all in your mind,” or Take a valium,” it’s time to get a second opinion ASAP. An A-Fib stroke is a fate worse than death, if you live through it. Doctors should become more aware of the increased danger A-Fib presents to women.
Surgeons and EPs Compliment Each Other’s Skills Dr. James Edgerton of Cardiovascular Specialty Associates of North Texas made some interesting comments about Surgeons and EPs (Electrophysiologists). Surgeons excel at making lesion lines. The smooth outside surface of the heart lends itself to this, and the surgeon’s tools are designed for linear ablation. They can see the lines they make and breaks in the lines. While EPs excel at “spot welding.” Catheter tips are punctate by design and can slip off of the uneven surfaces inside the heart. If epicardial (inside the heart) ablation fails, it is because it doesn’t penetrate the endocardium. If endocardial (outside the heart) ablation fails, it is because it doesn’t penetrate to the epicardium. Together these techniques complement each other. If surgeons put a line on the heart, they ought to have a mechanism to prove it is transmural or at least has acute conduction block. Surgeons have difficulty mapping epicardial lesions for several reasons:
- Pericardial attachments inhibit free movement of a mapping probe.
- Surgical mapping tools are homemade or (at best) first generation.
- Surgeons aren’t formally trained in mapping techniques.
- While EPs can move freely around the inside of the heart, have mature mapping technology, and are formally trained in these techniques.
The “Hybrid” Combined Surgery/Catheter Ablation
Dr. Edgerton described the “Hybrid” combined surgery/catheter ablation procedure which is similar to the “Convergent” Ablation Procedure demonstrated by Dr. Natale in the Satellite Case studies in that a surgeon and an EP work on the same patient. The surgeon, using a bipolar catheter, isolates the Pulmonary veins with encircling lesions, boxes off the posterior atrium wall, makes a connecting lesion to the base of the Left Atrial Appendage, then starts a lesion line down towards the Mitral Annulus which the EP will then finish from the inside of the heart. (Surgeons risk damaging the Circumflex Coronary if they were to continue the lesion line down towards the Mitral Annulus). The surgeon will also encircle and isolate the Superior Vena Cava with less risk of damaging the Phrenic Nerve than with catheter ablation. They simply lift the Phrenic Nerve out of the way before ablating. Surgeons can fully divide the Ligament of Marshall, if necessary. If Ganglionated Plexi are part of the operation, they are targeted and ablated. The EP from inside the heart then completes the line started by the surgeon, does a Caviotricuspid Isthmus line in the right atrium (which current surgery can’t currently access), ablates within the Coronary Sinus (which isn’t possible for surgery without significant risk of bleeding), uses mapping to find and ablate Flutter and CAFEs, and checks for entrance and exit block on all lesions. If part of the operation, they will also check the Ganglionated Plexi lesions.
Traditional Cox Maze Incisions
Convergent Procedure Ablation Lines as done by Dr. Andy Kiser of ACATI. The blue lines are done by the surgeon, the green lines by the EP. Unlike a regular Mini-Maze operation, the patient must be on warfarin for 90 days after the operation. Dr. Edgerton’s center has only done 5 patients so far. Five other centers are doing this “Hybrid” Ablation, but there is very little data available right now. Dr. Edgerton does not normally do Paroxysmal (Occasional) A-Fib cases. “I think they are very well treated with catheter ablation.”
Competition or Collaboration between Surgeons and EPs
Dr. Edgerton described an associate who by using direct patient marketing, evening seminars, etc. “does up to 400 inadequate (A-Fib operations) a year fully sidestepping cardiology and electrophysiology. Although you can get a lot of patients like that, I condemn it. It fully damages the collaborative approach.” Dr. Edgerton, in contrast, believes in working with a fully trained EP. EPs are his best supporters. He depends on EPs for cases. Every patient he has ever operated on had been turned down for a catheter ablation. But he acknowledges that in other parts of the country EPs may see Surgeons as competitors for the same patient base and may be concerned about a loss of revenue. Or there may be ego involved, “I can fix anything.” Or EPs may be concerned about a loss of quality control by sending patients to someone not formally trained in the field. But the Hybrid Ablation answers all these concerns and is the ultimate in collaboration. The EP is right there during the procedure, he has not lost control of the quality or direction of the care of his patient. Dr. Edgerton gave the example of the Medical College of Virginia where Dr. Ellenbogen was the driving force in starting the surgical program working with catheter ablation (but not a Hybrid approach—patients are directed to either catheter ablation or surgery depending on their individual needs). Volumes of both the catheter ablation and surgical programs increased. Patients flocked to a center that has multi-modal therapy available. Practical Problems Dr. Edgerton discussed some of the practical problems associated with the Hybrid Ablation: • Work Flow/Down Time Issues. How do you avoid down time when either the Surgeon or EP is waiting for the other to finish, or the problem of an EP lab or operating room not being used while the EP and Surgeon are working together? One solution is predictable operating times or starting the surgery early in the morning. But minimizing Surgeon down time is more difficult in a Hybrid Ablation. (Dr. Edgerton described how the original Hybrid Ablation procedure was to leave all Surgical wounds open while the EP performed the catheter ablation. The Left Atrial Appendage would be amputated only after all catheters were removed. Now the Surgeon finishes all his work before the EP starts.) • Stages or Simultaneous? It’s possible to do Hybrid Ablation Surgery on a patient, then months later do a catheter ablation. Advantages are that the Surgeon and the EP get to work in their home environment, there are no work flow issues, and maybe some patients won’t need an catheter ablation. Disadvantages are that patients are likely to refuse the second stage, because they feel better and because of the added expense. And two anesthesias increases the complication rate for patients. (One would expect the actual degree of collaboration between Surgeon and EP would be considerably less if they did their work three months apart.) (Northwest Memorial Hospital performs the “Hybrid Maze” in two stages. The Surgeon does a Mini-Maze operation through the chest, then after one month an EP does a catheter ablation. “Stage 1 can be up to 90% effective” and won’t require a Stage 2.)4 Dr. Edgerton prefers the approach where both the Surgeon and the EP take their best shot working together on a patient, the patient has a single anesthetic, and presumably a shorter hospital stay. (Dr. Edgerton’s approach is sequential in that first the surgeon works on a patient, then the EP takes over. In a different “Hybrid” approach, as used for example by Dr. Wilber Su of Heart Rhythm Specialists of Arizona, both the surgeon and the EP work on a patient at the same time. The EP can, for example, tell the surgeon immediately if a particular lesion is effective.) • Reimbursement Problems In the US system, if you take a patient to the OR and to the EP lab in the same hospital stay, only one will be paid for.
Editor’s comments: From this patient’s perspective, the “Hybrid” and “Convergent” ablations seem very similar. The “Hybrid” Ablation seems more Surgeon driven, while the “Convergent” Ablation seems more EP driven.
Surgeons working with EPs to improve the results of Mini-Maze operations seem to have the potential to improve the results of Mini-Maze surgeries for A-Fib patients.
But patients should consider that the surgery, though called “minimally invasive,” is still major heart surgery. It is invasive, traumatic, complicated, requires considerable surgical skills and experience, and is potentially risky. And added to this are the low but real risks of a catheter ablation. Combining these two levels of risk is probably more dangerous than the sum of the parts.
Which patients should consider a Hybrid Ablation? Possibly someone who has failed one or two catheter ablations, or someone who is morbidly obese (which causes problems for current catheter imaging systems). But it will take more time and data to determine if the “Hybrid” Ablation is better and more effective than current advanced catheter ablation strategies.
Dr. Kowey’s Statement about Ablation
(Due to bad weather the author’s original flight was cancelled. One presentation missed was a debate by Dr. Peter Kowey of Lankenau Hospital, Wynnewood, PA and Dr. Eric Prystowsky of The Care Group, Indianapolis, IN about the merits and proposed features of the SAFARI registry [the Safety of Atrial Fibrillation Registry Initiative]. [SAFARI is a program currently in the planning stages to establish a national registry for A-Fib ablation.]
Dr. Kowey issued a remarkable Disclosure statement which is quoted here. Please be advised it is written as humor and “tongue-in-cheek.”
- “Dr. Kowey doesn’t perform AF ablations, but does refer patients occasionally, and usually under duress.
- Dr. Kowey would have an AF ablation is he were half dead but awake enough to choose the ablationist.
- Dr. Kowey would enthusiastically recommend AF ablation for plaintiff malpractice attorneys—especially those who advertise for amiodarone patients on billboards.”
Dr. Kowey’s Disclosure statement also said that he is a consultant, speaker and grantee for over 20 pharmaceutical companies.
The author regrets not being able to report on what was probably a very interesting, lively debate.
Pulmonary Vein Isolation Alone for Long Standing Persistent A-Fib—Dr. Marchlinski
In another surprising presentation, Dr. Francis Marchlinski of the Un. of Pennsylvania said that his institution’s protocol for ablating long standing persistent A-Fib does not include CFAE ablation, Mitral Annular and Left Atrium roof lines, and Coronary Sinus Isolation. (These are considered important steps in other center’s protocols for ablating persistent A-Fib. See Boston AF 2008/Stepwise Approaches for Chronic A-Fib.)
Editor’s comment: Patients with chronic A-Fib may want to be aware that at this time (January 2011) Dr. Marchlinski doesn’t use the stepwise approach that others use, because he has not found the results to be significantly better.
Dr. T. Jared Bunch of the Intermountain Medical Center in Utah, in the question and answer session after his talk, gave an example that summed up his presentation. He described how in the hospital he was talking with his patient, a University Professor. The patient would begin a sentence, go into A-Fib and not be able to finish the sentence. Then he’d go back into sinus and finish the sentence. A-Fib was causing him to loose cardiac output and volume of blood to the brain.
Common Causes or Mechanisms of Both A-Fib and Dementia
Dr. Bunch pointed out that A-Fib and Dementia are two diseases that seem to parallel each other. Like A-Fib, Dementia seems to increase with age, diabetes, hypertension, heart failure, smoking history, and systemic inflammation. His center has identified other mechanisms of both A-Fib and Dementia: • Vitamin D Deficiency • ApoE/Genetics
(Dr. Bunch didn’t have time to elaborate on this genetic component of both A-Fib and Dementia. The author is corresponding with him to obtain more information on this potentially very important genetic finding.)
The above factors cause Microperfusion Deficit (less blood to the brain) and Chronic Hypoxia (loss of oxygen). They often develop Thromboemboli (mini clots) and vascular problems. Ablation Decreases Risk of Dementia and Risk of Stroke and Early Death Dr. Bunch cited several studies and the work of Intermountain Healthcare which showed that people with A-Fib who had an ablation had about the same risk of Dementia as normal people, while people with A-Fib who didn’t have an ablation had much more risk of developing Dementia. But he acknowledged that these studies may be selecting a healthier population rather than ablation having an effect on its own.
(In this patient’s opinion, ablation is probably responsible for decreasing the risk of Dementia by improving blood flow to the brain.)
And people with A-Fib who had an ablation had about the same risk of having a stroke and risk of dying within three years as normal people, while people with A-Fib who didn’t have an ablation were likely to get a stroke within 4-5 years and were more likely to die within three years. In particular, A-Fib patients who developed Alzheimer’s died within six months. Supplements and Drugs to Prevent Dementia Dr. Bunch discussed various supplements used to prevent Dementia:
- Antioxidant vitamins (E, C, Beta carotene, Flavonoids);
- They may decrease brain lesions associated with free radical exposure, but evidence is mixed.
- Vitamins B6, B12, Folate, D; Low levels of folate and D are associated with increased risk of Dementia. Dr. Bunch found that Vitamin D deficiency tracks with the development of both Dementia and A-Fib, but said it is unknown if supplementation reduces risk. (Intuitively one would expect that increasing Vitamin D levels would have a preventive effect on Dementia and possibly on A-Fib.)
- Omega Fatty Acids/Fish Oil Low intake is associated with Dementia. Studies do show benefit of fish consumption on the risk of Dementia, cognitive decline, or MRI white matter abnormalities.
- Active Lifestyle Dr. Bunch also pointed out that patients with more active lifestyles have lower risks of Dementia and cognitive decline.
Dr. Bunch also discussed various Pharmacologic Therapies used to prevent Dementia:
- Antihypertensive Agents: Unclear role in prevention, particularly with onset of cognitive decline.
- Cholinesterase Inhibitors: Long-term use with onset of cognitive decline mildly improves cognitive function compared to placebo.
- Hormone Therapy: No benefit found.
- NSAIDS: Lower levels of amyloidogenic Abeta42 protein. Mixed results in clinical trials. One terminated early due to higher risk of heart attack.
- Statins: Retrospective data suggest lower risk of Dementia. Prospective trials are mixed with some suggesting there is a higher risk of Dementia with statin therapy.Conclusions
- A-Fib was significantly associated with all types of dementia, particularly in the younger group (under 70 years of age). Patients with A-Fib have higher rates of Dementia compared to those without and have worse outcomes.
- Early intervention, such as A-Fib ablation, may improve long-term cognitive outcomes and reduce the risk of Dementia to that of patients with no history of A-Fib.
See also previous studies from the Intermountain Medical Center: A-Fib Patients at Risk of Dementia; Ablation of A-Fib Reduces Risk of Alzheimer’s and Dementia; A-Fib Patients at Greater Risk of Developing Alzheimer’s .
Mini-Symposium on Techniques in A-Fib Ablation
Measuring Quality in the EP Lab—Public Reporting “Pursuing Quality in the Interventional AF Ablation Laboratory” Dr. Douglas Packer of the Mayo Clinic in Rochester, MN discussed a topic very important to both doctors and patients—how to measure and report on quality in the EP Center. “Measure something, then you will know something.” “You can’t manage what you can’t measure.” The new health care law will require in two years that A-Fib centers publicly report measurements of efficacy, safety, and process (not just outcome). The Heart Rhythm Society has a task force to develop Performance Measures for A-Fib. Forms are available for doctors to use. The task force is trying to develop:
- Clear and Explicit Definitions
- Clinical Coherence of the Variables (a common language and terms)
- Sufficient and High Quality Timely Data
- Designation of Appropriate Reference Times
- Use of Appropriate Outcome and Standard Periods of Assessment and Observation
Dr. Packer described the Mayo Clinic’s recent experience with collecting data for the SAFARI Registry. One nurse had to be taken off line for two weeks to do the work. That kind of commitment isn’t sustainable for the average EP lab. The work needs to be distilled down to something doable. But Dr. Packer pointed out that if EP labs don’t do the work, third parties will, including self-appointed watchdogs that have nothing to do with the process.
Jet Ventilation “Maintaining Catheter Stability to Improve Ablation Outcomes: JET Ventilation, Sheaths and Imaging”
Dr. Francis Marchlinski of the Un. of Pennsylvania discussed how to improve catheter stability during ablations by:
- Using detailed landmark imaging to identify anatomic features like ridges which might cause stability problems,
- Using a steerable sheath catheter (FlexCath) which can bend 90 degrees and is more flexible than a non-steerable sheath catheter,
- Using High Frequency Low Volume Jet Ventilation to limit respiration movement. A low volume high pressure “jet” of oxygen flows into the airway for a brief time but at a high frequency. The patient receives enough oxygen, but with very little respiration movement. Because the catheter is stable and not affected by respiration movement, more effective lesions can be made.
Dr. Marchlinski’s colleagues at the Un. of Pennsylvania were so impressed and enthusiastic about using Jet Ventilation that he couldn’t pry it away from them to do a randomized study. He did observational studies which showed that when using Jet Ventilation (and steerable catheters), outcomes improved. Less veins reconnected after waiting 30 to 60 minutes after an ablation, and also after 6 months. PVI times were shorter. Patients who had to come back for a repeat ablation had less veins reconnected and smaller segments of veins that needed to be ablated. There was minimal downside risk to patients as long as attention was paid to factors such as CO2 retention. He also protects the patient by allowing for intermittent positive pressure ventilation.
Editor’s Comments: Using Jet Ventilation is a potential game changer for EPs (and perhaps for Surgeons also). Jet Ventilation is a medical breakthrough that could significantly improve catheter ablation.
Where and What to Ablate in the Right Atrium
Dr. Young-Hoon Kim from the Korea University Medical Center, Seoul, Korea, showed how in cases of long standing persistent (Chronic) A-Fib it is often necessary to ablate not only in the left atrium, but in the right atrium as well. CFAEs are often found particularly in the Crista Terminalis and High Septum areas. They are less frequently found at the Low Septum, the junction of the Superior Vena Cava and the Right Atrium, the Sinus Venosum, and the Neck of the Right Atrial Appendage. But when ablating in the Right Atrium, special attention must be paid to not damage the Sinus Node, AV Node, and Phrenic Nerve Sites.
The Role of Left Atrial Appendage Isolation in A-Fib Ablation
Dr. Andrea Natale of the Texas Cardiac Arrhythmia Institute in Austin, TX, described how in cases of patients needing re-do ablations or patients with long standing persistent A-Fib with extensive scarring/fibrosis (over 50%), triggers often originate from the Left Atrial Appendage (LAA). By electrically isolating the LAA through segmental ablation or more extensive ablation, 71% of these difficult patients were rendered A-Fib free. (They also found many A-Fib triggers in the Coronary Sinus.) Dr. Natale stressed the need to map and record from the LAA first, that A-Fib signals from the LAA can spread quickly throughout the heart and be mistakenly identified as coming from other areas. Does electrically isolating the LAA harm how the LAA functions (LAA velocity and mitral inflow)? Dr. Natale found that 2/3 of patients’ LAAs functioned completely normally even though they were electrically disconnected. He didn’t know why. He keeps the other 1/3 of patients on Coumadin to prevent clots forming in the LAA. Or he could use an occluder device such as the Watchman to close off the LAA. Dr. Natale’s findings compliment and confirm other research which points out the importance of the LAA in difficult A-Fib cases, such as the work of the French Bordeaux group which ablates the base of the LAA as part of the first step in ablating for Chronic A-Fib. See Boston AF 2007/Bordeaux Treatment for Chronic A-Fib.)
Improving Results with the CryoBalloon Catheter
Dr. Wynn Davies of St. Mary’s Hospital in London, England discussed the four types of catheters producing encircling lesions—balloon catheters (Cryo and Laser) and curvi linear multi-electrode and mesh catheters which use multi-phase RF. (See Research & Innovation/Technology Innovations/Balloon Catheters and MultiElectrode RF Ablation Catheters.) He has been using the Cryo Balloon catheter and had many tips on its use. He prefers to use an extra stiff guide wire for extra support and because it is more capable of bending into difficult branches of the PVs. Once the balloon is opened, it can be pushed into the PV antrum as hard as one likes. The contrast dye is used to show there is no leakage. When the Cryo power is applied, it produces an excellent freeze and isolation. A catheter is placed in the Superior Vena Cava to pace the phrenic nerve whenever Cryo energy is applied to the right PVs. The phrenic Nerve runs very close to the Right Superior Vein and can sometimes run close to the Right Inferior Vein. He waits for cryo adherence before starting phrenic nerve pacing. He primarily uses the larger 28mm balloon catheter. He starts in the left upper vein, then moves to the left lower vein, then moves to the right upper and lower veins. The encircling lesions overlap each other. He applies Cryo energy for five minutes per ablation, but others have used 4-6 minutes. Further studies are ongoing to determine how much time is necessary for a good CryoBalloon ablation. In a European study of 350 patients, an average of 11 Cryo ablations were required to isolate the PVs (under 3 per vein). 97% of the veins were isolated, the vast majority with the larger 28 mm balloon. 75% of Paroxysmal patients were A-Fib free after 18 months. Fluoroscopy time was around 40 minutes. Ablations times averaged 100 minutes less than RF. There were 26 Phrenic Nerve Palsy cases, 24 of those cases used the smaller 24 mm balloon catheter (the smaller balloon may penetrate too deeply into the vein and get too close to the Phrenic Nerve).
Coping with Reconnection
Dr. Hans Kottkamp of the Hirslanden Heat Center in Zurich, Switzerland, discussed how to recognize and deal with PV reconnection. “How to Identify Early Reconnection After Acute PV Isolation.” He showed how measuring Entrance Block alone may not reveal gaps in ablation lines. Both Entrance and Exit block (bidirectional block) are necessary to reveal gaps. He discussed studies in which doctors waited either 30 minutes or 60 minutes after an ablation to check for reconnection. 1/3 of early reconduction can be found if one waits 60 minutes to map for bidirectional block and close any gaps. Clinical outcomes are better if one waits 60 minutes rather than only 30.
Editor’s comment: The author wonders how practically doctors can afford to leave a patient for 6o minutes. Conscious sedation would be impossible. Would an extra hour of general anesthesia be good for a patient? Such a policy might cause serious problems for smaller operations, hospital administrators, and insurance companies who would have to pick up the tab for this extra ablation laboratory time. Larger operations with multiple laboratories might be able to schedule a 60 minute break for patients. But it seems unrealistic to expect most A-Fib ablation doctors to wait 60 minutes after an ablation to check for reconnection.
But Dr. Kottkamp pointed out that bidirectional conduction block is just a functional end point. It cannot differentiate between reversible and irreversible tissue excitability after ablation. He suggested that adenosine might be used to identify reversible tissue damage after ablation. “Adenosine restores PV LA conduction by hyperpolarizing PV cells and thereby enhancing sodium current availability.” It may reveal potentially reversible tissue injury which will react differently than tissue with permanent injury. He pointed out that RF tissue change including edema (swelling), and perhaps inflammation may contribute to late reversibility and reconnection. Strategies to Prevent Atrial-Esophageal FistulaDr. Vivek Reddy of Mount Sinai Medical Center in New York discussed different strategies to avoid Atrial-Esophageal Fistula (A Fistula is an abnormal duct or passage, in this case between the esophagus and the left atrium heart wall). 1. Minimizing power at the posterior wall when ablating. But we don’t know what the amount of power is that would minimize damage. Even applying 10 Watts can heat up the esophagus, because the posterior wall of the left atrium can be very thin in spots, and the esophagus can be found right next to the posterior wall of the left atrium. He showed a slide indicating the maximum temperatures where ulceration was seen and the maximum temperatures where ulceration was not seen. The marks overlapped. There was no “safe” threshold. Another study recommends limiting RF energy to under 20 Watts for less than 15-20 seconds when ablating in a region next to the esophagus.5 Temperature monitoring. Dr. Reddy cited studies which showed that using temperature monitors does reduce damage to the esophagus. Endoscopies of the esophagus were performed on each patient after their ablation to determine damage. But the type of temperature probe is very important. A temperature probe with a surrounding plastic sheath (like a stethoscope) can take 40 seconds to show a significant temperature rise. If you strip away the plastic cover, the temperature goes up in only a few seconds. In a typical ablation when the medical staff sees a temperature rise, they stop the ablation. But the temperature will continue to rise. After a 30 second ablation, it may take an additional 80 seconds for the temperature to come back down. Is this temperature rise causing damage to the esophagus? Temperature monitoring isn’t perfect. Where the temperature probe is located will change the readings. He cited animal studies where they inserted a balloon with many temperature probes into an esophagus. If the temperature probe was on the side where one was ablating, the rise in temperature was almost immediate. But if it was on the other side, there was a slow rise; and when the ablation was stopped, the temperature continued to rise before eventually falling. He cited a small study from Brazil where an catheter with a temperature probe was placed in the esophagus and moved side to side depending on where the heart ablation catheter was positioned. This system produced no ulceration. 3. Moving the esophagus. The esophagus can move spontaneously during an ablation. Can it be moved manually away from where a catheter is ablating? Using barium paste to identify the location of the esophagus, he showed an experimental system using a soft plastic tube with a stylet (a slender medical probe) to move the esophagus. But prospective randomized studies need to be done to determine if this system actually protects the esophagus. Can moving the esophagus cause other problems?
Editor’s Note: Moving the esophagus (combined with temperature monitoring) seems like an amazingly simple, practical method of avoiding damage to the esophagus. In fact, one of the vendor booths at the Symposium demonstrated such a system that was trying to get FDA approval.
4. Force monitoring. Force applied seems to make a difference, whether or not one uses temperature monitoring. 5. Conscious Sedation vs. General Anesthesia. Dr. Reddy describes studies by Dr. Natale in which 48% of patients under General Anesthesia (completely unconscious) had esophagus ulceration versus only 4% of patients under Conscious Sedation. 6. Protecting the Esophagus. Dr. Reddy described experimental studies in which a cooling balloon was positioned in the esophagus to protect it from heat from the ablation catheter. This decreased the chance of ulcer formation in the esophagus. But the cold might attenuate lesion formation by the RF catheter. 7. Cryo Ablation. Editor’s Note: Small studies have indicated that Cryo (Freezing) Focal Ablation at regions near the esophagus is safe. Cryo “can cause transmural injury to the esophagus but may be less likely to result in deep ulceration and fistula formation.”5However, this strategy involves removing an RF Catheter and inserting a Cryo Catheter which lengthens and complicates the ablation procedure. Hospital administrators and insurance companies may not approve of this strategy because of the added costs. 8. Proton Pump Inhibitors. Not discussed in Dr. Reddy’s talk that was limited to 10 minutes was a strategy to avoid esophageal fistula after, rather than during, an ablation. Most centers now put patients on Proton Pump Inhibitors like Nexium for 2-3 weeks after an ablation. Even if there is ulceration in the esophagus from the heat of an ablation catheter, the Proton Pump Inhibitors prevent gastric acids for backing up into the esophagus in case of Gastroparesis (weak stomach not emptying its contents) or GERD (Gastroesophageal Reflux Disease). Atrial-Esophageal Fistula usually occur 2-3 weeks after an ablation. It takes that long for gastric acids to burn through the esophagus areas structurally weakened by catheter heat from inside the heart. Some centers also treat patients for 2-3 week after an ablation with sucrafate (Carrafate), a medicine used to heal ulcers. Please be advised that Atrial-Esophageal Fistula is a very rare complication [approximately 1/1000+ cases] that is becoming even more rare because of the use of preventive strategies. Because Atrial-Esophageal Fistula is such a rare complication, it may be difficult for doctors to determine which of the above strategies is the best and most essential to be used. But from this patient’s perspective, anyone interested in getting a catheter ablation for A-Fib should ask their doctor what precautions they take to prevent Atrial-Esophageal Fistula.)
Return to Index of Articles: AF Symposium: Steve’s Summary Reports
Last updated: Friday, August 28, 2015
- http://www.stopafib.org/newsitem.cfm/NEWSID/317/fibrosis from atrial remodeling/atrial fibrillation stroke risk↵
- Bahnson, Tristram D. “Strategies to Minimize the Risk of Esophageal Injury During Catheter Ablation for Atrial Fibrillation.” Pacing and Clinical Electrophysiology, 2009;32(2):248-260. http://www.medscape.com/viewarticle/587908?src=emailthis↵
- Bahnson, Tristram D. “Strategies to Minimize the Risk of Esophageal Injury During Catheter Ablation for Atrial Fibrillation.” Pacing and Clinical Electrophysiology, 2009;32(2):248-260. http://www.medscape.com/viewarticle/587908?src=emailthis↵