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MOHAMED BASSIOUNY: Our topic today is catheter ablation of atrial fibrillation. I have no relevant disclosures. And as we all know, atrial fibrillation is the most common heart abnormality. It affects around three to six million people in the United States. About 9% of those above 65 years of age will have AFib at one point. The prevalence of AFib is increasing as the population ages.

AFib can have serious consequences if not managed well in increasing mortality. This is data from the Framingham study that showed that, over 10 years of follow up, patient men and women who have AFib have significantly higher mortality compared to those who did not. Moreover, the quality of life is significantly increased with AFib. There's an increased risk of stroke, increased risk of heart failure and dementia.

There are multiple risk factors for AFib. Advancing age is the most important one. However, high blood pressure and obesity are very important, too. We can see from this map that the prevalence of AFib is clustered around the eastern part of the United States. And the map is very similar to the prevalence of hypertension as well as the prevalence of obesity. And these are very strong risk factors for AFib.

The cornerstone of the management of AFib is prevention of stroke is the most important thing, followed by rate control and prevention of heart failure, and rhythm control achievement with AFib ablation or anti-arrhythmic drugs. And finally, most recently, we're trying to avoid, prevent AFib altogether by lifestyle changes and management of risk factors.

So our aim today is to restore normal rhythm. And to do that, we need to understand the mechanism of AFib. So the most important mechanism and the cornerstone of AFib is rapid from the pulmonary veins. The pulmonary veins have [INAUDIBLE]. And they are more prone to re-entry arrhythmias leading to rapid firing that triggers AFib.

In addition, the posterior will have abrupt changes in the muscle fibers, as you can see, and that abrupt changes can lead to disorganized conduction in initiation of AFib. As AFib progresses from paroxysmal to persistent AFib, more long term [INAUDIBLE] changes occur. The refractory period of the atrial cells decrease and they become more prone to go out of rhythm.

In addition, as the patient is in rapid atrial fibrillation, the atrium is beating 300 or even 500 beats per minute. Eventually, the atrium scars and dilates. So it becomes more persistent. All familiar with the AFFIRM study-- this is a study that was published in 2002. It compared rate control to rhythm control.

You can see that the mortality between the two strategies did not significantly differ. However, what you might not be aware is that this study was done before the era of catheter ablation. Out of more than 2000 patients, only 14 patients underwent AFib or atrial flutter ablation.

The majority of those patients were managed with antiarrhythmic drugs. 60% were on amiodarone, and 40% were on [INAUDIBLE]. But even the before, newer drugs like Tikosyn was only used in less than 1% of those patients. Rhythm control was achieved in less than 62% of those patients, and there was significant crossover between the groups. So it's hard to judge based on that study.

So nowadays, we know that antiarrhythmic drugs are not as effective as ablation. In fact, they actually have serious side effects that are not trivial they increase the risk of death, torsades de pointes in arrhythmias, neuropathy, thyroid dysfunction, and some less serious side effects. But definitely those side effects decrease the quality of life substantially.

So that brings us to catheter ablation. A lot of our patients present to us after either failing antiarrhythmic drug or not tolerating one or not preferring to be on antiarrhythmic drugs. And they've been suffering. The quality of life has been really low, and they come to us for help.

So we need to talk about the efficacy of catheter ablation. This is a study that was done in collaboration with the Cleveland Clinic, our group at Texas Cardiac Arrhythmia. And it was shown that the success of atrial fibrillation can reach up to 92% for paroxysmal AFib and 90% even in persistent AFib. Success decreases in long term persistence AFib. However, it's still very acceptable in patient population that probably most likely fail antiarrhythmic medication.

Perhaps the most important subgroup of patients who would benefit from atrial ablation is patients with heart failure. So in a landmark study that was just published in 2018, this study compared management of patients with severe systolic heart failure with rejection fraction less than 35%. And patients who underwent catheter ablation have a substantial decrease in heart failure, hospitalization, and death.

And as you can see, the curves separate nicely between medical therapy and ablation, with those who underwent ablation had less death and less hospitalization from heart failure. This is a patient of mine. She's an 80-year-old female patient that had severe cardiomyopathy, almost end stage cardiomyopathy.

She was on amiodarone, high dose amiodarone without success. This is her ejection fraction prior to ablation. It was 10%, very low rejection fraction. We're planning to put an ICB in.

And after an ablation, you can see that rejection fraction completely normalized. And she's off of amiodarone. And she's [INAUDIBLE] a but smaller here for more than six months now and she's doing very well. Nothing is more satisfying than seeing patients who have long-standing persistent AFib who are continuously 24 hours in AFib for years. And then after an ablation you can see that they are in AFib and regain sinus rhythm.

This is another study that's very interesting. This was published in Jack, and that study showed the benefit of AFib ablation. And patients who have heart failure were already rate controlled. So in the past, we think that the rate control would give you the best bang for your buck and would improve rejection fraction.

But this study showed that even in patients who were rate controlled that had a low rejection fraction, performing AFib ablation substantially improved rejection fraction. 18% increase compared to 4% in those who were medically [INAUDIBLE]. And that improvement was even higher in those patients who had an MRI done that showed no [INAUDIBLE] enhancements. So patients who had no [INAUDIBLE] enhancement, around 72% of those patients compared to 29% had their rejection fraction completely normalized after AFib ablation.

So one important thing to think about atrial ablation is when to refer for atrial ablation. In the past, we used to wait until the patient failed multiple antiarrhythmic medications and had become very persistent. And then we refer for atrial ablation. However, there's a lot of data that's coming up from recent studies that shows that the sooner we send those patients and perform atrial ablation on them, the higher the success rate.

You can imagine that the heart is beating upper-- let's say the atrium is beating 500 beats per second-- per minute, for several months. That would lead to significant scarring and dilation of the left atrium. And success rate of a patient decreases as we wait.

So this study compared performing ablation early on, within a year after living with persistent AFib, compared to waiting for several years. And the longer you wait, the lower the success. So high success was performing atrial ablation sooner than later.

And based on all of this data, the guidelines have changed. The indication for atrial ablation used to be that we have to wait until a patient fails antiarrhythmic drugs. And now it's a class 2A indication to go directly to atrial ablation in patients with paroxysmal or even persistent atrial fibrillation.

Another population that benefits from atrial ablation is patients who have tachy-brady syndrome. In the past, the only solution was to put a pacemaker in those patients to allow management with medication, including [INAUDIBLE] agents and antiarrhythmic drugs. And nowadays, especially in patients who are relatively healthy athletes who have a baseline low heart rate, that would not tolerate [INAUDIBLE], those patients would highly benefit from AFib ablation in getting rid of the arrhythmia. Thus, we don't need to use [INAUDIBLE].

So that brings us to atrial fibrillation procedure itself. The cornerstone of atrial fibrillation is isolating the pulmonary veins. As we said, 90% of the time, these are where the impulse or the rapid firing starts. And so isolating those veins would prevent AFib from occurring. And there's multiple technologies to achieve that.

The most commonly used and the first to be used is radial frequency energy. By delivering alternating current at the tip of the catheter, it heats up the tissue and leads to quite a bit of necrosis, creating a scar along the atrium of the pulmonary vein and preventing [INAUDIBLE]. There are other modalities that have been recently introduced to our arsenal.

And in the past, the beginning of this procedure, we used mostly depend on fluoroscopy to guide our ablation. So we had a circular catheter to place in the ostium of the pulmonary veins and a ablation catheter that we use to deliver the radio frequency energy. And that procedure was prolonged. We used to give us a lot of radiation, exposure to both the patient and the operator.

In addition, we had to memorize mostly where we're ablating and thus the success rate was not as good as nowadays. So one thing that improved the success rate significantly was electroanatomic mapping systems. Those systems use mechanic fields and electric currents to accurately locate our catheters. The accuracy is less than one millimeter, so it's super accurate, and we can mostly rely on them to guide our ablation.

So this is a 3D geometry of the heart, and we're looking from the posterior aspect of the left atrium. You can see the four pulmonary veins is the most common variety of anatomy. But sometimes, you have a left common vein. You have multiple right veins.

So you can see that the purple is healthy tissue, but the ostium is where we want to ablate. So we try to isolate those veins. Emphatically this is mostly an anatomical procedure.

And with the improvement in this mapping technology, nowadays we can even do the procedure completely without the use of fluoroscopy. So our group pioneered this approach. And since 2014 we've been using [INAUDIBLE] procedure with minimal use of fluoroscopy.

More advancement in ablation is the improvement of catheters technology. So in the past, the catheters didn't have-- the tip used to heat up and leads to charred formation. But they've introduced catheters that can irrigate its tip and cool down [INAUDIBLE]. This would prevent car from forming. More importantly, recently, we have catheters that have contact force senses at the tip that allows us to exactly know how much pressure we're exerting on the tip of the catheter on the walls of the left atrium and also deliver more durable radio frequency lesions.

This is a video that shows a procedure-- we're performing an ablation procedure. We're ablating or isolating the left veins. There you can see the catheter can show you exactly how much pressure you're applying on the wall. We're trying to keep it between 5 to 10 gams throughout the procedure.

That reduces the risk of perforation as well as injury to the esophagus behind the heart. More importantly, the catheters are so accurate that we can see exactly how many millimeters between each ablation points. And the aim of the procedure is not to leave any gaps between each point in ablation.

Even leaving one gap could lead to recurrence of AFib and recovery of conduction into the vein and failure of the procedure. So this technology and the accuracy of the ablation, the success rate has significantly improved. This is a typical lesion chart that we do for atrial ablation. The basic or the most important part of the ablation is to isolate the veins for each side. But as we said, the posterior wall is also highly arrhythmagenic. And it's very common for us to isolate that posterior wall as well.

So this is a case that shows the vasocatheter and the circular catheter in the right pulmonary veins. And we can see this was after isolating the pulmonary veins. You can see that the heart is in normal rhythm.

However, the vasocatheter, which is the blue catheter-- or the signals are at the bottom of the screen. You can see that there's very rapid firing coming from those veins. And if that vein was not isolated, probably the patient would go into AFib. So that is why we isolate those veins. 90% of the time, the triggers are coming from the veins.

Another advancement in mapping of atrial arrhythmia is the introduction of high density electroanatomical mapping. So there's various catheters that now has a lot of accelerator electrodes and can map a lot of delivery, map a lot of points in one application. So those catheters, we can use them to find out where exactly the electricity or the impulses are entering and exiting from the veins.

So here, we're using a catheter called the grid [INAUDIBLE]. And new software called [INAUDIBLE] can show you exactly where the impulses are entering and exiting from the vein. So the white spot is the earliest entry into the veins. And you can see here the impulse-- the local electrograms are big spikes. And within seven seconds of applying radio frequency energy, you can see those big spikes going away. And you're left with those smaller spikes, which are farfield [INAUDIBLE] current from surrounding structures.

Another important arrhythmias that we encounter are atrial flutters. These are not uncommon in patients who have persistent atrial fibrillation, as well as patients who have heart surgeries or prior catheter ablation. So matching those flutters used to take a long period of time.

But now with the high density mapping, we can take thousands of points within a few minutes. You can see that flutter is rotating around the back wall of the left-upper chamber and going across the room in a figure eight manner. And finding that critical isthmus, that area that's vulnerable, and ablating over that area in the back wall of the left upper chamber leads to termination of the [INAUDIBLE].

Another common atrial flutter is one that dates around the micro animus. That flutter can be abated by collecting a line from the pulmonary veins to the micro animus. But identifying where you need to ablate is very important, and that high density mapping helps us.

So we all know that the success of atrial fibrillation ablation is very high-- or, excuse me atrial fibrillation. The most challenging subset of patients are those with persistent atrial fibrillation. In our experience, ablating or isolating the veins only leads to low success. And we've been working hard on research to find the best approach for those patients. There's different modalities. We can ablate the veins. We can also create some [AUDIO OUT] isolate the posterior wall.

And most importantly, nowadays, we're looking into-- in those subset of patients with persistent and persistent AFib, it's not uncommon to find triggers that are not coming from the pulmonary veins-- non-pulmonary vein triggers. In addition, one of the Achilles hill of atrial fibrillation was recurrence of conduction of the pulmonary veins. So with the improvement of the catheter technology, this is a large study that 27 hospitals in the US and Canada. And it showed that atrial fibrillation using the new contact force catheters can have substantially improved outcomes.

And so this compared to ablating only the pulmonary veins compared to ablating the pulmonary veins in addition to other areas, including the posterior wall, or flutters as needed-- and then pulmonary vein triggers. You can see that the success rate improves significantly-- up to 80% clinical success, even in the difficult subset of patients persistent atrial fibrillation.

In our experience, especially in patients who have non-paroxysmal atrial fibrillation or those who have AFib or paroxysmal AFib with low rejection with systolic heart failure-- one of the most common drivers of AFib is non-pulmonary vein triggers. So in that large study, with more than 700 patients, our group was able to identify that ablating the non-pulmonary vein triggers improves the outcome significantly. And without those non-pulmonary vein triggers, the success rate can be as low as 30%. But by targeting the pulmonary vein as well as non-pulmonary vein triggers, we can improve the outcomes to up to 70% or 75%.

So how do we identify those non-pulmonary vein triggers? Basically, we first ablate the veins-- the basic veins in the posterior wall. But then we place catheters around different locations of the heart. And we challenge the patient with high doses of isoproterenol, up to 20 to 30 mics for 10 to 20 minutes. And we watch for areas that can fire and trigger AFib.

So if the earliest activation is coming from close to the crista terminalis, this is a [INAUDIBLE] catheter with approximate [INAUDIBLE] crista terminalis and the distant one in the CS. If the earliest activation is coming from crista terminalis, it's most likely that the trigger is coming from the SVC. And that section needs to be isolated.

If it's coming from the CS, that depends on the location. It can be coming from the CS itself. Or depending on the location in the CS, if it's coming from the proximal CS, could be coming from the septum or the medial aspect of the mitral [INAUDIBLE]. If it's coming from the distal aspect of the pulmonary sinus, it might be coming from the [INAUDIBLE] sinus itself or from the left atrial appendage or the vein of Marshall.

And in that situation, if we have constant triggers, we isolate those structures. Nowadays, we don't just go after the focal trigger, but isolating the whole structure would improve the success significantly. And here in this case, you can see that a single extra beat coming from the proximal coronary sinus leads to triggering AFib.

So it's not only the pulmonary veins that can trigger AFib However, in the majority of patients, it's the pulmonary veins. And mostly in patients who have paroxysmal AFib, it's most of the [INAUDIBLE] pulmonary veins. Also placing the LASSO catheter in the left superior pulmonary vein, it allows us to look at the farfield potentials coming from the left atrial appendage. And if we see a constant firing from the left atrial appendage, in some occasions, especially in patients who have high risk of recurrence-- like obese patients or patients who have advanced age or hypertrophic cardiomyopathy-- those patients, it's not unreasonable to isolate the left atrial appendage.

Perhaps another enhancement in imaging is the cardiac MRI. Not only that it show us the size of the left atrium and the anatomy of the veins, but it can also allow it to see the extent of scar tissue in the left atrium. And that would help us to plan ahead the process of ablation.

So as I told you, like, delivering [INAUDIBLE] radio frequency energy to isolate the veins is the most important thing. And newer technology, like ablation index, allows us to deliver enough energy to isolate the veins without causing complications. So that can allow us to get durable isolation of the pulmonary veins in 94%, 96% of those patients improving their success.

So over the past recent years, we've had new ablation modalities. There's a cryoballoon, laser, or using radio frequency. Those modalities are aiming to improve the success of the procedure and also the feasibility and make it easier to perform. So the cryoballoon is a balloon that can be advanced into the ostium of the pulmonary veins.

And then liquid nitrogen is introduced to cool down the [INAUDIBLE], leading to isolation. And initially, this balloon was mostly used in paroxysmal atrial fibrillation. However, there's promising studies that show that it can also work in patients with persistent atrial fibrillation. As I said, the freedom from AFib can reach up to 80% using the balloon, especially in paroxysmal atrial fibrillation.

A newer balloon is one that delivers radial frequency energy. It has 10 electrodes that can deliver simultaneously the radio frequency energy circumferentially. It can also up-titrate or down-titrate the energy according to the location of the balloon.

And so we can use less energy along the posterior aspect of the pulmonary vein to the [INAUDIBLE] of the phrenic nerve. And our group has been involved in the studies evaluating that catheter. We are actually the first one who did the first patient in the United States.

Perhaps the most promising technology is pulsed field ablation of the pulmonary vein. This is a new technology that is being developed, and it uses subsecond electric fields to ablate the pulmonary veins. The technology is based on the fact that myocardial cells or heart tissue is more sensitive to that subsecond electric field compared to the surrounding structures. So you can safely isolate the pulmonary veins without injuring the phrenic nerve or [INAUDIBLE] that would significantly improve our outcomes and also the safety.

So we're trying to decrease complication as much as possible. So we use ultrasound for guidance to get access into the veins. That has significantly decreased our bleeding complications. So we do all our procedure on uninterrupted [INAUDIBLE] anticoagulation. Our bleeding rate is less than 1%.

We also use intracardiac echo to guide our ablation. That allows us to exactly pinpoint where we're going to cross the [INAUDIBLE] tranceptor function. It also allows us to visualize the [INAUDIBLE] cathode, circular cathode, also in the pulmonary veins and avoid the bleeding inside the veins and have good contact. And so reduce the risk of pulmonary veins to those that improve [INAUDIBLE].

We can also use the ICE catheter to visualize the appendage in some locations and root out the presence of clots. In fact, we've [INAUDIBLE] we're using the ICE catheter to guide the delivery of the WATCHMAN device when we're planning on isolation of the appendage wall to decrease the risk of stroke. We can also detect complications, like cardiac perforations early on, and manage it quickly.

This is actually a huge pulmonary pre-cardiac infusion. And it wasn't an acute complication. It was basically pre-cardiac infusion that was noted incidentally in a patient with end-stage [INAUDIBLE] at the time of ablation. And it actually improved significantly after performing atrial ablation.

Another serious complication is injury to the esophagus behind the the left atrium. And that can be a [INAUDIBLE] complication. However, it's very rare. It's probably 1 in 1,000 rate. And we've been using this multi-electrode temperature probe to measure the temperature throughout the esophagus and interrupt anterior [INAUDIBLE] ablation if we find that there's a significant heat.

So in conclusion, atrial ablation has improved significantly over the past several years with the advancement in the technology and knowing which subset of patients would benefit more. But the success rate is higher in patients with paroxysmal atrial fibrillation. But more importantly, those with persistent atrial fibrillation can also derive benefit.

However, the earlier we perform the ablation, the better. Patients who have systolic heart failure would benefit significantly with reduction in heart failure and hospitalization and mortality-- as well as those patients with tachy-brady syndrome it can be atrial ablation instead of placing a pacemaker. Thank you very much.