Initial Experience with High-Density Grid Mapping: Interview with Dr. Roger A. Winkle

In this feature interview, EP Lab Digest speaks with Dr. Roger A. Winkle about his experience using the new Advisor^™ HD Grid Mapping Catheter, Sensor Enabled^™ (Abbott) at Silicon Valley Cardiology / Sutter Health in East Palo Alto, California. His cases are done at Sequoia Hospital in Redwood City, California. 

What mix of cases do you primarily treat?

The majority of cases that I treat are for atrial fibrillation and atrial flutter. We have an unusual mix of cases compared with many other centers, because we treat a lot of complex atrial fibrillation and atrial flutter cases. We see a lot of cases from other electrophysiologists who were unsuccessful in eliminating the arrhythmia or because the patients were too sick or had poor ventricular function or mechanical valves. We also get a number of failed surgical maze procedures. Therefore, we probably have fewer standard paroxysmal atrial fibrillation cases than most centers. We also treat other SVTs and VTs. 

How many and what kinds of cases have you performed with the Advisor HD Grid?

I’ve now performed 25 cases with the Advisor HD Grid (Figure 1), and they have been a variety of cases. I started out thinking I would be using the Advisor HD Grid only for complex atrial flutters or cases where mapping would be important. However, I’ve had such a great experience with this catheter, that I’ve now used it in every single case. Only four of those cases were for paroxysmal atrial fibrillation, but the Advisor HD Grid turned out to be very helpful in one of those cases, because the patient had an epicardial connection from the atrial septum to the right upper pulmonary vein that we were easily able to map and ablate. The more we do detailed ultra high density mapping, the more we realize how complicated the left atrial activation actually is. It is becoming increasingly common to see epicardial connections into the mid posterior wall, the left atrial appendage, or from the coronary sinus to the left atrium. The Advisor HD Grid helps identify all of these complexities. 

What attracted you to start using the Advisor HD Grid?

We have been long-time advocates of using ultra high density mapping to map out flutter circuits. A lot of people use entrainment mapping, but we rely almost completely on ultra high density mapping. I liked the theoretical basis of the Advisor HD Grid — that no matter which direction a waveform is coming from, you get a signal. It’s based on the physiology of bipolar electrograms — if you’ve got an activation wavefront coming toward your two electrograms and they are parallel, you’ll get a nice signal. However, if it’s coming perpendicular to your two electrodes, then you’ll get nothing, even though there is really a good signal there (Figure 2). I liked the idea that every single point you collect is going to give you a good electrogram unless it is scar. With the Advisor HD Grid, you will also collect a large number of electrograms at one time. It made a lot of sense from a theoretical standpoint, and that is why we were excited to start using the Advisor HD Grid. 

Has the Advisor HD Grid helped you to achieve successful results thus far?

Yes, and it has been surprising at how quickly I have been able to make maps. We have always been able to make ultra high density maps in about 10 or 15 minutes. However, we are now able to collect 4 to 5 times as many points in the same time with the Advisor HD Grid, so it’s been very helpful in providing even better quality and higher density maps. I’m also able to get a great map much more quickly with the Advisor HD Grid, because there is such a high percentage of the electrograms that are usable. 

Could you give an example with a recent case?

Probably the most interesting case we did with the Advisor HD Grid was a patient who had rheumatic mitral valve disease and also had two previous valvuloplasties, the last of which tore the atrial septum; ultimately, the patient had a surgical aortic and mitral valve replacement, and the surgeon had oversewn the torn septum, removed the left atrial appendage, and also had done a cut-and-sew maze on the patient. Post-maze, this patient was plagued with atrial flutter, and after a period of time, she went into heart failure. We used the Advisor HD Grid in her case, and it was very helpful (Figure 3). We found two right atrial flutters; one was a typical cavotricuspid flutter, and the other was a right atrial flutter that was going around scar in the atrial septum — probably where they had done the repair. There was also a third left atrial flutter (Figure 4) that was using a different part of the septum for the circuit. We were able to easily map out all three of those flutters and get rid of them, and at the end of the case, we had nothing inducible. It has now been more than a month and so far, the patient is doing great. The catheter was very helpful in that case. 

Has the catheter met or exceeded your expectations? How would you compare this mapping catheter to others you have previously used?

It has. To be fair, my expectations of what it would do were high to begin with, just based on how it works and how it collects the electrograms. Where it has really exceeded my expectations is how soft it feels in the atrium, and how easy it is to move around and map. With other mapping catheters, you never quite know if you’re actually touching the wall when you’re recording electrograms. However, this catheter is like a big pancake spatula that is very soft, so when you go up against the wall, you see it bend down like you’re getting under a pancake to flip it. When it flexes, you can tell you’re touching a wall, so you know where that wall is. The other aspect I like about the Advisor HD Grid is that because it is so soft, it doesn’t push out the wall. Sometimes with the circular catheters, you get a distorted geometry as you make a map because you push the wall and tent it a little bit. This catheter doesn’t do that, so you end up with more accurate geometry and much less to edit afterward. Therefore, the Advisor HD Grid has really exceeded my expectation from the standpoint of its ease of handling, softness, and safety feel. 

What advice would you have for your peers who are considering using this catheter?

I would tell them to try it. I use it now on all straightforward cases. There was one case where we found an epicardial connection into the posterior wall, and it was very easy to map and figure out what was going on. The one thing I would advise my peers is to simply trust the computer — as electrophysiologists, we are used to wanting to see every single electrogram. However, electrograms are collected so quickly with the Advisor HD Grid — 600 or 1000 a minute or more — that it's not possible to individually look at every one. Once you’ve collected 25000-30000 points, one can only do the map with a computer, so you have to trust it. I think my peers will be very pleased with the map accuracy in telling them exactly where the flutter circuits are. We’ve also used it in one or two patients where we had a little trouble isolating one of the veins. These days with contact force, you usually go around the veins and they’re isolated. But when they’re not, I very quickly do a map with the Advisor HD Grid, and it tells me exactly where the gap is and where I need ablate to isolate the vein. 

What features of the Advisor HD Grid do you value most in the diagnosis and treatment of complex cases?

I think the features I most value include the safety feeling of how soft it is, the ability to know when you’re touching the wall while making a map by seeing the catheter flex, and the speed of mapping. Not only do you quickly collect a lot of electrograms, but virtually every electrogram where there is not complete scar gives you usable signals. Therefore, your maps collect points extremely fast — it’s the combination of the Advisor HD Grid and the EnSite Precision Cardiac Mapping System that takes all this data in and turns it into a usable format.

Disclosure: Dr. Winkle has no conflicts of interest to report regarding the content herein.