2021 AF Symposium

Live Case: Pulsed Field Ablation for Atrial Fibrillation Using a Lattice-Tip Focal Catheter

In a live ablation case titled “Pulsed Field Ablation for Atrial Fibrillation Using a Lattice-Tip Focal Catheter”, Drs. Vivek Reddy and Petr Neuzil demonstrated a new, innovate strategy of using Pulsed Field Ablation (PFA) combined with RF ablation developed by the private company AFFERA, Inc. (Watertown, MA).

Dr. Vivek Reddy is with Mount Sinai Medical Center in New York City and Dr. Petr Neuzil is with Homolka Hospital, Prague, Czech Republic.

The AFFERA System

The AFFERA system

The AFFERA system uses a single lattice-tip catheter but two different energy generators, one for PFA and another for RF ablations.

One of the great advantages of Pulsed Field Ablation (PFA) is that the PF energy doesn’t damage adjacent tissue or structures such as the Phrenic nerve or the esophagus.

A simple foot pedal is used to switch between the two energy generators. A PF ablation appeared as a green dot on the mapping screen. An RF ablation appears as a red dot.

[For more about PFA, see 2020 AF Symposium: Pulsed Field Ablation—Emerging Tech for Atrial Fibrillation.]

Live Via Streaming Video

The Patient’s History: Dr. Reddy’ patient had been in persistent A-Fib, was cardioverted, but went into typical Flutter.

Live from Prague, Czech Republic: When the Symposium audience joined the live video feed from Prague, the doctors and their team had already started the procedure.

The Pulmonary Veins (PVs) were already isolated. They had created a Flutter map.

Posterior Wall Ablation Using PFA: The Symposium audience watched as Dr. Reddy used the system to make PF ablations in areas of the heart. Although near other structures the PF ablation energy only affected the heart tissue, not any of the nearby tissue or organs located just behind the heart.

Dr. Reddy had started working on ablating the posterior wall using 4-second PFA lesions. A bullseye symbol would first appear on the monitoring screen where the lesion was aimed. We were amazed at how fast Dr. Reddy could make a roof line on the posterior wall using PFA.

Dr. Reddy pointed out that there was no significant temperature change when applying PFA lesions. When asked about using a temperature probe in the esophagus, he explained that at first, they did use a temperature probe. After 70-80 cases, they didn’t see any significant temperature changes. Today they no longer use temperature probes in the esophagus.

PFA Faster Than RF Ablations

When switching to PFA, Dr. Reddy only had to apply PFA for 3-5 seconds which is much faster than typical point-by-point RF ablation. The entire lattice-tip delivered a series of micro-second PFA pulses. Saline irrigation was still used as in RF delivery [but one wonders why this is necessary]. There was no need for temperature feedback when using PFA.

In one instance, when a mitral line block was not achieved with the lattice tip, Dr. Reddy switched to RF to make a coronary sinus (CS) ablation. (Although, in most situations, PFA worked well to isolate the CS without having to use RF.)

Spacing Between Ablation Dots

Red dots are RF ablations; Green dots are PFA.

He explained that they are now using a 4 mm spacing PFA distance between ablation spots, but this may change with more experience and data. Spacing of 6 mm may be enough for isolation.

As Dr. Reddy moved away from near the esophagus, he double clicked on the pedal to switch to RF to make ablations in areas of the heart not adjacent to areas that could be damaged by RF energy, such as isolating/ablating around some of the Pulmonary Veins (PVs). When using RF, he increased his spacing between lesions to 6-7 mm. “With RF we think we get a much wider lesion.”

He showed how the AFFERA software showed a gap in blue which indicated too wide spacing. He had preset the software to show blue with any gap larger than 8 mm.

After finishing the mitral isthmus roof line, the Symposium moderator switched away from Dr. Reddy to another live streaming video presentation.

Why Use Both PFA and RF?

Dr. David Keane from St. Vincent’s hospital in Dublin, Ireland asked the question we all wanted to know. “Why? Why even bother with RF in these cases?” If PFA works so well, why use RF at all?

The Lattice catheter

Dr. Reddy stated, “I’m not saying we will never go to pure PFA.” But he also acknowledged that 60 to 70 percent of his ablations using the AFFERA system were made with PFA. In this study itself, they ablated 60-70 patients using only pure PFA.

Dr. Reddy indicated that being able to use RF at times during an ablation may give operators more flexibility to go after more elusive signals such as Atypical Flutter. “This approach may wind up being preferred in many patients. We will see.”

Technical Achievement: The Lattice-Tip Catheter

The Lattice-tip catheter is probably worth a report on its own. It looks like a sphere which can be changed and compressed to different shapes. It’s mounted on a deflectable catheter with an expandable 9-mm diameter nitinol lattice electrode which contains 9 mini-electrodes on the spherical surface.

It also has embedded thermocouples for temperature control and an irrigation pump for saline during RF ablation along with an integrated mapping system.

During this live procedure, Dr. Reddy demonstrated how the Lattice-tip catheter can be changed to shapes like a football or to function like a point-by-point RF catheter.

It can make lesions very rapidly because of its wide footprint and improved catheter stability. It can make wide ablation lines. And the compressibility of the lattice mesh and its spring-like interaction with tissue, make for better and wider lesions.

Being able to both map and create lesions using the same catheter is a technical achievement that will make EPs job much easier and more efficient.

Editor’s Comments

Some have said that, since almost all EPs are experienced in using RF, a combination system using both RF and PFA might be more easily used by EPs. EPs know from experience how well RF works and the durability of RF lesions. But to me the AFFERA system is at best a transitional treatment and can’t compare to pure PFA.

What was confusing, at least for me, was that at last year’s AF Symposium Dr. Reddy presented ground-breaking research on Pulsed Field Ablation using the Farapulse system. I only found out later that Dr. Reddy’s presentation this year about the AFFERA system was actually in competition with Farapulse.

Despite the technological innovation of the AFFERA, Inc. PFA and RF combination system, it’s unlikely that it will be adapted by the EP community in the long run. “Pure” PFA seems to work so well that there doesn’t seem to be a need for a combination system. But I could be proven wrong. Maybe there are difficult signal areas that PFA may not be able to adequately address with the same effectiveness as RF ablations.

The LIRYC Bordeaux group is starting a 5-year study to compare RF ablations  with PFA which should answer most of these questions. (Also see ’21 Symp: Pulsed Field Ablation Using Multielectrode Catheters and PFA Compared to RF Study)

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