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AF Symposium 2019: Live from Prague—Ablation Without touching the Heart Surface Using Ultrasound
By Steve S. Ryan
On the second day of the AF Symposium attendees viewed, live from the Czech Republic, a catheter ablation using an incredible new technology―Ultrasound Mapping and Ablation (Low-Intensity Collimated Ultrasound, LICU) from Vytronus, Inc.
“Collimated” refers to focusing ultrasound rays so that they are parallel and spread out minimally with minimum divergence.
The procedure was via live streaming video from Na Homolce Hospital in Prague. The doctors performing the A-Fib ablation were cardiac electrophysiologists Jan Petru, Moritoshi Funasako, and Petr Neuzil.
Near-Real Time Ultrasonic Imaging of the Heart
The system first robotically scanned the left atrium and Pulmonary Veins (PVs) to create a 3-D global image of the heart anatomy in near-real time using the same dual-purpose transducer tip that makes the ablation lesions. (Later the same process was used to verify ablation lesions and the effectiveness of the ablation.)
Automated Robotic Ultrasound Ablation
In this automated robotic ablation, the LICU ultrasound catheter with a dual-purpose transducer tip didn’t touch the heart surface to make ablation lines.
The EP created a robotic path for the ultrasound catheter to follow. Using electromagnetic navigation, the catheter automatically went to the spots and path the operator drew.
We watched as the catheter hovered over the heart surface while the highly directional ultrasound energy beam created the lesion lines.
It was amazing to watch!
If the heart surface was thicker, the ultrasound catheter slowed down thereby increasing the ultrasound dose and energy delivered. This made the continuous lesions deep enough and transmural. The catheter didn’t touch or make contact with the heart surface.
Flowing Blood in the Heart Doesn’t Affect the Ultrasound Beam
The choice of ultrasound frequency (approximately 10 MHz) means that the ultrasound beam is affected very little by blood in the heart. Blood is “transparent” to the ultrasound beam.
This also means that the distance from the catheter tip to the targeted tissue isn’t critical and can vary. Also, the ultrasound catheter tip is irrigated to cool the tissue and prevent the formation of char or thrombus.
Color-Coded Range Map
The system uses a color-coded ultrasound-generated range map which displays how far the tip of the catheter is from the tissue to be ablated in order to create good lesions.
If the operator sees purple, blue or green, the catheter is within therapeutic ablation range. Yellow, orange and red indicate the catheter is beyond therapeutic range. The therapeutic range can vary from 5 mm to 50 mm.
During the live ablation, the EP said that dark blue is the best, while purple may be too close.
VIDEO: Product Animation. Ultrasound Mapping and Ablation (Low-Intensity Collimated Ultrasound, LICU) from Vytronus, Inc. (2:22 min.)
Video playback controls: Controls are located in the lower right portion of the frame: Click on arrow icon to select.
Editor’s Comments:
Background: In the past, high-intensity focused ultrasound (HIFU) caused esophageal injury and was withdrawn from clinical use. But Low-Intensity Collimated Ultrasound (LICU) operates at a lower acoustic intensity than the previous HIFU. Lesion formation occurs at a more gradual fashion.
Though not yet approved for use in the U.S., development of an ultrasound LICU ablation catheter and mapping system is a most important innovation for A-Fib patients.
Near-Real-Time Mapping: The ability of the ultrasound catheter to create 3-D images of the atrium and PVs at almost the same time as the ablation is a major advantage over other mapping systems. It creates more accurate rendering of the targeted heart features. In other systems there can be map drifts/shifts, inaccuracies from heart motion, respiratory motion, and volume-related chamber enlargement.
Non-Contact Ablation: In an ultrasound LICU ablation the catheter doesn’t touch the heart tissue. The EP doesn’t have to worry about “contact force” measurement, i.e., whether they are applying enough or too much force to make good transmural lesions.
Robotically Controlled Ablation Process: To me the robotic ultrasound LICU system seems easier to use. The ultrasound lesions were created automatically. As compared to standard point-by-point RF ablation or even CryoBalloon ablation, it’s remarkably simple and requires much less EP involvement and skill.
From a patient’s perspective, you aren’t as dependent on the skill and manual dexterity of the EP (or whether they are on top of their game that day).
A Breakthrough but Not Yet Available: It was obvious to everyone in the AF Symposium audience that we were witnessing the dawn of a potential new age in catheter ablation.
Though still investigational and not yet approved in the U.S., robotic low-intensity ultrasound mapping and ablation seems like a radical breakthrough in ablation treatment.
More Studies Needed: Many studies of its safety and efficacy need to be made before ultrasound ablation becomes available to patients. But low-intensity robotic ultrasound ablation looks really promising.
If you find any errors on this page, email us. Y Last updated: Thursday, August 27, 2020
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