2020 AF Symposium Abstract

Live Case—AcQMap 3D Imaging, Mapping and Navigation System

by Steve S. Ryan

In a live case entitled “Dipole Density Mapping of Atrial Fibrillation”, Dr. Timothy Betts of Oxford University Hospitals in Oxford, United Kingdom, demonstrated the Acutus Medical AcQMap 3D Imaging, Mapping and Navigation System.

AcQMap 3D Imaging, Mapping and Navigation System

We first saw a live case demonstration of the Acutus AcQ Imaging and Mapping system (Non-Contact Dipole Density) at the 2017 AF Symposium 

The Acutus Medical Non-Contact Dipole Density AcQ Imaging and Mapping catheter uses a basket catheter with multiple electrodes and ultrasound anatomy reconstruction.

‘Non-contact’ means the basket catheter can float freely in the left atrium and doesn’t have to be applied to the surface of the heart to generate A-Fib maps.

The basket catheter has six splines each with eight nodules that contain 48 ultrasound transducers and 48 electrodes. The ultrasound pings the atrium wall and rapidly produces a 3D left atrium anatomy.

Electrical Measurement: Dipole Density vs Voltage

Dipole Density map on a 3D ultrasound reconstruction of the heart

For over one hundred years, voltage has been the major electrical measurement in cardiac medicine.

The limitation with using voltage in electrophysiology is that the reading includes both the localized charge (Dipole Density) as well as the sum of the surrounding sources providing a broad, blended view of cardiac activity.

According to Acutus Medical, by eliminating these surrounding sources, and using dipole density (instead of voltage) the field of view becomes sharper and narrower.

This more precise electrical activation is displayed as a Dipole Density map on a 3D ultrasound reconstruction of the heart.

Acutus Medical Illustration: localized charge (Dipole Density) with the sum of the surrounding sources

Patient with A-Fib Since 2001

The patient was a 62-year-old man (BMI 27) with persistent A-Fib. He first had developed persistent A-Fib back in 2001 which was controlled by drugs and cardioversion.

In 2015 he had a PVI and a left atrial roof line using the Hansen Robotic ablation system which they were using at that time. He was OK for around 18 months.

Then in 2018 he developed organized tachycardia/Flutter. He was cardioverted, but still developed recurrent palpitations which were very long lasting. He had an enlarged left atrium and high blood pressure.

This ablation by Dr. Betts and his colleagues was a “re-do”.

Ensite contact force sensing catheter

Dr. Betts explained that the patient was under general anesthesia and that they were using Jet Ventilation for stability. (see Jet Ventilation Live case. ) Along with the Acutus mapping system, they were using the Ensite contact force sensing catheter for ablations.

The Acutus Medical AcQ mapping system received FDA approval Feb. 19, 2020. The second generation received FDA approval September 18, 2020.

Acutus AcQ Mapping System Very Fast, Real Time, and Non-Contact

It was amazing to watch them using the Acutus AcQ basket mapping catheter which moves around the left atrium without having to be in contact with the atrium wall (SuperMap program). It took them only two minutes to produce the left atrium 3D geometry and structure (and one minute of processing time). That was definitely the highlight of the live case.

The Acutus system uses non-contact global mapping (real time ultrasound) to collect high density points throughout the atria. For each SuperMap, they showed a two-screen display with a sinus “bin” on one side and a tachycardia bin on the other.

Flutter, High-Density Activation Mapping

Acutus Medical image of AcQ Mapping System

They initially found right atrium Flutter in the patient which they ablated with a caviotricuspid isthmus ablation line. Then a right atrial SuperMap with Acutus confirmed caviotricuspid isthmus block.

They also found that one of the patient’s right pulmonary veins had reconnected which they fixed.

They paced the LAA. The Acutus SuperMap showed that the previous roof line was still blocked/isolated.

They induced a non-sustained flutter which degenerated into A-Fib after 90 seconds. The SuperMap was able to produce a high-density activation map that showed the transient flutter rotated clockwise around the mitral annulus. As these arrhythmias were not sustained, they were not targeted.

Time ran out before they could do much more. This case of long-standing persistent A-Fib was a real challenge, even with the best of equipment.

Follow-up to Live Case

After the AF Symposium, Dr. Betts emailed me that his patient was discharged from the hospital the following morning in sinus. “He has done very well, with no arrhythmia recurrences after 11 months follow-up. He is off all antiarrhythmic medications.”

Editor’s Comments:

Acutus AcQMap Importance: This case of a re-do ablation for multiple arrhythmia circuits showed how quickly the Acutus mapping system could create chamber geometry and collect high-density activation maps of sustained and non-sustained arrhythmias as well as assessing linear lesion conduction block with pacing.

May Replace Contact Mapping: Non-contact mapping is a significant innovation in catheter ablation and may eventually replace existing contact mapping catheters and make ablations easier. It also seems to require less technical skill than in a traditional contact mapping system.

No Radiation & Instantaneous: Using ultrasound to produce a 3D rendering of the heart is innovative and could change the way the anatomy of the heart is generated for an ablation. And unlike a CT scan, it doesn’t use radiation. Also, unlike a CT scan, the ultrasound images of the heart are generated instantaneously in real-time.

Higher Resolution: Dipole Density mapping may prove to be a higher resolution system than current mapping systems.

“Non-contact mapping is a significant innovation and may eventually replace existing contact mapping catheters.”—Steve Ryan

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