The new technology delivers short-duration electrical pulses to the cardiac tissue that causes pores, or holes, to form in the cellular walls of the myocytes. This irreversible electroporation process kills the cells without excess heat or cold, which can adversely effect healthy underlying tissues. This has a lot of appeal for electrophysiologists, because existing technologies can damage the esophagus, phrenic nerve, or cause pulmonary vein stenosis. Verma said anatomical structures around the right atrium are much more resistant to damage from electroporation. This fact alone makes it very appealing to electrophysiology to help avoid these major adverse events.
PULSED-AF clinical trial outcomes
The PULSED-AF trial treated both paroxysmal AFib and persistent AFib patients, and all of the patients were resistant to anti-arrhythmic drugs. The success rates were 66% among paroxysmal patients and about 55% in the persistent AFib cohort. Verma noted that this was using a very rigid definition of treatment endpoints. This included very rigorous monitoring and a definition of freedom or 30 seconds or more of atrial arrhythmia, no further ablation and no adjustment in anti-arrhythmic drugs.
“If we look at more traditional endpoints, which is freedom from any atrial arrhythmia of more than 30 seconds, the success was about 70% paroxysmal group and 62% in the persistent group,” Verma said.
It was the efficiency and the safety of the technology that really had the most impact.
“What was really impressive was efficiency and the safety,” Verma explained. “The overall safety event rate was less than 1%. It was just 0.7%, which is one of the lowest complication rates of any AFib ablation trial.”
In terms of efficiency, he said the dwell time in the right atrium was about 60 minutes. This is a far cry from the usually dwell time of a couple hours in traditional AFib ablation procedures.
“If you take out the mandatory 20-minute waiting period, these procedures were being done within about 40 minutes or so,” Verma said. “And most of these operators had only used the catheter once before they started enrolling in the trial, so it is pretty impressive.”
Comparison of success of pulsed field vs. cryo and RF ablation
Overall, Verma said the success rate of pulsed field ablation was about the same at traditional thermal ablation. So about a third of patients did not have their AFib resolved by the therapy during the first attempt procedure. But, he said the number of repeats procedures were very low.
“The biggest advance here is a the speed and safety,” Verma stressed. “Over time, I think we are going to see even better outcomes in terms of efficacy.”
How does pulsed-field ablation work?
The investigational Medtronic PulseSelect pulsed field ablation system is a round catheter with nine electrodes that create pulsed fields. It was designed to be placed around the ostium of the pulmonary veins. An operator can rotate the catheter two or three times to apply energy to create a a pulmonary vein isolation.
“That was part of the instructions for use we gave to operators to overlap the leasing. We told operators to not worry too much about over applying the energy because it is a very safe energy source, so we actually encouraged the use of repetitive applications to make sure we got lesions as deep as possible,” Verma explained.
Each treatment takes a fraction of a second. Unlike tradition catheter ablation, which requires a certain amount of pressure or force to be applied to ensure a good scar in the tissue, Verma said you just need to have contact with the tissue and contact force is not a factor.
Then the operator rotates the catheter and repeats the therapy to create a lesion that isolates any electrical activity from the pulmonary vein to the rest of the heart. The total application of energy for a full treatment in these patients was less than 30 seconds, Verma said.
“As long as you can visualize that contact with the catheter and the tissue on X-ray or intra-cardiac ultrasound, that is good enough,” Verma explained.
What is the future of pulsed-field ablation?
Based on the results on the PULSED-AF trial, Verma said he believes there will be a rapid adoption rate of the technology once it gains U.S. FDA clearance.
“I think over the next five years, we are really going to see pulsed field take up a lot of there thermal ablation space, especially for AFib,” he explained. “And I think this being one of the first global, pivotal trial results, it certainly is baring out in that direction.”
He expects to see pulsed field on a variety of platforms in the near future, including different types of catheter configurations.
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