Extravascular ICD works properly with few complications at 18 months
Key takeaways:
- An extravascular implantable cardioverter defibrillator delivered therapy successfully with low complication rates at 18 months.
- The device offers antitachycardia pacing, unlike the subcutaneous ICD.
An extravascular implantable cardioverter defibrillator was associated with effective treatment and low complication rates at 12 to 18 months, researchers reported at Heart Rhythm 2023.
As Healio previously reported, the extravascular ICD (EV ICD, Medtronic) was implanted safely, was able to detect and terminate ventricular arrhythmias and was associated with low complication rates at 6 months. Paul A. Friedman, MD, FHRS, professor of medicine and chair of the department of cardiovascular medicine at Mayo Clinic in Rochester, Minnesota, presented longer-term results from the global EV ICD pivotal study.
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“The extravascular ICD seeks to solve some challenges with defibrillators,” Friedman told Healio. “Implantable defibrillators are the most effective therapy we have to prevent sudden cardiac death in high-risk individuals. However, they have known complications including vascular injury, cardiac perforation, pneumothorax, hemothorax, injury to the valves and obstruction of veins, so the thought is that if you could defibrillate without placing leads into the heart and vasculature, it may reduce the complications associated with implantable defibrillators and make them more accessible.
“For that reason, a subcutaneous ICD (Emblem S-ICD, Boston Scientific) was developed a little over 10 years ago, where the lead goes just under the skin and the device sits in the midaxillary line, under the armpit,” Friedman told Healio. “It avoids a lot of those problems but has its own new limitations. It doesn’t pace except for 30 seconds right after a shock. It doesn’t have antitachycardia pacing. Because it sits outside of the thorax, the defibrillation threshold is higher, so the device has to be bigger, impacting battery longevity and, possibly, comfort. For those reasons, the extravascular ICD was developed. The main difference is that it was designed so that the lead, instead of going under the skin and above the sternum, goes below the sternum, so the lead is in juxtaposition to myocardial tissue. Because it is closer to the heart, it retains all of the benefits of not being in the heart, but it’s a smaller device with greater longevity, projected to be 11.7 years, it can deliver antitachycardia pacing and can give pause prevention pacing and post-shock pacing.”
The device is undergoing FDA review but is not yet approved for commercial use in the U.S.
The prospective, single-arm, nonrandomized global EV ICD pivotal study included 316 patients (mean age, 54 years; 75% men) who had a class I or IIa indication for an ICD. The device was successfully implanted in 299 patients, of whom 277 completed 12-month follow-up and 163 completed 18-month follow-up (mean follow-up, 17.1 months). The researchers calculated incidence rates using the Kaplan-Meier method.
At 18 months, 6.8% of patients had received appropriate therapy and 3.9% had received antitachycardia pacing, according to the researchers.
Friedman and colleagues reported that 19 patients had 80 ventricular tachycardia/ventricular fibrillation episodes treated with appropriate therapy, and the rate of discrete shock success was 100%. In addition, three patients had at least 12 episodes treated with pause prevention pacing.
The researchers also found that 67.3% of 52 episodes were successfully treated with antitachycardia pacing, and antitachycardia pacing prevented shocks in 37 episodes in nine patients.
Antitachycardia pacing was turned on in 79.4% of patients at 12 months, up from 66.8% before hospital discharge, whereas 3.6% of patients turned off antitachycardia pacing by 12 months follow-up, and no patient with successful antitachycardia pacing therapy had the feature turned off subsequently, according to the researchers.
At the mean 17.1-month follow-up period, 11.7% of patients had 93 episodes of inappropriate shocks (1-year rate, 10.2%), about half of which were due to cardiac oversensing, Friedman said, noting that these episodes were five times less frequent in those who were implanted later, reflecting a learning curve, and that there were no cardiac oversensing incidents after the 6-month results were published.
The rate of freedom from system- or procedure-related complications at 18 months was 91.9%, comparable to the rates seen in studies of the S-ICD, Friedman told Healio.
There were three lead fractures, all in the same location with the same mechanics, an issue that has been addressed by manufacturing adjustments, he said.
“In this study, the EV ICD effectively treated spontaneous episodes with an average follow-up of 17 months,” Friedman told Healio. “Shocks were avoided in nearly half of spontaneous episodes because of the availability of antitachycardia pacing, and the incidence of major system- and procedure-related complications remained low through 18 months. The initial experience has been very positive.”
Appropriate patients for the device include “patients with a class I or II indication for an ICD who have not had previous bypass surgery,” Friedman told Healio. “That group was not studied because there may be scarring or additional nuances for the implant, and could be a future cohort.”
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Friedman PA, et al. Late Breaking Clinical Trials and Science – CIED. Presented at: Heart Rhythm 2023; May 19-21, 2023; New Orleans (hybrid meeting).
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