After his second cardiac event in five years, US-based Joseph Mulligan was not surprised when his Northwestern Medicine cardiologist, James Flaherty MD, recommended an implantable cardioverter defibrillator (ICD) as a safeguard to help keep him alive if he were to have a sudden cardiac arrest.
At 84 years of age, Joseph knew many people with pacemakers and expected, like his friends, he would need a traditional transvenous defibrillator implant with thin leads threaded directly into his heart and veins to deliver an electric current to his heart if needed.
Then his medical team presented him with a unique option – Joseph was a candidate for a clinical trial to test the safety and efficacy of a first-of-its-kind extravascular implantable cardioverter defibrillator (EV ICD).
The Medtronic EV ICD is designed to treat dangerously fast heart rhythms that can lead to sudden cardiac arrest, while avoiding certain risks of traditional, transvenous ICDs.
“The EV-ICD involves placement of a special lead that is tunnelled under the sternum, so that the lead is not in the heart, but is very close to the outside of the heart,” says Bradley P. Knight, MD, medical director of electrophysiology at Bluhm Cardiovascular Institute.
“This allows for lower energy and smaller battery requirements to defibrillate the heart in the event of a cardiac arrest and for pacing of the heart to treat slow heart rates or to terminate fast ventricular tachycardias.”
Northwestern Medicine Bluhm Cardiovascular Institute was one of only 46 sites worldwide to participate in a pivotal study of the device.
The results of the trial were presented at the European Society of Cardiology (ESC) Congress 2022 in Barcelona and published in The New England Journal of Medicine.
Worldwide, hundreds of thousands of ICDs are implanted in patients every year to treat dangerously fast heart rhythms.
With traditional transvenous defibrillators, the lead is inserted through a vein and attached to the heart leaving the lead under constant stress from the heart beating and movement of the upper body, potentially causing breakage of the lead or blockage of the vein.
A totally subcutaneous defibrillator is currently available as an alternative to a transvenous defibrillator, but the device is very large and is unable to pace the heart.
The goal of the EV ICD system is to provide the benefits of current transvenous ICDs, but with a smaller device, greater device longevity and without placing leads in the heart or vasculature.
“By positioning the leads outside of the heart, there is less risk of long-term complications associated with leads in the heart and veins, such as the narrowing, blockage or compression of a vein and risks for blood infection,” said Dr Knight, a co-author on the study.
The EV ICD Pivotal study enrolled 356 patients in 17 countries across North America, Europe, the Middle East, Asia, Australia and New Zealand.
Participants in the trial, like Mr Mulligan, received the same therapies provided by traditional ICDs, including defibrillation, anti-tachycardia pacing and back-up pacing therapies, with this single implanted device.
The trial met its primary objectives: defibrillation therapy effectiveness at implant was 98.7 per cent.
This reflects a greater defibrillation efficacy for the EV ICD than historical transvenous ICD studies, and comparable efficacy to the subcutaneous ICD despite EV ICD’s smaller device size.
The study also exceeded its safety endpoint: at six months, 92.6 per cent of patients were free from major system and, or procedure-related major complications such as hospitalisation, system revision or death.
“The EV-ICD is a revolution in implantable defibrillator technology that addresses the limitations of our existing therapies that have been available for several decades,” said Dr Knight.
“With the promising data from this trial, we have an opportunity to evolve ICD technology in a safe, effective manner and improve this lifesaving therapy.”
Worldwide, the EV ICD system is investigational and not yet approved for sale or distribution.
Medtronic has received FDA approval for a Continue Access Study, and patients in the pivotal study will continue to be followed until Medtronic receives regulatory approval for the EV ICD system in the US.
The clinical trial was funded by Medtronic; ClinicalTrials.gov number, NCT04060680.
To learn more about cardiovascular clinical trials at Northwestern Medicine, visit the Bluhm Cardiovascular Institute – Clinical Trial Unit.
