Medtronic shows feasibility of extravascular ICD; in-human study next

A novel device placed under the sternum outside of the heart and veins has the potential to deliver pacing and defibrillation therapy, according to a feasibility study presented at the Heart Rhythm Society’s annual scientific sessions.

The international Acute Extravascular Defibrillation, Pacing and Electrogram (ASD2) study involved temporarily placing a lead below the breastbone of 79 patients. It confirmed Medtronic’s investigational extravascular device can offer the same types of therapy as conventional implantable cardioverter defibrillators (ICDs), according to a press release.

"Clinicians are highly interested in the potential for an extravascular ICD solution to provide both pacing and lifesaving defibrillation therapy without leads placed inside the heart or vasculature," said presenting author Lucas V.A. Boersma, MD, PhD, cardiologist at St. Antonius Hospital in the Netherlands. "The ASD2 study offers very encouraging clinical insights, which bring us closer to implanting the first chronic investigational system in ambulatory patients."

The study included 79 patients who were already scheduled for elective procedures for cardiac surgery or a subcutaneous or transvenous ICD. Each of them had an investigational extravascular lead temporarily placed beneath the sternum and evaluated with either a defibrillation patch or a defibrillator emulator. It took a median of 12 minutes to insert a lead.

Ventricular pacing was successful in 97 percent of patients and shocks terminated 83 percent of ventricular fibrillation episodes, which is consistent with prior studies of existing ICDs, according to Medtronic.

Seven adverse events occurred in six patients, four of which had no additional complications. However, one patient suffered a possibly related aystolic cardiac arrest 36 hours after being implanted with the ASD2 and a dual-chamber ICD but was transferred to a secondary center in stable condition. Another ultimately had supportive care withdrawn after improper substernal tunneling was found to contribute to tamponade with prolonged hypotension and subsequent hypoxic injury, according to Boersma’s presentation slides.

Mike Marinaro, a Medtronic vice president, said the company’s next step is to evaluate the device in an ambulatory patient population.

"The ASD2 feasibility experience is an important step in our investigational extravascular defibrillation program, and the results give us confidence to continue with this research," he said. "We look forward to our next clinical evaluation—a first-in-human, chronic study to assess the safety and efficacy of the investigational Medtronic EV-ICD system in an ICD patient population."