Arrhythmias such as ventricular fibrillation and ventricular tachycardia happen in the lower heart chambers, or ventricles. They are dangerous because they interfere with the normal coordinated filling and pumping of blood through the heart. These arrhythmias can cause collapse and death if not rapidly treated. The ability of implantable cardioverter-defibrillators (ICDs) to accurately detect and terminate ventricular arrhythmias in high-risk patients saves lives. Now, a new type of extravascular ICD using a lead (thin wire) placed behind the sternum has met safety and effectiveness goals for participants in a premarket global clinical study. The device effectively terminated acute and chronic life-threatening ventricular arrhythmias.

The global clinical trial conducted by researchers at the Mayo Clinic (Rochester, NY, USA) showed that Medtronic plc’s (Dublin, Ireland) investigational EV ICD System – a first-of-its-kind defibrillator with the lead placed under the breastbone, outside of the heart and veins – achieved a defibrillation success rate of 98.7% and met its safety endpoints. For study participants, the lead of the extravascular ICD was inserted under the sternum, compared to transvenous ICD leads that are inserted through the veins into the heart, or subcutaneous ICDs that have a lead placed beneath the skin above the sternum. Patients with prior open-heart surgery, or who required pacing for a slow heart rate or had a pacemaker, were not candidates for this study.

By placing the lead in this new position behind the sternum, the uncommon but serious risks associated with transvenous ICDs, such as lung collapse, damage to heart valves and heart perforation, can be avoided. Limitations of the subcutaneous ICD are also overcome. Since the lead is behind the sternum and close to the heart, pacing can be delivered, and defibrillation requires less energy with a longer battery life than with the subcutaneous ICD. Researchers from 17 countries participated in the study. Of the 316 patient participants with an attempted implant, 299 were discharged with a working extravascular ICD system. The defibrillation success rate was 98.7%. At six months, 92.6% of participants had no major system or procedure-related complications.

“The new extravascular ICD delivered anti-tachycardia pacing — rapid pacing — to painlessly terminate 70% of ventricular tachycardia episodes for which it was applied, (which is) at least as good as transvenous ICDs and not available in the subcutaneous ICD," said Paul Friedman, M.D., a cardiac electrophysiologist, and principal global investigator and first author of the study. "The extravascular ICD was also able to provide backup pacing to prevent pauses and was able to effectively defibrillate using a device half the size of the subcutaneous ICD."

"These pivotal data mark the start of a new era in ICD therapy for patients who are at significant risk of dangerously fast heart rhythms," said Alan Cheng, M.D., chief medical officer of the Cardiac Rhythm Management business, which is part of the Cardiovascular Portfolio at Medtronic. "Today's findings are an important clinical milestone toward our goal of delivering a one-system, one-procedure extravascular ICD solution that prevents sudden cardiac arrest while improving the patient experience with a smaller device and moving the lead out of the veins and placing it under the breastbone. The EV ICD system retains the benefits of a completely extravascular system while providing ATP, pause prevention pacing and low defibrillation energy." 

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