Cardiology, diagnostic imaging  

Medtronic begins European and US trial of MRI-compatible pacemaker system

Minneapolis, USA. Medtronic, Inc. (NYSE:MDT) has begun an international clinical study to confirm the safety and efficacy of its EnRhythm MRI SureScan pacing system, the first pacemaker system to be developed and tested specifically for safe use in magnetic resonance imaging (MRI) scanners under specified scanning conditions.

Pacemaker technology has extended the lives of thousands of patients with heart rhythm conditions, and each year nearly one million pacemakers are implanted in patients worldwide. While improvements to pacing technology have continued since its development nearly 50 years ago, this advance marks a concerted effort to pursue compatibility with MRI scans, an important healthcare diagnostic for many conditions.

“For important safety reasons, regulatory agencies worldwide prohibit individuals with implantable cardiac devices from receiving MRI scans,” said Steve Mahle, president of the Cardiac Rhythm Disease Management business at Medtronic. “Medtronic has thoroughly researched the risks to patients and designed a pacemaker and lead system from the ground up that we expect will help many, many patients take advantage of the benefits of MRI technology.”

The EnRhythm MRI SureScan pacing system consists of the new dual-chamber EnRhythm MRI SureScan pacemaker and CapSureFix MRI SureScan pacing leads (Model 5086MRI).

The first clinical trial devices were recently implanted in Europe by Prof. Dr. Firat Duru, University Hospital in Zürich, Switzerland; Dr. Helmut Pürerfellner, Elisabethinen Hospital in Linz, Austria; Dr. Gijsbert De Ruiter, Onze Lieve Vrouwe Gasthuis in Amsterdam, The Netherlands; and Dr. Stefan Spitzer, Praxisklinik Herz und Gefässe in Dresden, Germany.

The trial, a prospective, randomized controlled, unblinded, multi-centre study, is planned to occur at hospitals in Austria, Belgium, Canada, Denmark, France, Germany, Italy, Netherlands, Switzerland, United States, and United Kingdom; procedures are expected to begin outside Europe later in the year. Approximately 350 individuals will participate in the study, and eligibility is based on the clinical indication for pacemaker implantation and a willingness and ability to undergo elective MRI scanning.

All patients in the trial will receive an EnRhythm MRI SureScan pacing system, and approximately half of the participants will receive MRI scans; the trial’s first MRI scans will occur approximately two to three months after device implant. The study will compare the electrical and diagnostic system performance, as well as complication rates, among patients in both groups. The expected study duration is approximately 24 months.

“We see patients every week who aren’t able to get an MRI scan to determine the cause of a clinical issue and must use less effective diagnostic methods because they have a pacemaker,” said Prof. Dr. Richard Sutton, cardiologist in the Royal Brompton Hospital in London and European lead cardiology investigator for the EnRhythm MRI SureScan Pacing System Clinical Study. “The ability to perform MRI scans is a critical medical need, especially as the number of people who get medical devices increases; Medtronic’s new pacing system is designed to meet this need by enabling pacemaker patients to receive MRI scans.”

“MRI safety is an important issue,” said Prof. Dr. Torsten Sommer, chief of the cardiovascular section of the radiology department, University of Bonn, Germany, and European lead radiology investigator for the clinical trial. “It is critical to protect patients from electromagnetic fields that could contribute to a loss of pacing therapy. The only sure way to do this is to study a pacing system that was designed specifically for use in MRI systems.”

The EnRhythm MRI SureScan pacemaker includes modified hardware to minimize the level of energy transmitted through the lead/device connection point. The pacemaker also includes a new SureScan feature that can be programmed “on” before an MRI scan to eliminate the impact of MRI-generated electrical noise, which can prevent necessary pacing therapy or cause the device to oversense and deliver unnecessary pacing therapy. When the SureScan feature is on, the device’s data collection and monitoring functions are temporarily suspended, while allowing the device to continue providing asynchronous pacing if needed. The device and leads also contain radiopaque marks, viewable via X-ray, to indicate that the system is MRI-compatible.

The pacemaker incorporates all diagnostic and therapeutic features of the commercialized Medtronic EnRhythm pacemaker, including an exclusive pacing mode called MVP or Managed Ventricular Pacing, which enables the device to be programmed to deliver pacing pulses to the right ventricle only when necessary. MVP has been shown to reduce unnecessary right ventricular pacing by 99% (median value). Recent clinical studies have suggested that reducing this pacing stimulation may reduce the patient’s risk of developing heart failure and atrial fibrillation, a potentially life-threatening irregular heartbeat.

The CapSureFix MRI SureScan leads are modified versions of the active-fixation Medtronic CapSureFix Novus leads, the most-prescribed lead in the history of pacing. Leads are insulated wires that carry precisely timed electrical impulses from the pacemaker in the patient’s chest to a specific point on the inner heart wall. Available in three lengths, the atrial and ventricular CapSureFix MRI SureScan leads are designed with modified internal wiring composition to decrease the risk of overheating during an MRI scan without limiting the ability to conduct therapy.

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