Currently, individuals with implanted cardiac devices such as pacemakers, implantable cardioverter-defibrillators (ICDs) and cardiac resynchronization therapy (CRT) devices are prohibited from receiving MRI scans, since MRI machines may interact with traditional systems, potentially compromising therapy and patient safety.

“The U.S. Food and Drug Administration has clearly and widely expressed its viewpoint on the subject of MRI safety and implanted cardiac devices in recent years,” said Pat Mackin, president of the Cardiac Rhythm Disease Management business at Medtronic. “Medtronic understood the need to provide device patients with the means to undergo this commonly used diagnostic tool, which is why we’ve thoroughly researched the risks to patients and designed a pacemaker and lead system from the ground up that will enable patients to benefit from MRI technology.” “There are three million people living in the world today with pacemakers, all of whom are contraindicated for MRI scans,” said Bruce Wilkoff, M.D., director of Cardiac Pacing and Tachyarrhythmia Devices, Department of Cardiovascular Medicine, Cleveland Clinic, and professor of Medicine at Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, and coordinating clinical investigator for the U.S. clinical study. “This trial has been designed to address this unmet medical need.”

Extensive research and design efforts went into the EnRhythm MRI SureScan pacing system to address and mitigate interactions between the pacing system and the MR environment. The system 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 impact pacing therapy. The device and leads also contain radiopaque marks, viewable via X-ray, to indicate that the system is MR-Conditional (a term identifying a device that may be used during an MRI under specified scanning conditions). The CapSureFix MRI SureScan leads are modified versions of the active-fixation Medtronic CapSureFix® Novus leads, and are designed to decrease the risk of overheating during an MRI scan without limiting the ability to conduct therapy.

According to J. Rod Gimbel, M.D., FACC, East Tennessee Heart Consultants, who has been widely published on the subject of MRI and implanted cardiac devices, “Despite several small studies that have evaluated the effects of MRI on device patients, the scanning of device patients not approved for MRI remains rather risky. Several troubling events have occurred when scanning device patients, and the explanation for these events remains murky. Today, we go to the MRI suite with the device we have, not the device we wish to have. Physicians and patients would welcome a pacemaker and lead system that has been designed to address the unknowns, potential hazards and risks for a device patient in the MR environment.”

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. Recent clinical studies have shown that reducing this pacing stimulation may reduce the patient’s risk of developing heart failure and atrial fibrillation.

“MRI can non-invasively evaluate the brain, spine, and spinal cord more sensitively than any other test today. It can be used to help identify problems in joints, extremities, the liver, gallbladder, pancreas, kidneys and bladder, and can evaluate blood vessels almost anywhere in the body. For many patients, MRI is not simply a superior diagnostic tool, it may be the only available non-invasive diagnostic tool. Access to this technology can be important or even vital to all patients – even those with implanted cardiac devices,” said Emanuel Kanal, M.D., FACR, FISMRM, professor of Radiology at the University of Pittsburgh Medical Center, coordinating clinical investigator for the U.S. clinical trial, and chair of the American College of Radiology’s Blue Ribbon Panel on MR Safety. “One of the largest population of utilizers of MR technology are the elderly – who are also the most likely to require implanted cardiac devices.”

Pacemaker technology has extended the lives of millions of patients with heart rhythm conditions, and each year nearly 1 million pacemakers are implanted in patients worldwide. While improvements to pacing technology have continued since its development 50 years ago, this advance marks a concerted effort with the use of MRI scans, an important healthcare diagnostic for many conditions.

About the EnRhythm MRI SureScan Pacing System Trial

The trial is a prospective, randomized, controlled, unblinded, multi-center study, involving 470 individuals; 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 two-thirds 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 system performance, among patients in both groups. In addition, the study will assess the MRI-related complication rates in the month following the MRI scans. The expected study duration and follow up time is approximately 30 months.

About MRI

MRI lets doctors see internal organs, blood vessels, muscles, joints, tumors, areas of infection and more, without X-rays or surgery, and without exposing the patient to any ionizing radiation. The MRI machine creates a magnetic field, sends radio waves through the body, then measures the response with a computer, creating an image of the inside of the body. In many cases, MRI gives information that cannot be seen on an X-ray, ultrasound or computed tomography (CT) scan.

ASTM International, formerly known as the American Society for Testing and Materials, is an international standards organization that has developed a classification system for implanted and ancillary clinical devices, which is supported by the FDA:
MR Safe: An item that poses no known hazards in all MR environments.
MR Conditional: An item that has been demonstrated to pose no known hazards in a specified MR environment with specified conditions of use.
MR Unsafe: An item that is known to pose hazards in all MR environments.

About Medtronic

Medtronic, Inc. (www.medtronic.com), headquartered in Minneapolis, is the global leader in medical technology – alleviating pain, restoring health, and extending life for millions of people around the world.