Pacemaker Progress: The Dawn of MRI Compatibility
October 31, 2014
More than 2 million people have pacemakers or defibrillators. In the past, when such a patient needed an MRI, doctors were unable to perform the scan because they feared it could harm the device or the patient. However, pioneering studies, including those conducted by Raymond H. M. Schaerf, MD, showed these patients can be safely scanned. Now MRI-compatible pacemakers and defibrillators are becoming available. In April, Providence Saint Joseph Medical Center became the first hospital in the nation to conduct a cardiac MRI of a patient implanted with the new Accent MRI™ Pacemaker and Tendril MRI™ Lead.
We asked Dr. Schaerf to describe the latest developments.
What is an MRI-compatible pacemaker?
“It’s a pacemaker that has been specifically manufactured and tested so that patients can go through MRI studies. The original devices that were MRI-compatible were limited as to what MRI studies could be done. For example, you could do an MRI of the legs or arms but not the chest or abdomen and not the neck or most of the spine. But the newest devices allow you to scan the entire body. This is called whole-body MRI compatible.”
What permits this device to be MRI-compatible?
“It’s not just the device that is compatible, but the electrodes. You can put a device in, but if the electrodes aren’t compatible you can’t do the MRI. For MRI-compatible devices, the manufacturer has reduced the amount of iron in the device, and they’ve worked very hard so that the circuitry is shielded from the MRI. In addition, MRI studies expose the patient to radiofrequency and magnetic energy, which were also thought to be dangerous to patients with cardiac devices. The new, compatible devices allow us to address these issues safely.”
What were the risks to patients who had pacemakers that were not MRI-compatible?
“What happened in the past was anecdotal. We heard of patients who had very bad outcomes, including death, but these were not studies done in clinical trials. We also saw patients whose devices were severely damaged after an MRI study. We had concerns that the device could suddenly stop working. If the patient had a defibrillator, the defibrillator could shock the patient, or the radiofrequency could burn a hole in the heart. We were part of a large study—more than 1,500 scans—however, and found there weren’t many risks. The basic stumbling blocks to having more patients involved in our study were fear and misinformation among both physicians and patients.”
Why is it important that pacemaker patients have access to MRI, if needed?
“There are certain conditions where you need an MRI to know what the exact problem is and how it can be most effectively and appropriately treated. The two biggest areas where you need MRI are orthopedics and neuroradiology. We’ve had people who may have had a stroke or a brain tumor and there is no way to know that unless you can do an MRI. But in the past we’ve actually had patients who have had the device removed, then had the MRI, and then had a new pacemaker and electrodes put in. That costs about $20,000.”
So there were lots of people who faced difficult decisions when an MRI was recommended?
“Yes, a lot of people have pacemakers. According to the last study that was done on this, 50 percent to 70 percent of patients with new pacemakers or defibrillators implanted may need MRI studies within three years. The new MRI-compatible devices now allow patients to safely undergo these MRI studies.”
Is the device still considered investigational?
“The total body MRI-compatible device is still investigational. But there are limited MRI-compatible devices that are FDA-approved. I also think that within the next year or two a host of other MRI-compatible devices will come out.”
How long have you been involved in MRI studies?
“For 15 years. I was always hounding the device manufacturers about why you couldn’t do MRIs. I just thought, ‘I have all these patients who need MRIs, particularly the patients who need an MRI of the brain, back or knee, and we couldn’t get it done.’ So we did the first scan in the world using this device as part of a Phase I Food and Drug Administration study. At Providence Saint Joseph Medical Center, we’ve been very fortunate to get many Phase I studies here over the years. Providence Saint Joseph Medical Center has truly been a major testing site for many important innovations.”