The number of pacemakers in the United States is rising steadily, and over 600,000 people get them implanted each year. At the same token, about 50 to 75 percent of those people will need to get an MRI scan in their lives, according to the medical device manufacturer Medtronic. This raises a problem, as people with pacemakers and other implanted cardiac devices have generally been thought to be unlikely candidates for MRI scans.
Since the 1960’s, pacemakers have been a concern for radiologists. When they were first implanted at that time, the concern was that the patient’s pacemaker could mistake signals from the MRI’s time-varying magnetic fields for cardiac signals, and the mixed signals could throw off a patient’s pacing, which could be extremely dangerous and even fatal. Tobias Gilk, MRSO, senior vice president with RADIOLOGY-Planning and founder of Gilk Radiology Consultants in Overland Park, Kansas, says that historically the pacemaker is the device most frequently associated with patient’s death in the MRI machine. However, new strides have been taken, and according to Gilk, “It’s no longer the extreme danger it once was.”
The first goal was to make pacemakers and implantable defibrillators “MR-conditional,” which means they are safe when protocols are followed, and since 2000, these devices have been produced by manufacturers. The devices can be programmed so that the pacemaker works as needed, regardless of the signals it picks up from the magnet. The pacemaker can be left on and to an asynchronous mode (which provides a metronome like, fixed, regular pacing,) or turned off, depending on whether or not the patient is dependent on their pacemaker.
In 2011, Medtronic brought the first MR-conditional pacemaker to the US market, and they were also the first to receive FDA approval for an MR-conditional implantable defibrillator in 2015. Since that time, a number of additional MR-conditional devices have gone through the FDA process and similar organizations in Europe, according to Jerry Froelich, MD, a professor of medicine in radiology and cardiology at the University of Minnesota and chair of the ACR’s Committee on MR safety. He says that “These pacemakers are compatible, as long as the scan in performed by the guidelines set forth by the manufacturer and approved by the FDA.”
At some large hospitals and academic institutions, steps have also been taken to allow patients with older or conventional (nonconditional) implanted devices to undergo MRI scans safely. Froelich says continues, “If you need an MR and have a noncompatible device, my recommendation is to go to a center that has a clinical protocol in place to handle pacemakers that are non-FDA approved for MRI. Many freestanding centers will say no to doing an MRI on patients with nonconditional pacemakers, but there are probably several hundred institutions across the country that have Institutional Review Board or internal supervising protocols that allow people with conventional pacemakers to have MRI scans when they need them. In those cases, treating physicians have determined that MRI is the best test for the situation – no other imaging modality such as CT will do – and the benefits of undergoing the scan outweigh the risks.”
There is a huge gap in the system, however, even if the institution is willing to perform the scan, and it is that Medicare does not reimburse for MRI scans for patients with non-conditional pacemakers or other devices. Some places such as Froelich’s institute and the Mayo Clinic will perform MRI scans on those Medicare patients at no charge, but not every facility will do that. If the patients are part of a trial, Medicare may pay as well, but imaging facilities are “extremely reluctant” to provide MRI services for Medicare patients with non-conditional pacemakers, in part, because Medicare won’t reimburse. It should be noted that most private payers will reimburse for MRI scans deemed necessary for patients with pacemakers that are not MR-conditional.
Because of how many patients need pacemakers and defibrillators and because of how many need MRI scans or will need them in the future, physicians are choosing to implant MR-conditional pacemakers and defibrillators upwards of three-quarters of the time for patients receiving their first Medtronic device. There are now more than 600,000 device implants that are MRI-conditional.
Gilk mentions that “It’s a growing number, but it is still a minority,” and Froelich estimates that around 10% of people with pacemakers have newer MR-conditional devices. It’s a small number because the devices are so new, and MR-conditional pacemakers cost more than the average non-conventional pacemaker. Gilk also says that “Hospitals that get reimbursed on a fixed schedule may be reluctant to use the more expensive MR-conditional devices.”
The reason the MR-conditional pacemakers are so expensive is because they reflect the enormous efforts to research, develop, test, and validate them, according to Wolf Ruhnke, vice president of corporate product management for Biotronik, based in Berlin, Germany. “Our pricing is based on various features and that is one of the different features we price on,” he says. At Heart Rhythm 2014, it was discovered that approximately 20% of patients with MR-conditional pacemakers received an MRI scan within the first two years after their device was implanted.
There are still so many patients with legacy devices that it needs to be taken into consideration whether or not the conventional devices can be safely imaged via MRI scan, and the answer can mean better, timelier patient care. Therefore, a study is being conducted consisting of pacemaker patients who have a clinical need for MRI but who do not have MR-conditional devices implanted. The study is being done by several organizations and hopes to develop a registry that will answer some of the MRI scan safety questions that have come up. Currently, they are just in the beginning stages of understanding the impact the research studies may have on the care and treatment of the patient population.
The MagnaSafe Registry is the largest body of evidence on the use of MRI in patients with non-conventional devices, and is a large prospective multicenter registry that studied about 1,500 cases at 1.5T. It has not been published quite yet but was presented in abstract form at the American Heart Association meeting in 2013. So far the results have been promising: no deaths, device failures, or other adverse effects such as ventricular arrhythmias were reported for the first 1,189 cases enrolled in the registry.
In collaboration with 11 other societies worldwide, the Heart Rhythm Society is developing a consensus statement on imaging safety with implantable cardiac devices. Their timeline is to have a document by the end of the year and publish it in 2017. The main focus of the document is MRI for patients with implanted cardiac devices, but they are also looking at CT scanning and radiation therapy, especially for cancer patients undergoing radiation therapy, and they are looking at the evidence of the management of those patients.
As the evidence is reviewed so far, it has been concluded that the main recommendation is that a patient can safely have an MRI with a nonconditional device as long as all of the precautions are taken and the MRI is the best test for the condition. It hasn’t been discovered whether or not the document will persuade the Centers for Medicare & Medicaid Services (CMS) that Medicare should cover MRI for people with nonconditional devices. Right now the focus is reviewing the evidence and what is felt to be unsafe or safe.
Another problem is that if patients have retained leads from a previously removed pacemaker, MRI exams may still present safety concerns. The tips of each lead is sometimes left embedded in the heart muscle when the pacemakers are removed, and removing the tips may be dangerous, although the danger of retained or abandoned leads are an even bigger threat to MRI-induced cardiac stimulation and radiofrequency heating, meaning it’s not just the pulse generator that may present risks to cardiac device patients.
Looking ahead, manufacturers are continuing to improve their MR-conditional devices that they are bringing to the market, such as Medtronic and Biotronik, who have introduced MR-conditional devices that can be safely programmed by cardiologists before the patient goes into the MRI machine, that way the cardiologists don’t even have to be present for the scan. According to Steinhaus, Medtronic’s device can be put in an MR mode right before the scan and reprogrammed to its proper settings soon after. This is extremely helpful because it makes sure that the patient’s device is in MR mode for the shortest time without delaying the procedure or requiring more staffing during the scan.
MRI AutoDetect is a device from Biotronik, and allows patients to see their cardiologist up to two weeks before the scan to have it programmed. The device has a sensor incorporated, so it is able to take care of things itself. It is able to switch to MRI mode as soon as it recognizes an MRI environment, and once the patient leaves the MRI machine, the device is automatically reprogrammed to full therapy mode.
MRI AutoDetect also adds comfort for the patient, while optimizing workflow for the radiologist, technologist, cardiologist, and nursing staff. Although presently the device is only available in Europe, there is hope that soon it will be available in the U.S.
The agency was nervous when the FDA first approved MR-conditional pacemakers, and they only labeled pacemakers for scanning areas that did not immediately include the heart. They only approved MRI scans of the head or the pelvis areas and below, as the central thoracic region was not permitted.
The FDA has lifted the ban on cardiac thoracic scans of patients with many MR-conditional pacemakers, and they’re now approved for head to toe use. The reason for this is because the FDA requires that both the leads and the generator be MR-conditional. Mixing and matching leads and generators by cardiologists can negate the MR-conditional system labeling if all of the components haven’t been tested together as a single system. Patients who had MR-conditional pulse generators implanted could be frustrated to learn their leads are not MR-conditional, which therefore makes the whole system non-MR-conditional.
It will take quite a long time before the pacemakers improvements and research can convince people that those with nonconditional devices can be scanned safely if the proper protocols are followed strictly. 30 plus years of hearing the warnings of pacemakers and MRI scans will be difficult to reverse the effects of, especially since the market of MR-conditional devices is growing and will wind up making the safety of conventional pacemakers insignificant.
As life expectancy continues to increase and patient’s ages rise, so does the chance of them needing an MRI. “If the implanted device studies demonstrate the opportunity to scan patients with specific devices, and the devices are labeled as such in a clear, concise way, the MR imaging community, with radiologist support, can provide this service to a much broader patient population,” says Wendy J. Stirnkorb, CRA, RT(R)(MR), assistant director of imaging at Sibley Memorial Hospital, Johns Hopkins Medicine and president of her own imaging consultancy, Stirnkorb Consulting, LLC. “This would be a positive position for the medical community but, most importantly, a winning situation for the patient.”
Source: Radiology Today Magazine
