She's been a good friend for 23 years and an integral part of a team of healthcare providers. But now, she stands disheveled in a hospital room with one sock on and one sock off. She greets the nurse twice within five minutes of entering the room, tells the same joke over and over, and at sundown, morphs from Dr Jekyll to Mr Hyde. After a predictably nonspecific head CT, she desperately needs an MRI, but by the end of the day, two tertiary centers, one regional center, and her local hospital radiology department refused to place her in the MRI scanner because she has a pacemaker. It's not their fault, really.
If this patient's home address were Baltimore, for instance, her cardiologist would have dialed the radiology department at Johns Hopkins Hospital and heard a friendly but mechanical female voice invite her to "press 3 to order an MRI for a patient with a device." Instead, in a country where the latticework of web-based information rivals the neuronal complexity of the human brain, most hospitals still can't move forward on the MRI-device issue. Johns Hopkins Hospital has. It is part of a registry that opened a floodgate of diagnostic opportunity for cardiologists, orthopedists, and neurologists. With well over 1000 MRIs performed on device-laden individuals and no clinically adverse outcomes, it should be lauded as one of the country's leaders in MR imaging; but you can't be a leader in the US unless you have followers who can get past governmental constraints.
Dr Carsten Zobel (now at Marien Hospital Euskirchen, Germany) and colleagues from the University Hospital of Cologne, Germany, are also leaders. They published an excellent review on the history of MRI scanning in device patients in the April 2012 issue of Deutsches Ärzteblatt International[1]. It references another overview of MRI from Europace that revisited 10 deaths in the 1980s that were "poorly characterized with no ECG records for review"[2,3]. From 1992 to 2001, there were six deaths during or following MRI scanning in Germany, but no ECG records were available, and autopsy reports were unrevealing. The authors "guessed" the cause was "[ventricular fibrillation] due to inadequate asynchronous pacing on activation of magnetic function."
Things are different now. In Germany, there have been no deaths reported with MRI scanning in the past decade. Johns Hopkins Hospital, following the lead of physicians like Dr Robert Russo at the Scripps Institute, who championed the MagnaSafe registry, joined a handful of other facilities in the US that now scan frequently. It too has deciphered the formula for safety: sometimes resetting the device and performing an exit device interrogation and then a few follow-up interrogations over the coming weeks and months. There is beauty in the simplicity of those protocols, but to ignore the historic and complex mechanical, thermal, and electromagnetic concerns of scanning would do the topic a great injustice.
Modern Devices, Modern Scanners
Modern MRI scanners, for instance, create an electromagnetic field of only 1 to 3 T, far less than older scanners. The more recent legacy pacer components are far less magnetic, including both generators and lead tips.
Dog studies found no greater increase in lead tip temperature than a piddling 0.2°C. Pigs, however, demonstrate a 20° increase in temperature at the lead tip, "approaching ablation-range" thermal energy, but histological studies demonstrate no necrosis at the endocardium and little clinical implication for adverse outcomes[4].
The electromechanical jargon that generates the most concern is the issue of "reed switch activation," which can lead to asynchronous pacing "at an unpredictable rate." The reed switch trigger can inactivate ICDs as well.
The German review states, "There have been a few reports of a pacemaker reset, leading to activation of the device's standard configuration. The latter is generally a VVI (ventricular pacing, ventricular sensing, and inhibition of a sensed ventricular event) mode; therefore, pacer-dependent patients may be at risk of asystole from inhibition of pacing owing to misinterpretation of artifacts induced by the gradient fields.
"Furthermore, the standard parameters may not always suffice for effective stimulation in patients who need high initial energy. The main dangers are thus asystole from inhibition of pacing and induction of tachycardia by inadequate asynchronous pacing."
Pooling their data with published papers, the German authors found that 1043 patients with devices (including ICDs) had undergone MRI safely. "No life-threatening complications have been observed," they concluded. In addition, "in just 11 cases (1%), electrical resetting of the device was necessary, and a significant increase in pacing threshold (>1.0 mV) was seen in 16 cases (1.5%)." While they acknowledge that the study conditions varied widely, including differences in localization, field strength of the scanner, device, sensors, etc, their review provides a good estimation of how frequently complications can be expected.
A Q&A on the Johns Hopkins Experience
I reached out to Dr Saman Nazarian, an electrophysiologist at Johns Hopkins who has published on the institution's experience with MRI scanning of device patients[5]. Here is a review of that conversation.
Walton-Shirley: Do you agree that it's time to make MRI available to more patients with devices?
Nazarian: I agree. MRI is the imaging modality of choice for many disorders, and most patients who are currently denied an MRI due to a cardiac device could safely undergo imaging if a simple protocol such as ours were followed. We now have somewhere over 1000 who have undergone imaging safely and are analyzing the data.
Walton-Shirley: Why the slow uptake of imaging protocols?
Nazarian: In many cases, the main hindrance is a personnel issue. It does take resources from the division of cardiology to appoint someone to do the interrogations and monitoring during the scans. Additionally, that person should not be a device tech. That someone used to be me, but now we feel much safer and the number of scans has greatly increased. Ideally, someone who is [Advanced Cardiovascular Life Support] ACLS trained would be needed so he/she can act in case of an emergency. We designate a research nurse who is ACLS certified. We keep a cardiologist nearby and would not want a rep to be unsupported by a cardiologist.
Walton-Shirley: What are the obstacles to offering MRI to device patients?
Nazarian: Some radiologists and electrophysiologist are unconvinced of the overall safety and would not scan anyone unless the device were FDA approved with MRI labeling. Another issue is that [the Centers for Medicare & Medicaid Services] CMS pays for the MRI scan only if the scan in a device recipient is performed under an [institutional review board] IRB/CMS-approved protocol. Therefore, institutions without the research infrastructure would be unable to perform the scan for Medicare recipients.
[In March of 2011, Russo received approval from the CMS for payment for MRI scans if a facility agreed to participate in the MagnaSafe trial. Previously reported by heartwire , the trial was originally set to enroll 1500 participants and excluded pacer-dependent patients who have ICDs, abandoned leads, and abdominal implants. It also excluded those patients with any device with an FDA MRI-friendly label. According to Clinicaltrials.gov, there are 21 facilities in 14 states that are participating. The study is ongoing but not recruiting.]
Walton-Shirley: Could you get around the issue of scheduling by designating a "device" day per week or month in the MRI area?
Nazarian: That is an efficient way of setting up a program. We currently have appointed device MRI days. But as I mentioned before, it would not solve all the potential hurdles.
Walton-Shirley: Are there difficulties with obtaining MRI-compatible ECG monitoring equipment?
Nazarian: Scanners often have monitoring equipment that is filtered to minimize the noise. This is necessary for the scanners that perform cardiac MRI to synchronize image acquisition to cardiac motion. However, even such filtered ECGs can have noise during certain scans. We have learned to rely heavily on the pulse-oximetry signal. It almost never has noise (unless it's coming off the patient's finger or ear) and can give a reliable surrogate of the heart rate during the periods when the ECG signal is affected by artifact.
Walton-Shirley: Are there liability issues because there are no recently updated guidelines on MRI in device patients?
Nazarian: I think that is a possibility. However, if the patient and referring physicians are well-informed of the minute but possible risks and the patient signs an informed consent, the liability issues should be no different from any other procedure in medicine. We weigh the risks/benefits in each case and proceed only if we believe the risks for that patient are smaller than the potential diagnostic benefit of MRI. In most patients, this is the case, but we do turn certain patients away. There is a problem with viability studies. We can't evaluate the anterior-wall viability in patients with a device due to artifact.
Walton-Shirley: How often do you offer MRI for patients with devices?
Nazarian: At this point we are scanning approximately 20 to 30 patients per month.
Walton-Shirley: Do you have a protocol you'd feel comfortable sharing for device patients?
Nazarian: Sure. The protocol is published in Heart Rhythm[6].
Walton-Shirley: What about patients with capped tips? The German review article stated this was a contraindication.
Nazarian: There are some patients that have been reported to demonstrate superheating, but we've done five or six patients with capped leads who have had no difficulties. Additionally, we do scan patients with Medtronic MR-conditional devices, but the majority of patients scanned at Hopkins have legacy devices that we have found to be safe based upon prior in vitro/in vivo tests.
Walton-Shirley: Have there been any problems?
Nazarian: We've done experimental work with devices developed prior to the year 2000, and they did fry in the scanner. We were unable to communicate with them. This has not happened in devices developed after the year 2000.
What Will It Take for Things to Change in the US?
Despite the opportunity for entering patients in a scanning registry and the experience at European sites like University Hospital of Cologne in Germany, roughly 50% of US patients with devices who will need an MRI scan in the next year won't get one. Even at some of the registry sites, there is a reluctance to scan, and it's viewed as a hassle or a burden to the department staff. "What if I just mention your name as a perk for your hospital?" I asked one MRI director. "It would be great PR for your department to let folks know that you can perform an MRI in patients with devices."
"We don't need that kind of publicity," she said. "I won't scan a patient unless they have a doctor on our staff," but she confessed that they did scan a patient with a spinal-cord emergency once without a consult at the insistence of the neurosurgeon, who said the patient would otherwise die. They previously scanned patients with pain-control units at the insistence of a neurologist but stopped because the leads heated up and burned the patients. "I won't do things like a torn meniscus; I make all of them see our electrophysiologist," she added.
I wondered if she might feel differently if she was the one with a torn meniscus, where every single step is a painful navigation between gravity and locomotion, but I appreciated her concern for her patients nonetheless.
As I write this piece, all over the world, there are patients with headaches, paresthesias, and presumptive and unconfirmed diagnoses of MS, brain tumors, stroke, and multi-infarct dementia who still wait for an MRI because they have a device. For some, the progress made in this field will not reach their facility in time to help them.
My patient and my friend still waits. With thousands of safe scans documented, it's time to open the floodgate of diagnostic opportunities for all of these individuals even if scanning them is a bit of a hassle. Unfortunately, those of us outside the reach of a registry are still firmly stuck in that black hole that exists between knowledge and implementation.
It's high time to crawl out and expose cardiology's biggest lie, so here goes: Most of our device patients really can have an MRI safely after all.
© 2014 WebMD, LLC
Cite this: Cardiology's Biggest Lie: No MRI for Your Device Patient - Medscape - Jul 29, 2014.
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