Value of 'MRI-Safe' Pacemakers, ICDs Questioned in MagnaSafe

Marlene Busko

November 21, 2014

CHICAGO, IL — Patients with a conventional pacemaker or implanted cardioverter defibrillator (ICD) who need a definitive diagnostic nonthoracic MRI scan—of their brain, lower spine, hip, or knee, for example—can safely have the scan, according to final results of the large, prospective MagnaSafe Registry study[1].

The MagnaSafe analysis included 1500 patients undergoing such MRI scans who had been implanted with standard devices, as opposed to one of the available "MRI-conditional" devices (leads and a generator deemed safe for MRI under certain conditions). No patients died from the scans and in the one case of acute ICD failure, which was due to a programing error, the device was replaced immediately.

Thus, the study demonstrated that "clinically indicated nonthoracic MRI at 1.5 T can be performed for patients with standard nonconditional devices at no significant clinical risk when patients are appropriately screened and the device is appropriately programmed," said Dr Robert J Russo (Scripps Research Institute, La Jolla, CA) said, presenting MagnaSafe here at the American Heart Association (AHA) 2014 Scientific Sessions.

"We hope that the results . . . may change AHA/ACC recommendations [and] Centers for Medicare & Medicaid Services (CMS) coverage but, more important, will improve access to clinically indicated MRI for patients with standard pacemakers and ICDs," he stressed.

The assigned discussant, Dr Mark S Link (Tufts Medical Center, Boston, MA), who was not involved in the study, agreed that "it is time for us as a community to look at the risks and benefits of MRIs in our permanent pacemaker/ICD patients and not categorically exclude these patients from MRIs."

The researchers will soon submit the paper to a journal, and potentially the CMS could approve payment for MRIs for patients with non-MRI-conditional devices as early as June 2015, Russo speculated to heartwire .

Meanwhile, this remains a very controversial issue for day-to-day cardiology practice, as discussed by Dr Melissa-Walton Shelley and Dr John Mandrola on

Race to Develop MRI-Safe Pacemakers

MRI has been contraindicated because of concerns that the magnetic field might inhibit the pacemaker's function, and manufacturers have raced to get more MRI-conditional pacemakers or defibrillators to the marketplace.

Meanwhile, an estimated two million patients in the US have standard cardiac pacemakers and ICDs, and likely half of these patients will someday need an MRI.

Replacing a standard cardiac device with an MRI-conditional one entails risk; in the REPLACE study, generator replacement with or without lead replacement resulted in a 4% to 15% rate of major adverse cardiac events (MACE).

Meanwhile, several small studies showed that MRI can be performed with minimal risk if patients are properly monitored and the cardiac device programming is modified appropriately.

The current study included patients at 21 US sites who had a non MRI-conditional pacemaker that had been implanted after 2001; the patients were not pacemaker dependent. The researchers followed a protocol designed to minimize preventable potential adverse events.

The primary outcomes were death, new onset of arrhythmia, loss of pacemaker capture, or generator or lead failure during the scan, requiring immediate replacement.

The 1000 patients with a pacemaker had a mean age of 73 and had received their device about 3 years ago, and the 500 patients with an ICD had a mean age of 65 and had received their device 2.7 years ago. Overall, 60% of the patients were men.

They had had a nonthoracic MRI scan of their spine (40%), brain (35%), joints (10%), abdomen/pelvis (5%), or other area (10%), and the scans lasted an average of 45 minutes.

Positive Outcomes, Next Steps

No leads failed. In one patient with an inappropriately programmed ICD (tachycardia therapy was inappropriately left in the active mode with bradycardia therapy disabled during the MRI), the generator failed and was immediately replaced.

Six patients had episodes of atrial fibrillation; five of the patients had known atrial fibrillation and were on warfarin, and all cases resolved prior to discharge.

No patient had ventricular arrhythmia. Six patients with pacemakers had electrical reset of their devices.

Change in lead impedance was not associated with clinically significant parameter changes.

Whereas most patients had one scan, some patients—often those with brain tumors or stroke—had two to 10 scans, but this did not increase their risk, Russo said.

"Are MRIs and [standard] pacemakers and ICDs compatible? I would give a conditional 'yes,' " said Link. Programming of the device prior to the scan is critical, he noted.

To heartwire , he commented that if he had an ICD or pacemaker, he would go to his cardiologist and say, "Look at these data! Why can't I have an MRI? It's very safe as long as my [device] is appropriately programmed, before and after the MRI."

Dr Valentin Fuster (Mount Sinai Hospital, New York), who was not involved with the study, commented that perhaps while industry is scrambling to find "MRI-safe" cardiac-pacing devices, what cardiologists are looking for has been there all along.

"I have been following this field for 10 years, and I have been told that MRI-compatible devices are the answer, and now you say we don't have to [have industry develop] MRI-compatible devices . . . [since safe pacemakers and ICDs] were there all the time," he observed.

The FDA specifically asked the researchers to exclude patients who received thoracic MRI scans, since this was believed to be extremely high risk, but in subsequent research they will look at safety in patients with standard cardiac-pacing devices who have thoracic MRIs or have 3-T scans, said Russo.

The MagnaSafe registry was funded by unrestricted educational and research grants from Biotronik, Boston Scientific/Guidant, St Jude Medical, Hewitt Medical Research Foundation, and multiple philanthropic sources. Russo has received research grants from Biotronik, Boston Scientific, and St Jude Medical. Link and Fuster have reported they have no relevant financial relationships.


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