MRIs proven safe for patients with FDA-unapproved implantable devices

Longtime claims that heart patients fitted with implantable cardiac devices should forgo MRI testing for safety concerns could be incorrect and “outdated,” according to new research published in the New England Journal of Medicine.

Millions of patients fitted with pacemakers or defibrillators are recommended for MRI screenings on a regular basis, lead study author and University of Pennsylvania professor Saman Nazarian, MD, PhD, told Cardiovascular Business, but they’re often denied the procedure by CMS. CMS allows only beneficiaries with “MRI-conditional” devices—those deemed safe by the U.S. Food and Drug Administration (FDA)—to undergo the imaging test.

“Patients who have permanent pacemakers or implantable cardioverter-defibrillators are often denied the opportunity to undergo MRI because of safety concerns,” Nazarian said. “These concerns exist because of previous case reports in which appropriate protocols were not followed. While some resistance to MRI in the setting of pacemakers or ICDs exists in the cardiology and radiology communities, a main hurdle is (CMS).”

Nazarian and a team of Penn researchers performed a prospective, nonrandomized study of 1,509 patients to assess the safety of MRI at a magnetic field strength of 1.5 Tesla, according to the research. Of those participants, 58 percent had a pacemaker and 42 percent were fitted with an implantable cardioverter-defibrillator; no devices were considered “MRI-conditional.”

The patients underwent a cumulative 2,103 thoracic and nonthoracic MRI exams during the study period, and in all legacy devices pacing mode was changed to accommodate the screenings. Tachyarrhythmia functions were also disabled, Nazarian et al. wrote—and the thousands of exams yielded almost no negative results.

No long-term, clinically relevant adverse events were reported during the study, the team said, but in nine MRI exams a patient’s device reset to a backup mode—a finding that was transient in eight of the nine instances. Device parameters were changed, as well, with the most common immediate post-MRI instance being a decrease in P-wave amplitude in 1 percent of patients. In the long-term, the researchers observed further drops in P-wave amplitude in 4 percent of patients, increases in atrial capture threshold in 4 percent, increases in right ventricular capture threshold in 4 percent and increases in left ventricular capture threshold in 3 percent of the population pool. None of these changes in lead parameters were clinically significant, Nazarian said.

“We found MRI examinations to be safe in the setting of legacy cardiac pacemakers or ICD systems, when using a safety protocol,” he said. “The scans were safely performed even when performing thoracic or cardiac MRI and with patients that were dependent on cardiac pacing for every heartbeat.”

CMS’s reliance on FDA-approved devices could be skewed by the computer-generated data the claims are based upon, Nazarian said. The criteria outlined by the FDA for an “MRI-conditional” device are primarily based on computed simulation studies, rather than real-life clinical data.

“Given the results of our study and those of the MagnaSafe Trial, it is hard to understand the position of the Centers for Medicare and Medicaid Services to restrict access to patients with MRI conditional labeling of their leads and ICD systems,” he said. “Given this new data, the idea that access to the potentially lifesaving diagnostic data from MRI would be limited for patients with legacy pacemakers and ICD leads or generators is outdated. Additionally, no patient should ever be exposed to the risks of lead extraction to enable an MRI that could safely be performed with the leads in place.”

Nazarian said he was surprised at how little risk can be involved in such a procedure if a strict protocol to minimize electromagnetic interference is followed. He and his colleagues also found the potential clinical gain in terms of diagnostic accuracy to be significant in all cases during the study.

He said the millions of patients with a pacemaker or ICD system who have been told they need an MRI should contact a center “with the expertise to enable the imaging.”

“Many centers across the U.S. are capable of performing safe imaging despite your device,” he said. “MRI can be instrumental in providing the right data for appropriate treatment planning in the setting of many neurologic, cardiac and musculoskeletal disorders as well as malignancies.”