MRI safe for pacemakers, defibrillators

In the past, MRIs have been considered dangerous for people with implanted defibrillators and pacemakers.

However, new research has found that magnetic resonance imaging is safe for cardiac electronic devices, even for chest imaging, for both conditional and non-conditional devices.

Led by researchers from the Intermountain Medical Center Heart Institute in the US, ‘Real World MRI Experience with Non-Conditional and Conditional Cardiac Rhythm Devices After MagnaSafe’, published in the Journal of Clinical Electrophysiology, found that MRI imaging can be safely performed on patients with devices.

“Magnetic resonance imaging has become very popular,” said Dr Jeffrey Anderson, senior study author and cardiologist at the Intermountain Medical Center Heart Institute. “It’s excellent for looking at soft tissue changes. But it involves very high-strength magnetic fields, which means if a patient has any implanted metal devices containing iron, it could potentially cause harm.”

X-rays can see bone, but they don’t provide much information about soft tissues like the brain, the heart or other internal organs. “MRIs are marvelous for that,” Dr Anderson said.

The researchers evaluated 212 MRI studies in 178 patients with a cardiac implantable electronic device between February 2014 and August 2016. They didn’t find a single problem requiring remediation in the entire series, which involved a total of 418 implanted leads.

“That’s a pretty big number of leads exposed to these very strong MRI fields. You would think if there was even a 1% chance of having a problem, it would have shown up,” Dr Anderson said. “Not even one generator or lead needed more than a minor adjustment, if any at all.”

In the past, MRIs have been considered risky because of the fear a pacemaker or defibrillator device’s generator circuits could be disrupted; its metal leads could be pulled out of place by the magnetism; or the lead tips could become hot and scar surrounding tissues, interfering with pacing and defibrillating function.

To counter that, some newer devices have been specifically made and tested to be safe for use with MRIs under certain test conditions in magnetic fields. Devices in this category are referred to as ‘conditional CIEDs’ (cardiac implantable electronic devices) and have been approved for MRI use under imaging conditions implemented by the US Food and Drug Administration.

Most people who have implantable defibrillators and pacemakers don’t have these newer, more expensive conditional devices, however. Rather, they have standard non-conditional devices. In patients with non-conditional devices who have a medical need for imaging, and in whom MRI is deemed the most desirable diagnostic tool, MRI usually hasn’t been used, or the non-conditional devices and leads have been removed and replaced with conditional devices and leads beforehand.

Imaging decision-making for those with cardiac implantable electronic devices has started to change with publication this year of a large multicentre study called the MagnaSafe Registry study, which showed that non-conditional devices can be safely imaged by MRI if proper precautions are observed. Published in the New England Journal of Medicine, the study was limited in that it looked at the safety of MRIs only in parts of the body not in direct proximity to the implantable cardiac rhythm devices, which are typically in the chest under one of the collarbones.

The new Intermountain Medical Center Heart Institute study directly builds on the MagnaSafe study, validating findings of the main MagnaSafe cohort of 1500 patients and expanding that group of patients to include those who need an MRI of their lungs, heart or other organs within the chest.

In addition, the new study includes many patients with conditional devices, providing a side-by-side comparison of the two types of devices.

Dr Anderson said the research confirms the MagnaSafe findings and shows it is also safe to use MRI to look at the heart or lungs in patients with these implantable devices.

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