Some Types of Implantable Devices Might Not Rule Out MRI

Patients with non-conditional cardiac implantable electronic devices (CIEDs) may not have to avoid MR imaging, according to a study published in the Journal of Clinical Electrophysiology.

Researchers from Intermountain Medical Center Heart Institute in Salt Lake City, Utah, performed a prospective study to determine the safety of non-thoracic MR imaging with patients who have CIEDs. A total of 178 patients who underwent 212 MR imaging scans for clinical reasons participated in the study; 62 patients had implantable cardioconverter/defibrillators. Scans were done in standard modes with a limit of 2W/kg. Pacing modes were ODO or OVO for intrinsic rates over 40 and DOO or VOO for rates equal to or less than 40.

The scans were performed after the patients were cleared by radiology and cardiology, and pre- and post-scan CIED interrogations were performed.

Primary outcome events were:

• Death

• Generator failure

• Lead failure

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• Battery voltage loss of more than 0.04 V

• Decrease in P wave voltage of more than 50% or R wave voltage of more than 25%

• Threshold increase of more than 0.5 V

• Impedance change more than 50 Ω

Scan sites:

• C-spine/head/neck: 87 scans (41%)

• T-spine/cardiac/shoulder (thoracic): 28 (13%)

• L-spine/abdomen/pelvis: 69 (33%)

• Lower extremity: 28 (13%)

The results showed no primary or secondary outcome events occurred, and no peri-scan disruption of pacing was noted, the authors wrote.

"That's a pretty big number of leads exposed to these very strong MRI fields. You would think if there was even a 1 percent chance of having a problem, it would have shown up," senior study author Jeffrey L. Anderson, MD, a cardiologist at the Intermountain Medical Center Heart Institute, said in a release. "Not even one generator or lead needed more than a minor adjustment, if any at all."

The study was limited, looking only in parts of the body not in direct proximity to the implantable cardiac rhythm devices. The researchers concluded: “This experience validates and extends that of the large but inclusion-restricted MagnaSafe Registry, profiles MRI scanning in CIED patients in general clinical practice, and argues against replacing non-conditional with conditional devices when MRI is performed in a carefully controlled environment.”