Imaging patients with previous cardiac issues can be difficult using magnetic resonance imaging (MRI). This is because certain patients with cardiac issues may have a Cardiovascular Implantable Electronic Device (CIED). Previously CIED patients were not always considered safe to be imaged using MRI due to the metal and electronic components. The devices could also cause distortion and artifacts in the images. Since the introduction of MR Conditional and MR Safe devices, the use of MRI in patients with CIEDs has grown quickly.
What is a CIED?1
Cardiovascular Implantable Electronic Devices include a number of different devices that help to monitor a patient's heart and attempt to prevent further episodes. These include pacemakers, implantable cardioverter defibrillators (ICDs) and cardiac resynchronization therapy pacemakers and defibrillators (CRT-P/Ds). Each CIED contains metal or other aspects that could interfere with the electromagnetic field produced by an MRI scanner, including the battery, other electronic components or sometimes the device itself.
In the past, putting patients with CIEDs into an MR scanner caused concerns regarding lead heating, device migration and device malfunction, meaning the scans would not not be approved or allowed. Because of the way MRI exams are conducted, any metal inside the room could react to the electromagnetic field.
Before MR Conditional implants were introduced, they caused issues with scanning due to their metal components, though it can occur with other items. Metal containing items can heat up as they react to the field; the same sort of thing can happen with tattoos or clothing that contain metal. The best way to avoid this heating and the discomfort it can lead to is usually to leave any metal out of the MR suite altogether, which is required for anything with metal that can be removed. However, when the item is embedded in the patient, radiologists may struggle to conduct their exams.
What does MR Conditional device mean?
Since the introduction of CIEDs that have been labeled MR Conditional or MR Safe, MR imaging can be conducted on specific patients when specific conditions are met. There are few devices that meet the criteria to be labeled MR Safe, which leaves the option for certain patients to consider MR Conditional devices.
MR Conditional devices require modifications to be made to the MR scanner before the patients can be scanned.1 This includes the patient's device being programmed to correspond with the scanner's MRI mode. Additionally, the scanner must match the conditions of the device's labeling. There has been an increase in MR imaging volume in patients with CIEDs due to the adoption of MR Conditional devices. Modified protocols can also help to address common cardiac artifacts and distortions resulting from the device, battery or other electronic components that comply with MR Conditional device labeling.
The newer devices offer a greater resistance to electromagnetic interference from the environment.1 This includes the environmental factors caused by the super-conducting magnet inside the scanner. MR Conditional devices that have the approval from regulatory agencies, like the FDA, can be used with specific alterations to the scanner and the scan, as well as the use of patient-monitoring data, like ECG and pulse oximetry metrics.
Since the introduction of MR Conditional CIEDS, more than 100 patients with MR Conditional CIEDs were scanned in 2018 at the University of Wisconsin Hospital.1 These devices help to improve access and MR use in patients with CIEDs. The radiology department would follow the device's label to ensure it is MR conditional and use appropriate application s and settings while scanning this patient. This allows patients with implants to have MR exams, and their physicians to observe the valuable information provided by said exams.
- Cardiac MR in patients with CIEDs. SIGNA Pulse of MR. http://www.gesignapulse.com/signapulse/spring_2019/MobilePagedArticle.action?articleId=1488819&app=false#articleId1488819. Last accessed July 19, 2019.