Magnetic resonance imaging (MRI) is used increasingly for diagnostic purposes and to assess responses to treatment, and the recognition that many cardiac device (ILR, Pacemaker, and ICD) patients will have a clinical indication for an MRI scan, has led to the development of MRI conditional devices which allow patients to undergo MRI scanning. In addition, selected patients with non-MR conditional cardiac devices have undergone MRI scanning without deleterious effects on either the patient or on device function. The presence of a cardiac device is therefore, not a contraindication to an MRI scan.
MRI Scanning in Patients with MRI Conditional Devices
The development of MRI conditional devices has allowed patients with specified implantable cardiac monitors, pacemakers, ICDs & CRT-P/D devices to undergo MRI scanning safely. MRI “safe” activation reprograms the device to OOO for non-pacing dependent patients or VOO pacing for dependent patients, reducing the risk of inappropriate pacing inhibition.
Patients with MRI conditional systems undergoing scans within the indications of device should have the device programmed according to the manufacturer’s instructions and the patient monitored appropriately. There is little or no risk of significant harm to the patient. Implantable cardiac monitors (ECG loop recorders) should also be interrogated and the stored data downloaded, as it is likely to be erased by the strong magnetic field. Full details for all manufacturers’ devices are available through the website links below.
See table 1 below for checklist for patients with MRI conditional devices who require MR scanning.
Programming to MRI “Safe” Mode
All MRI conditional devices should be programmed to MR “safe” mode prior to scanning. It is important to record the lead and/or device parameters prior to scanning. This should be performed by a cardiac physiologist or cardiologist with specific training in this programming procedure. Some devices may be rendered MRI “safe” through an activating device or automatically in the presence of a strong magnetic field.
MRI Scanning in Patients with non-MRI Conditional Devices
MRI scans should in general not be performed in patients with non-MRI conditional cardiac devices unless there is no alternative method to obtain important clinical information and the information will change clinical management. For these patients referral to a centre with specific experience in MRI scanning of non-MRI conditional devices is recommended. See table 2 below for checklist for patients with non-MRI conditional devices who require MR scanning.
BHRS standards for CRM devices – centres
As part of the 2018 revised BHRS standards document for CRM devices new guidance mandates that each device implanting centre in the UK must ensure that arrangements are in place that allow their patients access to MRI scanning. For MRI conditional devices ideally this should be performed locally with an agreed standard operating policy or protocol to ensure patients are scanned in a timely manner. Patients should not be denied access to MRI scanning because of lack of these arrangements or resource.