Magnetic resonance imaging (MRI) is often considered a contraindication in patients with cardiac implantable electronic devices (CIED). However, there has been a growing demand for the utilization of MRI for diagnostic and therapeutic purpose to assist and enable optimal patient care. This demand has motivated device manufacturers to design MRI-compatible leads and devices. As the process to develop and achieve FDA approval of these devices takes time to accomplish and take effect, there remains a large patient population in need of MRIs who currently have available non-MRI conditional CIED systems. There have been numerous reports and several focused studies in the literature suggesting that MRIs are safe in carefully selected CIED patients. Many centers, however, struggle with the development and implementation of a protocol for selection and MR imaging of CIED patients. The purpose of this article is to describe the protocol that is used at the University of Michigan for patients with CIEDs who undergo MRIs. The protocol we currently use is a modified version of the protocol used by the Johns Hopkins group who pioneered the effort of scanning patients with CIEDs.
At the University of Michigan, the staffing, performing and interpretation of MRI procedures is the responsibility of the Department of Radiology. The care of patients with CIEDs is the responsibility of the Cardiac Arrhythmia Service. In order to develop a successful MRI/CIED, several inter- and intra-departmental disciplines need to establish a working relationship and shared goals with respect to patient safety. Key members from Radiology include the: attending physician, physicist, technician, and scheduler. Similarly, key members from Electrophysiology (EP) include the: attending physician, mid-level provider, CIED nurse, and scheduler. It is imperative for each member to understand their role in this process and to assure that clear channels of communication exist between these team members.
The MRI suite and control room must allow for electrocardiography (ECG), blood pressure (BP), and pulse oximetry monitoring for the duration of the MRI. It is also optimal to have a room adjacent to the MRI suite where device evaluation and programming can be performed pre and post MRI. A crash cart must be immediately available.
The field strength should be limited to 1.5 Tesla and the Specific Absorption Rate (SAR) to less than 2 watts per kilogram of body weight. The number and length of sequences should be minimized as well. If MR imaging is for brain examination, a transmit/receive volume coil is preferred.
Prior to the actual MRI, a prudent practice is to have the team members communicate. This is where the MRI procedure team will discuss the specifics regarding the patient condition and the scheduled MRI procedure. All team members will have clearly identified roles should the patient’s condition change. Roles should include: an individual to call for additional staff support, staff to transfer the patient out of the MRI suite to the adjacent room, and staff to ready the crash cart. The CIED nurse role should always be to quickly restore the CIED original settings and conduct advanced cardiac life support (ACLS) until further staff arrives. It should be made clear at this point that in case of an emergency, if the patient develops VT for example, the patient will need to be removed from the MR scanner in order to successfully enable device reactivation and potential resuscitation efforts, since the MR scanner cannot easily be turned off.
Main Contraindications to MRI
Until further research and safety analysis are conducted, it is recommended to consider the added risk for the patient should any of the following CIED-specific conditions be present and then to decide whether the risk/benefit ratio still remains favorable to proceed with MRI:
- Pacemaker dependence or the absence of a hemodynamically stable cardiac rhythm is currently considered an added risk factor for patients undergoing MRI especially in patients with implantable cardioverter defibrillators (ICDs). Although asynchronous pacing modes can be programmed in the vast majority of devices available today, there are some that do not provide this option. Further, the device manufacturers will also caution that despite permanent programming, devices may exhibit unpredictable behavior when in the MRI and active scanning environment. Power-on-reset has been described in rare instances resulting in resetting the device to nominal factory settings. Correction of this problem requires reprogramming the device since discontinuation of the electromagnetic field does not result in reversion to the intended programmed settings.
- ICDs manufactured prior to 2000 and pacemakers manufactured prior to 1996 have been reported to be more susceptible and exhibit interactions from MRI due to lack of updated shielding and algorithms utilized in modern devices.
- CIEDs at elective replacement indicator (ERI) or end of life (EOL) status is another contraindication since there is a possibility of further battery drain during the scan. Tachyarrhythmia monitoring should be turned off to avoid battery depletion. Prior publications, mainly those including devices manufactured before the year 2000 (ICDs) and 1996 (pacemakers), reported instances of rapid battery decline when exposed to the MRI environment.
- The presence and number of abandoned endocardial leads and free floating coils (thought to be more prone to heating) and epicardial leads (not cooled by blood flow) are considered a contraindication to MRI due to the possibility of heating and tissue damage where the lead tip and myocardium interface.
- Lead dysfunction such as lead fracture is also felt to increase the potential for lead heating and subsequent myocardial tissue damage.
- Newly implanted lead systems (duration <8 weeks) are generally considered a contraindication due to possible instability/movement of leads prior to complete lead/myocardium interface maturation.
Critical Protocol Components
It is imperative to follow a stepwise process to ensure that the requested MRI is necessary and critical to the care of the patient and cannot be answered by alternative imaging techniques. Further, numerous staff members are involved in the planning and coordination of these studies, and the order in which each step of the protocol is implemented will contribute to overall staff efficiency.
- The clinician ordering/requesting the MRI must document that the patient suffers from a life-threatening or severely debilitating condition for which MRI is critical to patient management.
- The attending radiologist must screen each patient and document the absence of alternative diagnostic modalities or previously performed diagnostic modalities that have been unsuccessful.
- A formal EP consultation should be performed approximately 2 weeks prior to the scheduled MRI. During this visit, complete device evaluation will be performed to confirm device and lead system integrity, pacemaker dependence, presence or absence of abandoned leads, and specific device programming. The evaluation will identify contraindications to testing other than the CIED and will outline detailed device programming required at the time of MRI should the examination be performed. This visit will also include informed patient consent when applicable and to advise the patient of recommended follow-up post MRI, which is 1 week and 3 months after the MRI at our institution.
- MRI/CIED evaluation should take place Monday through Friday during regular business hours when appropriate staff is on site. MR imaging is not intended for emergency care.
- Required staff during MRI/CIED procedure: the radiologist and radiology technician, CIED nurse with expertise in CIED evaluation, programming, current ACLS certification, and an available on-site electrophysiology physician.
- The CIED nurse role is especially critical to patient safety. It is the responsibility of the CIED nurse to perform a complete pre-MRI device evaluation to confirm device and lead stability and program it as specified in the prior inpatient or outpatient EP consult note. Pacemaker-dependent patients are placed in an asynchronous mode, tachycardia therapies are disabled, and other programmable options are disabled when applicable such as magnet response and noise reversion modes. It is also the CIED nurse responsibility to monitor the patient heart rhythm, blood pressure, and pulse oximetry for the duration of the MR examination. At the completion of the MRI, the device nurse will perform a complete device evaluation and reprogram to initial device parameters. The patient will be reminded and encouraged to comply with recommended device follow-up.
- For all CIED/MRI procedures, it is recommended for the device programmer to be in a room adjacent to the MRI suite. It should be plugged in and active, with the initial settings ready for quick reactivation of original device settings if it becomes urgently necessary.
- The MRI scanning should be terminated if the CIED system exhibits malfunction, if a clinically significant change in patient condition occurs, or at the patient, radiologist, or EP staff request. The MRI scanner cannot be turned off at will and therefore, the patient needs to be removed from the scanner for appropriate measures to be implemented elsewhere.
The described protocol can be overridden at the discretion of the attending radiologist or electrophysiologist in order to appropriately care for the treated patient.
We have been using this protocol at the University of Michigan since March 2013, and will be reporting the safety of this approach at Heart Rhythm 2015. It is our experience and opinion that MRIs can be safely performed in most patients with CIEDs.
As we advance further into the 21st century, the complexity of the patients with CIEDs has continued to challenge available imaging technologies. Given the beneficial impact of MRI as a critical and irreplaceable tool in diagnosis and treatment of countless disease entities, CIED technology is adapting to the requirements set forth by MR technology. For the CIED patient population, the device was once viewed as an impediment to advanced diagnostics, thus interfering with continuation of care. With the protocol outlined above, MRIs appear to be safe for the majority of patients with CIEDs. Implementation and success of such an endeavor relies on a multidisciplinary approach where communication, inter- and intra-departmental collaboration, and the use of experienced CIED nurses are key components to meet this challenge for our patients.
Disclosures: The authors have no conflicts of interest to report regarding the content herein.
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