Key Points
- MRI generates static and gradient magnetic fields as well as RF energy. The potential interactions between CIEDs and electromagnetic interference from MRI include the following:
- Magnetic field-induced force and torque due to ferromagnetic materials: CIED generator movement is extremely unlikely due to confinement in the subcutaneous tissues.
- Leads do not contain any significant ferromagnetic materials to cause movement in a magnetic field.
- Gradient magnetic field-induced electrical current: Gradient magnetic fields can induce current in conductive wires within the field that could lead to myocardial capture and potentially lead to atrial or ventricular arrhythmias.
- Heating and tissue damage: RF fields can lead to nonconditional CIED component heating and subsequent thermal damage to the surrounding tissue (functional ablation). Changes in sensing or capture thresholds can occur as a result of tissue damage near lead electrodes.
- Effects on reed switch activity: The reed switch is a feature that permits programming of the device by placement of a magnet. Magnetic fields might therefore affect the reed switch activity of a nonconditional CIED, leading to asynchronous pacing and inhibition of tachycardia therapies.
- Electrical reset: High-energy electromagnetic interference (EMI) can lead to electrical or power-on-reset, a backup demand mode, wherein pacing might be inhibited and tachyarrhythmia therapy activated.
- Power-on-reset parameters vary by vendor and type of CIED (See Tables 1 and 2), and can include reset of pacing polarity to unipolar.
- Inhibition of pacing function due to oversensing of MRI-generated signals or pacing at an output below threshold (bipolar or unipolar) in a pacemaker (PM)-dependent patient might occur in the setting of power-on-reset and must be recognized to prevent catastrophic consequences.
- Additionally, battery status can be affected, particularly for CIEDs that are near an elective replacement interval (ERI), which could result in unreliable function.
- Inappropriate function and therapies: EMI from RF energy pulses or rapidly changing magnetic field gradients might cause oversensing that can lead to inappropriate inhibition of demand pacing and possibly asystole in a pacing-dependent patient, or induction of therapies such as inappropriate shocks in a patient with an implantable cardioverter defibrillator (ICD). Other inappropriate tracking or programming changes can occur.
- Magnetic field-induced force and torque due to ferromagnetic materials: CIED generator movement is extremely unlikely due to confinement in the subcutaneous tissues.
- These effects are influenced by various factors, including magnet field strength, RF power, position of the patient and the CIED within the MRI bore, CIED characteristics, and the size of the patient.
The grading system for indication level of class of evidence was adapted based on that used by the ACC and the AHA. (A. K. Jacobs, Anderson, & Halperin, 2014) (Anderson, 2015)
Table 1. Programmed Parameters for PMs During Power-On Reset Mode
Manufacturer | Pacing mode | Pacing output | Pacing polarity | Sensitivity | Magnet1 response |
|---|---|---|---|---|---|
BIOTRONIK | VVI 70 bpm | 4.8 V @ 1.0 ms | Unipolar | 2.5 mV | Yes |
Boston Scientific2 | VVI 65 bpm | 5.0 V @1.0 ms | Bipolar | 1.5 mV | No |
Medtronic | VVI 65 bpm | 5.0 V @ 0.4 ms | Bipolar | 2.8 mV | Yes |
St. Jude Medical | VVI 67.5 bpm | 4.0 V @ 0.6 ms3 | Unipolar | 2.0 mV | No |
ELA-Sorin | VVI 70 bpm | 5.0 V @ 0.5 ms | Unipolar | 2.2 mV | No |
1 Magnet = device will/will not pace asynchronously in response to a magnet during safety mode/reset mode. 2 Boston Scientific CRT-P devices differ in pacing output (5 V @ 0.5 ms) and pacing polarity (right ventricle lead is unipolar and left ventricle lead paces from left ventricle to pulse generator). 3 St. Jude Medical Accent/Anthem and Frontier II models deliver 5 V @ 0.6 ms. | |||||
Table 2. Programmed Parameters for ICDs During Power-On Reset Mode
Manufacturer | Rate cutoff | Detection criteria | Sensitivity | Energy | Pacing mode | Pacing output |
|---|---|---|---|---|---|---|
BIOTRONIK | 150 bpm | 8/12 | 0.8 mV | 40 J × 8 | VVI 70 bpm | 7.5 V @ 1.5 ms1 |
Boston Scientific | 165 bpm | 8/10 | 0.25 mV | 41 J × 5 | VVI 72.5 bpm | 5.0 V @ 1.0 ms |
Medtronic | 188 bpm | 18/24 | 0.3 mV | 35 J × 6 | VVI 65 bpm | 6.0 V @ 1.5 ms |
St. Jude Medical2 | 146 bpm | 12 | 0.3 mV | 36 J × 63 | VVI 60 bpm | 5.0 V @ 0.5 ms |
ELA-Sorin | 190 bpm | 6/8 | 0.4 mV | 42 J × 44 | VVI 60 bpm | 5.0 V @ 0.35 ms |
All devices will respond to magnet application by temporarily disabling tachyarrhythmia detection. Pacing polarity for all devices is bipolar with the exception of Boston Scientific, which paces in a unipolar configuration. Energy values listed for Medtronic and St. Jude Medical represent energy delivered. The remaining represent energy charged. 1 In CRT devices, left ventricle lead output is 4.8 V @ 0.5 ms. 2 The St. Jude Medical Current and Promote family of devices revert to an autosense sensitivity setting, pace at VVI 67.5 beats per minute (bpm) with pacing outputs of 5.0 V @ 0.6 ms. 3 The St. Jude Medical Epic and Epic II family of devices delivers 30 J × 6. 4 ELA-Sorin LivaNova Ovatio family of devices: 34 J × 4. | ||||||
Device Parameters
Table 3. U.S. Food and Drug Administration (FDA)-Approved MR Conditional Devices
PMs | ICDs | Leads | Implantable Cardiac Monitors | |
|---|---|---|---|---|
BIOTRONIK | Eluna PM series (DR-T and SR-T) Entovis PM series (DR-T and SR-T) | Iforia (DR-T and VR-T DX) Iperia (DR-T and VR-T DX) Inventra (VR-T DX) | Setrox S, 53- or 60-cm length Protego DF-1 S DX (ICD) Linoxsmart S DX (ICD) | Bio Monitor 2 Implantable monitor |
Boston Scientific | Accolade MRI Essentio MRI | Emblem S-ICD | Ingevity MRI | |
Medtronic | Revo MRI™ Model RVDR01 Advisa DR MRI SureScan PM Model A2DR01 Advisa SR MRI SureScan PM Model A3SR01 Micra® Transcatheter Pacing System Model MC1VR01 (TPS) | Evera MRI XT VR (DVMB1D4) Evera MRI XT DR (DDMB1D4) Evera MRI S DR (DDMC3D4) Visia AF MRI VR (DVFB1D4) Amplia MRI CRT-D (DTMB1D4) Amplia MRI Quad CRT-D (DTMB1QQ) Compia MRI Quad CRT-D (DTMC1QQ) | CapSureFix Novus MRI SureScan 5076 lead CapSureFix MRI 5086MRI lead Sprint Quattro Secure MRI™ SureScan 6947M (ICD), 6935M (ICD) Attain Performa (4298, 4398, 4598) LV lead Attain Ability (4196, 4296, 4396) LV lead | Reveal implantable cardiac monitor LINQ implantable cardiac monitor |
ELA-Sorin LivaNova | – | – | – | – |
St. Jude Medical | Assurity MRI single-chamber Model PM1272 Assurity MRI dual-chamber Model PM2272 | – | Tendril MRI Model LPA1200M | Confirm implantable monitor |
Table 4. Definitions of CIED Systems in Relation to MRI
- MR conditional refers to any device for which a specified MRI environment with specified conditions of use does not pose a known hazard.
- For MR conditional CIED systems, the labeling requires testing sufficient to characterize the system behavior in the MRI environment. Such testing includes measuring magnetically induced force and torque, current induction, and RF heating. Other testing measures involve modeling of potential electromagnetic interference from the MRI environment with the CIED system.
- MR nonconditional systems include all CIED systems other than those that meet MR conditional labeling.
- Zone 4 refers to the MRI scanner room and is the physical space with the highest risk to patients and staff, including the potential for flying metal objects.
- Zone 3 is the space just outside the MRI scanner room (Zone 4), and includes the areas for patient holding and the control room.
- Zone 2 includes the patient reception and interview/screening areas.
- Zone 1 refers to regions that are accessible to the general public with no restrictions.
Table 5. Recommendations and Protocol for the Management of Patients with an MR Conditional Device Undergoing MRI
Recommendations | COR | LOE |
|---|---|---|
MR conditional devices should be considered MR conditional only when the product labeling is adhered to, which includes programming the appropriate "MR mode" and scanning with the prerequisites specified for the device. | I | A |
MR imaging in a patient with an MR conditional system should always be performed in the context of a rigorously applied standardized institutional workflow, following the appropriate conditions of use. | I | B-R |
It is recommended for patients with an MR conditional system that personnel with the skill to perform advanced cardiac life support, including expertise in the performance of CPR, arrhythmia recognition, defibrillation, and transcutaneous pacing, be in attendance with the patient for the duration of time the patient’s device is reprogrammed, until assessed and declared stable to return to unmonitored status. | I | B-R |
It is recommended for patients with an MR conditional system that ECG and pulse oximetry monitoring be continued until baseline, or until other clinically appropriate CIED settings are restored. | I | A |
All resuscitative efforts and emergency treatments that involve the use of a defibrillator/monitor, device programming system, or any other MRI-unsafe equipment should be performed after moving the patient outside of Zone 4. | I | C-EO |
It is recommended for patients with an MR conditional system that personnel with the skill to program the CIED be available as defined by the institutional protocol. | I | C-EO |
It is reasonable to perform an MR scan on a patient with an MR conditional system implanted more recently than the exempt period for conditionality of the system, based on assessment of risk and benefit for that patient. | IIa | C-EO |
Management of Patients with a CIED Referred for MRI
Table 6. Recommendations for the Decision to Perform an MRI on Patients with an MR Nonconditional CIED
Recommendations | COR | LOE |
|---|---|---|
It is reasonable for patients with an MR nonconditional CIED system to undergo MR imaging if there are no fractured, epicardial, or abandoned leads; the MRI is the best test for the condition; and there is an institutional protocol and a designated MR-responsible physician and CIED physician. | IIa | B-NR |
It is reasonable to perform an MR scan immediately after implantation of a lead or generator of an MR nonconditional CIED system if clinically warranted. | IIa | B-NR |
For patients with an MR nonconditional CIED, it is reasonable to perform repeat MRI when required, without restriction regarding the minimum interval between imaging studies or the maximum number of studies performed. | IIa | C-LD |
Table 7. Recommendations for the Management of Patients with an MR Nonconditional CIED Who Are to Have an MRI Scan
Recommendations | COR | LOE |
|---|---|---|
It is recommended for the patient with an MR nonconditional CIED that device evaluation be performed immediately pre and post-MRI with documentation of pacing threshold(s), P and R-wave amplitude, and lead impedance using a standardized protocol. | I | B-NR |
A defibrillator/monitor (with external pacing function) and a manufacturer-specific device programming system should be immediately available in the holding area adjacent to the MR scanner room while an MR nonconditional CIED is reprogrammed for imaging. | I | B-NR |
It is recommended that continuous MR conditional ECG and pulse oximetry monitoring be used while an MR nonconditional CIED is reprogrammed for imaging. | I | B-NR |
It is recommended that personnel with the skill to perform advanced cardiac life support, including expertise in the performance of CPR, arrhythmia recognition, defibrillation, and transcutaneous pacing, accompany the patient with an MR nonconditional CIED for the duration of time the patient’s device is reprogrammed, until assessed and declared stable to return to unmonitored status. | I | B-NR |
For patients with an MR nonconditional CIED who are pacing-dependent (PM or ICD), it is recommended that:
| I | B-NR |
For patients with an MR nonconditional CIED who are not pacing-dependent, it is recommended that:
| I | B-NR |
It is recommended that for the patient with an MR nonconditional CIED who is pacing-dependent to program their device to an asynchronous pacing mode with deactivation of advanced or adaptive features during the MRI examination, and the pacing rate should be selected to avoid competitive pacing. | I | B-NR |
All tachyarrhythmia detections for patients with an ICD should be disabled prior to MRI. | I | B-NR |
The MR-responsible physician who is accountable for overseeing the safety of the MRI environment, including the administration of any medication and/or contrast agents (if applicable) should be made aware of the presence of a patient with an MR nonconditional CIED. | I | C-EO |
It is recommended that ECG and pulse oximetry monitoring be continued until baseline or until other clinically appropriate CIED settings are restored for patients with an MR nonconditional CIED. | I | C-EO |
All resuscitative efforts and emergency treatments that involve the use of a defibrillator/monitor, device programming system, or any other MRI-unsafe equipment should be performed after moving the patient outside of Zone 4. | I | C-EO |
For a patient with an MR nonconditional CIED who is not pacing-dependent, it is reasonable to program their device to either a nonpacing mode (OVO/ODO) or to an inhibited mode (DDI/VVI), with deactivation of advanced or adaptive features during the MRI examination. | IIa | B-NR |
It is reasonable to program patients with an MR nonconditional CRT device who are not pacing-dependent to an asynchronous pacing mode (VOO/DOO) with deactivation of advanced or adaptive features during the MRI examination, and with a pacing rate that avoids competitive pacing. | IIa | C-EO |
Figure 1. Management Algorithm
Figure 2. Checklist for MRI Safety in the Setting of Implanted Devices (PM or ICD)
SECTION 1 – GENERATOR INFORMATION | SECTION 2 – LEAD INFORMATION | ||||||||
PM | ICD | Abandoned/Epicardial Lead(s) | RA | RV | LV | ||||
☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ||||
Manufacturer & Model # | Manufacturer & Model # | ☐ Note: CXR may identify if abandoned/epicardial leads are present. | Manufacturer & Model # | Manufacturer & Model # | Manufacturer & Model # | ||||
SECTION 3 – MR CONDITIONAL STATUS AND MANAGEMENT | SECTION 4 – PRE- & POST-MRI DEVICE PARAMETERS | ||||||||
MR Conditional System? Pre-MR imaging pacing/tachycardia mode activated? ☐ Yes ☐ No ☐ Monitor ECG and pulse oximetry by ACLS-trained personnel during the time the patient’s device is reprogrammed and until assessed and declared stable to return to unmonitored status. ☐ Keep external defibrillator and CIED programmer available (outside of zone 4). ☐ Conform to CIED manufacturer MRI recommendations including field strength, maximum estimated SAR, gradient slew rate, and transmit/receive coil. If the MR Conditional System was implanted less than the exempt period for conditionality (e.g., 6 weeks), is the MRI scan considered clinically useful based on assessment of risk and benefit for that patient? ☐ Yes ☐ No | RA | RV | LV | ||||||
Pre-MRI | Post-MRI | Pre-MRI | Post-MRI | Pre-MRI | Post-MRI | ||||
Sensing (mV) | |||||||||
Capture Threshold (V @ _____ms) | |||||||||
MR Nonconditional System:
| Impedance (Ω) | Pace Shock | Pace Shock | ||||||
Pacing Dependent | ☐ Yes | ☐ No | ||||||||
☐ If yes, CIED must have asynchronous (VOO/DOO) pacing capability. ☐ Program pacing to VOO/DOO. Deactivate tachycardia detection and therapies. | Battery Voltage (V) | ||||||||
☐ If programming VOO/DOO and there is an underlying rhythm, program the pacing rate faster than the underlying rate to avoid competitive pacing. ☐ Deactivate magnet, rate & noise response, and all advanced features.* ☐ Monitor ECG and pulse oximetry by ACLS-trained personnel during the time the patient’s device is reprogrammed and until assessed and declared stable to return to unmonitored status. ☐ Keep external defibrillator and CIED programmer available (outside of Zone 4). | SECTION 5 – MANAGEMENT FOLLOWING MRI | ||||||||
☐ Keep on ECG monitor after MRI until initial device programming has been restored and patient is assessed and declared stable to return to unmonitored status. ☐ Restore all original programming unless pacing output or sensing needs to be adjusted based upon post-MRI CIED evaluation. ☐ Advise follow-up in device clinic in 3–6 months after MRI unless earlier follow-up (within a week) is indicated for the following: Any capture threshold increase >1.0 V, sensing drop >50%, pacing impedance change >50 Ω, or shock impedance change >5 Ω. | |||||||||
Table 8. Implantable Loop Recorder
Recommendations | COR | LOE |
|---|---|---|
It is recommended that prior to MRI scanning patients with an implantable loop recorder (ILR) that the ILR be evaluated and that any desired recorded information be removed/downloaded from the system and cleared after the MRI. | I | B-NR |
MR scanning of MR conditional ILRs should be performed within labeled scanning prerequisites specific to each device manufacturer. | I | C-LD |
Table 9. Employee Safety
Recommendations | COR | LOE |
|---|---|---|
It is recommended that the MR suite has a clearly delineated 5 gauss boundary and visible signs to advise individuals who have an implantable cardiac device, regardless of MR conditional labeling, to stay outside of the 5 gauss boundary at all times. | I | C-EO |
Table 10. Recommendations for the Management of Patients with a CIED Undergoing CT Imaging
Recommendations | COR | LOE |
|---|---|---|
It is recommended that patients with a CIED undergo clinical diagnostic CT without any additional device interrogation, programming, or monitoring. | I | B-NR |
It is reasonable to exclude the device from the field of view of 4D CT and cone-beam CT scans if the images are not compromised. | IIa | C-EO |
It might be reasonable to monitor patients who have an ICD or who are pacing-dependent by ECG or pulse oximetry if the CIED will undergo prolonged, uninterrupted exposure by CT. | IIb | C-EO |
