Magnetic Resonance Imaging and Radiation Exposure in Patients with Cardiovascular Implantable Electronic Devices
Key Points
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.
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 |
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. | ||||||
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
....S. Food and Drug Administration (FD...
...efinitions of CIED Systems in Relation...
...Table 5. Recomme...
...l devices should be considered MR conditional on...
...in a patient with an MR conditional syst...
...is recommended for patients with an M...
...t is recommended for patients with an MR c...
...l resuscitative efforts and emergency tr...
...recommended for patients with an MR con...
...asonable to perform an MR scan on a patient with a...
Management of Patients with a CIED Referred for MRI
...Management of P...
...Table...
...asonable for patients with an MR noncondition...
...ble to perform an MR scan immediately...
...with an MR nonconditional CIED, it is reasonabl...
...Table...
...commended for the patient with an MR nonconditiona...
.../monitor (with external pacing function) an...
...mmended that continuous MR conditional ECG an...
...ed that personnel with the skill to perform...
...s with an MR nonconditional CIED who are p...
...ents with an MR nonconditional CIE...
...commended that for the patient with an MR nonco...
...tachyarrhythmia detections for patients wi...
...ble physician who is accountable fo...
It is recommended that ECG and pulse o...
...suscitative efforts and emergency t...
...with an MR nonconditional CIED who is not p...
...reasonable to program patients with an MR...
...Management Algorithm...
...cklist for MRI Safety in the Setting of Impl...
...Table 8. Imp...
...nded that prior to MRI scanning patients w...
...anning of MR conditional ILRs should be...
...Table 9. Empl...
...ommended that the MR suite has a clearly delinea...
...Table 10. Recomm...
...is recommended that patients with a CIED...
...sonable to exclude the device from the...
...ight be reasonable to monitor patients who ha...
Management of Patients with a CIED Undergoing CT Imaging
...Management of...
...ondary Neutron-Producing Radiation in Vari...
Prior to the initiation of radiation treatme...
...-producing treatment is preferred over neutr...
...rm weekly complete CIED evaluations...
...evaluation should be performed at the conclus...
...s visual and voice contact is reco...
...relocation is recommended if its c...
...ight be reasonable to perform a complete CIED...
...elocation is NOT recommended for devices rec...
Management of Patients with a CIED Undergoing Radiation Therapy
...Managem...
...list for Performance of Radiation Treatment...
...Management for Radiation Therapy...