Magnetic Resonance Imaging and Radiation Exposure in Patients with Cardiovascular Implantable Electronic Devices

Publication Date: May 11, 2017

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.
  • 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

Having trouble viewing table?


Pacing mode

Pacing output

Pacing polarity


Magnet1 response


VVI 70 bpm

4.8 V @ 1.0 ms


2.5 mV


Boston Scientific2

VVI 65 bpm

5.0 V @1.0 ms


1.5 mV



VVI 65 bpm

5.0 V @ 0.4 ms


2.8 mV


St. Jude Medical

VVI 67.5 bpm

4.0 V @ 0.6 ms3


2.0 mV



VVI 70 bpm

5.0 V @ 0.5 ms


2.2 mV


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

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Rate cutoff

Detection criteria



Pacing mode

Pacing output


150 bpm


0.8 mV

40 J × 8

VVI 70 bpm

7.5 V @ 1.5 ms1

Boston Scientific

165 bpm


0.25 mV

41 J × 5

VVI 72.5 bpm

5.0 V @ 1.0 ms


188 bpm


0.3 mV

35 J × 6

VVI 65 bpm

6.0 V @ 1.5 ms

St. Jude Medical2

146 bpm


0.3 mV

36 J × 63

VVI 60 bpm

5.0 V @ 0.5 ms


190 bpm


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

...Device Parameters...

...3. U.S. Food and Drug Administration (FDA)-Appro...

.... Definitions of CIED Systems in Relation to MRIH...

...Table 5. Recommendat... devices should be considered MR c...

...a patient with an MR conditional syste...

...ecommended for patients with an MR co...

...d for patients with an MR conditional system t...

...ive efforts and emergency treatments that inv...

...ded for patients with an MR conditi... perform an MR scan on a patient...

Management of Patients with a CIED Referred for MRI

...Management of Patie...


...onable for patients with an MR nonc... perform an MR scan immediately after impla...

...h an MR nonconditional CIED, it is reasonabl...

...Table 7....

...ed for the patient with an MR nonconditional CIED...

...defibrillator/monitor (with external pacing... recommended that continuous MR condit...

...commended that personnel with the skill to...

...h an MR nonconditional CIED who are pacing-depende...

...ith an MR nonconditional CIED who are not p...

...recommended that for the patient with an MR nonco...

...achyarrhythmia detections for patients...

...-responsible physician who is acco...

...mmended that ECG and pulse oximetry monitoring...

...ll resuscitative efforts and emergency tre...

...nt with an MR nonconditional CIED who...

It is reasonable to program patients with an...

...gure 1. Management A...

...e 2. Checklist for MRI Safety in the Set...

...Table 8. Implantable L... recommended that prior to MRI scanning...

...MR conditional ILRs should be performed wi...

It is recommended that the MR suite has a cle...

...mended that patients with a CIED undergo...

...ble to exclude the device from the field...

...t might be reasonable to monitor patients wh...

Management of Patients with a CIED Undergoing CT Imaging

...Management of Patients...

...condary Neutron-Producing Radiation in Va...

...Table 12....

...nitiation of radiation treatment, a complete CIED...

...ucing treatment is preferred over ne...

...erform weekly complete CIED evalua...

...e CIED evaluation should be performed at the concl...

...isual and voice contact is recommended during...

...ocation is recommended if its current locat...

...ght be reasonable to perform a complete CIE...

...IED relocation is NOT recommended for devices...

Management of Patients with a CIED Undergoing Radiation Therapy

...Management of Patient... for Performance of Radiation Treatmen...

...IED Management for Radiation Therapy...