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?

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

Having trouble viewing table?

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

...e Parameters...

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


...initions of CIED Systems in Relation to MRIHav...


...endations and Protocol for the Manage...

...conditional devices should be considered MR...

...g in a patient with an MR conditional syst...

...mmended for patients with an MR conditional sys...

...s recommended for patients with an MR...

...ive efforts and emergency treatments t...

...recommended for patients with an MR conditi...

...ble to perform an MR scan on a patient...


Management of Patients with a CIED Referred for MRI

...Patients with a CIED Referred for MRI...

...ommendations for the Decision to Perform an MRI...

...le for patients with an MR noncondit...

...to perform an MR scan immediately aft...

...th an MR nonconditional CIED, it is reasonab...


...mendations for the Management of Patie...

...s recommended for the patient with an MR non...

...or/monitor (with external pacing function)...

...recommended that continuous MR condi...

It is recommended that personnel with the sk...

For patients with an MR nonconditional CIED w...

...ents with an MR nonconditional CIED who...

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

...ll tachyarrhythmia detections for pati...

...MR-responsible physician who is account...

...t is recommended that ECG and pulse oximetry monit...

...suscitative efforts and emergency treatment...

...th an MR nonconditional CIED who is n...

...nable to program patients with an MR noncondi...


...igure 1. Management...


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


...Implantable Loop Recorder...

It is recommended that prior to MRI scanni...

...ning of MR conditional ILRs should be perfor...


...e 9. Employee Safety...

...mended that the MR suite has a clearly delineated...


...e 10. Recommendations for the Management of...

...ended that patients with a CIED undergo clinical...

...ble to exclude the device from the fie...

...ht be reasonable to monitor patients...


Management of Patients with a CIED Undergoing CT Imaging

...of Patients with a CIED Undergoing CT Imagi...

...le 11. Secondary Neutron-Producing R...


...Recommendations and Protocol for the Managem...

...to the initiation of radiation treat...

...producing treatment is preferred over neu...

...weekly complete CIED evaluations for pati...

...lete CIED evaluation should be performed at th...

...ntinuous visual and voice contact is re...

...is recommended if its current location will inte...

...ght be reasonable to perform a complet...

...tion is NOT recommended for devices rec...


Management of Patients with a CIED Undergoing Radiation Therapy

...nt of Patients with a CIED Undergoing Radiation...

...Checklist for Performance of Radiation Treatm...


...ure 4. CIED Management for Radia...