MRSO Cardiac Implantable Electronic Devices (CIEDs) and MRI Safety 3

Question 1

Gradient switching can induce voltages in pacemaker leads. What is the primary clinical concern for pacemaker-dependent patients?

Accepted Answer

Oversensing of gradient-induced voltages causing inappropriate pacing inhibition

Answer

Permanent alteration of stored pulse generator programming parameters

Answer

Delivery of inappropriate ICD therapy triggered by gradient electrical noise

Answer

Inductive heating of lead insulation producing insulation breakdown and short circuit

Question 2

Why is an implantable loop recorder (ILR) generally considered lower MRI risk than a transvenous pacemaker?

Accepted Answer

ILRs use only short subcutaneous sensing electrodes with no intracardiac leads, minimizing RF coupling length and cardiac heating risk

Answer

ILRs are classified MR Safe with no field strength or SAR restrictions

Answer

ILRs contain no electronic components that interact with magnetic or RF fields

Answer

ILRs must always be surgically removed before any MRI examination

Question 3

A CRT-D (cardiac resynchronization therapy defibrillator) presents greater MRI complexity than a standard single-chamber pacemaker primarily because:

Accepted Answer

Three leads — including a coronary sinus lead and a defibrillation coil — increase total conductor length and RF coupling surface area

Answer

CRT-D batteries contain cobalt compounds that are displaced by the static magnetic field

Answer

CRT-D devices cannot be switched to asynchronous pacing mode before MRI

Answer

CRT-D devices employ stronger reed switch magnets that activate at lower field strengths

Question 4

What information obtained during pre-scan CIED interrogation is most essential for confirming MRI eligibility?

Accepted Answer

Device model, lead type, battery voltage, and current programmed parameters needed to verify MR-conditional compatibility and establish a baseline

Answer

The patient's pacing rate trends and arrhythmia burden over the prior 12 months

Answer

The number of times the reed switch has been activated by external magnets previously

Answer

Remaining device longevity expressed in years to assess whether battery can withstand RF exposure

Question 5

Under which circumstance is MRI of a patient with a non-MR-conditional (legacy) CIED considered acceptable by current HRS/ACR guidance?

Accepted Answer

When the clinical benefit clearly outweighs the risk and a physician-supervised protocol with continuous cardiac monitoring is in place

Answer

Never — all non-MR-conditional devices are an absolute contraindication to MRI under all clinical circumstances

Answer

Only when written permission is obtained from the original device manufacturer

Answer

Only for head MRI, where the device is farthest from the isocenter and RF deposition over leads is lowest

Question 6

How does the subcutaneous ICD (S-ICD) differ from a transvenous ICD in its MRI safety profile?

Accepted Answer

The S-ICD carries lower MRI risk because its electrodes are entirely subcutaneous and it has no intracardiac leads that can heat myocardial tissue

Answer

The S-ICD is more dangerous because its long subcutaneous electrode creates a larger current loop near the skin surface

Answer

The S-ICD and transvenous ICD present identical MRI risks due to equivalent internal electronic circuitry

Answer

The S-ICD is classified MR Safe and can be scanned at any field strength without restrictions

Question 7

Which scenario represents the highest MRI safety risk for a CIED patient?

Accepted Answer

Pacemaker-dependent patient with non-MR-conditional device, abandoned transvenous lead, epicardial leads, and no electrophysiology support available

Answer

MR-conditional dual-chamber pacemaker implanted 10 weeks ago, extremity imaging at 1.5T within device SAR limits

Answer

MR-conditional single-chamber pacemaker, pacemaker-dependent patient, brain MRI at 1.5T with electrophysiologist on-site

Answer

Non-pacemaker-dependent patient with MR-conditional ICD, brain MRI at 1.5T per device labeling requirements