MRSO Cardiac Implantable Electronic Devices (CIEDs) and MRI Safety

Question 1

Which ASTM/ISO designation applies to a pacemaker that may be used in MRI only when all specified conditions of field strength, SAR, and gradient slew rate are met?

Accepted Answer

MR Conditional

Answer

MR Safe

Answer

MR Compatible

Answer

MR Tolerant

Question 2

Which mechanism is the primary source of cardiac injury risk from MRI in patients with implanted pacemaker leads?

Accepted Answer

RF-induced resistive heating concentrated at the electrode-tissue interface

Answer

Magnetization of ferromagnetic alloys within the lead body

Answer

Gradient switching causing mechanical vibration and lead fracture

Answer

Static magnetic field torque displacing the pulse generator

Question 3

What was the central finding of the MagnaSafe Registry regarding MRI performed in patients with non-MR-conditional CIEDs?

Accepted Answer

Clinically significant adverse events were rare when a standardized monitoring protocol was followed

Answer

Non-MR-conditional devices were permanently damaged in 12% of cases

Answer

MRI should be avoided in all patients with non-MR-conditional CIEDs

Answer

Only 1.0T scanners were proven safe for patients with legacy devices

Question 4

Which whole-body average SAR limit is most commonly specified in MR-conditional pacemaker labeling to reduce the risk of RF-induced lead tip heating?

Accepted Answer

2.0 W/kg

Answer

0.1 W/kg

Answer

1.0 W/kg

Answer

4.0 W/kg

Question 5

Why are abandoned (non-functional) pacemaker leads considered particularly hazardous during MRI compared to connected leads?

Accepted Answer

Without a connected generator, RF-induced current concentrates entirely at the lead tip, maximizing heating

Answer

They are manufactured from more ferromagnetic alloys than active leads

Answer

They frequently dislodge during gradient switching due to lack of fibrous fixation

Answer

Abandoned leads automatically switch to asynchronous mode during MRI

Question 6

What occurs in most conventional pacemakers upon entering the static magnetic field of an MRI scanner?

Accepted Answer

The reed switch closes, switching the device to asynchronous (fixed-rate) pacing mode

Answer

The pulse generator is demagnetized and permanently ceases function

Answer

Battery voltage drops by 30%, slowing the pacing rate proportionally

Answer

The device enters sensing-only mode to protect against inappropriate inhibition

Question 7

Which CIED type carries the greatest overall MRI risk due to its high-voltage capacitors and defibrillation coil design?

Accepted Answer

Implantable cardioverter-defibrillator (ICD) with defibrillation coil

Answer

Single-lead rate-responsive pacemaker

Answer

Dual-chamber pacemaker with bipolar leads

Answer

Implantable loop recorder (ILR)