Cardiac pacemakers and implantable cardioverter defibrillators: in vitro magnetic resonance imaging evaluation at 1.5-tesla.

RATIONALE AND OBJECTIVES

To evaluate the effect of Magnetic Resonance Imaging (MRI) performed at 1.5-Tesla on current generation pacemakers and ICDs to identify safe parameters for MRI examinations.

METHODS

Pacemakers (Identity ADx XL DR+ 5386 and Identity ADx DR + 5380 generators; 1688T/52-cm atrial and ventricular leads) and ICDs (Atlas + V-243, Epic + V-236, and Epic + HF V-350 generators; Riata 1581/65-cm and QuickSite 1056K/75-cm leads; St. Jude Medical, Sylmar, California, USA) were evaluated for magnetic field interactions. MRI-related heating was assessed using various levels of RF power (SARs) and conditions that included scans on different body regions. Functional aspects of the devices were evaluated immediately before and after MRI procedures utilizing nine different pulse sequences. Induced currents were measured using a custom built system.

RESULTS

Magnetic field interactions will not create a hazard for these pacemakers and ICDs. All scans of the "head" and "lumbar" regions resulted in temperature changes < or =0.5 degrees C at SARs ranging from 2.0 to 3.0-W/kg. For the "chest" area, temperature increases ranged from 0.4 degrees C to 3.6 degrees C at an SAR of 2.0-W/kg. No memory corruption, hardware changes, or changes in device parameters were seen. Magnetic field gradients have a low likelihood of inducing currents that would stimulate the heart.

CONCLUSIONS

No hazardous magnetic field interactions or physiologically significant heating occurred for certain conditions. There was no permanent effect on device function. By following specific conditions, these pacemakers and ICDs may be safe for patients scanned at 1.5-Tesla.