New Pacemaker System Safe for Use With MRI: Presented at ESC

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Title: New Pacemaker System Safe for Use With MRI: Presented at ESC
URL: http://www.pslgroup.com/dg/22A5FA.htm
Doctor's Guide
September 1, 2008

By Chris Berrie

MUNICH, Germany -- September 1, 2008 -- A new pacemaker system designed for use with magnetic resonance imaging (MRI) is both efficacious and safe for patients with pacemaker implants, according to the results of an international, prospective, nonblinded, randomised, controlled trial.

Torsen Sommer, MD, Cardiovascular Imaging, University of Bonn, Bonn, Germany, presented this study on behalf of the EnRhythm MRI clinical investigators here on August 31 at the European Society of Cardiology 2008 Congress (ESC).

MRI is one of the most widely used noninvasive imaging modalities, and the number of MRI procedures continues to increase. Similarly, pacemaker and defibrillator procedures are increasing, and 50% to 75% of these patients are indicated for MRI over the lifetime of their device.

However, as Dr. Sommer said, "The presence of a pacemaker device is still considered a contra-indication by most institutions."

The purpose of the study was to evaluate efficacy and safety of a new pacemaker and the lead design system intended for safe use during an MRI and to demonstrate the absence of clinically relevant acute or chronic effects on the performance of the pacing system after this MRI exposure.

The criteria for inclusion were an indication for class 1 or 2 dual-chamber pacemaker implantation and an eligibility to undergo MRI scan.

At 9 to 12 weeks after successful implantation, patients were randomised to either the control/no MRI group (1 hour waiting between device checks instead of having an MRI) (n = 101) or to undergo an elective MRI (n = 90). The MRI scan procedure included 15 clinically relevant head and lumbar spine sequences performed with a magnetic field strength of 1.5 T, a gradient system slew rate of <=200 T/m/s, and a specific absorption rate of 2 W/kg.

Dr. Sommer also said, "The positioning of the isocentre of the RF [radiofrequency] coil was excluded below vertebra C1 and above T12."

For the overall safety at 1-month follow-up, 83.9% of patients were free from complications of implantation, pacing, and MRI. Dr. Sommer noted here, "This was adversely affected by a high number of pneumothoraces [n = 7], which were only implant-procedure-related and mainly came from one centre [n = 5]."

For the MRI group, there were no MRI-related complications, interference with pacemaker functionality, or unexpected lead performance issues.

For the comparison of patient capture threshold equivalence between the control and MRI groups, there were no significant differences for the atrial or ventricular leads. No differences in the atrial and ventricular sensing amplitudes were reported for the 2 treatment groups.

Dr. Sommer thus indicated that these results confirm the safety and efficacy of this pacing system when used in accordance with the system's labelling. "The new system provides the opportunity for safe MRI of pacemaker patients not only at highly experienced centres but also for a larger group of hospitals or even in the outpatient setting," he concluded.

[Study title: Safety and Efficacy of New Pacemaker System That Can Be Used in MRI Environment: First Clinical Trial Results. Abstract 388]

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