New Cardiac Pacemaker Avoids MRI Interference

MUNICH — A new type of cardiac pacemaker was safe in patients undergoing an MRI examination, with no need for a special imaging protocol in a randomized study with 151 evaluable patients.

“The functionality of the new pacemaker is the same as a conventional pacemaker, but one is MRI safe and the other is not,” Dr. Torsten Sommer said at the annual congress of the European Society of Cardiology. There is no apparent downside to the new pacemaker, except that it may cost more than current units do, he said.

Patients with a standard pacemaker face “a huge limitation” by not being able to easily undergo MRI imaging, which has become a practice staple, said Dr. Sommer, chief of the cardiovascular imaging section at the University of Bonn (Germany). He estimated that an average pacemaker patient today has a 50%–75% lifetime chance of needing at least one MRI exam.

The major danger that MRI poses to a patient with a conventional pacemaker (or other implanted cardiac device) is heating of the lead tips by radiofrequency radiation. Other concerns are interference with pacemaker function and risk of an electrical reset of the device.

A special MRI protocol has been reported that avoids these problems, but the method is complicated and available only at a limited number of experienced imaging centers, commented Dr. Christopher Cannon, a cardiologist at Brigham and Women's Hospital and Harvard Medical School, Boston. Having a new pacemaker without the MRI limitation would be “very helpful,” he said in an interview.

The new pacemaker, called EnRhythm, was developed by Medtronic Inc., which funded the current study. Dr. Sommer is a consultant to Medtronic, but he and his associates in Bonn do not hold any patents on the new device or technology. The data he reported came from the first phase of a study designed to eventually place the new pacemaker in 470 patients. When the final results are available, Medtronic will apply for marketing approval from the Food and Drug Administration, a step that the company hopes to take in 2010, said Tracy McNulty, a Medtronic spokeswoman.

The new, dual-chamber pacemaker features a reduced number of ferromagnetic parts, better protection of internal circuits, and altered software. But the implantation technique is the same as for a standard pacemaker, Dr. Sommer said.

The study is being done at 53 centers in the United States, Canada, and Europe. So far, 245 patients with a class I or II indication for a pacemaker have been implanted with the EnRhythm device. Ninety patients were randomized to undergo MRI imaging and 101 were randomized as controls who received no imaging.

The MRI exam was done on a 1.5-T unit and involved 15 clinically relevant head- and lumbar spine-imaging sequences. To maximize safety during the first phase of testing, no magnetic coils were placed directly above a spinal region that extended from the C1 to the T12 level. But even with this limitation, full imaging of the chest region was obtained, Dr. Sommer said.

Follow-up data collected 1 month after the MRI exam were available for 70 patients and for 81 of the matched controls. The results showed no adverse events or complications triggered by the MRI exam, and no electrical resets of the pacemakers. During follow-up, no patients had sustained arrhythmias and the pacemakers did not show any changes in their rhythm-capture thresholds or any other performance changes.

'The functionality … is the same as a conventional pacemaker, but one is MRI safe and the other is not.' DR. SOMMER

MUNICH — A new type of cardiac pacemaker was safe in patients undergoing an MRI examination, with no need for a special imaging protocol in a randomized study with 151 evaluable patients.

“The functionality of the new pacemaker is the same as a conventional pacemaker, but one is MRI safe and the other is not,” Dr. Torsten Sommer said at the annual congress of the European Society of Cardiology. There is no apparent downside to the new pacemaker, except that it may cost more than current units do, he said.

Patients with a standard pacemaker face “a huge limitation” by not being able to easily undergo MRI imaging, which has become a practice staple, said Dr. Sommer, chief of the cardiovascular imaging section at the University of Bonn (Germany). He estimated that an average pacemaker patient today has a 50%–75% lifetime chance of needing at least one MRI exam.

The major danger that MRI poses to a patient with a conventional pacemaker (or other implanted cardiac device) is heating of the lead tips by radiofrequency radiation. Other concerns are interference with pacemaker function and risk of an electrical reset of the device.

A special MRI protocol has been reported that avoids these problems, but the method is complicated and available only at a limited number of experienced imaging centers, commented Dr. Christopher Cannon, a cardiologist at Brigham and Women's Hospital and Harvard Medical School, Boston. Having a new pacemaker without the MRI limitation would be “very helpful,” he said in an interview.

The new pacemaker, called EnRhythm, was developed by Medtronic Inc., which funded the current study. Dr. Sommer is a consultant to Medtronic, but he and his associates in Bonn do not hold any patents on the new device or technology. The data he reported came from the first phase of a study designed to eventually place the new pacemaker in 470 patients. When the final results are available, Medtronic will apply for marketing approval from the Food and Drug Administration, a step that the company hopes to take in 2010, said Tracy McNulty, a Medtronic spokeswoman.

The new, dual-chamber pacemaker features a reduced number of ferromagnetic parts, better protection of internal circuits, and altered software. But the implantation technique is the same as for a standard pacemaker, Dr. Sommer said.

The study is being done at 53 centers in the United States, Canada, and Europe. So far, 245 patients with a class I or II indication for a pacemaker have been implanted with the EnRhythm device. Ninety patients were randomized to undergo MRI imaging and 101 were randomized as controls who received no imaging.

The MRI exam was done on a 1.5-T unit and involved 15 clinically relevant head- and lumbar spine-imaging sequences. To maximize safety during the first phase of testing, no magnetic coils were placed directly above a spinal region that extended from the C1 to the T12 level. But even with this limitation, full imaging of the chest region was obtained, Dr. Sommer said.

Follow-up data collected 1 month after the MRI exam were available for 70 patients and for 81 of the matched controls. The results showed no adverse events or complications triggered by the MRI exam, and no electrical resets of the pacemakers. During follow-up, no patients had sustained arrhythmias and the pacemakers did not show any changes in their rhythm-capture thresholds or any other performance changes.

'The functionality … is the same as a conventional pacemaker, but one is MRI safe and the other is not.' DR. SOMMER

MUNICH — A new type of cardiac pacemaker was safe in patients undergoing an MRI examination, with no need for a special imaging protocol in a randomized study with 151 evaluable patients.

“The functionality of the new pacemaker is the same as a conventional pacemaker, but one is MRI safe and the other is not,” Dr. Torsten Sommer said at the annual congress of the European Society of Cardiology. There is no apparent downside to the new pacemaker, except that it may cost more than current units do, he said.

Patients with a standard pacemaker face “a huge limitation” by not being able to easily undergo MRI imaging, which has become a practice staple, said Dr. Sommer, chief of the cardiovascular imaging section at the University of Bonn (Germany). He estimated that an average pacemaker patient today has a 50%–75% lifetime chance of needing at least one MRI exam.

The major danger that MRI poses to a patient with a conventional pacemaker (or other implanted cardiac device) is heating of the lead tips by radiofrequency radiation. Other concerns are interference with pacemaker function and risk of an electrical reset of the device.

A special MRI protocol has been reported that avoids these problems, but the method is complicated and available only at a limited number of experienced imaging centers, commented Dr. Christopher Cannon, a cardiologist at Brigham and Women's Hospital and Harvard Medical School, Boston. Having a new pacemaker without the MRI limitation would be “very helpful,” he said in an interview.

The new pacemaker, called EnRhythm, was developed by Medtronic Inc., which funded the current study. Dr. Sommer is a consultant to Medtronic, but he and his associates in Bonn do not hold any patents on the new device or technology. The data he reported came from the first phase of a study designed to eventually place the new pacemaker in 470 patients. When the final results are available, Medtronic will apply for marketing approval from the Food and Drug Administration, a step that the company hopes to take in 2010, said Tracy McNulty, a Medtronic spokeswoman.

The new, dual-chamber pacemaker features a reduced number of ferromagnetic parts, better protection of internal circuits, and altered software. But the implantation technique is the same as for a standard pacemaker, Dr. Sommer said.

The study is being done at 53 centers in the United States, Canada, and Europe. So far, 245 patients with a class I or II indication for a pacemaker have been implanted with the EnRhythm device. Ninety patients were randomized to undergo MRI imaging and 101 were randomized as controls who received no imaging.

The MRI exam was done on a 1.5-T unit and involved 15 clinically relevant head- and lumbar spine-imaging sequences. To maximize safety during the first phase of testing, no magnetic coils were placed directly above a spinal region that extended from the C1 to the T12 level. But even with this limitation, full imaging of the chest region was obtained, Dr. Sommer said.

Follow-up data collected 1 month after the MRI exam were available for 70 patients and for 81 of the matched controls. The results showed no adverse events or complications triggered by the MRI exam, and no electrical resets of the pacemakers. During follow-up, no patients had sustained arrhythmias and the pacemakers did not show any changes in their rhythm-capture thresholds or any other performance changes.

'The functionality … is the same as a conventional pacemaker, but one is MRI safe and the other is not.' DR. SOMMER