HRS: Patients with new pacemaker system can safely undergo MRI
BOSTON--In the MRI environment under specific guidelines, a new pacemaker system facilitates access to this diagnostic imaging technique with no evidence of clinical (bradycardia or tachycardia), subclinical (pacemaker performance) or technical (pacemaker or lead damage) deficits in patients, according to a late-breaking clinical pivotal trial presented May 14 at the 2009 meeting of the Heart Rhythm Society (HRS).
The EnRhythm MRI SureScan system from Medtronic is currently an investigational system in the U.S., but obtained the European Union CE Mark in November 2008.
"Each year, approximately one million people are implanted with a pacemaker, thousands of whom should receive diagnostic MRI scans," said lead investigator Bruce L. Wilkoff, MD, director of cardiac pacing and tachyarrhythmia devices at Cleveland Clinic, who presented the study.
He said that the patient population with pacemakers, especially those over 65 years, often require MRI imaging. However, there are currently FDA contraindications to the procedure, due to the safety concerns. Wilkoff explained that the potential electromagnetic interference from an MRI could result in under/oversensing thermogenic damage, device malfunction or even life-threatening cardiac arrhythmias.
In the study, once the pacemaker and leads were successfully implanted, patients were randomized to MRI or no MRI, the latter of which was the control arm. At nine to 12 weeks, the MRI patients received 14 clinically relevant head and lumbar scan sequences performed on a 1.5T system maximizing gradient slew rate and/or transmitted power up to specific absorption rate of 2 W/kg, and control patients waited one hour with no MRI. All patients were evaluated before, one week and one month after MRI scan/control visit.
Wilkoff reported that a total of 464 patients were implanted at 41 centers in the U.S., Europe, Canada and Middle East in the prospective, randomized trial; 244 MRI scan visits occurred and 44 patients were followed one month after MRI scan/control visit. They found that no MRI-related complications or MRI-attributed sustained ventricular arrhythmias, asystole episodes or pacemaker malfunctions occurred. The system-related, complication-free rate was 91.7 percent.
After one month post-control MRI/control visit, Wilkoff reported that the capture thresholds, sensing amplitudes and lead impedance were stable and similar between MRI and control patients. He said that pacing capture threshold increases were at least less than 0.5 V, except in one control ventricular lead. Also, sensing amplitude decreases by greater than 50 percent, or to less than 1.5mV in atrial lead or less than 5mV in ventricular lead, occurred for atrial leads in 5.3 percent of MRI patients vs. 7.2 percent of control patients, and ventricular leads in 3 percent of MRI patients vs. 5.1 percent of control patients.
"Currently, the decision to scan a patient with a pacemaker requires a considerable risk-benefit analysis due to the complication rates associated with the FDA-approved pacemaker system and requires intensive monitoring of the patients," Wilkoff said. However, he added that these new data suggest an alternative to the current concerns.
"This investigational study showed positive results, indicating that many more patients may have access to MRI, a vital and often irreplaceable tool in detecting and managing conditions such as cancer and neurological disorders," he said.
Wilkoff is a paid consultant for Medtronic in the development of this therapy.
The EnRhythm MRI SureScan system from Medtronic is currently an investigational system in the U.S., but obtained the European Union CE Mark in November 2008.
"Each year, approximately one million people are implanted with a pacemaker, thousands of whom should receive diagnostic MRI scans," said lead investigator Bruce L. Wilkoff, MD, director of cardiac pacing and tachyarrhythmia devices at Cleveland Clinic, who presented the study.
He said that the patient population with pacemakers, especially those over 65 years, often require MRI imaging. However, there are currently FDA contraindications to the procedure, due to the safety concerns. Wilkoff explained that the potential electromagnetic interference from an MRI could result in under/oversensing thermogenic damage, device malfunction or even life-threatening cardiac arrhythmias.
In the study, once the pacemaker and leads were successfully implanted, patients were randomized to MRI or no MRI, the latter of which was the control arm. At nine to 12 weeks, the MRI patients received 14 clinically relevant head and lumbar scan sequences performed on a 1.5T system maximizing gradient slew rate and/or transmitted power up to specific absorption rate of 2 W/kg, and control patients waited one hour with no MRI. All patients were evaluated before, one week and one month after MRI scan/control visit.
Wilkoff reported that a total of 464 patients were implanted at 41 centers in the U.S., Europe, Canada and Middle East in the prospective, randomized trial; 244 MRI scan visits occurred and 44 patients were followed one month after MRI scan/control visit. They found that no MRI-related complications or MRI-attributed sustained ventricular arrhythmias, asystole episodes or pacemaker malfunctions occurred. The system-related, complication-free rate was 91.7 percent.
After one month post-control MRI/control visit, Wilkoff reported that the capture thresholds, sensing amplitudes and lead impedance were stable and similar between MRI and control patients. He said that pacing capture threshold increases were at least less than 0.5 V, except in one control ventricular lead. Also, sensing amplitude decreases by greater than 50 percent, or to less than 1.5mV in atrial lead or less than 5mV in ventricular lead, occurred for atrial leads in 5.3 percent of MRI patients vs. 7.2 percent of control patients, and ventricular leads in 3 percent of MRI patients vs. 5.1 percent of control patients.
"Currently, the decision to scan a patient with a pacemaker requires a considerable risk-benefit analysis due to the complication rates associated with the FDA-approved pacemaker system and requires intensive monitoring of the patients," Wilkoff said. However, he added that these new data suggest an alternative to the current concerns.
"This investigational study showed positive results, indicating that many more patients may have access to MRI, a vital and often irreplaceable tool in detecting and managing conditions such as cancer and neurological disorders," he said.
Wilkoff is a paid consultant for Medtronic in the development of this therapy.