Keeping the Beat on Orlando Medical News

Keeping the Beat

By: J.L. WEBB

Orlando Health Deeply Involved in Groundbreaking Pacemaker Study

Interventional cardiologists in the United States should not have to wait much longer for the results of an international study that has the potential to transform the way they prescribe pacemakers.

The first crucial phase of a clinical trial to evaluate Medtronic's EnRhythm® MRI SureScan™ pacing system has been completed, and findings have been submitted to the New England Journal of Medicine for publication, possibly as early as this month, according to David Bello, MD, one of the principal investigators for the study. Bello is director of cardiovascular imaging at Orlando Health, which was the first hospital – and one of only two – in Florida to participate in the study.

Bello, who also is a partner at Mid-Florida Cardiology Specialists, said he was "part of the committee that designed this" technology and "one of only a few people in the United States" to contribute on both those fronts.

The trial, which began two years ago, aims to prove the EnRhythm® MRI SureScan™ system can enable patients with pacemakers to safely undergo magnetic resonance imaging scans. Up until now, pacemaker recipients have not been allowed to take advantage of an MRI's superior diagnostics. That is because the magnet can disrupt the cardiac unit's pacing system and trigger improper heart rhythms. Another concern has been that the tips of the wires that connect the pacemaker to the heart can overheat during an MRI and sear heart tissue.

According to Orlando Health officials, Medtronic's pacemaker includes modified hardware designed to minimize the energy transmitted and also eliminates the impact of electrical noise from the MRI, which can result in pacemaker malfunctions.

Medtronic claims its pacemaker will eliminate all those concerns, and preliminary results that already have been released overseas support the company's position. Safety and efficacy data that was presented last summer to the European Society of Cardiology Congress showed no complications related to MRIs for recipients of Medtronic's pacemaker, including no arrhythmias or asystole.

The data from the clinical trial participants in the U.S., presuming it confirms the results in Europe, likely will result in the approval by the federal Food and Drug Administration, which is needed before cardiologists can order MRIs, rather than just computed tomography (CT) scans for patients with pacemakers.

The design of the study of this interventional tool, according to the National Institutes of Health, has been randomized, open label, active control and unblinded and had 471 enrollees worldwide. With 14 patients, Bello said he had the third-largest pool of participants in the U.S. "They were randomized 50-50," said Bello. "Each patient got an MRI-compatible pacemaker, but half got MRIs and the other half did not. Assessing the results 'narrowly,' there has been no significant difference between these two groups."

Being able to perform MRIs on individuals with implantable cardiac devices is significant, Bello explained.

"An MRI is an important diagnostic tool. At some point or another, almost 75 percent of the United States population will probably require an MRI," Bello said. "One of the main limitations (for cardiologists) is that once you place a pacemaker you can no longer have an MRI. The reason this study is important is that it's the first time we have specifically designed a pacemaker to be compatible with an MRI," he said. "We were the first in Florida and one of the first in the United States to actually implant this improved device as part of a clinical research trial."

Even though the first phase of the clinical trial is complete, Bello said it has several phases. "The first phase is required by the FDA … The phase that we're in right now (in January) includes the spine and brain sequences for MRIs," said Bello, who is board-certified in internal medicine with a subspecialty of cardiovascular disease and electrophysiology. Bello also is board-certified in nuclear medicine and concentrates on cardiac CTs, MRIs and implantation and management of internal cardiac defibrillators and permanent pacemakers.

Of the five percent of United States residents who have pacemakers, about 75 percent will be candidates for MRIs at some point to diagnose a health condition, Bello said. Therefore, "MRI safety has great clinical importance," he said.

"If the New England Journal of Medicine accepts our publication, those results will be released (soon)," Bello said. "It's an important study, it was well-designed, it cost a lot of money and it is a multi-centered trial,'' he said, referring to the study's 51 trial locations.

According to the NIH, the study will:

Assess the safety of pacemaker system in MRI machine.
Assess the performance of a pacemaker system in the top and bottom heart chambers following MRI scans.
Summarize the number of abnormal heart beats during MRI scans.
Summarize all harmful events (study related and non-study related) during the study.
Compare pacemaker lead (wire) performance to currently available leads

Indeed, the symbiotic justification to absorb pacemaker patients into the candidates for MRIs is evident. Pacemakers have extended the lives of millions who have heart-rhythm conditions. Worldwide, almost 1 million pacemakers are implanted annually. At the same time, physicians routinely use MRIs to evaluate the brain, spine and other parts of the body, including joints, extremities, major organs, blood vessels and infections. By creating a magnetic field and sending radio waves through a patient's body, an MRI often provides an image that cannot be seen through a CT, ultrasound or X-Ray. It is one of the most, if not the most, non-invasive diagnostic tools available to physicians.

This clinical trial hopes to extend that advantage to people who have pacemakers. To learn more about the clinical trial, visit the following Web site: http://clinicaltrials.gov/ct2/show/NCT00433654.