BACKGROUND: Since the first battery-powered pacemaker was invented more than 50 years ago, the device has helped extend the lives of millions of patients. The pace of the heart is naturally regulated by the sinoatrial (SA) node, a small mass of specialized cells located in the upper right atrium. The SA node sends out electrical impulses that control the beating of the heart. When the heart's natural pacemaker malfunctions, the heart beat becomes irregular. An artificial pacemaker assists the heart in beating properly by sending electrical impulses to the heart. Pacemakers are sometimes permanently implanted or used externally for a given period of time.
UNWANTED INTERFERENCE: Magnetic resonance imaging (MRI) uses radiofrequency waves and a strong magnetic field instead of X-rays to provide clear and detailed pictures of internal organs, blood vessels, muscles, joints, tumors and more. The powerful magnet attracts metal objects, which are normally not placed near the machine. MRI can compromise a pacemaker's ability to regulate the heart by interrupting the electric output of the device. The tips of the wires used to connect the device to the heart may also heat up during a scan, causing heart tissue to burn. 2.25 million people had pacemakers implanted in the United States between 1990 and 2002. Most of them were 70 years or older. With MRIs being increasingly used to diagnose cancer and neurological disorders, they are especially useful for this age group. Currently, 60 million MRI scans are performed worldwide every year.
A recent multi-center safety and efficacy study involving 470 individuals revealed a new pacemaker is safe to use in MRI scanners. Medtronic's EnRhythm MRI SureScan device is the first of its kind. Up to half of patients across the world that have implanted cardiac devices are expected to require an MRI scan at some point. The new pacemaker offers those patients a solution to this dilemma. Results of the clinical trial showed no complications from MRI when using the SureScan. In addition, the heart rhythm suffered no problems during the scan and continued to respond appropriately to the electrical impulses.
The SureScan's hardware is modified to minimize energy transmitted during an MRI scan and eliminate electrical noise, which can cause a pacemaker to malfunction. Medtronic plans to distribute the SureScan outside of the United States as early as this year, and it may be approved for use in the United States in 2009.
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