Pacemaker People

Pacemaker people are cautioned against a variety of things: arc welding equipment, for one. Industrial-strength magnets for another. And magnetic resonance imaging (MRI) scans.

For many pacemaker people, these things are easily avoided. But many people need regular MRI scans to monitor ongoing conditions, such as cancer. Besides that, people really cannot predict if they might suddenly be put in a situation where an MRI scan is prudent if not crucial. But if you have a pacemaker, that's a no-no.

An MRI is a special imaging technique that helps doctors get a visual picture of soft tissues, including organs and possibly tumors. Many MRIs are like giant tubes; the patient is placed on a gurney and then pushed inside the MRI. The MRI machine takes a sequence of images which are then assembled together by the device's software to create the scans. During the sequence of images, the MRI may make a noisy pounding noise. An MRI can take many minutes to produce. In recent years, the claustrophobia-inducing tube-type MRI machine has been replaced by so-called "open MRI" machines and even standing MRIs (that's where you stand up throughout the scan).

The problem with MRIs and pacemakers is inherent in the "M" in MRI. MRIs use powerful magnets to create their images. Magnets can mess with the pacemaker's internal workings. In fact, one way to "reset" a pacemaker and cause it to "safety pace" (pace without sensing) is to put a magnet directly over it. Furthermore, the pacemaker is made out of metal and the magnetic force of the MRI machine can pull on the pacemaker as attracts it.

But an even bigger issue is that the MRI machine can start to heat up the pacemaker and the lead. If the pacemaker and lead(s) get too hot, they burn delicate cardiac tissue. An MRI can be potentially life threatening to a pacemaker person!

Right now, most pacemaker people who need some kind of scan of soft tissue can opt for a CT-scan (or "CAT" scan) which is generally considered safe for pacemaker patients. However, there are times when an MRI is better for what the doctor needs to see. In 2007, a total of 26 million MRIs were conducted in the U.S.; it's a familiar and reliable and frequent type of medical imaging.

Medtronic, the world's largest pacemaker manufacturer, has a new pacemaker on the way to approval. It's called EnRhythm MRI SureScan. The pacemaker was explicitly designed to be MRI-safe. It is rumored–but we cannot confirm it–that other manufacturers are working on similar producs.

Right now, EnRhythm MRI SureScan is not commercially available. It is currently under consideration by the FDA.

So how did a woman from the little town of Wimberley, Texas, get the first one ever to be implanted? The 45-year-old woman found out she needed a pacemaker after suffering some fainting spells. The problem was that she had Cushing's disease, which was caused by a couple of tumors on or around her pituitary gland. The woman needed to get an MRI every six months to monitor the condition which is associated with fatigue, weakened bones, and muscle weakness.

Her conundrum was that the pacemaker she needed would make it impossible to monitor her Cushing's disease. She visited a hospital in Austin and talked to a cardiologist there who knew about the MRI-safe pacemaker in development. The cardiologist got in contact with the Medtronic's representative who worked with officials at the company and the FDA to get special permission to use the new pacemaker before it is officially approved. This kind of special dispensation is known in the business as "compassionate use."

Compassionate use of a device allows the FDA to waive restrictions and will let the woman get a pacemaker that is not yet commercially on the market. To get a compassionate use waiver, one has to work with both the manufacturer and the FDA (not to mention the doctor) and complete a great deal of paperwork.

Fortunately for the woman from Wimberley, Texas, it was completed relatively quickly and she was able to get her MRI-safe pacemaker and also make some news as the first woman to get the MRI-safe pacemaker.

Although it is always a little bit tricky to "predict" when products will be approved by the FDA, it is anticipated that the MRI-safe pacemaker will be cleared for market release in the spring of 2010.