WASHINGTON - More than 2 million Americans depend on pacemakers or defibrillators to keep their hearts beating right, but those lifesaving implants come with a price: They're not allowed in MRI machines, leaving these patients out of luck if they later need scans to detect cancer, stroke or myriad other ailments. That's poised to change.There are very few medical tests or procedures that come without any risk. I have long felt that MRIs could be done on people with pacemakers(Only once did I ever have a patient sent for an MRI who had one. Sent by their family physician!), technology could be adapted or precautions taken. The MRI is such an excellent diagnostic tool, its use for diagnosing and preventive medicine should be available for everyone. Good luck Johns Hopkins.
Doctors at a handful of hospitals are beginning to give MRIs to certain patients despite those implants — in careful experiments of ways to shield the heart devices from potentially deadly meltdowns or misfires. And the first human study of a pacemaker specially designed to withstand MRIs is expected to begin by year's end.
The attempts come none too soon. Use of the heart implants is growing rapidly, and already hundreds of thousands of recipients every year are estimated to be turned away from MRIs that their doctors wanted to help diagnose or manage other diseases.
"It's a critical issue," says Owen Faris, a heart device specialist at the
Food and Drug Administration, which has long urged manufacturers to create MRI-compatible implants.
The irony is that for most people, an MRI is super-safe. The scanner itself is a powerful magnet. Most modern implants are made with materials that aren't too magnetic, meaning an MRI won't move them around once they've healed in the body.
But MRIs are off-limits for a handful of implants — mostly pacemakers, heart-shocking defibrillators, and some brain devices — because the scans can heat them, burning surrounding tissue. Also, MRIs emit radiofrequency waves that can confuse electronic implants, leading them to either quit working or fire when they shouldn't.
Baltimore's Johns Hopkins University Hospital, a leader in the fledgling MRI trend, is getting two or three requests a day to scan pacemaker or defibrillator recipients, after scientists there reported safety steps that have allowed MRIs for more than 100 of the risky patients so far.
"Even with all these precautions, we can't guarantee that nothing adverse would happen," warns Dr. Saman Nazarian, a Hopkins cardiac electrophysiologist who monitors patients' hearts while they're inside the scanner, ready to intervene at signs of trouble.
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