Market growing for 'black boxes' in human beings

ARDEN HILLS, Minn. -- Data recorders in airplanes, the so-called black boxes, describe what went wrong after a disaster. Now, medical devices are emerging to act like a black box in the human body, except they're being used to prevent disaster.

Though still in an early stage, a market is growing for implantable monitors, tiny devices that track the function of a person's organs.

Five years ago, Medtronic Inc. released its first implantable monitor for people with mysterious fainting spells. Though a niche product for the giant maker of pacemakers and defibrillators, it was a breakthrough, giving doctors far more data about effects on a fainting person's heart.

Two product generations later, Medtronic has sold more than 25,000 of the 2-inch-long monitors, which weigh just a few grams. They're placed in a person's pectoral muscle, sometimes for just a few days, and track heart activity in a 42-minute loop.

When a person recovers from a fainting incident, he or she stops the monitor. A doctor or nurse can then retrieve the data with a special radio receiver, and restart the loop.

Other implants are being readied to monitor blood pressure and heart rate -- even inside the heart itself.

The Medtronic monitor, known as Reveal, has become useful beyond fainting spells.

Detected stroke risk

Robert Willoughby, 71, who had one of the monitors implanted in his chest almost two years ago, suffers from myotonic dystrophy, a degenerative muscle condition often marked by an irregular heartbeat.

Willoughby, of Lapel, Ind., tried wearing an external electrocardiogram monitor to watch for unusual heart events, but the bulky device was a nuisance.

His implanted monitor, by contrast, is constantly alert to capture and store up to 13 unusual events that occur during its loop. Its information is downloaded in quarterly visits to his doctor.

A year after receiving it, Willoughby's device detected atrial fibrillation, an irregular heartbeat that can increase the risk of stroke. His doctor prescribed blood thinners.

"I don't mind dying suddenly from a heart attack," the former General Motors tool-and-die worker said. "But I don't relish the idea of spending days in an infirm condition in a nursing home."

Quality of diagnoses up

Immediately after Medtronic's device hit the market, the quality of diagnosis for people with infrequent fainting spells shot up.

"A lot of the pull for the device came from patients, people who were frustrated, weren't able to drive, in disarray because fainting messed up their lives," said Brian Lee, the device's co-inventor.

The Reveal is just the start for implanted monitors.

The advance of wireless technology and the Internet allowed makers of other implants, such as pacemakers and defibrillators, to add monitoring features.

Medtronic and rival Biotronik Inc. in the past year began selling such products.

With the Baby Boomer generation hitting old age in the next two decades, doctors hope implantable monitors will help them treat patients for less cost with fewer hospital visits.

Developers envision implantables that track pressure in the brains of spina bifida patients who require fluid-draining shunts. For paraplegics who have lost sensitivity in their bladder, an implant could signal when it's time to urinate.