(This story has been posted on The Wall Street Journal Online's Health Blog at http://blogs.wsj.com/health.) By Christopher Weaver The spread of an advanced medical-technology -- tiny, wireless computers, embedded in surgically implantable defibrillators -- has come up against an unlikely obstacle: The devices rely on old-fashioned landlines, quickly vanishing from American households, to relay data to doctors and companies. The little computers wirelessly transmit medical data, such as patients' heart rates, to bedside monitors in patients' homes. They also detect electrical irregularities in the potentially life-saving devices, which shock irregular heartbeats back to normal rhythm, allowing doctors to predict dangerous device failures, as WSJ reports. But the monitors, which seamlessly download information from the matchbox-sized "smart" defibrillators as patients sleep, use traditional phone lines to fire the information back to device makers, such as Medtronic and St. Jude Medical. Only then is the critical data relayed to doctors via company-run websites. That cuts off the promising technology from one-third of all U.S. households, those that have gone wireless, according to a December 2011 report published by the Centers for Disease Control and Prevention. It's a barrier industry recognizes. "Wireless is essential for the future," said Elizabeth Hoff, Medtronic's general manager for Cardiac Connected Care, the unit that makes its CareLink monitoring system. "My mother, who eventually will have an [implantable defibrillator], will not even know her device is transmitted wirelessly up to the cloud." Even among adults over age 65, 8% of households are completely wireless, four times the rate reported in late 2007, according to the CDC. The least hard-wired group is adults between ages 25 and 29, who are nearly 60% wireless, according to the report based on National Health Interview Survey data collected in the first half of 2011. Across the medical-device industry, between 45% and 69% of patients' whose defibrillators could be enrolled in remote monitoring actually are, depending on the company, WSJ reports. The landline gap is a key problem, doctors say. For instance, all of Dr. Westby Fisher's defibrillator patients are sent home with a monitoring box to plug into a phone jack in their bedrooms. Only 60% ever do, says Fisher, who practices at NorthShore University HealthSystem near Chicago. "The technology has not evolved to being able to use someone's cell phone" readily, when patients don't have analogue landlines at home, Fisher says. Medtronic and St. Jude received Food and Drug Administration approval of cellular accessories for their monitoring systems in 2010, but while the landline systems are free, someone must foot the cellphone bill for adapters and it isn't clear who would do so. Boston Scientific, another defibrillator maker, is awaiting FDA approval of its own cellular monitor. More broadly, device makers seeking to go wireless have butted heads with the communications industry and other customers. For instance, the health-care unit of Royal Philips Electronics and other technology companies battled the U.S. airline industry for access to bandwidth the electronics makers plan to use for hospital-based wireless monitoring equipment. The bandwidth was previously reserved for flight-safety testing. To realize the full potential of data medical devices collect for patient care -- and profit -- the medical-technology industry says it has to defer to outside players, such as cellular carriers. That's an "ecosystem the [device] industry doesn't necessarily control," says Medtronic's Hoff. But, a wireless, data-driven future is very much in Medtronic's sights. "What we're doing now is recognizing that were putting computers into patients bodies, and there is so much value in the data," she says. "Our strategy is to exploit the data." -For continuously updated news from The Wall Street Journal, see WSJ.com at http://wsj.com.