Selling cardiac rhythm devices in the United States might not be the fantastically booming business it once was, but that doesn't mean competitors don't bare their knuckles every once in a while.

On Monday, Medtronic announced it has received Food and Drug Administration approval to market its Viva cardiac device (CRT-D), which it says more efficiently synchronizes the beating of the heart to combat heart failure. Not long after, and not to be outdone, competitor Boston Scientific sent an ad to doctors basically saying its device is better.

Its headline spared no punches: "Medtronic just launched their new high-voltage platform. We just have one question... Why another sub 5-year CRT-D?" The Boston Scientific ad went on to compare its Incepta CRT-D device and two Medtronic models, including the just-approved Viva. Boston Scientific said when set at similar energy levels, its device has a 7.7-year life span while Medtronic's Viva lasts only 4.6 years.

Medtronic, which said Viva uses software to coordinate the heart's 100,000 contractions each day and automatically adjusts to its patient's activity levels, quickly cried foul. Viva, Medtronic said, has better medical outcomes than previous products introduced to the market over the last 10 years — and Boston Scientific is wrong it its comparisons.

'Frankly misleading'

"Today, Boston Scientific sent out an ad to physicians that is frankly misleading. Boston Scientific's projected comparisons are based on very specific programming settings that do not accurately reflect how Medtronic devices are programmed in patients," Medtronic said in a statement.

The Fridley-based company went on to say that based on actual programming data for the vast majority of its patients, the Viva device "has a longevity of 7.1 years."

Officials with Boston Scientific responded Tuesday with a prepared statement: "We stand firmly behind the data in our ad. Whether based on each manufacturer's product manuals or product performance reports, longevity comparisons for contemporary Boston Scientific devices demonstrate our sizable longevity advantage. Further, only Boston Scientific offers device warranties out to 10 years on some models of ICDs and six years on CRT-D devices."

Not to be outdone, Med­tronic sent doctors some information of its own, called: "Reality Check." In it, Medtronic said that "seven independent studies, including over 10,600 patients at 15 centers confirm Medtronic devices last longer."

Cardiac therapy sends electrical impulses to both lower chambers of the heart to help them beat together in a more synchronized pattern. This improves the heart's ability to pump blood and oxygen to the body. A CRT-D combines that therapy with a defibrillator to detect and treat dangerously fast heart rhythms.

Cuts admissions 21 percent

In touting its new Viva cardiac therapy with defibrillator device, Medtronic said studies show it cuts heart failure hospital admissions 21 percent, when compared with patients with standard CRT-D devices. Dr. Jagmeet Singh, director of the advanced therapeutics program at Massachusetts General Hospital in Boston, said the device improves patients' response to CRT-D therapy by 12 percent, which can help reduce medical costs and hospital admission rates.

Thomas Gunderson, a senior analyst with Piper Jaffray & Co., said that in general, Medtronic has by far the largest share — about half — of an $18 billion cardiac rhythm management market. Boston Scientific and St. Jude Medical split most of the rest, he said. In this highly competitive arena, Gunderson said that companies jockey to differentiate themselves not just along the lines of quality, but affordability. And everything from longer battery life to decreasing hospital admission rates becomes a factor in making the affordability argument.

"The customer for these companies has shifted from the physician to the hospital," Gunderson said. "What do hospitals want? Cost savings ... and to stay out of [Medicare's] re-hospitalization spotlight."

James Walsh • 612-673-7428