Such wires may fracture, decay or lead to infection. Sometimes do-over procedures are needed to place them in a narrow vein outside the heart muscle. Misplaced wires near the left heart may trigger hiccups by stimulating the nerve that controls the diaphragm, or deliver energy to damaged tissue that doesn’t respond to the therapy.

The result is billions of health care dollars wasted on ineffective pacing of the left heart. However, a California medical device company with Minnesota financial backing, EBR Systems, says it has invented a device it calls the WiSE System to pace the left side of the heart using sound waves directed to a pacemaker electrode the size of a grain of rice.

The 9-millimeter electrode is implanted inside the heart’s left ventricle, where scar tissue permanently embeds it in the heart. The electrode does not contain a battery, but rather converts ultrasound energy into electricity. The ultrasound waves come from a pulse generator implanted between the ribs and powered by a third component, a replaceable battery, also under the skin.

The current design requires the patient to have a traditional pacemaker or implantable defibrillator for the right ventricle that determines when the left-ventricle device should fire. Typically, those devices need a wire in the heart’s coronary sinus vein to pace the left heart, which limits where the power can be applied. The WiSE System is said to work better because its location is not limited to where the vein goes, and because pulses delivered inside the heart are more effective than outside it.

EBR Systems received permission to sell this complicated medical device for heart failure last fall in Europe. The company is now in talks with the U.S. Food and Drug Administration about starting a clinical trial involving hundreds of U.S. patients.

The technology would fall within a fast-growing niche of experimental, ultrasmall pacemakers that don’t use wires to pace the heart. Medtronic and St. Jude Medical are both testing inside-the-heart pacemakers called the Micra and Nanostim, respectively.

So far, 47 WiSE systems have been implanted in humans worldwide, and U.S. approval is at least three years away. But private investors have stuck with the firm, even after it canceled its first clinical trial in Europe and spent more than a year redesigning the catheter that implants the electrode in the left ventricle.

“We think the opportunity is significant, to put it mildly,” said Josh Baltzell, a partner with Twin Cities-based venture capital firm Split Rock Partners. “It is a new way of doing things. It’s just like when the first pacemaker came out. … It was a big advancement, and we feel like the WiSE system is similar.”

Split Rock and St. Paul Venture Capital have together invested an undisclosed eight-figure sum in EBR Systems, Baltzell confirmed. Several other VC firms and one publicly traded medical device company have economic interests in EBR, as well, he said.

The reason for the excitement is that EBR’s technology has the potential — “I want to underline potential. It’s not reality yet,” Baltzell said — to address a huge unmet need in cardiac medicine.

EBR CEO Allan Will said it’s an open secret in the heart-device industry that at least a quarter of the 200,000 Cardiac Resynchronization Therapy (CRT) pacemakers sold each year fail to make the patients’ hearts pump blood better than before.

At roughly $26,000 per CRT device, that amounts to well over $1 billion spent on devices each year that do not improve patient health after six months, he calculates. “It’s clear. Everybody knows it,” Will said. “The patients are spending probably $30,000 a year in hospitalizations, plus they have a $26,000 implant that failed. So these are very expensive patients. This is why we chose to focus this wireless pacing on CRT … because there is this Achilles’ heel here that we can focus on.”

The world’s largest makers of CRT devices all operate in Minnesota — Boston Scientific Corp., Medtronic, and St. Jude Medical.

Will, a serial med-tech entrepreneur who has been involved in selling two companies to Medtronic, noted that the WiSE technology could be valuable to any of Minnesota’s heart-device makers because they’re hungry for growth in the slowly growing cardiac rhythm management market.

Will said that someday the device might be designed to work in the right heart in place of traditional pacemakers and implantable defibrillators. “Down the road, we could do more,” he said. “But right now we have focused on replacing the function of the coronary sinus [wire] for CRT.”

Twitter: @_JoeCarlson