Manny Villafana could have retired comfortably in his early 40s, but the prospect of languorous afternoons on the golf course did little to pique the attention of a businessman famous for his restless energy.

After co-founding Cardiac Pacemakers Inc. in 1972, the serial entrepreneur went on to found St. Jude Medical Inc. and four more companies, and now he is back again, this time with a device for heart bypass surgery.

"This is the biggest thing I've ever done,'' Villafana promised with characteristic confidence.

To be sure, Villafana has not always hit home runs. Many investors are still chafing from the failure of CABG Medical Inc. in 2006. The company, which went public in 2004 at $5.50 a share, raising some $38 million, dissolved after the failure of clinical trials testing its surgical device.

Villafana, who walked away with $8.5 million, claims that most other shareholders recouped 40 percent to 92 percent of their investment. "I gave back $30 million to shareholders,'' he said. "Some people made money. ... But that's all behind us.''

Many investors agree and continue to place their confidence in Villafana. "He's the Cardiac Kahuna," said Dan Carr, CEO of the Collaborative, a Minneapolis group that assists entrepreneurs. "His place in what is still the dominant industry in Minnesota -- medical devices -- is a rarefied one."

This time the legendary investor is jumping into the market for heart surgery devices. He and an unnamed partner have plowed $10 million into Kips Bay Medical Inc., which is developing a mesh device to support veins in bypass surgery. The device has been tested in primates, dogs and sheep, and human trials began abroad in August, with 14 patients enrolled so far. Villafana says early results have been promising.

Each year, about 469,000 Americans undergo bypass or open-heart surgery, according to the American Heart Association. Bypass surgery uses healthy blood vessels taken from the legs, arms, chest or abdomen and connects them to arteries in the heart so that blood is bypassed around a diseased or blocked area. Typically, two to three grafts are used in each procedure.

But veins taken from the legs often collapse under the intense pressure of the heart. If they fail -- one Mayo Clinic surgeon says half of his vein grafts fail within 10 years of surgery -- a second operation may be needed.

To protect those veins from collapse, Fridley-based Medtronic Inc. had been developing a product known as the eSVS Mesh device for about seven years. Villafana recently acquired the technology for an undisclosed sum. (A Medtronic spokesman could not be reached to comment on the deal.)

Unlike a heart stent, which props open an artery from the inside, the eSVS nickel titanium device supports the vein from the outside. "The concept is really very simple," Villafana says. "You take a vein, apply the mesh, and make it smaller and stronger, like an artery."

The device is currently being tested in a clinical trial in South Africa, Spain, New Zealand, Australia and the United Kingdom that will ultimately enroll 100 to 150 patients. The idea is to use the results from studies abroad before applying for approval from the Food and Drug Administration (FDA), which would clear the device for sale in the United States.

Some investors may find it odd that Villafana remains interested in bypass devices after the blockbuster launches in recent years of drug-coated heart stents, which are used in many cases instead of open-heart surgery. (CABG Medical tried to develop, albeit unsuccessfully, an artificial graft for use in bypass surgery.)

Stents, which are inserted during angioplasty in a minimally invasive procedure to prop open blocked arteries, have grown into a $4 billion worldwide market. The number of angioplasty procedures has climbed sharply in the last three decades, according to the Heart Association and in 2005 reached 1.3 million, half of which involved stents. When Johnson & Johnson and Boston Scientific introduced drug-coated stents in the United States in 2003 and 2004, respectively, many cardiologists and industry analysts predicted that the number of bypass surgeries would plummet.

Beyond the benefits of minimally invasive surgery, stenting is cheaper than bypass surgery -- $44,110 compared with $85,653, according to the Heart Association.

But recent concerns related to potentially fatal blood clots that may form in stent patients have curbed the enthusiasm of doctors. A September study in the New England Journal of Medicine indicated that surgery is a better option for the sickest patients.

Villafana, predictably, is bullish about the prospects of bypass surgery and his company's new device. "This is going to be bigger than pacemakers," he said. "We'll create a new industry."

Not everyone is convinced. Dr. Thoralf Sundt, a heart surgeon at the Mayo Clinic who has no connection to Kips Medical, says the number of bypass surgeries will likely decline in the future for a different reason. More patients will fend off heart disease by taking cholesterol-fighting drugs such as Lipitor, and by improving their health through exercise, diet and smoking cessation.

"I'm sure there will always be a place for coronary bypass surgery. I think it's going to get smaller,'' he said. "That's probably a good thing. But it's not going to completely go away.''

Janet Moore 612-673-7752