In the latest installment of the battle of two fierce rivals, Medtronic Inc. (NYSE:MDT) filed two lawsuits against Edwards Lifesciences Corp. (NYSE:EW) on allegations of patent infringement on heart valve technologies.

Medtronic maintained that Edwards’ products, including the Embol-X Glide Protection System and the Perimount Mitral Valve, use patented technology without permission in a lawsuit filed last week in St. Paul, Minn.

In a second case filed yesterday in California, Medtronic’s CoreValve unit accused the Edwards’ Sapien transcatheter valve of infringing a separate patent.

Medtronic seeks cash compensation and order to prevent future infringement, Bloomberg reported.

The companies have duked it out in court and the EU market for years.

In April 2010, a jury found that CoreValve willfully infringed an Edwards patent, awarding $73.5 million in damages, but in February of this year Judge Gregory Sleet of the U.S. District Court for Delaware  rejected an Edwards motion to enjoin Medtronic from making and selling the aortic valve replacement device. Edwards promised to appeal the unfavorable rulings.

The disputes involved three patents covering “collapsible and expandable tissue valve prostheses and methods for replacing human heart valves using minimally invasive catheterization procedures,” the so-called Andersen patent family.

Edwards has lost a few skirmishes along the way, with a German court deciding that CoreValve’s transcatheter aortic valve does not infringe on Edwards’ patent in that country and Judge Sleet throwing out Edwards’ claims for one of the patents in the Delaware suit.

Edwards’ Sapien device is undergoing review by the U.S. Food & Drug Administration and is on track to have a healthy head start on rival Medtronic and its CoreValve system in the robust replacement heart valve market. Medtronic is about two years behind Edwards in the U.S., where Sapien is expected to hit the market by the end of this year.

An estimated 100,000 U.S. patients are seen as candidates for the therapy, which involves replacing the diseased aortic valve without open heart surgery. That’s roughly a third of the global market.

The Sapien device will get its much-anticipated date with the FDA in July. Edwards filed its PMA application in October 2010 and has staked its flag on an October 2011 release, sinking about $40 million into a launch that CEO Michael Mussallem said will allow the company to compete in 200 to 400 centers in the U.S.

Medtronic has not revealed its hopes for a U.S. launch timetable should it win a regulatory nod. But even with court battles over the technology going back four years, you can be sure the fight is just heating up. Edwards may have a step on Medtronic, but the Minnesota monolith has much deeper pockets. Stay tuned.