MINNEAPOLIS--(BUSINESS WIRE)--Medtronic, Inc. (NYSE:MDT), today announced the first patient enrollments in two separate clinical trials studying the use of the Valiant Thoracic Stent Graft system for treating descending thoracic aortic aneurysms and descending thoracic aortic dissections, respectively. The Valiant device is Medtronic's next generation thoracic endograft designed for minimally-invasive treatment of potentially fatal thoracic aortic conditions that affect tens of thousands of people each year.