PROJECT SUMMARY Coronary Heart Disease (CHD) claims over 7 million lives each year ? more lives than all communicable, maternal, neonatal and nutritional disorders combined, and more than twice the number of deaths due to all cancers. For the past three decades, the standard treatment for CHD has been the deployment of a metal stent in the occluded artery to restore blood flow. In the US alone, over 1 million patients receive stents each year. However, the permanent and rigid nature of metal stents inhibits arterial vasomotion and induces serious complications such as Late Stent Thrombosis (LST). A promising new alternative to metal stents are Bioresorbable Vascular Scaffolds (BVSs). Unlike permanent stents, BVSs are transient implants that provide support to the artery for the first 6 months, but completely dissolve in 2 years, leaving behind an artery capable of vasomotion with no incidence of LST. BVSs derive their transient nature from the material they are made of ? the semicrystalline polymer poly L-lactide (PLLA) that hydrolyses to L-lactic acid, a metabolic product processed by the body. The clinical success of BVSs provides an impetus to make them broadly applicable to the treatment of CHD. Current BVSs are nearly two times thicker (~150m) than metal stents (~80m) due to a disparity in strength between PLLA and metal alloys. Consequently, BVSs need to be much thicker to have the strength needed to hold the artery open. A thinner BVS is easier to implant and can access smaller and complex arterial lesions. Thus, there is a critical need to reduce the thickness of BVSs so that a broader patient population can benefit from transient vascular implants. At present, the manufacture of BVSs is largely based on trial-and-error because there is limited understanding on how to control the BVS?s microstructure, which is responsible for the BVS?s strength and clinical success. This proposal will develop novel methodology and instrumentation that offers precise control of the BVS?s microstructure to enhance strength in a thinner profile. The proposed instrumentation will be the first of its kind that can relate the evolving structure of BVSs during manufacture to the BVSs? bulk strength. The connection between structure and strength, the lack of which is an obstacle to progress in the BVS community, will enable the rational design of next generation BVSs to meet the evolving needs of cardiovascular disease.