a guide catheter includes a tubular section formed of a shape memory polymer that can transform dynamically between first and second states or conditions , or among three states or conditions , to provide a wide range of properties of the guide catheter as desired during delivery of the guide catheter through the vasculature to a target site , and removal of the guide catheter from the target site and vasculature . the states or conditions of the shape memory polymer be dynamically changed to vary properties of the tubular section such as stiffness , flexibility , shape , or biodegradability , which can be controlled by exposure of the shape memory polymer to temperature changes , electric fields , magnetic fields , wavelengths of light , and chemical solutions .