A micro catheter and guidewire system for use in tortuous regions of a vasculature includes a catheter body having a distal end, a guidewire lumen, a proximal region with an outer diameter, and a distal region with an outer diameter. The ratio of the proximal region outer diameter to the distal region...http://www.google.co.uk/patents/US6533751?utm_source=gb-gplus-sharePatent US6533751 - Micro catheter and guidewire system having improved pushability and control
