Intravascular arterial to venous anastomosis and tissue welding catheter

A method of creating an AV fistula between adjacent first and second vessels, comprising:

• inserting a guidewire from the first vessel into the second vessel;
• inserting a catheter comprising a proximal member and a distal member over the guidewire such that a distal tip of the distal member comes into contact with a selected anastomosis site;
• advancing the distal member into the second vessel until a distal face of the proximal member contacts a tissue wall of the first vessel so that the proximal member remains in the first vessel thereby enlarging an aperture between the two vessels;
• moving the distal member and the proximal member together to clamp tissue surrounding the aperture between the distal face of the proximal member and a proximal face on the distal member;
• applying energy to an active heating member on the proximal member to cut and form the aperture, and to weld the edges thereof in order to create a desired fistula between the two vessels;
• and
• using a passive heating member disposed on the distal member to create a heating gradient across a tissue contacting surface of the distal member.