Endovascular near critical fluid based cryoablation catheter having superelastic treatment section

A cryoablation catheter for creating an elongated lesion in tissue, the catheter comprising:

• a proximal section,
• an intermediate section;
• and
• a distal treatment section comprising:
• a proximal end;
• a distal end;
• a treatment zone between the proximal end and the distal end;
• at least one fluid delivery tube;
• at least one fluid return tube;
• and
• a flexible member at least partially surrounding the at least one fluid delivery tube and the at least one fluid return tube,
• wherein the distal treatment section has a constrained state and an unconstrained state different than the constrained state, and
• wherein the unconstrained state defines a shape of the elongated lesion.

An endovascular cryoablation method for creating an elongate lesion in cardiac tissue in a heart, the method comprising:

• percutaneously inserting a catheter comprising a constrained superelastic distal treatment section into a patient's vasculature;
• navigating the superelastic distal treatment section to the heart and through an opening in the heart until the superelastic distal treatment section is within a space in the heart;
• unconstraining the superelastic distal treatment section such that the superelastic distal treatment section makes continuous contact along a curved target section of cardiac tissue along an interior wall of the heart;
• commencing flow of a cryogen to the superelastic distal treatment section through at least one fluid delivery tube and at least one fluid return tube extending through the superelastic distal treatment section, and
• creating the elongate lesion in the cardiac tissue.