| CPC A61B 18/1492 (2013.01) [A61B 2018/00083 (2013.01); A61B 2018/00095 (2013.01); A61B 2018/00148 (2013.01); A61B 2018/00178 (2013.01); A61B 2018/00357 (2013.01); A61B 2018/00714 (2013.01); A61B 2018/00767 (2013.01); A61B 2018/00875 (2013.01); A61B 2018/1475 (2013.01)] | 19 Claims |

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1. A method, comprising:
extending a distal tip of a guidewire disposed within an insulating sheath a first distance distal to a distal end of the insulating sheath, the guidewire including a conductive outer region and an insulating collar disposed between the distal tip and the conductive outer region, the distal tip of the guidewire and the distal end of the insulating sheath being disposed proximate to a septum of a heart of a patient;
disposing the distal tip of the guidewire against the septum;
delivering, after disposing the distal tip of the guidewire against the septum, radiofrequency (RF) energy to the septum via the distal tip;
further extending the distal tip of the guidewire distally while delivering the RF energy to form a perforation in the septum; and
in response to extending the distal tip of the guidewire a second distance distal to the distal end of the insulating sheath, exposing the insulating collar and at least a portion of the conductive outer region of the guidewire such that an exposed surface area of the portion of the conductive outer region reduces a RF current density around the distal tip of the guidewire.
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