Steerable guidewire having electrodes for measuring vessel cross-section and blood flow

A small diameter steerable guidewire comprising:

• a conductive main tube having a proximal end and a distal end;
• a conductive wire extending through said main tube and having a tapered distal region extending beyond the distal end of said main tube, said wire being electrically insulated from said main tube;
• a distal, conductive, helically-wound spring receiving at least a portion of the distal region of said wire, said distal spring constituting a distal electrode and being electrically connected to said wire;
• a proximal, conductive electrode tube having the distal region of said wire extending therethrough, said proximal electrode tube constituting a proximal electrode and being electrically connected to said main tube;
• and
• means for spacing said distal and proximal electrodes by a predetermined distance on the distal region of said wire, said conductive electrode tube minimizing an induced voltage in said conductive wire when an electrical current passes through said proximal electrode so that an electrical current between said proximal electrode and said distal electrode can be measured accurately.

Apparatus for measuring the cross-sectional area of a blood vessel comprising:

• a small diameter steerable guidewire comprising:
• a conductive main tube having a proximal end and a distal end,
• a conductive wire extending through said main tube and having a tapered distal region extending beyond the distal end of said main tube, said wire being electrically insulated from said main tube,
• a distal, conductive, helically-wound spring receiving at least a portion of the distal region of said wire, said distal spring constituting a distal electrode and being electrically connected to said wire,
• a proximal, conductive electrode tube having the distal region of said wire extending therethrough, said conductive electrode tube constituting a proximal electrode and being electrically connected to said main tube, and
• means for spacing said distal and proximal electrodes by a predetermined distance on the distal region of said wire;
• means connected to said main tube and said wire for applying an AC electrical voltage between said proximal electrode and said distal electrode;
• and
• means connected to said main tube and said wire for measuring an electrical current between said proximal electrode and said distal electrode in response to said AC voltage, said electrical current being representative of the cross sectional area of said blood vessel, said conductive electrode tube minimizing an induced voltage in said conductive wire when said electrical current passes through said proximal electrode so that said electrical current can be measured accurately.