Active fixation lead with a dual-pitch, free spinning compound screw

An active fixation cardiac lead, comprising:

• an elongated flexible lead body having a proximal end and a distal end, said lead body including an interior cavity adapted to receive a rotatable stylet therein, an insulating sheath and at least one conductor mounted within said insulating sheath, said cavity, insulating sheath and at least one conductor extending longitudinally from said proximal end to said distal end;
• and
• an electrode assembly carried at said distal end of said lead body, said electrode assembly comprising:
• a generally cylindrical electrode housing having at least one electrode electrically coupled to said at least one conductor and having a conduit therein,
• a compound screw having a distal end and a proximal end and being adapted to be rotated by said stylet for extension and retraction with respect to said electrode housing, said screw being positioned within the conduit of said electrode housing and including a threaded coupling screw, a head positioned at a proximal end of said coupling screw, said threaded coupling screw comprising a shaft positioned between said head and a distal end of said compound screw, said shaft having a thread of predetermined pitch and a thread trough thereon, said head being adapted for engagement and rotation by said stylet, and a fixation coil fixably attached to said threaded coupling screw and extending distally therefrom, said fixation coil having a thread pitch greater than the thread pitch of said threaded coupling screw.

An active fixation cardiac lead, comprising:

• an elongated flexible lead body having a proximal end and a distal end, said lead body including an interior cavity adapted to receive a rotatable stylet therein, an insulating sheath and at least one conductor mounted within said insulating sheath, said cavity, insulating sheath and at least one conductor extending longitudinally from said proximal end to said distal end;
• and
• an electrode assembly carried at said distal end of said lead body, said electrode assembly comprising:
• a generally cylindrical electrode housing having at least one electrode electrically coupled to said at least one conductor and having a conduit therein,
• a compound screw having a distal end and a proximal end and being adapted to be rotated by said stylet for extension and retraction with respect to said electrode housing, said screw being positioned within the conduit of said electrode housing and including:
• a threaded coupling screw having a head adapted to be engaged and rotated by said stylet and being positioned on a proximal end of said screw, said threaded coupling screw comprising a shaft having a thread of predetermined pitch and a thread trough thereon, said shaft being positioned between said head and a distal end of said compound screw, and a fixation coil fixably attached to said threaded coupling screw and extending distally therefrom, said coil having a pitch greater than the predetermined pitch of said thread.

An active fixation cardiac lead for implantation into a patient's heart, comprising:

• an elongated flexible lead body having at least one insulated conductor and having a proximal end and a distal end.
• an electrode housing positioned at the distal end of said lead body and having a generally centrally located conduit therein, said housing including at least one electrode electrically coupled to said at least one insulated conductor;
• a rotatable screw positioned within said electrode housing conduit, said screw including a proximal screw portion having threads therein and being adapted to move axially with respect to said electrode housing from a retracted position to an extended position when rotated in a first direction, and from said extended position to said retracted position when rotated in an opposite second direction, said screw including a distal coil portion having threads, said distal coil portion being adapted to engage tissue in the patient's heart;
• means for rotating said rotatable screw with respect to said electrode housing;
• and
• a free spinning mechanism coupled to said proximal screw portion and responsive to the arrival of said screw at its extended position for limiting said axial movement of said screw while allowing continued first direction rotation of said screw with respect to said electrode housing, whereby said distal coil portion is adapted to draw heart tissue into firm contact with said electrode at the distal end of said lead with continued rotation of the screw after it has reached its extended position.

An active fixation cardiac lead, comprising:

• an elongated flexible lead body having a proximal end and a distal end, said lead body including an interior cavity adapted to receive a rotatable stylet therein, an insulating sheath and at least one conductor mounted within said insulating sheath, said cavity, insulating sheath and at least one conductor extending longitudinally from said proximal end to said distal end;
• and
• an electrode assembly carried at said distal end of said lead body, said electrode assembly comprising:
• a generally cylindrical electrode housing having at least one electrode electrically coupled to said at least one conductor and having a conduit therein,
• a compound screw having a distal end and a proximal end and being adapted to be rotated by said stylet for extension and retraction with respect to said electrode housing, said screw being positioned within the conduit of said electrode housing and including:
• a threaded coupling screw, a head positioned at a proximal end of said coupling screw, a zero pitch track positioned immediately distal to said head, said threaded coupling screw comprising a shaft positioned between said zero pitch track and a distal end of said compound screw, said shaft having a thread, said head being adapted for engagement and rotation by said stylet, and a fixation coil fixably attached to said threaded coupling screw and extending distally therefrom, and
• a free spinning mechanism, said mechanism including;
• a first ball bearing positioned within said conduit in a generally fixed location with respect to said electrode housing and positioned within said zero pitch track when the threaded coupling screw is fully extended and, otherwise, positioned within the thread trough of said threaded coupling screw, said first ball bearing being adapted to rotationally engage said threaded coupling screw with said electrode housing, an aperture extending through said electrode housing positioned a generally fixed interval distal to said first ball bearing, a spring member located generally peripheral to said aperture exerting a force to the interior of said electrode housing, and a second ball bearing adapted to be forced into said aperture by said thread when the screw is rotated to full extension and said first ball bearing enters said zero pitch track and, otherwise, adapted to be forced into said conduit and within said thread trough by said spring member to rotationally engage said threaded coupling screw with said electrode housing.