Endovascular device configured for selective narrowing

1. An endovascular device, comprising:

an elongated flexible sheath defining a lumen with an inner opening sized for enabling selective advancement of an endovascular instrument therethrough, the sheath having at least a first region and a second region;

an electrode within the first region of the sheath; and

a constrictor associated with the first region of the sheath, the constrictor being configured, while at least the first region and the second region of the sheath are positioned within a body and in response to an input received from outside the body, to reversibly narrow the lumen of the sheath in an area adjacent the electrode to thereby bring the electrode into contact with an adjacent portion of the endovascular instrument.

2. The endovascular device of claim 1 , constructed such that during a constriction of the first region of the sheath, the second region of the sheath is configured to remain unconstricted.

3. The endovascular device of claim 1 , wherein the endovascular instrument is an endovascular coil configured for bending within a hollow body structure upon discharge from the sheath, and wherein the electrode is located in a distal region of the sheath and is configured to sever the endovascular coil following discharge of at least a portion of the coil from the sheath.

4. The endovascular device of claim 1 , wherein the electrode is configured to make physical contact with the endovascular instrument during a constriction to enable the electrode to deliver energy to the endovascular instrument.

5. The endovascular device of claim 4 , wherein the electrode is configured to deliver energy in an amount sufficient to sever the endovascular instrument while at least the first region and the second region of the sheath are positioned within the body.

6. The endovascular device of claim 4 , further comprising electrical circuitry, wherein the electrode is configured for connection to the circuitry for selectively delivering the energy to the electrode.

7. The endovascular device of claim 4 , wherein the electrode is configured to deliver electrical energy to the endovascular instrument and wherein the constrictor is configured to press the electrode and the endovascular instrument together in a manner reducing electrical impedance during energy delivery.

8. The endovascular device of claim 1 , wherein the constrictor is configured such that a constriction of the first region of the sheath closes an electrical circuit including the electrode and the endovascular instrument.

9. The endovascular device of claim 1 , wherein during a constriction, the constrictor is configured to obstruct axial advancement of the endovascular instrument within the first region of the sheath.

10. The endovascular device of claim 1 , wherein a first section of the lumen within the first region of the sheath has a circular cross-section during a non-constriction, and wherein the constrictor is configured to cause the cross-section of the first section of the lumen in an area of the constrictor to become non-circular.

11. The endovascular device of claim 10 , wherein a second section of the lumen within the second region of the sheath has a circular cross-section during a constriction.

12. The endovascular device of claim 1 , wherein the constrictor is configured to selectively narrow the lumen in response to a control signal received from a control device positioned outside the body.

13. The endovascular device of claim 1 , wherein the constrictor is configured to selectively narrow the lumen in response to at least one of:

a change in temperature of at least a portion of the constrictor,

delivery of electric current to the constrictor,

an application of electromagnetic force on the constrictor, or

an application of mechanical force on the constrictor.

14. The endovascular device of claim 1 , wherein at least a first portion of the constrictor is located within the lumen of the sheath during a constriction, and wherein at least a second portion of the constrictor is located outside the lumen of the sheath, adjacent an external surface of the sheath.

15. The endovascular device of claim 1 , wherein the constrictor includes at least one obstructer configured to:

lie substantially flush with an outer surface of the first region of the sheath when the first region is non-constricted, and

protrude into the lumen of the sheath when the first region is constricted.

16. The endovascular device of claim 15 , wherein the at least one obstructer includes a selectively inflatable balloon configured for expansion into the lumen of the sheath when inflated.

17. The endovascular device of claim 15 , wherein the at least one obstructer includes at least two obstructers spaced about a circumference of the lumen of the sheath.

18. The endovascular device of claim 15 , wherein the at least one obstructer includes at least one of:

a plurality of obstructers located substantially at a same distance from a distal tip of the endovascular device, or

a plurality of obstructers, each located at differing distances from the distal tip of the endovascular device.

19. The endovascular device of claim 1 , wherein the constrictor is configured to cause exertion of a stronger friction force on the endovascular instrument when constricted than when unconstricted.

20. The endovascular device of claim 1 , wherein the constrictor is configured to:

constrict the first region of the sheath, and

automatically unconstrict the first region of the sheath after a specified period of time.

21. The endovascular device of claim 1 , wherein after narrowing the lumen of the sheath in response to the input received from outside the body, the constrictor is configured to widen the lumen in response to a second input received from outside the body.