Intravascular filter
An intravascular filter includes at least one elongated support member configured to assume a retention configuration, such as a generally helical form about a central axis, and at least one flexible elongated filter member supported by the support member. The filter member is configured to assume a predefined filter form in such a manner as to form an obstacle to passage through the vessel, in a direction parallel to central axis, of particles having dimensions greater than the predefined value. The support member and the filter member are preferably prepared in a generally straight configuration to facilitate minimally invasive deployment.
1. An intravascular filter for minimally invasive deployment within a vessel so as to obstruct the passage of particles of dimensions greater than a predefined value through the vessel, the intravascular filter comprising:
(a) a flexible support structure configured to assume a retention configuration for retaining and supporting the filter in a predefined orientation relative to a central axis of a surrounding vessel; and
(b) a filter configuration connected to said at least one support structure, said filter configuration including a flexible wire configured to assume a predefined filter form including a plurality of lobes, said predefined filter form being circumscribed by a first virtual cylinder of a given diameter D each of said lobes being formed by a segment of said flexible wire extending from within a second virtual cylinder coaxial with said first virtual cylinder and having a diameter D/2, passing outwards towards said first virtual cylinder and passing back to within said second virtual cylinder, said plurality of lobes being deployed angularly spaced around said central axis in such a manner as to form an obstacle to passage along the vessel, in a direction parallel to said central axis, of particles having dimensions greater than the predefined value.
2. The intravascular filter of claim 1 , wherein said predefined filter form is substantially angularly periodic about said central axis.
3. The intravascular filter of claim 1 , wherein said predefined filter firm exhibits non-reversing curvature.
4. The intravascular filter of claim 1 , wherein said predefined filter form includes a plurality of connecting wire segments each passing through said second virtual cylinder interconnecting between successive of said lobes and curving around said central axis, wherein each of said connecting wire segments undergoes an angular deflection of no more than about 60°.
5. The intravascular filter of claim 4 , wherein of each said connecting wire segments undergoes an angular deflection of no more than about 40°.
6. The intravascular filter of claim 1 , wherein said retention configuration is axially progressive with respect to said central axis.
7. The intravascular filter of claim 1 , wherein said predefined filter form is axially progressive with respect to said central axis.
8. The intravascular filter of claim 1 , wherein said retention configuration and said predefined filter form are axially co-progressive with respect to said central axis.
9. The intravascular filter of claim 1 , wherein said retention configuration has a substantially helical form extending for at least about one turn about said central axis.
10. The intravascular filter of claim 9 , wherein said substantially helical form extends for n complete turns, said plurality of lobes being spaced around said central axis at angles of approximately 2πn/p radians where p is a positive integer no less than 3, n is a positive integer smaller than p, and p and n are relatively prime.
11. The intravascular filter of claim 9 , wherein said substantially helical form includes at least a first portion which is a right-handed substantially helical fonn and at least a second portion which is a left-handed substantially helical form.
12. The intravascular filter of claim 9 , wherein said substantially helical form approximates to a helix modulated by an undulating pattern having a maximum amplitude not significantly greater than a diameter of said helix.
13. The intravascular filter of claim 9 , wherein said support structure and said filter configuration are formed primarily from a super elastic alloy, said support structure and said filter configuration being elastically biased to said substantially helical form and said filter form, respectively, and being elastically deformable into a substantially straight configuration in which said support structure and said filter configuration are substantially straight to facilitate minimally invasive deployment.
14. The intravascular filter of claim 9 , wherein said support structure and said filter configuration are formed primarily from a shape-memory material, said support structure and said filter configuration being set to said substantially helical form and said filter form, respectively, and being subsequently deformed to provide a substantially straight configuration in which said support structure and said filter configuration are substantially straight to facilitate minimally invasive deployment.
15. The intravascular filter of claim 14 , wherein, subsequent to a transition from said substantially straight state to said pie-set state, said support structure and said filter configuration are deformable so as to return to a substantially straight state to facilitate minimally invasive retrieval.
16. The intravascular filter of claim 9 , wherein said filter configuration further includes at least a second wire connected to said support structure, said second wire being configured to assume an additional predefined filter form configured to complement said filter form of said wire so as to form an enhanced obstacle to passage through the filter, in a direction parallel to said central axis, of particles having dimensions greater than the predefined value, wherein said support structure and said filter configuration are prepared in a substantially straight configuration to facilitate minimally invasive deployment.
17. The intravascular filter of claim 1 , wherein said support structure is formed with a plurality of small longitudinal slits and is configured to open up said slits to form a latticework type effect.
18. The intravascular filter of claim 1 , wherein said support structure and said filter configuration are formed as an elongated flat strip subdivided along a majority of its length by an elongated slit.
19. The intravascular filter of claim 1 , wherein said support structure and said filter configuration are formed as two lengths of wire connected together at at least one connection position.
20. The intravascular filter of claim 1 , wherein at least one of said support structure and said filter configuration is attached to, or integrally formed with, a guidewire in such a manner that the intravascular filter can be drawn into a catheter by withdrawal of said guidewire.
21. The intravascular filter of claim 1 , wherein said support structure and said filter configuration are formed primarily from Nitinol.
22. The intravascular filter of claim 1 , wherein said predefined filter form is a non-self-overlapping form as viewed parallel to said central axis.