Fistula formation devices and methods therefor
Described here are devices, systems, and methods for forming a fistula between two blood vessels. Generally, the systems may comprise a first catheter and a second catheter, which may comprise one or more fistula-forming elements. The first and second catheters may comprise one or more magnets, which may be used to assist in bringing the first and catheters in closer proximity to facilitate fistula formation. In some variations, the magnet may have a plurality of magnetic domains each characterized by a magnetic flux vector, with the magnetic flux vectors of the magnet passing through a common magnetic origin.
1. A system for creating a fistula between two vessels, comprising:
a first catheter comprising a first magnet; and
a second catheter comprising a second magnet;
wherein at least one of the first and second catheters comprises a fistula-forming element; and
wherein the first magnet is a focused magnet characterized by a first magnetization pattern comprising a first plurality of magnetic flux vectors, wherein each of the first plurality of magnetic flux vectors intersects a first magnetic origin located a first measurable distance away from the first magnet.
2. The system of claim 1 , wherein the first magnet comprises a longitudinal axis, and wherein the first magnetic origin comprises a line oriented parallel to the longitudinal axis of the first magnet.
3. The system of claim 2 , wherein the first magnet has an approximately D-shaped cross-section and a longitudinal apex, wherein the magnetic origin is offset from the longitudinal apex by between about 0.25 mm and about 0.5 mm.
4. The system of claim 1 , wherein the second magnet is a focused magnet characterized by a second magnetization pattern comprising a second plurality of magnetic flux vectors, wherein each of the second plurality of magnetic flux vectors intersects a second magnetic origin located a second measurable distance away from the second magnet.
5. The system of claim 4 , wherein the first plurality of magnetic flux vectors is directed toward the first magnetic origin and the second plurality of magnetic flux vectors is directed away from the second magnetic origin.
6. The system of claim 5 , wherein the first magnetic origin and the second magnetic origin at least partially overlap.
7. The system of claim 4 , wherein the second magnet comprises a longitudinal axis, and wherein the second magnetic origin comprises a second line oriented parallel to the longitudinal axis of the second magnet.
8. The system of claim 1 , wherein the first magnet comprises a longitudinal axis, and wherein the first magnetic origin comprises a first line oriented perpendicular to the longitudinal axis of the first magnet.
9. The system of claim 1 , wherein the first and second magnets are configured such that when rotational misalignment between the first and second magnets is greater than about 35 degrees, an attractive force between the first and second magnets is less than about 50 percent of an attractive force when the rotational misalignment between the first and second magnets is zero.
10. The system of claim 1 , wherein the fistula-forming element comprises an electrode.
11. A system for creating a fistula between two vessels, comprising:
a first catheter comprising a first magnet, wherein the first magnet is a focused magnet comprising a first magnetization pattern characterized at least partially with a first plurality of magnetic flux vectors, wherein a first portion of the first plurality of magnetic flux vectors is oriented in a first orientation and a second portion of the first plurality of magnetic flux vectors is oriented in a second orientation non-parallel to the first orientation; and
a second catheter comprising a second magnet;
wherein at least one of the first and second catheters comprises a fistula-forming element.
12. The system of claim 11 , wherein the second magnet is a focused magnet comprising a second magnetization pattern characterized at least partially with a second plurality of magnetic flux vectors, wherein a first portion of the second plurality of magnetic flux vectors is oriented in a third orientation and a second portion of the second plurality of magnetic flux vectors is oriented in a fourth orientation non-parallel to the third orientation.
13. The system of claim 12 , wherein the first and second portions of the first plurality of magnetic flux vectors are directed toward a first common locus, and wherein the first and second portions of the second plurality of magnetic flux vectors are directed away from a second common locus.
14. The system of claim 13 , wherein the first common locus and the second common locus at least partially overlap.
15. The system of claim 11 , wherein the fistula-forming element comprises an electrode.