Graft Systems Having Semi-Permeable Filling Structures and Methods for Their Use

• US 20120203264A1
• Filed: 01/23/2012
• Published: 08/09/2012
• Est. Priority Date: 01/21/2011
• Status: Active Grant

• Current Assignee: Endologix
• Original Assignee: Endologix
• Inventors: Karwa, Anupama, Colton, Clark K., Rao, K.T. Venkateswara, Ganpath, Raj P.
• Granted Patent: US 8,801,768 B2
• Time in Patent Office: Days
• US Class Current: 606/194
• CPC Class Codes: A61B 17/12118 for positioning in conjunction with a stent
• CPC Class Codes: A61B 17/12136 Balloons
• CPC Class Codes: A61B 17/12195 comprising a curable material
• CPC Class Codes: A61F 2/07 Stent-grafts
• CPC Class Codes: A61F 2/90 characterised by a net-like or mesh-like structure
• CPC Class Codes: A61F 2002/075 the stent being loosely attached to the graft material, e.g. by stitching
• CPC Class Codes: A61F 2002/077 having means to fill the space between stent-graft and aneurysm wall, e.g. a sleeve
• CPC Class Codes: A61F 2230/0034 D-shaped
• CPC Class Codes: A61F 2250/0003 having an inflatable pocket filled with fluid, e.g. liquid or gas

Abstract

Aneurysms are treated by filling at least one double-walled filling structure with a filling medium within the aneurysm, such as filling structures having a membrane that allows water molecules to permeate across the membrane in response to a water potential differential across the membrane. The transport of fluid across the membrane allows the bag to expand or shrink to accommodate changes in the size or shape of the aneurysm, thereby maintaining a seal between the filling structure against the vessel wall and maintaining apposition of the filling structure against the inside surface of the aneurysm. Transport of water molecules into or out of the filling structure is controlled by adjusting for the osmolarity of the filling fluid medium. The filling structures may be delivered over balloon deployment mechanisms in order to shape occlude the aneurysm and open a tubular lumen for flow of blood through the filling structure.

Claims

1. A system for treating an aneurysm in a blood vessel, said system comprising:

at least a first double-walled filling structure comprising an outer wall, an inner wall, and a fillable space there-between such that when filled, the outer wall conforms to the inside surface of the aneurysm and the inner wall forms a first generally tubular lumen to provide a path for blood flow, wherein the filling structure further comprises a membrane, the membrane permeable to water molecules so as to allow transport of water molecules across the membrane when a water potential differential exists across the membrane; and

a fluid filling medium for filling said fillable space, the fluid filling medium having a dissolvable solute.

2. The system according to claim 1, wherein the transport of water molecules across the membrane is caused by an osmotic gradient induced by a difference in osmolarity across the membrane.

3. The system according to claim 1, wherein the membrane comprises a semi-permeable material such that an osmotic gradient across the membrane causes water molecules to permeate across the membrane.

4. The system according to claim 1, further comprising:

a scaffold placed within at least a portion of the generally tubular lumen

5. The system according to claim 1, wherein the fluid filling medium comprises one or more fluid filling media that include a hardenable polymer.

6. The system according to claim 5, wherein the fluid filling medium comprises a hydrophilic polymer having dissolvable solutes sufficient to induce a desired osmotic gradient across the membrane.

7. The system according to claim 5, wherein the fluid filling medium further comprises serum and/or transudate.

8. The system according to claim 1, further comprising:

a scaffold placed within at least a portion of the generally tubular lumen.

9. The system according to claim 5, wherein the fluid filling medium further comprises a hyperosmotic medium relative to human blood.

10. The system according to claim 5, wherein the hardenable polymer comprises an aqueous polyethylene glycol (PEG)-diacrylate based formulation comprising a solute designed to maintain hypertonic and hyperosmotic conditions within the fillable space.

11. The system according to claim 1, wherein the outer and/or inner walls comprise ePTFE having an internodal distance ranging from 0.3 nanometers to 5 microns.

12. The system according to claim 1, wherein the fillable structure has a flux rate of water through the membrane of between 0.01 to 0.03 mL/day/cm².

13. The system according to claim 1, wherein the filling structure has a total filling capacity that is greater than the aneurismal space so as to allow for expansion of the filling structure to accommodate changes in a volume of the aneurysm.

14. The system according to claim 1, wherein the filling structure comprises one or more discrete semi-permeable bags that can separately expand when filled with fluid in response to transfer of fluid into the fillable space.

15. A self-adjusting endograft for treating an aneurysm in a blood vessel, said endograft comprising:

a generally tubular lumen to provide a path for blood flow body through the endograft;

a fillable component having a fillable space in fluid communication with an exterior environment surrounding the endograft across a semi-permeable membrane;

wherein the semi-permeable membrane allows transfer of fluid into the fillable space when a water potential within the fillable space is less than a water potential of an environment directly outside the endograft;

wherein the semi-permeable membrane allows flow of fluid out from the fillable space when the water potential within the fillable space is greater than the water potential of an environment directly outside the endograft; and

an outer wall adapted to conform to the inside surface of the aneurysm when the fillable space is filled.

16. A method for treating an aneurysm, said method comprising:

positioning at least a first double-walled filling structure across the aneurysm, the filling structure comprising a fillable space in fluid communication with an external environment surrounding the structure through a semi-permeable membrane;

filling the space with a fluid filling medium so that the outer wall conforms to and contacts an inside surface of the aneurysm and an inner wall forms a first generally tubular lumen to provide a first blood flow path across the aneurysm;

maintaining apposition of the outer wall with the inside surface of the aneurysm through controlled fluid transfer across the semi-permeable between the fillable space and the external environment.

17. The method of claim 16, wherein filling the filling structure comprises filling the structure with a fluid filling medium having an osmolarity sufficient to induce an osmotic pressure differential across the membrane so as to cause transport of water molecules across the membrane until an equilibrium point is reached, wherein a water potential inside the fillable space is roughly equal to the water potential surrounding the filling structure at the equilibrium point.

18. The method of claim 16, wherein the filling structure has a volume greater than a volume of the aneurysm and the outer wall comprises folds, and maintaining apposition of the outer wall with the aneurysm comprises:

filling the structure with water through the semi-permeable membrane to further expand the filling structure thereby unfurling the folds of the outer wall to maintain apposition between the outer wall and the inside surface of the aneurysm.

19. The method of claim 16, wherein the fluid filling medium comprises a hardenable polymer, the method further comprising:

placing at least a first scaffold within at least a portion of the first generally tubular lumen and expanding the first scaffold;

supporting the tubular lumen with the first scaffold during and/or after the filling structure is being filled; and

hardening the filling medium

20. The method of claim 16, wherein maintaining apposition comprises providing a salinity within the fillable space of the filling structure that is slightly higher than high range of blood salinities of a patient population so as to create a slightly positive osmotic pressure inside the fillable space.

21. The method of claim 16, wherein maintaining apposition comprises providing a salinity within the fillable space of the filling structure so as to provide an osmotic pressure gradient across membrane so as to avoid shrinkage of the filling structure over time.