Devices and methods for treating edema
The disclosure relates to devices and methods for the treatment of edema, which devices use a restrictor for flow compensation. Devices and methods of the invention further use a flow-restrictor in the circulatory system, upstream of an intravascular pump, to balance pressure changes induced by the pump and to compensate for downstream flow. The device may be provided as an indwelling, intravascular catheter with a mechanical pump such as an impeller and a selectively deployable restrictor such as an inflatable balloon. Congestive heart failure or edema is treated by\operating the pump in an innominate vein and using the restrictor for flow compensation, to restrict the upstream flow and thus amplify or maintain pressure reduction at the lymphatic outlet.
1. A device comprising:
a catheter with a proximal portion and a distal portion;
an impeller assembly connected to the distal portion, the impeller assembly comprising a housing with an inlet region, an outlet region, and an axis, and an impeller operably disposed within the impeller assembly; and
an expandable member disposed on an exterior surface of the impeller assembly, wherein, when in an expanded state, the expandable member comprises a proximal exterior surface extending at least partially parallel to the axis of the impeller assembly into the inlet region to form an outer boundary surface extending proximally over a portion of the inlet region, wherein the outer boundary surface defines a smooth, continuous funnel surface configured to direct flow into the housing without recirculation.
2. The device of claim 1 , wherein the impeller assembly comprises an inner cylindrical core coaxial with the impeller and extending through at least a portion of a length of the impeller, the cylindrical core comprising a proximal region, a central region, and a distal region, the cylindrical core extending between the inlet region and the outlet region of the housing, wherein the housing and the cylindrical core at least partially define a flow channel extending between the inlet region and the outlet region.
3. The device of claim 2 , wherein a core diameter at the proximal region of the cylindrical core is less than a core diameter at the distal region of the cylindrical core.
4. The device of claim 2 , wherein a core diameter in the central region of the cylindrical core is less than a core diameter at the proximal end and/or a core diameter at the distal end of the cylindrical core.
5. The device of the claim 4 , wherein the core diameter comprises a smooth tapered surface between the core diameter at the proximal end of the cylindrical core to the core diameter at the central region of the cylindrical core and from the core diameter of the central region to the core diameter of the distal region of the cylindrical core.
6. The device of claim 2 , further comprising a cuff positioned at the distal portion of the catheter and extending into a proximal portion of the impeller assembly, wherein the housing is attached to the cuff via one or more struts.
7. The device of claim 6 , wherein the one or more struts is substantially parallel to an axis of the impeller and protrudes radially inward from at least a portion of an inner surface of the housing.
8. The device of claim 6 , wherein a proximal end of the cylindrical core is spaced apart from a distal surface of the cuff, wherein the proximal end of the cylindrical core and the distal surface of the cuff comprise a controlled gap.
9. The device of claim 8 , wherein the gap is configured to remain fixed during operation of the impeller to define a transition between the cuff and the impeller such that blood flows across the gap without flow disturbance, flow recirculation, and/or vortices.
10. The device of claim 9 , wherein the impeller assembly is configured such that an axial velocity of fluid on a distal end of the gap is at least substantially equal to the axial velocity of fluid on a proximal side of the gap.
11. The device of claim 6 , wherein a cross-sectional diameter of the cuff decreases along a proximal end to a distal end in a substantially smooth transition.
12. The device of claim 11 , wherein the cross-sectional diameter of the cuff forms a guide surface configured to smoothly change a cross-sectional area at the inlet region, such that smooth contact surfaces are provided to achieve blood flow through the housing without recirculation.
13. The device of claim 12 , wherein the housing, the cuff, and the struts define inlets with rounded corners within the inlet region such that flow into the inlets and into the impeller assembly is achieved without recirculation.
14. The device of claim 6 , wherein the expandable member comprises a balloon.
15. The device of claim 14 , wherein the strut comprises an inflation lumen extending exterior to the strut for inflating the balloon disposed around the proximal portion of the impeller housing.
16. The device of claim 1 , wherein the expandable member comprises an expanded state and a collapsed state, wherein, when not expanded, the expandable member is attached to an outer surface of the impeller housing distal to the inlets.
17. The device of claim 16 , wherein an inner diameter of the expandable member is substantially equivalent to an outer diameter of the impeller housing, wherein a central axis of the expandable member and a central axis of the housing are substantially the same.
18. The device of claim 17 , wherein the inlet region comprises a distal rim comprising a bevel configured to provide a transition for the blood flow into the housing, wherein the expandable member is coupled to the housing along the distal rim such that the expandable member, when expanded, directs flow into the inlet region without recirculation.
19. The device of claim 1 , wherein the inlet region comprises one or more generally rectangular inlets configured to provide a larger inlet area at a distal-most region of the inlet region and the outlet region comprises one or more outlets around a distal portion of the impeller assembly, wherein operation of the impeller within a blood vessel drives blood into the impeller assembly via the generally rectangular inlets and out of the impeller assembly via the outlets such that the blood exhibits flow without recirculation or vortices.
20. The device of claim 1 , wherein when the impeller operates within a blood vessel, blood flows through the housing of the impeller without recirculation.
21. The device of claim 19 , wherein the outer boundary surface, the inlet region, and an inner surface of the housing are configured to form a smooth, continuous surface to align the fluid flow before entering the housing and to funnel fluid through the housing to minimize recirculation at the inlet region.
22. The device of claim 19 , wherein the funnel surface is configured to modulate a fluid pressure in a vicinity of the inlet region.
23. The device of claim 1 , wherein the expandable member is directly coupled to an exterior surface of the housing between the inlet region and the outlet region.
24. The device of claim 1 , wherein, when in an expanded state, at least a portion of the funnel surface extends parallel to the axis of the housing.
25. The device of claim 1 , wherein, when in an expanded state, the expandable member conforms to a vessel wall at a region of apposition.
26. The device of claim 1 , wherein, when in an expanded state, the expandable member defines a torus.
27. The device of claim 1 , wherein, when in an expanded state, the expandable member surrounds the impeller housing.
28. The device of claim 1 , wherein the axis of the housing is configured to be positioned substantially parallel to an axis of a vessel.
29. The device of claim 1 , wherein the housing comprises a rigid housing material.