Blood vessel tube
Apparatus and methods are described including a tube ( 20 ) that defines a flared downstream portion ( 30 ) that diverges toward a downstream end ( 32 ) of the tube, and a flared upstream portion ( 26 ) that diverges toward an upstream end ( 28 ) of the tube, such that a central portion ( 34 ) of the tube is narrower than at the ends of the tube. The tube defines a plurality of lateral openings ( 36 ). A support frame ( 24 ) supports the tube within a subject's vena cava, such that the downstream portion is sealed with respect to the wall of the vena cava downstream of junctions of the vena cava with all of the subject's renal veins, and the upstream portion is sealed with respect to the inner wall of the vena cava upstream of junctions of the vena cava with all of the subject's renal veins. Other applications are also described.
1. Apparatus for use with renal veins and a vena cava of a subject, the apparatus comprising:
a tube that defines:
a flared downstream portion thereof that diverges toward a downstream end of the tube, and a flared upstream portion thereof that diverges toward an upstream end of the tube, such that a narrow central portion of the tube is narrower than at the ends of the tube, and
a plurality of lateral openings; and
a support frame configured to support the tube within the subject's vena cava, such that:
the downstream portion of the tube is sealed with respect to an inner wall of the vena cava at a location that is downstream of junctions of the vena cava with all of the subject's renal veins, and
the upstream portion of the tube is sealed with respect to the inner wall of the vena cava at a location that is upstream of junctions of the vena cava with all of the subject's renal veins,
wherein the tube is configured to generate a region of low pressure within the narrow central portion, by blood flowing from the upstream end of the tube and through the narrow central portion of the tube,
the tube thereby being configured to reduce renal venous pressure of the subject by drawing blood from the subject's renal veins into the low pressure region via the lateral openings.
2. The apparatus according to claim 1 , wherein the plurality of lateral openings are shaped such as to converge toward a longitudinal axis of the tube.
3. The apparatus according to claim 1 , wherein an inner diameter of the tube at a location at which the inner diameter is at its maximum is greater than 12 mm.
4. The apparatus according to claim 1 , wherein an inner diameter of the tube at a location at which the inner diameter is at its minimum is less than 8 mm.
5. The apparatus according to claim 1 , wherein a ratio between an inner diameter of the tube at a location at which the inner diameter is at its maximum and an inner diameter of the tube at a location at which the inner diameter is at its minimum is greater than 3:1.
6. The apparatus according to claim 1 , wherein a length of the tube is greater than 20 mm.
7. The apparatus according to claim 1 , further comprising:
one or more blood pressure sensors configured to measure blood pressure within the vena cava; and
a computer processor configured to modulate a diameter of the central portion of the tube responsively to the measured blood pressure.
8. The apparatus according to claim 7 , wherein the one or more blood pressure sensors are configured to measure an indication of renal venous pressure of the subject.
9. The apparatus according to claim 7 , wherein the one or more blood pressure sensors are configured to measure an indication of central venous pressure of the subject.
10. The apparatus according to claim 7 , wherein the one or more blood pressure sensors are configured to measure an indication of lower-body venous pressure of the subject.
11. The apparatus according to claim 1 , wherein a ratio between an inner diameter of the tube at the upstream end of the tube and an inner diameter of the tube within the narrow central portion is greater than 3:1.
12. A method for use with renal veins and a vena cava of a subject, the method comprising:
providing a tube that defines:
a flared downstream portion thereof that diverges toward a downstream end of the tube, and a flared upstream portion thereof that diverges toward an upstream end of the tube, such that a narrow central portion of the tube is narrower than at the ends of the tube, and
a plurality of lateral openings; and
placing the tube within the subject's vena cava, such that:
the downstream portion of the tube is sealed with respect to an inner wall of the vena cava at a location that is downstream of junctions of the vena cava with all of the subject's renal veins, and
the upstream portion of the tube is sealed with respect to the inner wall of the vena cava at a location that is upstream of junctions of the vena cava with all of the subject's renal veins,
the tube generates a region of low pressure within the narrow central portion, by blood flowing from the upstream end of the tube and through the narrow central portion of the tube, and
the tube thereby reduces renal venous pressure of the subject by drawing blood from the subject's renal veins into the low pressure region via the lateral openings.
13. The method according to claim 12 , wherein providing the tube comprises providing the tube, the plurality of lateral openings being shaped such as to converge toward a longitudinal axis of the tube.
14. The method according to claim 12 , wherein providing the tube comprises providing the tube, an inner diameter of the tube at a location at which the inner diameter is at its maximum being greater than 12 mm.
15. The method according to claim 12 , wherein providing the tube comprises providing the tube, an inner diameter of the tube at a location at which the inner diameter is at its minimum being less than 8 mm.
16. The method according to claim 12 , wherein providing the tube comprises providing the tube, a ratio between an inner diameter of the tube at a location at which the inner diameter is at its maximum and an inner diameter of the tube at a location at which the inner diameter is at its minimum being greater than 3:1.
17. The method according to claim 12 , wherein providing the tube comprises providing the tube, a length of the tube being greater than 20 mm.
18. The method according to claim 12 , further comprising:
measuring blood pressure within the vena cava; and
modulating a diameter of the central portion of the tube responsively to the measured blood pressure.
19. The method according to claim 18 , wherein measuring blood pressure within the vena cava comprises measuring an indication of renal venous pressure of the subject.
20. The method according to claim 18 , wherein measuring blood pressure within the vena cava comprises measuring an indication of central venous pressure of the subject.
21. The method according to claim 18 , wherein measuring blood pressure within the vena cava comprises measuring an indication of lower-body venous pressure of the subject.
22. The method according to claim 12 , further comprising identifying the subject as suffering from a condition selected from the group consisting of: cardiac dysfunction, congestive heart failure, reduced renal blood flow, increased renal vascular resistance, arterial hypertension, diabetes, and kidney dysfunction, wherein placing the tube within the subject's vena cava comprises placing the tube within the subject's vena cava, in response to identifying the subject as suffering from the selected condition.
23. The method according to claim 22 , wherein placing the tube within the subject's vena cava comprises treating the selected condition by reducing renal venous pressure of the subject.
24. Apparatus for use with renal veins and a vena cava of a subject, the apparatus comprising:
a tube that defines:
a flared downstream portion thereof that diverges toward a downstream end of the tube, and a flared upstream portion thereof that diverges toward an upstream end of the tube, such that a central portion of the tube is narrower than at the ends of the tube, and
a plurality of lateral openings;
a support frame configured to support the tube within the subject's vena cava, such that:
the downstream portion of the tube is sealed with respect to an inner wall of the vena cava at a location that is downstream of junctions of the vena cava with all of the subject's renal veins, and
the upstream portion of the tube is sealed with respect to the inner wall of the vena cava at a location that is upstream of junctions of the vena cava with all of the subject's renal veins;
one or more blood pressure sensors configured to measure blood pressure within the vena cava; and
a computer processor configured to modulate a diameter of the central portion of the tube responsively to the measured blood pressure.
25. A method for use with renal veins and a vena cava of a subject, the method comprising:
providing a tube that defines:
a flared downstream portion thereof that diverges toward a downstream end of the tube, and a flared upstream portion thereof that diverges toward an upstream end of the tube, such that a central portion of the tube is narrower than at the ends of the tube, and
a plurality of lateral openings;
placing the tube within the subject's vena cava, such that:
the downstream portion of the tube is sealed with respect to an inner wall of the vena cava at a location that is downstream of junctions of the vena cava with all of the subject's renal veins, and
the upstream portion of the tube is sealed with respect to the inner wall of the vena cava at a location that is upstream of junctions of the vena cava with all of the subject's renal veins;
measuring blood pressure within the vena cava; and
modulating a diameter of the central portion of the tube responsively to the measured blood pressure.