Adjustable vascular ring, means for treating SFS syndrome and implantable kit comprising such a ring, mould and method for obtaining such a ring

Abstract

The invention relates to a perivascular ring having an inner diameter adjustable by inflation/deflation and adapted to be implanted and closed about a vessel for controlling the inner diameter of said vessel and thus the flow and/or pressure of a fluid flowing in said vessel. The ring of the invention is capable of regulating blood flow to the liver, in particular after an hepatectomy or hepatic transplant, and to substantially improve the survival chances of the patient. The ring according the invention has an adjustable inner diameter (O.sub.i) for implantation and locking about a vessel.

Claims

1. A ring for treating Small For Size syndrome suitable for hepatectomies and liver transplants, the ring having an adjustable inner diameter and being intended to be implanted and closed around the portal vein, upstream of the liver, in order to control the diameter of the portal vein and thus the flow rate and/or pressure of a fluid circulating in the portal vein, the ring comprising: an outer belt comprising two outer lips extending in the centrifugal direction and capable of being joined to one another in a diametral plane, in a reversible manner, in order to put the ring in a closed position around the portal vein, the outer belt having a constant diameter in the closed position; an inner chamber that can be inflated and deflated in the closed position, so as to vary an inner diameter of said inner chamber; a flexible inflation/deflation tube, a proximal end of which is connected to the inner chamber and a distal end of which is intended to be connected to inflation means; inflation means connected to the distal end of the flexible tube; and at least one suture to join the outer lips to one another to close the ring, the suture being selected to break in the event of overpressure in the ring, the outer belt and the inner chamber forming open collars, at least one of which is equipped with means for closing the ring around the portal vein; wherein the inner chamber, at rest and in the closed position, has an inner diameter corresponding to a smallest reduced diameter required when in use for controlling the diameter of the portal vein, the inner diameter of the inner chamber being configured to reduce by at the most 55% the diameter of the portal vein D.sub.vp to a minimal value D.sub.vpr, the inflation means being controlled to allow the modulation of the diameter of the portal vein D.sub.vp between the minimal value D.sub.vpr and a normal diameter D.sub.vpn in which the ring does not reduce the diameter of the portal vein D.sub.vp, said modulation consisting in deflating the ring in order to increase the inner diameter, so as to reduce the portal pressure downstream of the ring and maintain the intrahepatic pressure at a value less than or equal to 20 mm Hg.

2. The ring according to claim 1, wherein the inner chamber has no invagination at rest and in the closed position of the ring and in that the inner edge of the inner chamber intended to be in contact with the portal vein has a substantially circular shape.

3. The ring according to claim 1, wherein the inner diameter of the inner chamber decreases by inflation and increases by deflation.

4. The ring according to claim 1, wherein the reopening of the ring, after it is implanted and closed around the portal vein, is achieved by over-inflation of the inner chamber.

5. The ring according to claim 1, wherein said suture is threaded through at least one perforation made in said outer lips.

6. The ring according to claim 5, wherein the suture is resorbable.

7. The ring according to claim 1, comprising at least one radio-opaque part.

8. A kit that can be implanted by surgical route, allowing the adjustment of the inner diameter of a duct and thus the flow rate of a fluid circulating in this duct, this kit comprising: a ring according to claim 1; an inflation/deflation module intended to be connected to the distal end of the flexible inflation/deflation tube, in order to allow the in situ injection of an inflation/deflation fluid into the inner chamber or the in situ extraction of an inflation/deflation fluid out of the inner chamber.

9. The ring according to claim 1, wherein the inner diameter is adapted to reduce by at the most 50% the diameter of the portal vein D.sub.vp to the minimal value D.sub.vpr.

10. The ring according to claim 1, wherein the inflation means are controlled to reduce the portal pressure downstream of the ring and maintain the intrahepatic pressure at 15 mm Hg.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The following description of a preferred embodiment of the ring according to the invention, will highlight other remarkable features.

(2) This detailed description is given with reference to the attached figures in which:

(3) FIGS. 1A & 1B represent perspective views of the ring according to the invention, deflated and in the closed and open positions respectively.

(4) FIGS. 2A, 2B & 2C represent top views of the ring according to the invention, at rest and respectively in closed (2A) and open positions according to a preferred embodiment (FIG. 2C) and according to an embodiment variant (FIG. 2C), ready to be positioned around the duct.

(5) FIG. 3 is a longitudinal cross-sectional view along the cutting plane of FIG. 2A, 2B or 2C.

(6) FIGS. 4A & 4B are front views of the ring shown in FIGS. 2A & 2B or 2C respectively.

(7) FIG. 4C is a longitudinal cross-sectional view along the cutting plane IV-IV of FIG. 3.

(8) As shown in the attached figures the ring (1) according to the invention is a ring that can be inflated and deflated so as to vary its inner diameter (O.sub.i) so as to be able to compress and release the segment of biological duct for example of blood vessel such as the portal vein, around which said ring (1) is intended to be implanted and closed for controlling the flow circulating in the duct/vessel (2) represented by dot-and-dash lines in the figures.

(9) The ring (1) comprises: an outer belt (3); an inner chamber (4) that can be inflated and deflated; a flexible inflation/deflation tube (5).

(10) The outer belt (3) has a substantially constant inner diameter and outer diameter. This outer belt (3) is similar to an open collar (FIGS. 1B, 2B, 2C & 4B) the 2 free ends of which have closing means (7) comprising two outer lips (3.sub.1, 3.sub.2) extending in the centrifugal direction and having faces (3.sub.3, 3.sub.4) opposite one another in the open collar (FIGS. 1B, 2B, 2C & 4B) and in contact with one another in the closed collar (FIGS. 1A, 2A & 4A). As shown in FIGS. 2A, 2B, 2C and 3. These lips (3.sub.1, 3.sub.2) each comprise at least one, in the case in point one, perforation (3.sub.5), allowing the passage of at least one suture (not shown in the drawings) preferably resorbable, in order to ensure the closing (FIGS. 1A, 2A & 4A) of the ring (1) after implantation around the vessel (2) the flow rate of which is to be regulated. This suture completes the closing means (7). Advantageously, this suture is selected in order to break in the event of overpressure of the inner chamber (4) of the ring (1). This arrangement is a safety feature for preventing a stenosis of the duct, which could have irreversible consequences for the patient. This arrangement also allows the surgeon to open the ring (1) by over-inflation, before proceeding to remove this ring (1).

(11) This outer belt (3) is made of a semi-rigid material of hardness D1 and selected from the group of biocompatible elastomers, comprising or, even better, constituted by silicone elastomers or analogues.

(12) The inner chamber (4) is an inflatable and deflatable balloon having, at rest and in the closed position (FIG. 2A), a diameter (O.sub.ir), which corresponds to the minimum diameter value (+/−10%) desired for use, namely a diameter which restricts the diameter Dc of the duct around which it is positioned as soon as it is put in place. In the case of the human portal vein, the normal diameter or maximum value D.sub.vpn before reduction is, for example, comprised between 10 mm and 20 mm. The ring put in place and locked around the portal vein has an inner diameter O.sub.ir which determines a reduction of the portal flow rate preferably by at the most 50%.

(13) Under the effect of the inflation, the inner chamber (4) increases in volume in a centripetal direction, which reduces its inner diameter O.sub.i. The deflation produces a reduction in the volume of the inner chamber (4), in centrifugal direction, in order to compress or release respectively the vessel (2) of a patient (e.g. portal vein), around which the ring (1) is put in place and closed using the means (7).

(14) In the preferred embodiment shown in FIG. 2B, the open collar constituted by the outer belt (3) has an opening extending along a narrow channel delimited by the parallel faces 3.sub.3 and 3.sub.4 of the outer lips 3.sub.1 & 3.sub.2.

(15) In the embodiment variant shown in FIG. 2C, the open collar constituted by the outer belt (3) has an opening extending over an angular sector α.sub.3 equal to approximately 10° in this example. In this variant, the inner chamber (4) is an open collar the ends of which delimit an opening extending over an angular sector α.sub.4 equal to approximately 5°.

(16) As shown by the figures, in particular FIG. 3, this inner chamber (4) is annular and comprises, in the example shown in the drawings (FIG. 3), an outer wall (4.sub.1) in contact with and/or firmly fixed to the outer belt (3) and a curved inner wall (4.sub.2), the outer wall (4.sub.1) and the inner wall (4.sub.2) being connected to one another by lateral faces that are substantially straight in the example selected, but which could be curved and are denoted by the reference numbers (4.sub.3, 4.sub.4). The inner chamber (4) could be toroid-shaped according to a variant.

(17) The inner wall (4.sub.2) forms the inner edge of this inner chamber (4). This inner edge (4.sub.2) has a circular shape, when the ring is at rest (neither inflated: no internal overpressure, nor deflated: no internal low pressure) in the closed position (FIGS. 1A, 2A & 4A), and not arranged around a duct. According to the invention, this circular shape of the inner edge (4.sub.2), and, more generally, of the inner chamber (4) is maintained once the ring is arranged around a duct (e.g. vein) and during the inflation and deflation operations. This means that the inner chamber (4) forms no invagination, fold or bulge, either in the rest state, in the inflated state, or in the deflated state. The shape of the inner edge (4.sub.2) and, more generally, of the inner chamber (4), remains “substantially” flat and circular, once the ring is arranged around a duct (e.g. vein), from the inflated rest state to a further inflated state and a deflated state corresponding to the requirements of use. In the case of adjustment of the human portal flow rate, these inflated and deflated states are included, for example, within the following inner diameter O.sub.i limits (in mm and in increasing order of preference): [5-25]; [6-24]; [7-20].

(18) As shown in FIGS. 2A, 2B, 2C, 3, 4C, a radio-opaque band (4′) is inserted between the inner chamber (4) and the outer belt (3), in the outer wall (4.sub.2).

(19) The inner chamber (4) is, for example, made of a flexible material of hardness D2 and selected from the group of biocompatible flexible elastomers comprising or, even better, constituted by silicone elastomers or analogues.

(20) According to a preferred feature of the invention, the hardness D1 of the outer belt (3) is greater than the hardness D2 of the inner chamber (4). For example, D1 is comprised between 60 and 100, preferably 70-90, for example of the order of 80 Shore A.

(21) According to another preferred feature of the invention, the hardness D2 of the inner belt (4) is comprised between 5 and 40, preferably 10 and 30, and even more preferably of the order of 20 Shore A.

(22) The flexible inflation/deflation tube (5) is connected by its proximal end (5p) to the inside of the inner chamber (4) and by its distal end (5d) to inflation means not shown in FIG. 3. The inflation/deflation tube (5) is diametrically opposite the opening of the ring (1) as can be seen in FIGS. 1A, 1B, 2A, 2B, 2C, 3 and 4C. The outer belt (3) has an end piece (6) which extends towards the outside and which receives the proximal end (5p) of the inflation tube (5). This inflation tube (5) can be equipped with a plastic non-return valve.

(23) The inflation tube (5) can be made of the same material as the inner chamber (4), for example, with a hardness D3 comprised between D1 and D2, e.g. of the order of 60 Shore A.

(24) The inflation/deflation means (not shown in the drawings) are constituted for example by a syringe, preferably a screw syringe making it possible to make precise inflation/deflation adjustments by injection/tapping of the inflation/deflation fluid. The ring (1) according to the invention can be put in place around the vessel (2) by the standard surgical route (laparotomy) or by the coelioscopic route. The closing of the ring (1) is carried out by suture with resorbable sutures, though the perforation (3.sub.5) of the inner chamber (3)—closing means (7)—. The ring (1) thus positioned has a reduced inner diameter (O.sub.ir)) which restricts the vessel (2) to the smallest reduced diameter required for use (Dvpr) and thus limits the flow rate or pressure, for example blood, to a given level dependent on O.sub.ir. The practitioner then proceeds to adjust the flow rate and/or pressure, by inflation/deflation. In the case of hepatectomy or liver transplant, this adjustment aims to maintain an intrahepatic pressure less than or equal to 20 mm Hg, preferably 15 mm Hg. O.sub.i is gradually increased by deflation. D.sub.vp and with it the flow rate and/or the blood pressure in the portal vein therefore also increase(s) gradually, until D.sub.vp reaches D.sub.vpn (normal diameter or maximum diameter of the portal vein). The time taken for this rise of D.sub.vpr to D.sub.vpn is that which is necessary for hepatic parenchyma in order to recover a capacity to contain the intrahepatic pressure below 20 mm Hg, preferably below 15 mm Hg, for the pressure and/or the flow rate downstream of the ring, corresponding to a portal diameter equal to D.sub.vpn.

(25) This significantly limits the risks of SFS syndrome for the patient.

(26) The ring according to the invention, once closed by a suture or sutures, preferably bioresorbable, can be reopened by over-inflation of the inner chamber, which causes the suture or sutures to break. After opening the ring (1), the practitioner can also take advantage of the over-inflation of the ring (1), in order to keep the free ends of the ring (1) apart from each other and thus facilitate its extraction. This has the advantage of avoiding further anaesthesia and its associated risks.