GB2411842A - Balloon obturator for the aorta - Google Patents

Abstract

An aortic obturator comprises a sheath 24 adapted to be inserted through a suture secured to an ascending aorta 12. A balloon 32 is inserted through the sheath 24 and inflated with saline solution through cannula 28 to occlude the aorta 12. The balloon may be deflated and removed from the aorta using cannula 28 leaving the sheath 24 in place. A cardioplegia cannula 26 may be incorporated into the obturator. The cannula may be formed with and bend 30 near the balloon 32 which is straightened by a guide wire during insertion of the cannula 28, 26 through the sheath 24. The sheath 24 may include a pair of wings 22 which can be sutured to the aorta 12.

Description

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241 1 842 Title: Device and method for aorta occlusion during surgery on the heart or surrounding tissues

Field of invention

This invention concerns a method of occluding the aorta during surgery on the heart or surrounding tissues, and a device for use in the method. The method and device is intended to be employed in cardiac surgical procedures where the aorta needs to be occluded to isolate the heart from the rest of the patient circulation, to allow surgical corrections or repairs to be performed on the heart or the surrounding tissue.

Background

Current surgical practice is to use an external cross-clamping device and to separately perforate the wall of the ascending aorta to administer cardioplegia solution, to vent the aorta to clear it of excess blood and air, and to directly monitor the blood pressure in the aorta to gain diagnostic information in the case of particularly sick patients.

In conventional cardiac surgery the patient is subjected to the risk of particulate embolism as the current cross-clamping devices are quite traumatic to the aorta wall and can disrupt atheromatus plaque from the inner surface of the aorta wall which can then enter the blood stream and be carried to the brain, where the plaque can lodge in the capillary bed of the brain. This can result in a variable but permanent level of cerebral dysfunction.

Object of the invention It is an object of the invention to provide an improved aortic clamp which will reduce the embolitic risk to the patient. It is also an object of the invention to provide an improved method of aortic occlusion. It is also an object of the invention to provide a device and method which requires a smaller number of aorta perforations than has hitherto been required, thereby to enable surgery on the heart or surrounding tissue to be performed more safely and easily.

Summary of the invention

According to one aspect of the invention an aortic clamp comprises a sheath adapted to be inserted through a suture secured to an ascending aorta, and an inflatable balloon, which in use and in a deflated condition is inserted through the sheath into the aorta, a source of saline solution, and means for supplying saline solution to inflate the balloon when located within the aorta so as to occlude the aorta to enable surgery to be performed on the heart or surrounding tissue, and means for deflating the balloon by withdrawing the saline solution to enable the deflated balloon to be removed leaving the sheath in place to serve as a de-airing or pressure monitoring port, prior to removal and closure of the suture at the end of the procedure.

According to another aspect of the invention the saline for inflating the balloon is supplied thereto via a cannula which extends in use through the sheath and by which the deflated balloon can be extracted and removed.

According to a further aspect of the invention a cardioplegia cannula employed during surgery to supply cardioplegia solution to the heart, may be combined with the inflation cannula, so that in use both can be introduced into and removed from the aorta via the sheath.

A preferred sheath includes a pair of wings by which it can be sutured to a patient's ascending aorta.

According to another aspect of the invention, where the surgical procedure involves the use of aortic perfusion cannulae which are used to transmit (infuse) blood between the patient and a cardio-pulmonary bypass (CPB) machine, the sheath may be combined with one of the aortic perfusion cannulae which form an integral part of a CPB machine.

The invention therefore also lies in a combination of sheath as aforesaid and an aortic perfusion cannula, which combination in use is to be placed in an area of an aorta which is to be occluded to enable surgery to be performed on the heart or surrounding tissue.

Combining the sheath and one of the cannulae further simplifies the procedure for the surgeon as well as reducing the number of incisions in the aorta.

With the proposed device no additional perforations need be made into the aorta, therefore there is reduced risk to the patient.

Occluding the aorta from within by balloon inflation greatly reduces the amount of distortion of the aorta and therefore the disturbance of plaque lining the internal wall of the aorta.

One method of clamping an aorta during surgery comprises the following steps: 1) The patient is anaesthetised, the chest is opened via the sternum exposing the heart and aorta, to enable the patient to be connected to a cardio-pulmonary bypass (CPB) machine, in known manner, 2) A purse-string suture is sown to the apex of the patient's ascending aorta, 3) Using an introducer needle, a sterile sheath with tie-ring is inserted into the centre of the purse-string suture, which is then tightened in a known manner to produce a blood/air tight seal, 4) The introducing needle is removed, 5) A deflated balloon is then inserted through the sheath into the aorta until the balloon section is clear of the sheath, 6) Cardioplegia cannula and vent ports are then filled by pressure of the aorta to de-air them and they are then connected to the cardioplegia source machine, 7) The balloon is inflated with saline solution to a point where aortic occlusion is achieved, and 8) Cardioplegia solution is then delivered in known manner through the cardioplegia cannula to arrest and protect the heart so that surgery can proceed.

After surgery is completed the balloon is deflated and removed leaving the sheath available as a de-airing or pressure monitoring port until the surgeon is ready to close the chest.

Thereafter the sheath can be removed from the aorta and the purse-string suture is pulled together to control bleeding from the site.

Where the sheath also serves as a guide and entry passage for the cardioplegia solution delivery cannula, another method of clamping an aorta during surgery comprises the following steps: 1) The patient is anaesthetised, the chest is opened via the sternum exposing the heart and aorta, to enable the patient to be connected to a cardio-pulmonary bypass (CPB) machine, in known manner, 2) A purse-string suture is sown to the apex of the patient's ascending aorta, 3) Using an introducer needle a sterile sheath having a tie-ring is inserted into the centre of the purse-string suture, which is then tightened to produce a blood/air tight seal, s 4) The sheath tie ring is then sutured to the aorta so as to hold the sheath at a desired orientation relative to the aorta, 5) The introducing needle is removed, 6) An inflation cannula having a deflated balloon attached to its far end and itself jointed to a cardioplegia delivery cannula are inserted through the sheath into the aorta until they are clear of the sheath and the balloon is located wholly within the aorta, 7) If necessary, the cannulae are adjusted so as to position the deflated balloon on the aortic valve side of the sheath, 8) The cardioplegia cannula is then filled by pressure of the aorta to de- air it and it is then connected to a cardioplegia source, 9) The balloon is inflated with saline solution to a point where aortic occlusion is achieved, and lO)Cardioplegia solution is then delivered in known manner through the cardioplegia cannula to arrest and protect the heart so that surgery can proceed.

After surgery is completed the balloon is deflated and the deflated balloon, inflation cannula and cardioplegia delivery cannula, are removed, leaving the sheath as a de-airing or pressure monitoring port until the surgeon is ready to close the chest. Thereafter the sheath can be removed from the aorta and the purse-string suture is pulled together to control bleeding from the site.

During insertion a guide wire may be inserted into and through one of the cannulae, preferably the cardioplegia delivery cannula, and is withdrawn before the balloon is inflated.

In a preferred method, the two cannulae are joined so as to constitute a single entity for insertion and removal through the sheath so that only a single guide wire is necessary for straightening the two cannulae.

The cardioplegia cannula may be pre-formed with an elbow bend, the inflation cannula follows the shape of the former, and the guide wire causes the elbow to be straightened to permit insertion through the sheath.

After cardioplegia solution has been delivered the cardioplegia delivery cannula can be used to vent the heart chambers of excess blood and air.

The invention also lies in a device for insertion into the aorta to occlude the latter for use in either of the above methods.

In such a device, the cardioplegia delivery cannula may also serve as a vent to allow excess blood and air to be removed from the heart, and in this event the cannula may branch externally into a cardioplegia delivery port and a vent port, and in that event the cardioplegia cannula, the cardioplegia delivery port and the vent port, are all filled by aorta pressure, to de-air both ports and the cannula, before connection to the CPB machine.

Preferably the balloon is to be positioned centrally of the aorta before inflation and accordingly in a device embodying the invention, the balloon is preferably attached to the end of and communicates with a cannula which includes a pre-formed right angled elbow near the junction with the balloon but which is formed from resiliently deformable material and is maintained generally straight for the purpose of inserting it through the sheath by means of a stiff guide wire threaded through the cannula. After the balloon is clear of the inner end of the sheath, the wire is withdrawn to allow the elbow to reform and position the non- inflated balloon centrally of the aorta, ready for inflation.

Where the cardioplegia delivery cannula is also to enter the aorta through the sheath it is necessary for the delivery end of the cannula to communicate with the aorta on the aortic valve side of the inflated balloon. To this end, in a device embodying the invention the cardioplegia delivery cannula may also be pre-formed with an elbow similar to that provided in the inflation cannula and is formed from similar resiliently deformable material and the balloon is shaped like a doughnut and the delivery end of the cardioplegia cannula extends through and is sealed to the wall of the balloon which defines the central opening in the doughnut shape. The cardioplegia cannula is similarly straightened before insertion by a guide wire which, once it and the balloon have been fully inserted, is also withdrawn along with the guide wire through the balloon inflation cannula, so that the elbow can form in both cannulae.

In a preferred arrangement of device embodying the invention, the inflation cannula is a flexible tube joined along at least some of its length to the cardioplegia delivery cannula so that it will generally conform to the shape of the latter along its length, and the guide wire for the cardioplegia delivery cannula serves to straighten both cannulae to assist insertion, and when withdrawn, the pre-formed elbow in the cardioplegia delivery cannula forces a corresponding elbow to be formed in the inflation cannula. In this event only one guide wire Is required.

Preferably at least the cardioplegia delivery cannula is marked externally to indicate the direction in which the elbow will form and therefore the direction in which the open delivery end of the cannula will point after the guide wire is withdrawn. After the cannula has been inserted it (or both in the case of combined inflation and delivery cannulae) can be rotated in the sheath, if necessary, so that when the guide wire is withdrawn the elbow will position the balloon on the aortic valve side of the sheath and likewise point the open delivery end of the cardioplegia delivery cannula towards the aortic valve.

More preferably the cannulae are introduced into the sheath so that no rotation of either cannula is required after they have been pushed through the sheath.

Since it is preferable not to have to rotate the cannulae in the sheath, and to assist in correctly introducing the cannulae, in a device embodying the invention the interior of the latter and the exterior of the combined cardioplegia and inflation cannulae may be keyed or shaped so as to only permit insertion through the sheath with the cannulae correctly positioned relative to the sheath, so that the elbow will form in only one direction relative to the sheath, and preferably the sheath is marked so as to indicate which way it should be positioned relative to the aorta before being secured in plate, to ensure that the balloon and delivery end of the cardioplegia cannula are positioned on the aortic valve side of the opening through which the sheath protrudes.

In practice, most surgeons prefer to place a purse string suture before incising the aorta.

The methods proposed by the invention still enable a surgeon to do so.

The introductory (or introducer) needle is also relevant to reducing blood loss via the sheath. When the sheath is first inserted into the aorta it will be subjected to the blood pressure in that vessel which would cause blood to be ejected from the sheath. With an introducer needle blocking its lumen this would be prevented. After the sheath is in place, the needle is partially removed to allow the sheath to be clamped, and then fully removed, the clamp now stopping blood loss. The balloon device is then partially inserted into the sheath and the clamp is removed, (the balloon device is now stopping any major blood loss), and the balloon device is then fully inserted into the aorta and correctly orientated.

The invention also has application in the field of graft bypass surgery. In such a procedure, after the distal graft end has been sutured to the heart, the balloon clamp is deflated and removed through the sheath, "hereafter it can be replaced by a filter mesh (typically 120 micron mesh size) and the aorta is clamped using a side-clamp to allow the proximal graft end to be sutured to the aorta - a procedure known as proximal anastomosis. The action of the side- clamp is similar to a cross-clamp, therefore a deployed filter will catch any debris dislodged by the clamp. Once the side-clamp is removed the filter mesh can be retracted from the sheath and the procedure completed.

Accordingly the invention also comprises a combination of sheath and cannula, an inflatable balloon which can be inserted through the sheath in an uninflated condition and inflated to occlude an aorta and removed after deflation, and a filter mesh adapted to be inserted through the sheath and which after insertion is adapted to block the aorta with the mesh thereby to collect any debris while a further procedure is performed.

The invention will now be described by way of example with reference to the accompanying drawings in which: Fig 1 illustrates how the ascending aorta is conventionally occluded using a cross-clamp and shows the separate entry for the cardioplegia solution delivery cannula, Fig 2 is a cross-section through an aorta to which a sheath has been secured so as to protrude through the aorta wall to serve as a guide for both an inflation cannula and a cardioplegia delivery cannula, (which may also comprise the antegrade cannula connection to a heart bypass machine) in which the aorta is occluded by inflating a balloon at the end of the inflation cannula, Fig 3 is a similar view to that of Figure 1 in which the cross clamp and cannula 16 are replaced by the sheath 24 through which cannulae can protrude, so leaving clearer the area in which the surgeon is to operate, Fig 4 shows a luer connection combined with the sheath to accept monitoring or de-airing lines and give a blood/air tight seal for devices to be inserted, Fig 5 shows how an aortic cannula can be combined with the sheath and illustrates a balloon inserted after insertion, Fig 6 shows how a filtration mesh can be inserted in place of the balloon clamp, to collect debris dislodged during final stages of the procedure, and Fig 7 shows the use of a side clamp together with filtration mesh to give a surgeon a

blood-free field for proximal anastomosis.

In the drawings: A cross clamp 10 is shown closing off the ascending aorta 12 leading from the heart 14. A cardioplegia solution delivery cannula 16 is shown inserted through the aorta wall on the aortic valve side of the cross clamp 10. Other cannulae such as the arterial cannula 18 and the venous cannula 20 are also shown.

Fig 1 illustrates how the working environment for the surgeon in the immediate vicinity of the heart can rapidly become cluttered with the different cannulae and the protruding arms of the cross clamp 10. Any reduction in the number of protruding devices is therefore to be welcomed.

A preferred form of construction of a device embodying the invention is shown in Fig 2.

This device comprises an internally occluding device and combined cardioplegia solution delivery cannula, which can also serve as a vent and heart pressure monitoring port.

Instead of clamping the ascending aorta as shown in Fig 1, a purse-string suture 22 is sown to the wall of the aorta near the position of the clamp 10 in Fig 1, (instead of the clamp).

A device embodying the invention is then located in position, and comprises a tubular sheath 24 which is inserted centrally of the purse-string suture. By tightening the purse- string, the suture is sealed to the sheath to prevent loss of blood from, and entry of air into, the aorta.

Once inserted in the sheath a cardioplegia delivery cannula 26 and an inflation cannula 28 extend in parallel through the sheath. The former includes a pre-formed 90 elbow at 30 and the latter is sufficiently flexible and is joined to the delivery cannula 26 to allow it to follow the shape assumed by 26, and enters an uninflated balloon 32 which when inflated will assume a generally doughnut cannula shape. The point of entry is near the central opening of the doughnut shape.

The cardioplegia delivery cannula 26 extends through the central opening in the balloon cannulas and is sealed in the opening by being bonded to the balloon material as denoted by the bonding lines 25, 27.

Initially a straight stiff guide wire (not shown) is threaded through 26 to straighten the cannula (and with it the inflation cannula 28) to allow them to be inserted through the sheath 24. After insertion, and provided the uninflated balloon 32 is on the aortic valve side of the sheath 24 (and after withdrawal of the wire), to allow the 90 elbow 30 to reform in the cannula 26 (and therefore also the inflation cannula 28) the balloon is inflated using saline solution. This is supplied to the balloon via insertion cannula 28 under appropriate pressure via the luer lock 34 at the external end of the inflation cannula 28.

A port 36 at the outboard end of a pipe 38 serves as a guide wire entry. The pipe 38 merges with the cardioplegia delivery cannula 26 at 40 to become a common pathway below the junction. After the wire is removed, and after cardioplegia solution has been delivered to the heart via a luer lock 42, the cardioplegia cannula 26 can also serve as a vent.

Cardioplegia is a high potassium solution used to arrest the heart during surgery. It is delivered to the coronary arteries, and the cardioplegia delivery caMula is connected to a source of cardioplegia solution (not shown) via the luer lock 38.

Each luer lock 34 and 42 is a standard connection device for medical devices such as needles and syringes. The "lock" is a ring-like device which prevents accidental disconnection.

As previously mentioned, in order to allow the cannulae to be inserted through the sheath, 26 and 30 are held straight by a stiff metal guide wire (not shown) inserted through 36.

Once the cannulae are in place, the guide wire is removed, the cannula 26 can resume its pre-formed 90 elbow shape, and with it the cannula 28, and the balloon can be inflated.

After inflation by saline solution, the balloon will be doughnut shaped as shown in Fig 2, with the 90 bend 30 in 26 causing the cardioplegia solution to be delivered to the aortic valve side of the inflated balloon sited in the aorta.

At present, during most open-heart operations the aorta is occluded with a metal clamp to prevent blood flow to the coronary arteries. There are many papers suggesting that it is this action which significantly increases the release of debris and thus the increase in risk of cerebral damage.

It is believed that the inflatable balloon occlusion device proposed by the invention is a much safer and gentler way of occluding the aorta, and one which will release less debris into the bloodstream and thereby reduce the risk of cerebral damage.

Whilst the replacement of the clamp with an inflated balloon represents an advantage over current procedures, a further advantage is gained if the inflation cannula is combined with a cardioplegia delivery cannula (as shown in Fig 2), since this negates the need for a further incision in the aorta to accommodate the cardioplegia cannula.

Once the cardioplegia has been administered the delivery cannula can be disconnected from the source of cardioplegia solution and is available to be used as an aortic root vent if required. Aortic root venting involves sucking excess and unwanted blood which can accumulate in the aortic root from the chambers of the heart, whilst it is arrested for surgery.

After surgery is complete, if desired a wire can be reinserted through 36 to straighten the elbow 30, the balloon 32 can be deflated and withdrawn by withdrawing the cannulae 28 and 26, and the empty sheath 24 can be used to de-air the aorta very efficiently by virtue of its position, either passively or actively. In this connection passive de-airing is effected l by allowing air to auto-vent under its own pressure, whereas in active de-airing the sheath 24 is connected to an extraction pump or vacuum system to remove air from the aorta.

The empty sheath 24 can also be used for measuring direct aortic pressure by linking it to a blood pressure monitor once blood flow has resumed.

In order to accommodate different sizes of aorta which typically can vary from 30mm to SOmm in diameter, different balloon sizes are envisaged, having differing inflated diameters. Typically the different sizes involve Smm steps in inflated diameter although if the balloon material is sufficiently flexible lOmm steps in diameter could be envisaged.

Comparing Fig 1 with Fig 3 shows how the invention reduces the clutter in an already busy area.

According to a further aspect of the invention the sheath 24 may be combined with the arterial or aortic cannula 18 (see Figs 1 and 3) to further reduce the number of incisions which have to be made in the wall of the aorta. In such a combination the cannula 18 may also extend through the sheath 24. However whereas the balloon is positioned on the aortic valve side of the point of entry of the cannulae 26, 28 into the aorta, and the cannula 26 is arranged relative to the balloon 32 so that it will communicate with the aorta on the aortic valve side of the balloon when the latter is inflated, the cannula 18 is adapted to communicate with the interior of the aorta on the opposite side of the inflated balloon from that with which the cannula 26 communicates. Combining the cannula 18 and sheath 24 further reduces the equipment around the heart, thereby creating an even clearer environment in which a surgeon can operate.

In Fig 4 the sheath 24 is combined with a luer connection serving as an aortic cannula 18.

The sheath can accept monitoring or de-airing lines (not shown) and provides a blood/air tight seal for a device such as an inflatable balloon, to be inserted.

Fig 5 shows the combined aortic cannula 18 and sheath 24 of Fig 4 after a balloon has been inserted through the sheath 24 and inflated.

Figs 6 and 7 show how a filter mesh can be deployed through the sheath in place of a balloon. This is an advantage during graft bypass surgery. In such a procedure, the aorta is blocked using a balloon clamp inserted through a sheath as aforesaid, and after the distal end of the graft has been sutured to the heart (a procedure known as distal anastomosis), the balloon clamp is deflated and removed through the sheath and in accordance with another aspect of the present invention, a filter mesh 42 is inserted through the sheath and expanded within the aorta to filter the blood flow. The aorta wall is clamped using a side clamp 44 (see Fig 7) to allow the proximal graft to be sutured to the aorta wall (a procedure known as proximal anastomosis). The action of the side-clamp is similar to a cross-clamp, therefore a deployed filter will catch any debris dislodged. Once the side- clamp is removed the filter mesh 42 can be retracted from the sheath 24, and the general procedure completed.

The mesh size of the filter is typically 120 microns.

Typically the filter mesh is stretched over a generally circular ring which is formed from resiliently deformable material so that the filter can be crushed into a narrow pod-like configuration to enable it to be pushed through the sheath. Once it escapes from the lower end of the latter the ring resumes its normal shape and the mesh is stretched across the aorta cross-section, so as to filter any debris from blood flowing therethrough.

Claims (14)

1. An aortic clamp comprising a sheath adapted to be inserted through a suture secured to an ascending aorta, an inflatable balloon, which in use and in a deflated condition is insertable through the sheath into the aorta, a source of saline solution, means for supplying saline solution to inflate the balloon when located within the aorta so as to occlude the aorta to enable surgery to be performed on the heart or surrounding tissue, and means for deflating the balloon by withdrawing the saline solution to enable the deflated balloon to be removed leaving the sheath in place to serve as a de-airing or pressure monitoring port, prior to removal and closure of the suture at the end of the procedure.

2. An aortic clamp as claimed in claim 1 further comprising a cannula which in use extends through the sheath for the supply of saline for inflating the balloon and by which the deflated balloon can be extracted and removed.

3. An aortic clamp as claimed in claim 2 further comprising a cardioplegia cannula which is employed during surgery to supply cardioplegia solution to the heart, and which is combined with the inflation cannula, so that in use both can be introduced into, and removed from, the aorta via the sheath.

4. An aortic clamp as claimed in any of claims 1 to 3 wherein the sheath includes a pair of wings by which it can be sutured to for example a patient's ascending aorta, typically to a purse-string suture sown to the ascending aorta.

5. An aortic clamp as claimed in any of claims 1 to 4 wherein an aortic perfusion cannula is combined with the sheath, and in use the combination is placed in an area of an aorta which is to be occluded to enable surgery to be performed on the heart or surrounding tissue, thereby to simplify the procedure and reduce the number of incisions in the aorta.

6. An aortic clamp as claimed in any of claims 3 to 5 further comprising a guide wire adapted for insertion in use through one of the cannulae.

7. An aortic clamp as claimed in any of claims 3 to 6 wherein the two cannulae are joined so as to constitute a single entity for insertion and removal through the sheath.

8. An aortic clamp as claimed in claim 6 or 7 in so far as it depends from claim 6 wherein the guide wire is removable prior to inflating the balloon.

9. An aortic clamp as claimed in any of claims 6 to 8 wherein the cardioplegia cannula is pre-formed with an elbow bend and in use the inflation cannula follows the shape of the cardioplegia cannula and the guide wire straightens the elbow section to permit insertion through the sheath.

10. An aortic clamp as claimed in any of claims 2 to 9 wherein the balloon is attached to the end of and communicates with the cannula which includes a pre-formed right angled elbow near the junction with the balloon and is formed from resiliently deformable material and for the purpose of inserting it through the sheath is maintained generally straight by means of a stiff guide wire threaded through the cannula, whereby in use, after the balloon is clear of the inner end of the sheath, the wire can be withdrawn to allow the elbow to reform and position the non-inflated balloon centrally of the aorta into which it has been introduced, ready for inflation.

ll.An aortic clamp as claimed in claim 10 wherein a cardioplegia delivery cannula is combined with the inflation cannula, and the cardioplegia delivery cannula is also pre- formed with an elbow similar to that provided in the inflation cannula and is formed from similar resiliently deformable material, and the balloon is shaped like a doughnut having a central opening, and the delivery end of the cardioplegia cannula extends through and is sealed to that part of the wall of the balloon which defines the central opening in the doughnut shape, and whereby in use the cardioplegia cannula is similarly initially straightened by a guide wire which, once the cannulae and the balloon have been fully inserted, is also withdrawn along with the guide wire through the balloon inflation cannula, so that the elbow can form in both cannulae.

12. An aortic clamp as claimed in claim 10 wherein a cardioplegia delivery cannula is combined with the inflation cannula and the inflation cannula is a flexible tube joined along at least some of its length to the cardioplegia delivery cannula so that it will generally conform to the shape of the latter along its length, and a guide wire for the cardioplegia delivery cannula serves to straighten both cannulae to assist insertion, and when withdrawn, the pre-formed elbow in the cardioplegia delivery cannula forces a corresponding elbow to be formed in the inflation cannula, so that only one guide wire is required.

13. An aortic clamp as claimed in claim 11 or 12 wherein at least the cardioplegia delivery cannula is marked externally to indicate the direction in which the elbow will form and therefore the direction in which the open delivery end of the cannula will point after the guide wire is withdrawn.

14. An aortic obturator as claimed in claim 12 or 13 N7herein the filter is collapsible to allow it to he pushed through the sheath and is resiliently expansils71e to fi]1 the aorta when inserted.

14. An aortic clamp as claimed in any of claims 11 to 13 in which the interior of the sheath and the exterior of the combined cardioplegia and inflation cannulae are keyed or otherwise shaped so as, in use, to only permit insertion of the cannulae through the sheath in one orientation to assist in correctly introducing the cannulae, and so that the elbow will form in only one direction relative to the sheath.

15. An aortic clamp as claimed in claim 14 wherein the sheath is marked so as to indicate which way it should be positioned relative to an aorta before being secured in place, to ensure in use that the balloon and delivery end of the cardioplegia cannula are positioned on the aortic valve side of the opening through which the sheath protrudes.

16. A clamp as claimed in any of claims 1 to 15 when used to occlude the aorta of a patient during surgery.

17. An aortic clamp as claimed in any of claims 1 to 15 further comprising a filter mesh adapted to be inserted through the sheath after the balloon has been deflated and removed and which after insertion is adapted to block the aorta with the mesh thereby to collect any debris while a further procedure is performed.

18. An aortic clamp as claimed in claim 17 wherein the filter has a 120 micron mesh size.

19. An aortic clamp as claimed in claim 17 or 18 wherein the filter is collapsible to allow it to be pushed through the sheath and is resiliently expansible to fill the aorta when inserted.

20. A method of clamping an aorta during surgery comprising the following steps: l) The patient is anaesthetised, the chest is opened via the sternum exposing the heart and aorta, to enable the patient to be connected to a cardio-pulmonary bypass (CPB) machine, 2) A purse-string suture is sewn to the apex of the patient's ascending aorta, 3) Using a needle a sterile sheath having two wings is inserted into the centre of the purse-string suture, which is then tightened in a known manner to produce a blood/air tight seal, 4) The introducing needle is removed, 5) A deflated balloon is inserted through the sheath into the aorta until the balloon section is clear of the sheath, 6) Cardioplegia cannula and vent ports are de-aired as they are filled by pressure of the aorta, and they are then connected to the cardioplegia source machine, 7) The balloon is inflated with saline solution to a point where aortic occlusion is achieved, and 8) Cardioplegia solution is then delivered in known manner through the cardioplegia cannula to arrest and protect the heart so that surgery can proceed.

21. A method as claimed in claim 20 wherein 1) after surgery is completed the balloon is deflated and removed leaving the sheath available as a de-airing or pressure monitoring port until the surgeon is ready to close the chest, and 2) thereafter the sheath is detached from its tie-wing sutures and removed from the aorta and the purse-string suture is pulled together to control bleeding from the site.

22. A method of clamping an aorta during surgery in which an inserted sheath also serves as a guide and entry passage for the cardioplegia solution delivery cannula, comprising the following steps: 1) The patient is anaesthetised, the chest is opened via the sternum exposing the heart and aorta, to enable the patient to be connected to a cardio-pulmonary bypass (CPB) machine, 2) A purse-string suture is sewn to the apex of the patient's ascending aorta, 3) Using a needle a sterile sheath having a tie-ring is inserted into the centre of the purse-string suture, which is then tightened to produce a blood/air tight seal, 4) The sheath tie ring is then sutured to the aorta so as to hold the sheath at a desired orientation relative to the aorta, 5) The introducing needle is removed, 6) An insertion cannula having a deflated balloon attached to its far end and itself jointed to a cardioplegia delivery cannula are inserted through the sheath into the aorta until they are clear of the sheath and the balloon is located wholly within the aorta, 7) If necessary, the orientation of the cannulae is adjusted so as to position the deflated balloon on the aortic valve side of the sheath, 8) The cardioplegia cannula is then filled by pressure of the aorta to de- air it and it is then connected to a cardioplegia source, 9) The balloon is inflated with saline solution to a point where aortic occlusion is achieved, and 10) Cardioplegia solution is then delivered in known manner through the cardioplegia cannula to arrest and protect the heart so that surgery can proceed.

23. A method as claimed in claim 22 wherein 1) after surgery is completed the balloon is deflated and the deflated balloon, inflation cannula and cardioplegia delivery cannula, are removed, leaving the sheath as a deairing or pressure monitoring port until the surgeon is ready to close the chest, and 2) The sheath is removed from the aorta and the purse-string suture is pulled together to control bleeding from the site.

24. A method as claimed in claim 20 or 23 wherein during insertion a guide wire is inserted into and through one of the cannulae and is withdrawn before the balloon is inflated.

25. A method as claimed in claim 24 wherein the guide wire is inserted through the cardioplegia delivery cannula.

26. A method as claimed in any of claims 20 to 25 wherein the two cannulae are joined so as to constitute a single entity for insertion and removal through the sheath, so that only a single guide wire is necessary for straightening the two cannulae.

27. A method as claimed in any of claims 20 to 26 wherein the cardioplegia cannula is pre- formed with an elbow bend, the inflation cannula follows the shape of the former, and the guide wire causes the elbow to be straightened to permit insertion through the sheath.

28. A method as claimed in any of claims 20 to 27 wherein after cardioplegia solution has been delivered the cardioplegia delivery cannula is used to vent the heart chambers of excess blood and air.

29. A method as claimed in any of claims 20 to 28 wherein the cardioplegia delivery cannula also serves as a vent to allow excess blood and air to be removed from the heart.

30.A method as claimed in claim 29 wherein the cannula branches externally into a cardioplegia delivery port and a vent port, and in step 6 of claim 17 or step 8 of claim 19 the cardioplegia cannula, the cardioplegia delivery port, but the vent port are all filled by aorta pressure, to de-air both ports and the cannula, before connection to the CPB machine.

31.A method as claimed in any of claims 20 to 30 wherein the balloon is positioned centrally of the aorta before inflation.

32.A method as claimed in claim 31 whereinthe balloon is attached to the end of and communicates with a cannula which includes a pre-formed right angled elbow near the junction with the balloon but which is formed from resiliently deformable material and is maintained generally straight for the purpose of inserting it through the sheath by means of a stiff guide wire threaded through the cannula, such that in use, after the balloon is clear of the inner end of the sheath, the wire is withdrawn to allow the elbow to reform and position the non-inflated ballooon centrally of the aorta, ready for inflation.

33. A method as claimed in any of claims 20 to 32 where the cardioplegia delivery cannula is also to enter the aorta through the sheath, and wherein the delivery end of the cannula communicates with the aorta on the aortic valve side of the inflated balloon.

34. A method as claimed in claim 33 wherein the cardioplegia delivery cannula is also pre- formed with an elbow similar to that provided in the inflation cannula and is formed from similar resiliently deformable material and the balloon is shaped like a doughnut and the delivery end of the cardioplegia cannula extends through and is sealed to that part of the wall of the balloon which defines the central opening in the doughnut shape, and the cardioplegia cannula is similarly straightened before insertion by a guide wire which, once it and the balloon have been fully inserted, is also withdrawn along with the guide wire through the balloon inflation cannula, so that an elbow can form in both cannulae.

35. A method as claimed in claim 33 wherein the inflation cannula is a flexible tube joined along at least some of its length to the cardioplegia delivery cannula so that it will generally conform to the shape of the latter along its length, and the guide wire for the cardioplegia delivery cannula serves to straighten both cannulae to assist insertion, and when withdrawn, the pre-formed elbow in the cardioplegia delivery cannula forces a corresponding elbow to be formed in the inflation cannula.

36. A method as claimed in any of claims 33 to 35 wherein at least the cardioplegia delivery cannula is marked externally to indicate the direction in which the elbow will form and therefore the direction in which the open delivery end of the cannula will point after the guide wire is withdrawn, and in use after the cannula has been inserted it (or both in the case of combined inflation and delivery cannulae) can be rotated in the sheath, so that when the guide wire is withdrawn the elbow will position the balloon on the aortic valve side of the sheath and likewise point the open delivery end of the cardioplegia delivery cannula towards the aortic valve.

37. A method as claimed in any of claims 33 to 35 wherein the cannulae are introduced into the sheath so that no rotation of either cannula is required after they have been pushed through the sheath.

38. A method as claimed in claim 37 wherein the interior of the sheath and the exterior of the combined cardioplegia and inflation cannulae are keyed or shaped so as to only permit insertion through the sheath with the cannulae correctly positioned relative to the sheath, so that the elbow will form in only one direction relative to the sheath, to assist in correctly introducing the cannulae.

39. A method as claimed in claim 38 wherein the sheath is marked so as to indicate which way it should be positioned relative to the aorta before being secured in place, to ensure that the balloon and delivery end of the cardioplegia cannula are positioned on the aortic valve side of the opening through which the sheath protrudes.

40. A method as claimed in any of claims 20 to 39 wherein a purse string suture is put in place before incising the aorta.

41. A method as claimed in claim 20 or 22 or any claim dependent thereon, wherein the introducer needle is employed to block the sheath and prevent blood loss, the needle is partially withdrawn to allow the sheath below the needle to be clamped to prevent blood loss, after which the needle is fully removed from the sheath, and therafter the deflated balloon is introduced into the sheath, the clamp is removed and the balloon device is fully inserted into the aorta, the presence of the balloon device serving the same purpose as the introducer needle previously, in stopping significant blood loss until inflated when all further blood loss is prevented.

42. A method as claimed in any of claims 19 to 40 when employed in a surgical procedure involving the grafting of a bypass between heart and aorta, wherein after the distal graft end has been sutures to the heart, the balloon clamp is deflated and removed through the sheath, "hereafter it is replaced by a filter mesh and the aorta is clamped using a sideclamp to allow the proximal graft end to be sutured to the aorta, the filter serving to catch any debris dislodged by the clamp.

43. A method as claimed in claim 42 wherein after the side-clamp is removed the filter mesh is retracted from the sheath and the procedure completed.

Amendments to the claims have been filed as follows

AS

1. An aortic obturator comprising a sheath adapted to be inserted through a suture secured to an ascending aorta, an inflatable balloon, which in use and in a deflated condition is :insertahle through the sheath into the aorta, a source of saline solution, means for supplying saline solution to inflate the balloon when located within the aorta so as to occlude the aorta to enable surgery to be performed on the heart or surrounding tissue, and means for deflating the balloon by withdrawing the saline solution to enable the deflated balloon to be removed leaving the sheath in place to serve as a de-airing or pressure monitoring port, prior to removal and closure of the suture at the end of the procedure, further comprising a cannula which in use extends through the sheath for the supply of saline for inflating the balloon and by which the deflated balloon can be extracted and removed, and a cardioplegia cannula which is employed during surgery to supply cardioplegia solution to the heart, and which is combined with the inflation cannula, so that in use both can be introduced into, and removed from, the aorta via the sheath, a guide wire adapted for insertion in use through one of the cannulae, and wherein the cardioplegia cannula is pre-formed with an elbow bend and in use the inflation cannula follows the shape of the cardioplegia cannula, but on being inserted the guide wire straightens the elbow section to permit insertion through the sheath.

2. An aortic obturator as claimed in claim 1, wherein the sheath includes a pair of w ings by which it can be sutured to a p,atient.'s ascending aorta, typically to a purse-string suture soon to the ascG-rdingi aorta.

3. An aortic obturator as claimed claims 1 or 2, wherein an aortic perfilsion cannula is combined faith tne sheath, and in use The comhinatiQn is placed In an area Off an aorta N'hiCh iS lo lie.:,ccluded co enable surger to be performed fin the heart or qurrrinndir! tissue, thereby to simplify the procedure and reduce iDe number of incisions in the aorta.

4. An aortic obturator as claimed in any of claims 1 to 3, wherein the two cannulae are joined so as to constitute a single entity for insertion and removal through the sheath.

5. An aortic obturator as claimed in any c,f claims I to 4, in so far as it depends from claim 6 Wherein the guide wire is rerr.orable prior to inflating tile balloon.

6. An aortic obturator as claimed in any of claims 1 to 5 wherein the balloon is attached to the end of and communicates with the cannula Which includes a pre-formed right angled elbow near the junction with the balloon and is formed from resiliently deformable material and for the purpose of inserting it through the sheath is maintained generally straight by means of a stiff guide wire threaded through the cannula, whereby in use, after the balloon is clear of the inner end of the sheath, the wire can be withdrawn to allow the elbow to reform and position the non-inflated balloon centrally of the aorta into which it has been introduced, ready for inflation.

7. An aortic obturator as claimed in claim 6 wherein a cardioplegia delivery cannula is combined with the inflation cannula, and the cardioplegia delivery cannula is also pre- formed With an elbow similar to that,oroNtided in the inflation cznula and is also formed from resiliently deformable material, and the balkori is shaped like a doughnut having a central opening, and the delivery end of the cardioplegia cannula extends through and is sealed to that part of the wall of the balloon Which defines the central OPeT1inO IT), the doJglnut shape, and -'.ere,y;r' vise the cardic,l-,]cgia cannuia is similarly initially' .stra;rhtened h>' a Guide N'irC Which, once the cannulae and the i,i'iI:i<,;i ii-c Cecil,1]! iil.s-icu i.< aisle:<i,ncia aim Ni.f the ouiclc bare itrcugI ale balloon ir.Tlarion cadenza, so mat Able eil:!ow can term in both cannulae.

S. An aortic obturator as claimed in claim IS, wherein a cardiopleia deliN!ely cannuia is :1;' ;!n he '"-t'!-; '' ,1,! --3 I- : -- :;l-: . . A-: ::; ,- . ill, a; along at least some of its length to the cardioplegia delivery cannula so that it will generally conform to the shape of the latter along its length, and a guide wire for the cardioplegia delivery cannula serves to. straighten troth cannulae to accist insertion' and when withdrawn, the pre-formed elbow in the cardioplegia delivery cannula forces a corresponding elbow to be formed in the inflation cannula, so that only one guide wire is required.

9. An aortic obturator as claimed in claim 7 or 8, wherein at least the cardioplegia delivery cannula is marked externally to indicate the direction in Which the elbow will forth and therefore the direction in which the open delivery end of the cannula will point after the guide wire is withdrawn.

10. An aortic obturator as claimed in any of claims 7 to 9, in which the interior of the sheath and the exterior of the combined cardioplegia and inflation cannulae are keyed or otherwise shaped so as, in use, to only permit insertion of the cannulae through the sheath in one orientation to assist in correctly introducing the cannulae, and so that the elbow will form in only one direction relative to the sheath.

11.An aortic obturator as claimed in claim 10 wherein the sheath is marked so as to indicate which way it should be positioned relative to an aorta before being secured in place, Lo ensure in use that the balloon and delivery end of the cardioplegia cannula are positioned on the aortic valve side of the opening through which the sheath protrudes.

12. An aortic obturator as c]ain:ed in any of claims i to 1 I further comprising a filter mesh adapted tc, be inserted thr,ooh tl?e llec.th, a ft:er tl-!O >4llo.':in has l-,een de:-lated and removed.

I?. Ion,.or,i Obtcli-aeG: As;:lai;^;ed in Claire 12 Abel i'-i iDe Wilier has a 12G -micron inesh size.