Intravascular cannulation apparatus and methods of use

This invention is a cannulation apparatus, and related methods for providing indirect access to a surgical site within a patient. The cannulation apparatus includes at least two fluid flow paths that are slidable coupled (40) (50) to one another, and selectively positional within the patient. The first, the second flow path s may be advanced through a single incision disposed remotely from the surgical field to first, and second predetermined locations within the patient. Exemplary sites for the incision include the groin region or in the neck region of the patient. The cannulation apparatus, and method of the present invention are particularly suited for use in providing cardiopulmonary support during cardiac surgery, including coronary artery bypass graft surgery. The cannulation apparatus of the present invention also provides an entry site for one or more support devices used in the surgical procedure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and devices for cannulation and, more particularly, to an intravascular cannulation assembly having at least two flow paths slidably coupled to one another suitable for use in a variety of cardiac procedures.

2. Description of Related Art

Cannulas and cannulation techniques are used in medical applications for transporting fluid into or out of the body. An area of proliferated use is cardiac surgery, where cannulation is routinely employed to transport fluid into, out of, or between various points in the circulatory system. This may be done for the purpose of performing cardiac procedures including, but not limited to, cardiopulmonary bypass (CPB), as well as left-heart and/or right-heart assist procedures.

The role of cannulation in cardiac surgery may be described by way of example with reference to coronary artery bypass graft (CABG) surgery. CABG surgery involves connecting a source of arterial blood downstream from a narrow or occluded section of a coronary artery for the purpose of providing an improved supply of oxygenated blood to the vasculature of the heart. The source of blood is often an internal artery, and the target is typically among the anterior or posterior coronary arteries. CABG surgery may be either open chest or closed chest (minimally invasive). Open chest CABG involves performing a sternotomy to spread the chest apart and provide access to the heart. Closed chest CABG surgery involves accessing the heart through conduits extending into the chest cavity, such as by thoracotomy. CABG surgery may also be performed on a stopped heart or a beating heart.

During stopped heart and beating heart CABG surgery, it is necessary to provide additional circulatory support in order to maintain the hemodynamic stability of the patient. For stopped heart CABG surgery, this is accomplished by establishing full cardiopulmonary bypass (CPB), wherein blood is diverted from the lungs for artificial oxygenation at a remote location. This may be referred to as providing “full” cardiac support. For beating heart CABG surgery, this is preferably accomplished by providing right-heart and/or left-heart assistance, wherein blood is rerouted from one location in the heart to another under the direction of a blood pump so as to obviate the need for an artificial oxygenator, filter, tubing, saline, etc. This may be referred to as providing “partial” cardiac support. Rerouting the blood during beating heart surgery may also serve to unload a selected chamber of the heart in an effort to stabilize the tissue and thus make it easier for the physician to perform the grafting procedure.

The process of placing a patient on full or partial cardiac support is conventionally accomplished using two cannulas. In stopped heart CABG surgery, the first cannula is placed in the right atrium as an inflow or suction cannula, while the second cannula is placed in the aorta as an outflow or return cannula from the oxygenator. In beating heart CABG surgery, the first cannula may be placed in the right or left atrium, and the second cannula placed within the aorta or pulmonary artery depending upon what side of the heart is being assisted. In either case, placement of the cannulas may be direct or indirect. Direct cannulation involves introducing the cannula directly into the desired heart chamber or major vessel extending directly from the heart (i.e. aorta or pulmonary artery). Indirect cannulation involves advancing the cannula intravascularly into the desired heart chamber or major vessel extending directly from the heart (i.e. aorta or pulmonary artery).

Direct cannulation systems of the prior art suffer a variety of drawbacks. A first drawback is that cannulation can only be performed so long as the chest cavity is maintained open. Another drawback is that introducing the cannulas and related tubing through the chest cavity reduces the field of surgery, that is, the amount of space within which the surgeon has to operate. In addition to reducing the field of surgery, the surgeon must make separate incisions for each cannula, with each incision presenting a potential site for leakage and infection. Direct cannulation through the chest cavity also lengthens the overall time required to perform a CABG procedure because the surgeon must personally position each cannula after opening up the chest cavity. This increases the overall time that the patient's chest will be open and exposed to atmosphere. It is also more costly and ties up valuable hospital resources (i.e. beds, staff, etc . . . ) for a longer period, which can be especially troubling in emergency room situations where a limited number of beds and staff are commonplace.

Indirect cannulation overcomes many of the above-enumerated drawbacks associated with direct cannulation. Indirect cannulation advantageously provides the ability to perform closed chest cardiac surgery in that a sternotomy is not required to access the heart. Indirect cannulation can also be maintained well after the given cardiac procedure is completed. This is advantageous in providing continued circulatory support after a procedure has been completed, as well as providing the ability to close the chest following open chest surgery without jeopardizing cannulation. Indirect cannulation also reduces the clutter from the field of surgery so as to avail more space for the surgeon. It provides the ability to have someone other than the physician establish cannulation. In so doing, indirect cannulation allows the doctor to perform the cardiac procedure in the least amount of time, thereby reducing cost.

While indirect cannulation presents significant improvements over direct cannulation, the prior art indirect cannulation systems are nonetheless flawed. One disadvantage of prior art indirect cannulation systems is that the cannulas are rigidly fixed to one another and thereby do not provide any degree of adjustability between the distal ends of the cannulas. This severely restricts the ability to place a particular cannula assembly in the appropriate locations in the circulatory system. In so doing, it will result in much guess-work in selecting a cannulation assembly of the appropriate size. Inefficiency in selecting and placing an appropriately sized cannulation assembly translates into increased costs, both in terms of hospital resources (i.e. beds, staff, etc . . . ) as well as the unnecessary costs associated with discarding cannulation assemblies that were introduced into the circulatory system and later found out to be inappropriately sized for the intended cardiac support function. Prior art indirect cannulation systems are also limited in terms of their flow characteristics.

The present invention is directed at eliminating and/or reducing the effects of the foregoing drawbacks of prior art.

SUMMARY OF THE INVENTION

One aspect of the present invention involves a cannulation assembly for providing circulatory support. The cannulation assembly comprises a first flow path for transporting blood between a pump and a first predetermined location within the circulatory system of a patient. A second flow path is provided for transporting blood between a pump and a second predetermined location within the circulatory system of a patient. The first and second flow paths are slidably coupled to one another and dimensioned to extend, in use, into the respective first and second predetermined locations through a single incision formed in the vascular system of the patient.

In one embodiment of the cannulation assembly, the first and second flow paths are disposed in a generally coaxial arrangement with the second flow path disposed at least partially within the first flow path.

In one embodiment of the cannulation assembly, the first and second flow paths are coupled together in a generally side-by-side arrangement.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an auxiliary lumen.

In one embodiment of the cannulation assembly, the auxiliary lumen is sized to receive at least one of a guide wire, a pressure sensor, and an optical instrument.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an expandable guiding structure.

In one embodiment of the cannulation assembly, the first flow path intakes blood to the pump and the second flow path outputs blood from the pump.

In one embodiment of the cannulation assembly, the first flow path outputs blood from the pump and the second flow path intakes blood to the pump.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with at least one of a flow rate sensor, a pressure sensor, and an optical sensor.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an auxiliary fluid flow lumen.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with a bend for directing the flow path to the respective first or second predetermined location in the circulatory system.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths includes a section of material capable of being selectively deformed to create a bend in the flow path to facilitate guiding the flow path into the respective first or second predetermined location in the circulatory system.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with a plurality of apertures for facilitating fluid flow into or out of the respective first or second flow paths.

In one embodiment of the cannulation assembly, the first flow path includes a plurality of drainage apertures to facilitate fluid flow through the first flow path.

In one embodiment of the cannulation assembly, the second flow path includes a narrow region that, in use, is disposed approximately adjacent to the drainage apertures of the first flow path.

In one embodiment of the cannulation assembly, the second flow path includes a wide region that, in use, is disposed approximately adjacent to the drainage apertures of the first flow path.

In another aspect of the present invention, a cannulation assembly is provided comprising a first flow path slidably coupled to a second flow path such that the first and second flow paths may be introduced into the vascular system of a patient through a single incision and positioned at respective first and second predetermined locations within the circulatory system of the patient.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is independently positionable relative to the incision after being inserted into the vascular system of the patient.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is the distance between a distal end of the first flow path and the distal end of the second flow path may be selectively adjusted by selectively sliding one of the first and second flow paths relative to the other.

In one embodiment of the cannulation assembly, the first and second flow paths are configured such that, in use, the distal end of the second flow path will be located a fixed distance from the distal end of the first flow path.

In one embodiment of the cannulation assembly, the first and second flow paths are disposed in a generally coaxial arrangement with the second flow path disposed at least partially within the first flow path.

In one embodiment of the cannulation assembly, the first and second flow paths are coupled together in a generally side-by-side arrangement.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an auxiliary lumen.

In one embodiment of the cannulation assembly, the auxiliary lumen is sized to receive at least one of a guide wire, a pressure sensor, and an optical instrument.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an expandable guiding structure.

In one embodiment of the cannulation assembly, the first flow path intakes blood to the pump and the second flow path outputs blood from the pump.

In one embodiment of the cannulation assembly, the first flow path outputs blood from the pump and the second flow path intakes blood to the pump.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with at least one of a flow rate sensor, a pressure sensor, and an optical sensor.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with an auxiliary fluid flow lumen.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with a bend for directing the flow path to the respective first or second predetermined location in the vascular system.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths includes a section of material capable of being selectively deformed to create a bend in the flow path to facilitate guiding the flow path into the respective first or second predetermined location in the vascular system.

In one embodiment of the cannulation assembly, at least one of the first and second flow paths is equipped with a plurality of apertures for facilitating fluid flow into or out of the respective first or second flow paths.

In one embodiment of the cannulation assembly, the first flow path includes a plurality of drainage apertures to facilitate fluid flow through the first flow path.

In one embodiment of the cannulation assembly, the second flow path includes a narrow region that, in use, is disposed approximately adjacent to the drainage apertures of the first flow path.

In one embodiment of the cannulation assembly, the second flow path includes a wide region that, in use, is disposed approximately adjacent to the drainage apertures of the first flow path.

A still further aspect of the present provides a method for providing circulatory support. The first step involves withdrawing blood from a first predetermined location in the circulatory system of a patient. The second step involves returning the withdrawn blood to a second predetermined location in the circulatory system of the patient. The steps of withdrawing and returning are performed by providing a cannula having a first flow path slidably coupled to a second flow path, wherein the first and second flow paths are dimensioned to extend, in use, respectively into the first and second predetermined locations through a single incision formed in the vascular system of the patient.

In one embodiment of the circulatory support method, the incision is formed in one of the aorta, carotid artery, femoral artery, radial artery, axillary artery, interior jugular vein, external jugular vein, inferior vena cava, superior vena cava, brachiocephalic vein, radial vein, pulmonary artery, and pulmonary vein.

In one embodiment of the circulatory support method, the incision is formed at one of a location between the aorta and carotid artery, the aorta and the femoral artery, the aorta and the radial artery, the aorta and the axiallary artery, the inferior vena cava and the femoral vein, the superior vena cava and the interior jugular vein, and the superior vena cava and the brachiocephalic vein.

In one embodiment of the circulatory support method, the first and second predetermined locations comprise respectively the right atrium and the pulmonary vein.

In one embodiment of the circulatory support method, the first and second predetermined locations comprise respectively the left ventricle and the aorta of the patient.

In one embodiment of the circulatory support method, the second flow path is coaxial with and extends at least partially within the first flow path.

In one embodiment of the circulatory support method, the first and second flow paths are coupled together in a generally side-by-side arrangement.

In one embodiment of the circulatory support method, the first flow oath is advanced to the first predetermined location using the Seldinger technique.

In one embodiment of the circulatory support method, the second flow path is advanced to the second predetermined location using a guiding device.

In one embodiment of the circulatory support method, the second flow path is advanced to the second predetermined location using a flow directed guiding device.

In one embodiment of the circulatory support method, the guiding device comprises a guide wire supported within a dedicated auxiliary lumen formed in the second flow path.

In one embodiment of the circulatory support method, at least one of the first and second flow paths is advanced using the cut down technique.

Yet another aspect of the present invention provides a method for inserting a cannula assembly into a patient. The method comprises the steps of: (1) forming a single incision in the vascular system of the patient; (2) providing a cannula assembly having a first flow path slidably coupled to a second flow path; (3) advancing a distal end of the first flow path through the incision to a first predetermined location within the circulatory system of the patient; and (4) advancing a distal end of the second flow path through the incision to a second predetermined location within the circulatory system of the patient.

In one embodiment of the cannula assembly insertion method, the incision is formed in one of the aorta, carotid artery, femoral artery, radial artery, axillary artery, interior jugular vein, external jugular vein, inferior vena cava, superior vena cava, brachiocephalic vein, radial vein, pulmonary artery, and pulmonary vein.

In one embodiment of the cannula assembly insertion method, the incision is formed at one of a location between the aorta and carotid artery, the aorta and the femoral artery, the aorta and the radial artery, the aorta and the axiallary artery, the inferior vena cava and the femoral vein, the superior vena cava and the interior jugular vein, and the superior vena cava and the brachiocephalic vein.

In one embodiment of the cannula assembly insertion method, the first and second predetermined locations comprise respectively the right atrium and the pulmonary vein.

In one embodiment of the cannula assembly insertion method, the first and second predetermined locations comprise respectively the left ventricle and the aorta of the patient.

In one embodiment of the cannula assembly insertion method, the second flow path is coaxial with and extends at least partially within the first flow path.

In one embodiment of the cannula assembly insertion method, the first and second flow paths are coupled together in a generally side-by-side arrangement.

In one embodiment of the cannula assembly insertion method, the first flow path is advanced to the first predetermined location using the Seldinger technique.

In one embodiment of the cannula assembly insertion method, the second flow path is advanced to the second predetermined location using a guiding device.

In one embodiment of the cannula assembly insertion method, the second flow path is advanced to the second predetermined location using a flow directed guiding device.

In one embodiment of the cannula assembly insertion method, the guiding device comprises a guide wire supported within a dedicated auxiliary lumen formed in the second flow path.

In one embodiment of the cannula assembly insertion method, at least one of the first and second flow paths is advanced using the cut down technique.

A still further aspect of the present invention provides a method for providing circulatory support. The method comprises the steps of: (1) providing a first flow path slidably coupled to a second flow path; (2) advancing a distal tip of the first flow path through an incision formed in the vascular system of a patient to a first predetermined location in the circulatory system of a patient; (3) advancing a distal tip of the second flow path through the incision to a second predetermined location in the circulatory system of the patient; (4) withdrawing blood from the first predetermined location in the circulatory system of the patient; and (5) returning the withdrawn blood to the second predetermined location in the circulatory system of the patient.

In one embodiment of the circulatory support method, the incision is formed in one of the aorta, carotid artery, femoral artery, radial artery, axillary artery, interior jugular vein, external jugular vein, inferior vena cava, superior vena cava, brachiocephalic vein, radial vein, pulmonary artery, and pulmonary vein.

In one embodiment of the circulatory support method, the incision is formed at one of a location between the aorta and carotid artery, the aorta and the femoral artery, the aorta and the radial artery, the aorta and the axiallary artery, the inferior vena cava and the femoral vein, the superior vena cava and the interior jugular vein, and the superior vena cava and the brachiocephalic vein.

In one embodiment of the circulatory support method, the first and second predetermined locations comprise respectively the right atrium and the pulmonary vein.

In one embodiment of the circulatory support method, the first and second predetermined locations comprise respectively the left ventricle and the aorta of the patient.

In one embodiment of the circulatory support method, the second flow path is coaxial with and extends at least partially within the first flow path.

In one embodiment of the circulatory support method, the first and second flow paths are coupled together in a generally side-by-side arrangement.

In one embodiment of the circulatory support method, the first flow path is advanced to the first predetermined location using the Seldinger technique.

In one embodiment of the circulatory support method, the second flow path is advanced to the second predetermined location using a guiding device.

In one embodiment of the circulatory support method, the second flow path is advanced to the second predetermined location using a flow directed guiding device.

In one embodiment of the circulatory support method, the guiding device comprises a guide wire supported within a dedicated auxiliary lumen formed in the second flow path.

In one embodiment of the circulatory support method, at least one of the first and second flow paths is advanced using the cut down technique.

Another aspect of the present invention provides a method of circulating fluid through a cannula system comprising a cannulation assembly including at least two flow paths slidably coupled to each other. The method comprises the steps of: (1) inserting the cannulation assembly into a first predetermined location in a body through a vascular incision; (2) establishing flow communication between a first one of the flow paths and the first predetermined location; (3) slidably moving a second one of the flow paths into a second predetermined location spaced apart from the first predetermined location; (4) establishing flow communication between the second flow path and the second predetermined location; (5) coupling the first and second flow paths to a pump system; and (6) operating the pump system to transport fluid from the first predetermined location for introduction into the second predetermined location.

DETAILED DESCRIPTION OF THE INVENTION

The present invention involves a cannulation assembly for use in any of a number of broad ranging applications involving the introduction and/or removal of fluids into and/or from the body. The cannulation assembly of the present invention is particularly suited for use in cardiac applications, although it is to be readily understood that the cannulation assembly and methods of the present invention are not to be limited to cardiac applications. By way of example only, the cannulation assembly of the present invention is useful in certain cardiac application, including, but not limited to, procedures involving coronary bypass graft (CABG), cardiopulmonary bypass (CPB), left-heart and/or right-heart assist, open chest and closed chest (minimally invasive), cannulation of a vessel, bridge-to-transplant and/or failure-to-weanfrom-bypass.

The term “cannula” as used herein is to be defined as a hollow (although not necessarily tubular) instrument designed to be introduced into a body cavity for the purpose of transporting fluid into or out of the body cavity. The term “catheter” as used herein is to be defined as a slender flexible tube of minimal diameter that can be inserted into a bodily channel, such as a vein, for guiding and/or sensing purposes. The term “vascular system” as used herein is to be defined as the network of arteries and veins in the body with the exception of the heart and major vessels extending directly therefrom. The term “circulatory system” as used herein is to be defined as the entire network of arteries and veins in the body, including the heart and major vessels extending directly therefrom. The term “incision” as used herein is to be construed as any hole, opening, or aperture formed in a vessel or body.

FIG. 1illustrates an exemplary embodiment of a cannulation assembly30of the present invention. Cannulation assembly30includes an inner cannula40and an outer cannula50. The proximal ends of inner cannula40and outer cannula50remain outside the patient's body31during use. Inner and outer cannulas40,50may be connected to a pumping system (not shown) used for augmenting blood flow during beating heart surgery. One exemplarly pump is a reverse flow pump of the type described in the commonly assigned, co-pending PCT Application No. PCT/US97/18674, the contents of which are hereby incorporated by reference. A major advantage of such an arrangement is the placement of the pump system and attendant connections, sensors, and other equipment out of the immediate vicinity of the beating heart surgical procedure, freeing up space in which the surgeon can operate. Other advantages include a low priming volume requirement as the pump system can be located closer to the patient's body (i.e. near the patient's neck region) since that region is not being operated on. Additionally, the insertion procedure for the cannulation assembly can be performed prior to the surgical operation, by someone other than the surgeon, such as the anesthesiologist, thereby reducing the length of time required for the heart surgery itself.

The cannulation assembly30can be adapted for use in various applications in which fluids are introduced and removed from the body. For purposes of more clearly describing the present invention, the cannulation assembly30will be described in terms of use in providing right heart support through the internal jugular vein. However, it is to be understood that the assembly30can be configured and adapted by, for example, increasing or decreasing the cannula size and/or number such that the assembly30can be beneficially used for other medical applications in which fluids are introduced and removed from the body. More specifically, the device of the present invention may be utilized to provide circulatory support through indirect or remote access of the patient's circulatory system. As used herein, the terms “indirect access” or “remote access” refers to accessing the patient through an incision formed in the patient's vascular system. Indirect or remote access is differentiated from direct access in that direct access typically involves a sternotomy in order to access the patient's circulatory system. Exemplary points for indirectly accessing the patient in accordance with the present invention include, but are not necessarily limited to, the brachiocephalic vein, carotid artery, axillary artery, and femoral vein.

InFIG. 1, the cannulation assembly30of the present invention is shown an assembled configuration. The outer cannula50, which forms part of an outer cannula assembly70, is dimensioned to receive the inner cannula40through an interior lumen (not shown). In the embodiment shown, a y-connector55is provided for sealingly mating with the outer cannula50to form an outer cannula assembly70. It is to be readily appreciated that the connector55is presented by way of example only and that the cannulation assembly30of the present invention is not dependent upon a particular type of connector. During operation, distal end58of outer cannula50and distal end49of inner cannula40lie in the patient's body, penetrating through an incision in the patient's tissue31. In one embodiment, the distal end58of outer cannula50serves to withdraw blood and the distal end49of inner cannula40serves to reintroduce the blood into the body. Proximal end48of inner cannula40and proximal end56of outer cannula50protrude out of the patient's body and interface with surgical equipment such as a reverse flow pump system (not shown) for augmenting the blood flow as discussed above.

As seen inFIGS. 2 and 3, inner cannula40comprises a substantially tubular structure having a wall44defining a main lumen42. The length of the cannula40is application specific and depends for example on the size of the patient and the distance from the incision in the neck to the destination in the patient's pulmonary system. In a CPB application, the pulmonary artery is the destination into which blood is returned into the patient from the pump system via inner cannula40, and the dimensions of inner cannula40are selected accordingly.

Inner cannula40is provided at its proximal end48with a connector46, which is suitably sized to interface with various surgical instruments (not shown), such as the output (or intake, in some applications) portions of a reverse flow pump (not shown). Inner cannula40may be provided with one or more holes43disposed at distal end49, in addition to the open tip47of its substantially cylindrical structure, in order to permit more efficient fluid passage. Further, distal tip49of inner cannula40is tapered to allow insertion into the internal jugular vein.

FIGS. 4 and 5show the details of outer cannula assembly70, which generally comprises an outer cannula50mated with a y-connector55. Outer cannula50has a main lumen52defined by a substantially tubular wall54. Main lumen52extends longitudinally between the proximal end56and distal end58of the outer cannula50. Again the length of the cannula50and main lumen52are selected depending on the size of the patient and other factors as discussed above. Tubular walls44and54of cannulas40and50can be formed of materials ranging from rigid to flexible, and in the preferred embodiment comprise a semi-rigid transparent material such as polyurethane or silicone having a hardness of between about30A and90A on a Shore durometer scale and capable of withstanding sterilization by ethylene oxide (ETO). Rigid clear materials can be used for the y-connector55, and preferably y-connector55is constructed of polycarbonate or polyvinyl chloride. The cannulas40and50may also contain radiopaque markings (not shown) to determine placement within the patient's body. To provide structural reinforcement, a spiraling wire (not shown) can be provided for support of the walls44and54. The spiraling wire (not shown) may be molded into the walls or is otherwise supported therein, and may extend either partially or fully across the length of the cannulas40and50. The wire facilitates handling of the cannulas and reduces the possibility of the cannulas' collapsing or being pinched shut and thus closing off the flow of fluid to or from the patient. Other ways of reinforcing the tubular bodies of the cannulas40and50are known in the art and will adapt equally well to the present invention. In addition, no reinforcement may be needed if the cannula material is sufficiently rigid or if sufficient fluid flow is present within the cannulas.

One or more pre-formed curves may be provided in the inner cannula40and/or the outer cannula50. Referring briefly toFIG. 2, the preformed curves, designated as32and34in inner cannula40, facilitate cannula maneuverability during insertion in the patient's body, permitting the negotiation of tortuous passages such as through the atria, ventricular valve and pulmonary valve. The angle of the pre-formed curves may be anywhere in the range of 0-180°, with the curves being disposed anywhere along the length of the cannulas40,50and in any one or more distinct planes, depending on the particular application. The curves may also be of an adjustable angle, formed by expandable joints. In one such construction, illustrated inFIG. 6, the inner cannula40may be provided with expandable joint82for changing the length and/or orientation of distal end49with respect to the body of inner cannula40by passing a current through or eliminating a current through joint82. Joint82is constructed of a memory shaped material which, in the presence of current, will either change length or shape depending upon the characteristics of material used. An example of such a material for use in joint82is Nitinol™, commercially available from Educational Innovations, Inc. 151 River Road, Cos Cab Conn. 06807. As illustrated inFIG. 7, distal end49of cannula40may be initially bent as shown, whereby a strip84of Nitinol™ is placed within the tubular wall of cannula40and initially shaped to form curvature83in cannula40. Curvature83may be selectively changed by passing a current within the Nitinol™ wire84, thereby allowing the operator to change the position and orientation of distal end49. In another construction of an adjustable lumen, cables may be provided which serve to impart or relieve forces inducing deformation and curvature of the cannula.

Referring once again toFIGS. 4 and 5, attached at distal end58of outer cannula50is tip60formed of a bio-compatible, preferably polymeric, material adapted to rigidly retain the inner cannula40in position within outer cannula50. The diameter of lumen52is selected to be larger than the outer diameter of inner cannula40to thereby permit fluid passage through main lumen52in the presence of inner cannula40in main lumen52. Tip60is preferably of a more rigid construction than the material of tubular wall54to provide better support for cannula40and for insertion into the body. In addition to a main channel62for passage of inner cannula40, tip60is also provided with peripheral holes64for efflux of fluid to or from outer cannula50. Peripheral holes64are formed between supports65extending substantially longitudinally along tip60, preferably having a tapered shape with a decreasing diameter in the direction of the distal end of tip60. The combined area of the holes64is greater than the sectional area between the inner cannula40and outer cannula50, thereby allowing partial blockage of holes64without loss of flow through tip60or outer cannula50.

Y-Connector55provides a means for interfacing the inflow and outflow portions of the pump system (not shown) with the cannulas40and50. It is to be understood that other types of connectors can be used to effect this interface. Additionally, the range of different types of pumps with which the invention can be practiced is broad because of the reduced priming volume and the novel arrangement of the cannulas with respect to the patient. Examples of possible pumps include, but are not limited to, co-axial reverse flow pumps, roller pumps, and centrifugal pumps.

As shown in more detail inFIG. 8, y-connector55comprises first channel57and second channel59, defined by substantially tubular walls, which converge into main channel61extending co-axially with first channel57. Hemostasis valve63(FIG. 9) is provided at proximal end66of y-connector55and serves to form a seal around for example inner cannula40once inner cannula40is fitted therethrough. A fitting67is provided at distal end68of y-connector55, fitting67adapted to mate with proximal end56of outer cannula50to form a fluid-tight seal therewith. Additionally, a fitting69is provided at channel59to facilitate mating with other cannulas or similar apparatus (not shown) such as PVC tubing adapted to receive an ultrasonic flow meter like that used in the Transonic T110 lab tubing flow meter known in the art. Fitting69can be similar or identical to fitting67.

FIGS. 10-12show an exemplary arrangement of a second type of connector—parallel connector100—which can be used to achieve a cannulation assembly90similar to cannulation assembly30in accordance with the invention. Specifically, outer cannula50is provided at its proximal end56with a tube86inserted into main lumen52. Also inserted into main lumen52and adjacent tube86is inner cannula40, and a suitable, bio-compatible adhesive87is used to retain tube86and cannula40in place in outer cannula50. An exemplary adhesive which may be used is an ultraviolet-cured bio-compatible glue. Surrounding tube86, inner cannula40, outer cannula50and adhesive87, at the juncture of these components, is sheathing structure85operating to form a fluid-tight seal. Sheathing structure85may for instance comprise a heat responsive material disposed over the juncture and then heated for activating and shrinking it to the appropriate size and specification.

The surgical procedure in accordance with the invention generally follows the Seldinger technique, adapting it to the novel use for entry through the brachiocephalic (jugular) vein or carotid artery using the unique cannula arrangement herein disclosed. Accordingly, the first step of the procedure involves locating and piercing the patient's vessel using a long, hollow needle89attached to a syringe88as seen in FIG.13. When blood enters the syringe88, the distal end of a thin guide wire35is inserted through the needle89and into the vessel92. The needle is then removed, leaving guide wire35in place in the vessel92(see FIG.14). The proximal end of guide wire35is passed through a dilator33, disposed axially within the outer cannula assembly70such that its end36protrudes through tip60as shown in FIG.15. (At this point, outer cannula50does not contain inner cannula40—that is, cannulation assembly30is not in the assembled configuration). Distal end36of dilator33, appropriately shaped, is inserted into the vessel to thereby expand the incision, followed by outer cannula50, which is then either partially or fully inserted into the vessel (FIG.16). Dilator33is then withdrawn.

The above procedure is followed by the inner cannula insertion procedure required to achieve the assembled configuration of the cannulation assembly30in accordance with the invention. Inner cannula insertion can be performed using one of several options. One option involves withdrawing guide wire35and inserting a balloon catheter (not shown) through hemostasis valve63. Balloon catheters are known in the art and generally comprise an inflatable balloon disposed at a distal tip of a catheter having a fluid channel for transferring inflating fluid. The balloon catheter is threaded through the outer cannula assembly70, the brachiocephalic vein, the superior vena cava, right atrium and into the pulmonary artery. The balloon catheter is advanced into position by operation of the balloon as a “sail”, whereby the balloon is inflated using the inflating fluid and powered by the natural blood flow to the destination. The balloon catheter is then used to guide the inner cannula40into place in the same manner as a guide wire, with the inner cannula40being threaded over the balloon catheter and advanced into position. With the cannulation assembly30thus in the assembled configuration and the inner and outer cannulas40and50in the desired bypass positions in the body as shown exemplarily inFIG. 17, the balloon catheter is withdrawn and the bypass operation commenced.

A second option for inserting inner cannula40into position within the patient's body is to use the guide wire35itself to guide the inner cannula40to its final destination. A particularly suitable guide wire for this would be one of the J-hook type which would facilitate negotiation of the tortuous turns involved, especially between the right atrium and pulmonary artery. Additionally, as discussed above, this negotiation is further facilitated by the one or more preformed curves32,34provided at distal end49of inner cannula40. Alternatively, a guidewire may be inserted into the balloon catheter to stiffen the catheter so that the cannula can be placed within the patient's body.

Alternatively, insertion in accordance with the invention may be effected utilizing the “cut down” techniques, whereby prior to insertion an incision is made in the patient's tissue, exposing the vein or artery to be accessed. The tissue and nerves surrounding the vein/artery are retracted and an incision is made in the vein/artery. After making the incision the cannula is placed within the vein/artery and advanced into the desired position. If the cannula cannot be advanced through the incision in the vein/artery, an optional dilator may be utilized to expand the diameter of the vein/artery.

It is contemplated that devices such as a steerable obturator can be used to guide inner cannula40—and, with suitable modification,.outer cannula50—into place in the surgical site. Moreover, although during the guiding process the guiding devices such as the balloon catheter and the guide wire35are advanced through cannulas40and50via main lumens42and52, respectively, it is also contemplated that dedicated secondary lumens127and129may be provided in the cannulas for this purpose as illustrated inFIGS. 30 and 31. Secondary lumens127and129may be formed integrally in the walls of the cannulas during the manufacturing process of the cannula, with the lumens being utilized to support the guiding device as the cannula is advanced to its destination, thus freeing up main lumens42and52for other device applications, such as equipment to monitor saturated venous oxygen (SV02), pressure and flow rate monitoring devices, etc.

Alternatively, as detailed below, these devices can be integrated into the cannula or supported in secondary lumens127and129. For example, as shown inFIGS. 18 and 19, secondary lumens37and38can be configured for fluid communication with main lumen52via ports41and51and used to house therein differential pressure transducers45,47and attendant wiring39used in the determination of fluid flow rate inside or outside cannulas40and50as described in more detail in the commonly owned and co-pending U.S. patent application Ser. No. 09/280,970 the contents of which are hereby incorporated by reference. Other types of pressure transducers can also be used and mounted in pairs (see transducers74and75ofFIG. 20) integrally in the tubular wall of the cannulas in proximity to either the interior or exterior of the cannula-depending on whether an interior or exterior fluid flow rate determination is desired, thereby dispensing with the need for dedicated secondary lumens.

Secondary lumens are suitable to serve in a variety of surgery-facilitating fashions. For example, as shown inFIGS. 21 and 22, lumens37and38can adjustably support one or more light guides53,71for projecting light, via a projecting tip72, from the cannula to aid in its visualization as detailed in the commonly owned, co-pending U.S. patent application Ser. No. 09/280,967 (the contents of which are hereby incorporated by reference) or for optically sensing specific blood parameters such as oxygen saturation level. Similarly, lumens137and138provided in inner cannula40can be used for delivery of fluid to or from the distal tip49, in order to for example dispense medication or, as shown inFIGS. 23 and 24and detailed in the commonly owned and co-pending U.S. patent application Ser. No. 09/280,970, to inflate a balloon73provided at the tip of inner cannula40to aid in guiding the cannula to its destination during insertion without relying on separate guiding means.FIGS. 25 and 26respectively show the use of cannulas40and50in conjunction with heating elements76,77and thermistors78,79disposed on a surface thereof. Thermistors78and79operate to measure fluid temperature downstream from the heating elements76and77to thereby determine fluid flow rate based on the deviation from the starting temperature as is known in the art. The measurements are relayed to appropriate processing circuits80and81for implementing the flow rate calculations. Those of ordinary skill in the art will recognize that the utility of the secondary lumens37,38,137and138can be extended to other applications, and the examples mentioned above are not intended to be limiting. Additionally, combinations of the above applications for the secondary lumens can be used in either or both inner cannula40and outer cannula50in accordance with the invention without inventive departure from the spirit and scope thereof.

FIG. 27illustrates a cannulation assembly91provided in accordance with a further embodiment of the present invention. Cannulation assembly91includes a first cannula93slidably coupled to a second cannula94.FIGS. 28A-28Dillustrate a variety of exemplary coupling mechanisms95that can be employed to provide the slidable relation between the first cannula93and second cannula94. In the embodiments shown, coupling mechanisms95generally comprise an elongated engagement member disposed along all or certain portions of one of the two cannulas93,94capable of matingly engaging with an elongated groove or channel disposed along all or certain portions of the other cannula93,94.

In an important aspect, this allows the user great flexibility in selectively positioning the distal tip96of the first cannula and the distal tip97of the second cannula94within the circulatory system of a patient. For example, the slidable function of the present invention may be employed to selectively position the distal end96of cannula93in a first predetermined location and selectively position the distal end97of cannula94in a second predetermined location. Cannulation assembly91is introduced into the patient through an incision formed in the vascular system. This may preferably be accomplished utilizing the Seldinger technique as described above. In an exemplary embodiment, distal end96of first lumen93may be selectively advanced into the patient's atrium, thereby allowing the user to utilize the first lumen93as an inflow conduit. Under this same example, distal end97of second lumen94may be selectively advanced to the patient's pulmonary artery. It will be appreciate that the engagement members which form part of the coupling mechanism95may extend along all or portions of the respective length of the cannula93,94. Also, as illustrated in FIGS.29and30A-30B, the slidable coupling mechanism between the individual cannulas93,94may also be constructed from a barrel portion98fixedly attached to the first cannula93. In so doing, the first and second cannulas93,94may be selectively positioned independent of the other based on this slidable coupling.

FIGS. 33-39illustrate several exemplary embodiments of a second main type of cannulation assembly in accordance with the present invention. A multiple lumen cannula assembly130in accordance with the present invention is provided comprising an inner cannula140slidably disposed within an outer cannula150having a plurality of drainage apertures151. Outer cannula130may be mated with a y-connector to form outer cannula assembly170. As noted above, the y-connector may be exchanged with any number of different connecting mechanisms without departing from the scope of the invention. Outer cannula150is generally cylindrical in shape having a main lumen152defined by a substantially tubular wall154. Main lumen152extends longitudinally between the proximal end156to distal end158of outer cannula150. The length of the cannula assembly170is selected depending upon the size of the patient as discussed above.

The drainage apertures151of outer cannula150extend through wall154and are in fluid communication with main lumen152. As will be appreciated, drainage apertures151permit the egress or ingress of fluid (depending upon the application) into or from the lumen152of outer cannula150. Drainage apertures151may be disposed along the entire length of the outer cannula150. In suction mode, then, blood may flow into the lumen152along the entire length of the outer cannula150. This effectively decreases the distance that the blood will have to travel to reach the pumping system. It also decrease the resistance encountered by the blood being removed through the lumen152such that the pump will be able to pump more blood out of the outer cannula140at a given motor speed, thereby reducing hemolysis.FIGS. 33 and 34illustrate alternative embodiments.FIG. 33illustrates an embodiment wherein the inner cannula140includes a narrow region (shown in phantom) which, in use, extends along at least a portion of the apertures151formed in the outer cannula150.FIG. 35illustrates an embodiment wherein the inner cannula140includes a wide region (shown in phantom) which, in use, extends along at least a portion of the apertures151formed in the outer cannula150.

Cannula assembly130further comprises inner cannula140formed of a substantially tubular structure having a wall144defining a main lumen142. The length of the cannula140is application specific and depends for example on the size of the patient and the distance from the incision in the neck to the destination in the patient's pulmonary system. In a CPB application, the pulmonary artery is the destination into which blood is returned into the patient from the pump system via inner cannula140. As shown inFIG. 37, inner cannula140is provided at its proximal end with a connector146, which is suitably sized to interface with various surgical instruments (not shown), including the output (or intake, in some applications) port of a reverse flow pump. Inner cannula140may be provided with one or more apertures143disposed at distal end149, in addition to the open tip147of its substantially cylindrical structure, in order to permit more efficient fluid passage therethrough. Further, distal tip149of inner cannula140is bullet shaped to allow insertion into the jugular vein. Inner cannula140may further contain one or more preformed curves, designated as132, to facilitate cannula maneuverability during insertion in the patient's body. The angle of the pre-formed curves may be anywhere in the range of 0-180°, with the curves being disposed anywhere along the length of the cannulas and in any one or more planes, depending upon the particular application.

As shown inFIGS. 37 and 39, inner cannula140may be sized to maximize flow through main lumen142. Inner cannula140may be formed having varying diameter. Inner cannula140may also contain taper144adjacent to pre-formed section132. The diameter of inner cannula140is less than the diameter distal taper144. When inner cannula140is disposed within main lumen152of outer cannula150, taper144is disposed proximal to distal end158, or outer cannula150. The resultant structure is an interior portion145disposed in outer cannula150and an exterior portion148disposed outside of outer cannula150, with interior portion145having a relatively smaller outer diameter than exterior portion148in order to minimize obstruction of fluid flow in main lumen152of outer cannula150exterior on inner cannula140.FIG. 39is an illustration of an alternative embodiment of cannula140, whereby cannula140further includes balloon173disposed radially on cannula140and adjacent to distal tip149. Cannula140may further have drainage apertures143disposed proximal balloon173. Balloon173may be selectively inflated/deflated through lumen137disposed within or upon the wall of cannula140. The distal end of lumen137is in fluid communication with balloon173. The proximal end of lumen137is adapted to receive medical devices such as a syringe or other inflation means.

Tubular walls of cannulas140and150can be formed of materials ranging from rigid to flexible, and in the preferred embodiments comprise semi-rigid transparent material such as polyurethane or polyvinyl chloride having a hardness between about30A and about 90A on a Shore durometer scale and capable of sterilization by ethylene oxide (ETO). Rigid clear materials can be used for the y-connector55, and preferably y-connector55is constructed of polycarbonate. The cannulas140and150may also contain radiopaque marking s (not shown) to determine placement within the patient's body. To provide structural reinforcement, a spiraling wire (not shown) can be provided to support the walls144and154, and is either molded into the walls or is otherwise supported therein, and extends either partially or fully across the length of the cannulas140and150. Additionally, cannulas140and150may further contain lumens (not shown) disposed within the walls as described above. Additional medical devices may be disposed within these lumens such as guidewires, catheters, blood monitoring equipment, or pressure transducers.

The advantages of the invention are many-fold. One advantage is the ability to decrease the size of the heart during surgery, thereby providing the surgeon with valuable additional space within the chest cavity. The decreased heart size is achieved by either partial or complete bypass of the heart's pumping function using the cannulas and techniques of this invention. Such bypass results in a natural decompression of the heart due to the reduced blood volume. Decompression of the heart allows a greater degree of freedom to rotate and manipulate the heart for better access to target bypass vessels. This is particularly important in endoscopic surgery.

While this invention has been described for use for right heart support, this does not limit the applications of this invention for use in right heart support only. The invention herein disclosed can be utilized in other applications apparent to those skilled in the art.