Abstract:
A cannula assembly provides access to an interior body region. The cannula assembly defines a lumen having a distal region. The lumen includes a bend in the distal region to guide deployment in the body region. A closure assembly can be provided to open and close the cannula assembly to fluid flow.

Description:
RELATED APPLICATIONS  
       [0001]     This application is a continuation application of U.S. patent application Ser. No. 09/470,697 filed on Dec. 23, 1999, which is a continuation-in-part application of U.S. patent application Ser. No. 09/099,713 filed on Jun. 19,1998 (now abandoned) and claims the benefit under Title 35, U.S.C. 119(e) of U.S. Provisional Application Ser. No. 60/113,727 filed on Dec. 23, 1998 entitled “Cannula Assembly Having Bend Distal Tip and Methods of Use.” 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention is directed to related apparatus systems, equipment and methods for entering cavities of the body.  
       BACKGROUND OF THE INVENTION  
       [0003]     The current trend in medicine is to perform less invasive procedures so as to minimize the trauma to the patient and shorten the recovery period. A major emphasis is to make as few incisions and as small of an incision as is possible to gain access to the interior of the patient. One area of medicine in which these techniques are being used more frequently is in heart surgery. Open heart surgery typically requires significant hospitalization and recuperation time for the patient. While very effective in many cases, the use of open heart surgery to perform various surgical procedures such as, coronary artery bypass grafting (CABG) is highly traumatic to the patient. In addition, open heart procedures require the use of cardiopulmonary bypass (CPB) which continues to represent a major assault on a host of body systems.  
         [0004]     The CABG procedure generally involves open chest surgical techniques where the patient&#39;s chest is cut and retracted to provide access to the heart. During surgery the heart is stopped, and through the use of CPB blood is diverted from the lungs to an artificial oxygenator. In general, a source of arterial blood is then connected to a coronary artery downstream from the occlusion. The source of blood is often an internal artery, and the target coronary artery is typically among the anterior or posterior arteries which may be narrowed or occluded.  
         [0005]     The leading cause of morbidity and disability following cardiac surgery is cerebral complications. At each incision, there is a risk of gaseous and solid micro and macro emboli, and less often perioperative cerebral hypoperfusion, which produce neurologic effects ranging from subtle neuropsychologic deficits to fatal stroke. Therefore, there is a need to minimize the number and size of incisions.  
         [0006]     Open heart surgery is just one area of medicine, that would benefit from less invasive apparatus and procedures, others include dialysis and laparoscopic surgery just to name a couple.  
         [0007]     Two obstacles to performing surgery is the number of incisions that must be made in various arteries, vessels, ventricles, atriums and cavity walls of the patient and the safe insertion and withdrawal of various devices and elements through those incisions.  
         [0008]     One application for cannulas involves the augmenting or supplementation of pulmonary blood flow through the beating heart during heart surgery by use of one or more cannulas involved in the intake and return of blood into the circulatory system. The cannulas interface between the patient&#39;s circulatory system and the mechanical pumps that power the argumentation procedure.  
         [0009]     When performing cardiac surgery cannulas are placed within the patient&#39;s blood stream and used for inflow and outflow of blood or other fluids. One such bypass circuit would be a cardiopulmonary bypass circuit (CPB), in which an outflow cannula is placed in the patient&#39;s right atrium and a return cannula is placed in the aorta. The outflow cannula can be further connected to an oxygenator, blood filter, or blood heater. Even though there are negative side effects of using on pump bypasses, doctors continue to do so because of the ease and reliability of establishing the circuit.  
         [0010]     Though presently there is a movement away from stopped heart CPB to beating heart surgery. The movement to beating heart surgery is hampered by common bypass techniques and equipment. One such problem occurs while performing a coronary artery bypass graft (CABG) on the back side of the heart. In order to access vessels on the back side of the heart the surgeon must rotate the heart. Though rotating the heart while the heart is still beating raises new complications that were not present during stopped heart surgery. Many times rotating the beating heart leads to further complications such as a decrease in pulmonary pressure which results in a decrease in oxygen content in the patient&#39;s blood. Thus many times when a surgeon is performing a graft on the back side of the heart, the heart must be rotated and replaced many times to stabilize the patient&#39;s blood pressure.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention provides cannula devices which can be inserted through an incision in a body cavity to allow ingress and egress in separate cannulas simultaneously through the incision with minimal trauma.  
         [0012]     One aspect of the present invention provides a cannula device which has at least two openings, at least one of which initially is concealed or closed but which, after being inserted through the wall of a cavity. (for example, the aorta),can be opened to allow ingress and egress through the two openings simultaneously through the incision in the wall of the cavity. One embodiment provides a cannulation device for access to an interior body region comprising a cannula body having a distal end for insertion through an incision and including first and second interior flow paths to circulate fluid. A conduit communicates with one of the first and second flow paths and extends beyond the distal end of the cannula body to input or outflow fluid at an area of the interior body region spaced from the distal end. A port communicates with the other one of the first and second flow paths to input or outflow fluid at the distal end. A closure assembly on the cannula body operates in a first condition to close the port, thereby preventing fluid circulation within the cannula body between the first and second flow paths. The closure assembly operates in a second condition to open the port, thereby allowing fluid circulation within the cannula body between the first and second flow paths.  
         [0013]     Another aspect of the invention provides a system for circulating blood in a heart. The system comprises a cannula body having a distal end for insertion through an incision and including first and second interior flow paths to circulate blood. A conduit communicates with one of the first and second flow paths. The conduit is sized to extend, in use, beyond the distal end of the cannula body for passage into a heart chamber, to thereby input or outflow blood from the heart chamber. The conduit includes a preformed, bent region to direct its passage from the distal end into the heart chamber. A port communicates with the other one of the first and second flow paths to input or outflow blood at the distal end.  
         [0014]     Another aspect of the invention provides a cannula for access to an interior body region comprising a body defining a lumen having a distal region. The lumen includes a two dimensional configuration, e.g., one or more bends, in the distal region to aid placement of the cannula in the interior body region.  
         [0015]     Another aspect of the invention provides a system for circulating blood in a heart. The system comprises a cannula body having a first distal tip and a second distal tip for insertion through an incision and including a plurality of interior flow paths to circulate blood. A first conduit is provided in fluid communication with one of the flow paths. The first conduit is sized to extend, in use, beyond the first distal tip of the cannula body for passage into a heart chamber, to thereby input or outflow blood from the heart chamber. The first conduit includes a preformed, bent region to direct its passage from the first distal end into the heart chamber. A second conduit is provided in fluid communication with one of the flow paths. The second conduit is sized to extend, in use, beyond the second distal tip of the cannula body for passage into another heart chamber, to thereby input or outflow blood from the heart chamber. The second conduit includes a preformed, bent region to direct its passage from the second distal end into the heart chamber. In one embodiment, a dilator and guidewire may be employed to position the second conduit within the left atrium or left ventricle. In either case the guidewire pierces the atrial wall and the dilator expands the opening, thereby allowing the cannula to pass through the atrial septum.  
         [0016]     Any aspect of the invention is usable in association with a pump, which operates, in use, to intake fluid and output fluid. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Many objects and advantages of the present invention will be apparent to those skilled in the art when this specification is read in conjunction with the attached drawings wherein like reference numbers are applied to like elements.  
         [0018]      FIG. 1  is a cross-sectional view of a cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region to direct passage into a heart chamber and a closure assembly that opens and closes fluid circulation within the cannula, the closure assembly being shown in the closed condition;  
         [0019]      FIG. 2  is a cross-sectional view of the cannula of  FIG. 1 , with the closure assembly shown in the opened condition and with a pump attached.  
         [0020]      FIG. 3  is a cross-sectional view of the cannula as taken along line  3 - 3  of  FIG. 2 ;  
         [0021]      FIG. 4  is an enlarged cross-sectional view of the inner cannula of  FIG. 1 ;  
         [0022]      FIG. 5  is an enlarged cross-sectional view of a flange adapter that the cannula shown in  FIG. 1  includes;  
         [0023]      FIGS. 6 and 7  are enlarged cross-sectional views of another embodiment of a cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0024]      FIGS. 8 and 9  are enlarged cross-sectional views of another cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0025]      FIG. 10  is an enlarged cross-sectional view of another cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0026]      FIG. 11  is an enlarged cross-sectional view of another cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0027]      FIG. 12  is an enlarged cross-sectional view of another cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0028]     FIGS.  13  to  15  are enlarged cross-sectional views of another cannula capable, in use, of being inserted through the wall of a cavity, and having a bent distal region and a closure assembly that opens and closes fluid circulation within the cannula;  
         [0029]      FIG. 16  is a side view of a cannula system capable, in use, of being inserted through the wall of a cavity, and having a bent distal region that aids insertion of a cannula into a heart chamber;  
         [0030]      FIG. 17  is a sectional view of the cannula system shown in  FIG. 16 ;  
         [0031]      FIG. 18  is a cross sectional view taken about line  18 - 18  of  FIG. 16 ;  
         [0032]      FIG. 19  is a side sectional view of the cannula system shown in  FIG. 16  after insertion of an obturator;  
         [0033]      FIG. 20  is a side view of another cannula system capable, in use, of being inserted- through the wall of a cavity, and having a bent distal region that aids insertion of a cannula into a heart chamber;  
         [0034]      FIG. 21  is a cross sectional view about line  21 - 21  of  FIG. 20 ;  
         [0035]      FIG. 22  is a side view of another cannula system capable, in use, of being inserted through the wall of a cavity, and having a distal region having multiple bends that aids insertion of a cannula into a heart chamber;  
         [0036]      FIG. 23  is a view of a cannula system having a bent distal region inserted into the right heart;  
         [0037]      FIG. 24  is a side view of another cannula system capable, in use, of being inserted through the wall of a cavity, and having a bent distal region that aids insertion of a cannula into a heart chamber;  
         [0038]      FIG. 25  is a cross sectional view about line  25 - 25  of  FIG. 24 ;  
         [0039]      FIG. 26 a  side view of another cannula system capable, in use, of being inserted through the wall of a cavity, and having a distal region with resistive wire disposed within the cannula wall to bend the distal region to aid insertion of a cannula into a heart chamber;  
         [0040]      FIG. 27  is a side view of the cannula system shown in  FIG. 26  after activating the resistive wire to bend the distal region;  
         [0041]      FIG. 28  is a side view of another cannula system capable, in use, of being inserted through the wall of a cavity, and having first and second bent distal regions that aid insertion of first and second cannulas into one or more heart chambers;  
         [0042]      FIG. 29  is a cross sectional view about line  29 - 29   FIG. 28 ;  
         [0043]      FIG. 30  is a sectional view of the cannula system as shown in  FIG. 28 ; and  
         [0044]      FIG. 31  illustrates a cannula system having a first bent distal region directing a first cannula into the pulomnary artery for right heart support and a second bent distal region directing a second cannula through the atrial septum and into the left atrium for left heart support. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0045]     In a first embodiment of the present invention, a cannula system  120  ( FIG. 1 ) utilizes a concentric double-wall cannula having an outer cannula  123  forming an annular space  24  around a portion of an inner cannula  121 . The cannula system  120  can be a conduit for naturally flowing fluid, pressurized fluid, or can be connected to a miniaturized reverse flow pump  124  shown diagrammatically in  FIG. 2 . The concentric double cannula system  120  is inserted into a body cavity  22 , such as in the wall of the aorta, abdomen, or any body cavity through a single incision such that the inner cannula  121  provides intake for the fluid entering the reverse flow pump  124  and the outflow of the reverse flow pump feeds into the outer cannula  123 , or vice versa.  
         [0046]     Referring to  FIG. 1 , before the double cannula system  120  with flexible inlet conduit  34  attached thereto is inserted through the incision in the body cavity  22 , the inner cannula  121  is moved proximally within the outer cannula  123  so that a seal exists as shown generally at  18  between the distal portion  26  of the flange connector  28  and the outer diameter of the inlet. In this way, the system is inserted through the incision with a single outside diameter and a concealed or closed flow outlet but which provides maximum fluid flow during operation. As one of ordinary skill will appreciate, the outside diameter depends on the type of body cavity to be entered and the age and size of the patient. For example, the diameter might be as large as 60 French for abdominal access, 28 French or less for the aorta, 44 French for the right or left atrium, 12 French for a baby, or even 8 French for pumping blood in a 300 pound male&#39;s coronary artery. Once the system is fully inserted into the incision, the inner cannula  121  is moved distally within the outer cannula  123  to open the flow outlet as shown in  FIG. 2 . For easy withdrawal, the inner cannula is retracted to close the outlet and the cannula system is withdrawn through the incision. A preferred reverse flow pump  124  is disclosed in copending U.S. application Ser. No. 08/933,566 filed Sep. 19, 1997, the disclosure of which is incorporated herein by reference. While  FIG. 2  illustrates a preferred pump configuration, it is apparent any suitable pump design or configuration can be used in this invention. For example, the drive motor can be integral with pump  124 , as shown diagrammatically, or can be a remote motor (not shown) connected to the pump by a sheathed flexible drive cable (not shown). While the concentric double cannula system  120  is particularly useful with the reverse flow pump, other commercially available pumps can be used with such a cannula system. For example, other pumps which can be adapted for use in this invention are disclosed in U.S. Pat. Nos. 4,625,712, 5,376,114 and 5,695,471, the disclosures of which are incorporated herein by reference.  
         [0047]     The pump and cannula system  10  of the first embodiment can best be understood by reference to the illustration in  FIG. 2 , which shows the pump  124  diagrammatically and double cannula system  120  in place in the body cavity  22  through a single incision in the wall of body cavity  22  as illustrated. The double cannula system  120  is inserted into the incision such that a cylindrical distal portion  26  of a flange connector  28  ( FIG. 5 ) forms a seal with the wall of the body cavity  22  at the incision. The proximal portion  27  of flange connector  28  receives the distal portion  30  of the outer cannula  123 . As will be recognized by one of ordinary skill in the art, it is within the scope of the invention for flange connector  28  to be an integral portion of outer cannula  123  as shown in some of the embodiments discussed below. Flange  29  of flange connector  28  abuts the outer wall of body cavity  22  to improve the seal between the flange connector  28  and the body cavity  22  and for optional purse string anastomosis to prevent fluid loss. In this regard, an inflatable annular balloon (not shown) can be provided around the distal portion  26  of flange connector  28  which can be inflated after the cannula system  120  has been inserted through the incision to form an improved seal along the inner surface of the body cavity. A typical procedure would involve incision, cannulation, opening the concealed port, hemostasis control at the proximal end, and attachment of the pump.  
         [0048]     The annular space  24  between outer cannula  123  and inner cannula  121  allows outflow of fluid from pump  124 . The inner cannula  121  has an adapter portion  32  ( FIG. 4 ) which can be integral with or attached to the inner cannula  121  and flexible inlet conduit  34 , which inlet conduit extends along a portion of the length of the body cavity  22  as shown in  FIG. 2 . The flexible inlet conduit  34  is illustrated as a right angled conduit and the flange connector  28  is illustrated as being, inserted perpendicular to the body cavity but it is within the scope of the invention for the flange connector to enter the body cavity at an angle less than 90 degrees and for the flexible inlet conduit to have a more gradual bend rather than a 90 degree bend. The adapter portion  32 , best seen in  FIG. 4 , has an enlarged cylindrical distal end  36  mating the inlet conduit  34  to the adapter portion. The cylindrical distal end  36  tapers down internally and externally along section  38  to generally cylindrical section  40 . The internal reduction in section  38  reduces the inner diameter of the inlet conduit  34  down to the inner diameter of the generally cylindrical section  40  to funnel the fluid flow into inner cannula  121 . The adapter portion  32  has a constant inner diameter along substantially all of the length of generally cylindrical section  40  which then flares open to a larger inner diameter at the proximal end  37  of the adapter  32  to mate with the larger, relatively speaking, inner diameter of the inner cannula  121 . Section  40  of the adapter  32  is described as being generally cylindrical rather than strictly cylindrical because the outside diameter of section  40  increases gradually from about the vanes  42  to its proximal end  37 . Vanes  42  act to center the adapter portion  32  and thus inner cannula  121  in the flange connector  28  and outer cannula  123  while allowing blood to pass from annular space  24  into aorta  22  as shown in  FIGS. 2 and 3 . Each of the elements have been shown and described as being generally cylindrical but it is within the scope of the invention that those elements be elliptical or other shapes. The double cannula for intake and output can have any desired configuration, such as side-by-side cannulas, multi-cannula tubing, axially offset cannulas ( FIGS. 6 and 7 ), and others which will be apparent to one skilled in the art.  
         [0049]      FIGS. 8 and 9  are enlarged cross-sectional views of a third embodiment of the present invention that provides the same benefit of easy insertion and withdrawal of a single outside diameter and concealed port as described above. The flange connector  128  has at least one but preferably three openings  44  (only 1 shown) through its wall at distal end  26 . Flange connector  128  has a corresponding number of seal flaps  46  which initially cover corresponding openings  44  for insertion (and -withdrawal) of the cannula system through the incision in the body cavity. An actuator  48  (e.g., NITINOL™ shape memory alloy wire) is located in a slot in the flange connector  128 . After the cannula system is inserted into the body cavity  22 , the actuator  48  is pushed into the slot in the seal flap  46  to open the outlet  44  and seal alone, the inner wall of the body cavity.  FIG. 10  is an embodiment very similar to the third embodiment of  FIGS. 8 and 9  except that the conduits are offset similar to  FIGS. 6 and 7  and the flap  146  slides proximally to expose the outlet.  
         [0050]     Two more embodiments that are similar are shown in  FIGS. 11 and 12 . The fifth embodiment shown in  FIG. 11  has a balloon  51  located at the distal end  26  of the outer cannula  123  which when inflated as shown occludes the opening, to form the seal shown generally at  18  between the inner and outer conduit. When inflated for insertion, the balloon  51  provides a smooth rounded outer surface for inserting through an incision. The balloon can be attached to the outer cannula  123  or the inner cannula  121 . In the sixth embodiment shown in  FIG. 12 , the outer diameter of the inner conduit  121  (which extends beyond the distal end  26  of the outer conduit  123 ) is shaped to provide a smooth transition with the inflated balloon  51 .  
         [0051]     The seventh embodiment shown in  FIGS. 13-15  has two outer cannulas  62  and  64 . The outermost cannula  64  slides over the cannula  62  with the opening,  66  in cannula  62  initially being offset from opening  68  in cannula  64  as shown in  FIGS. 14 and 15 . The outermost cannula  64  and cannula  62  are slid over the inner cannula  121  until coming in contact with the outer diameter of the inner cannula as shown in  FIG. 15  to form a seal therebetween. The cannula system  70  is inserted into a body cavity with the two openings  66  and  68  misaligned. The outermost cannula  64  is rotated with respect to the cannula  62  to align the openings  66  and  68  to allow fluid to flow therein or out therefrom.  
         [0052]     In a preferred embodiment of the present invention, the longer inner cannula  121  is extended through the aortic valve (not shown) into the left ventricle (not shown) by way of the adapter portion  32  and flexible inlet conduit  34 . Insertion of conduit  34  into the left ventricle may be accomplished with use of a guidewire. The length in which conduit  34  extends into the left ventricle depends on the beating or still heart bypass surgery procedures performed and on other factors known by those of ordinary skill in the art. The blood flow from the pulmonary vein (not shown) enters the left atrium (not shown) and is normally pumped through the left ventricle (not shown) into aorta  22 . With the pump and cannula system of this invention, a portion or all of the blood from the left atrium enters pump  124  through the inlet conduit  34  and inner cannula  121  and is pumped through the annular space between outer cannula  123  and inner cannula  121  into the aorta  22  to assure the maintenance of adequate aortic blood flow during beating or still heart surgery. The pump and cannula system of the present invention is capable of maintaining a flow of five liters per minute, and more preferably, seven liters per minute. As will be recognized by one skilled in the art, the above discussed cannulas and conduit will be made of appropriate flexible bio-compatible materials which have sufficient flexibility, radial stiffness and other strength properties appropriate to the function intended in this invention. In most applications the cannulas and conduit utilized in this invention must have appropriate radial strength and stiffness to resist collapsing or kinking under the stresses and compressive loads imposed on them when inserted in the appropriate blood vessels during, beating or still heart bypass surgery. In some instances, soft and flexible materials such as silicones may be desirable and may need to be reinforced with wire or other material to provide the radial stiffness and resistance to collapsing necessary to be useful in the present invention.  
         [0053]     The pump(s) of the systems of the present invention can be controlled in response to conventional parameters, such as oxygen level measured by conventional means, blood pressure measured by conventional means, or other parameters desired to assure proper patient support during and after surgery.  
         [0054]     Another advantage of the system of the present invention is that the dual cannula in combination with the reverse flow miniature pump, such as disclosed in copending U.S. application Ser. No. 08/933,566, enables the installation of the pump essentially adjacent to the incision where the dual cannula is inserted into the aorta or other appropriate location. Thus, the priming volume of the pump and cannula system is minimized to less than about 1,000 ml, preferably less than about 500 ml, and more preferably less than about 200 ml. In this context, “priming volume” refers to the volume of the pump and cannula which is external of the patient and does not include the volume of the portions of the cannula and inlet conduit which are inserted into the patient and thus are immersed in the blood flow. It Is especially preferred that the pump and cannula system priming volume be very small, typically less than 30 ml, preferably less than 20 ml, and most preferably less than about 10 ml. In this regard, it is within the scope of the invention and definition of the outer cannula that its length be very short so as to appear as a plug at the incision.  
         [0055]     Another advantage provided by the cannula system of this invention is that, by having the capability of placing the small priming volume pump adjacent to or very near the incision, the distance the blood must travel outside the body is minimized. Contact of the blood with tubing, pump components and other apparatuses is minimized, therefore the pump can operate essentially at body temperature. This eliminates the necessity of cooling or warming the blood, particularly because the blood is outside the body a very short distance and for a very short time. With this system the entire cannula system can be positioned near the chest cavity, within the chest cavity itself, near or adjacent to the heart to obtain the minimum possible pumped blood flow path. Other advantages include the fact that with the cannula system miniaturized and configured to be contained in the chest cavity, this system eliminates the disadvantages of having numerous tubes, cables, etc., extending from the patient&#39;s chest cavity to external equipment. In the preferred embodiment of the present invention, the only line extending from this system to external equipment is a single cable from the pump to the external power supply for providing power to the pump. This single cable may contain an electrical connection for supplying electrical power to the pump motor near the heart or may be a flexible drive cable for transmitting power from a remote motor to the pump in or near the heart. Thus, the cannula system of this invention provides the surgeon better surgical access to the heart and visibility of the heart by eliminating the CPB tubing and other associated cables and pumps which are conventionally used in bypass surgery.  
         [0056]     Another advantage of the present invention is that the fluid in the outer cannula acts as a safety feature preventing air from being drawn into the body cavity. If the inner cannula was not drawing fluid, rather than pulling air in around the distal end  26  of the flange adapter, the system would draw the fluid from the annular space  24  into the body cavity to prevent embolism. As will be apparent to one skilled in the art, the above description of the cannula system and reverse flow pump having a minimum priming volume constitute preferred embodiments of the present invention, but other pump and cannula configurations and designs may be employed in the cannula systems of the present invention. For example, an inner cannula may be inserted to draw fluid into an in-line pump which can then return the fluid through a looped conduit back to the outer cannula. Thus, various conventional pumps can be used in accordance with the cannula systems of this invention, even those of large priming volume.  
         [0057]     Another embodiment of the present invention provides a cannula assembly which has been specifically adapted for insertion within the patient&#39;s heart. The cannula assembly allows, for example, the user to insert a first outer cannula into the right atrium and advance the distal tip of the first outer cannula into the right ventricle. The distal tip of the first cannula is curved, to guide a second inner cannula through the first cannula and advance the second cannula into the pulmonary artery. After placing the second cannula through the first cannula and into the pulmonary artery, a blood pump can be attached to the proximal end of the cannula assembly. Thereafter the pump and cannula assembly may be utilized to provide support to the right side of the beating heart.  
         [0058]     The cannula assembly comprises a substantially tubular, semi-flexible material adapted for fluid transport while inserted in a patient&#39;s body, and is provided with a curved distal tip or guide tube. The cannula assembly may further be adapted to support a stiffening wire to aid the operator in its insertion through the patient&#39;s body, and/or a light source to provide a visual reference during the insertion procedure. Further the cannula assembly may contain lumens disposed within the wall of the cannula, these lumens may be utilized to inflate or deflate balloons disposed about the outer surface of the cannula, or alternatively at least one pressure transducer may be disposed sufficiently closed to the main lumen of the cannula for pressure measurements. Still further, the cannula assembly may contain more than one pressure transducer disposed adjacent to the inner wall, thereby allowing the user to determine a flow rate within the cannula.  
         [0059]     An exemplary arrangement of such a cannula assembly  210  is shown in FIGS.  16  to  19 . The cannula assembly  210  comprises a substantially cylindrical structure having main tube  220  with wall  218  defining a main lumen  211 , an inflow port  230 , and a formed curved portion  240 . Wall  218  can be formed of materials ranging from rigid too flexible, and in the preferred embodiment comprises a semi-rigid transparent material such as polyurethane, polyvinyl chloride (PVC) or other material. Lumens other than main lumen  211  may also be provided, as described below.  
         [0060]     To lend structural support, spiraling wire (not shown) may be provided for reinforcement, which is generally molded into the wall  218  of cannula assembly  210 . The wire further facilitates handling of cannula assembly  210  and reduces the possibility of cannula assembly  210  collapsing or being pinched shut and thus closing off the flow of fluid to or from the patient or preventing the user from passing a inner cannula through lumen  211  of cannula assembly  210 . Other ways of reinforcing the tubular body of cannula assembly  210  are 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 pressure is present within the cannula. The pitch in which the wire is wound within cannula wall  218  can be altered to vary the stiffness of cannula assembly  210 . By altering the winding pitch during the manufacturing process the stiffness of curved portion  240  can be altered. Thus the curved portion  240  may be formed so that it is sufficiently stiff to provide the user with the ability to align distal tip  241  with the patient&#39;s pulmonary artery so that a second cannula may be passed through lumen  211  and into the pulmonary artery. Still, the curved portion  240  must be sufficiently flexible such that when the heart is rotated curved portion  240  will deflect or rotate with the heart. Alternatively, the curved portion  240  may not be reinforced with wire.  
         [0061]     As illustrated in FIGS.  16  to  22 , cannula assembly  210  is constructed by combining main body  220 , the inflow port  230 , and the curved portion  240 . Inflow port  230  may be molded of polyurethane, or polyvinyl chloride, although most preferably inflow port  230  is constructed of urethane. As illustrated in  FIGS. 16 and 17 , inflow port  230  contains openings  232 , distal end  231 , and proximal end  233 . Proximal end  233  of inflow port  230  is adapted to receive distal end  221  of tube  220  of cannula assembly  220 . Distal end  231  of inflow port  230  is adapted to receive proximal end  243  of curved portion  240 .  
         [0062]     The curved portion  240  may be constructed of materials ranging from rigid too flexible, and in the preferred embodiment comprises a semi-rigid transparent material such as polyurethane, polyvinyl chloride or other material. Further, curved portion  240  may contain apertures  245  disposed adjacent to distal tip  241  and along the length of the curve. Distal tip  241  is preferably formed sufficiently smooth such that tissue will not be damaged if contacted. Distal tip  241  is further adapted to provide a seal about cannula  260  when cannula  260  is disposed through tip  241  (see  FIG. 23 ). Curved portion  240  and distal tip  241  may be constructed of different materials that are then bonded together through the use of solvents or heat. Curved portion  240  may be constructed having varied wall thickness. Further curved portion  240  may be constructed of a material having a different durometer than distal tip  241 .  
         [0063]     As illustrated in  FIGS. 16 and 20 , distal tip  241  may be constructed of a similar material as the curved portion  240  though of a different durometer. Tip  241  may be constructed of a more resilient material than curved portion  240  such that if tip  241  contacts the patient&#39;s tissue it will not abrade the patient&#39;s tissue thereby causing further damage.  
         [0064]     As illustrated in  FIG. 19 , prior to insertion into the patient&#39;s body, cannula  210  may be equipped with a flexible obturator  270  disposed within main lumen  211 . Distal tip  271  of obturator  270  is adapted to seal inflow port  242  during insertion and to provide a smooth transition between distal tip  271  of obturator and distal tip  241  of cannula assembly  210 . Proximal end  272  of obturator  270  further contains handle  273 . During assembly handle  273  of obturator  270  is placed such that when obturator  270  is fully inserted within cannula assembly  210 , distal tip  271  seals inflow port  242  of distal tip  241  of cannula assembly  210 . Placement of handle  273  further ensures that distal tip  271  of obturator  270  does not protrude substantially beyond distal tip  241  of cannula assembly  210 .  
         [0065]     As illustrated in  FIGS. 20 and 21 , cannula  310  may be constructed as a unitary construction having a smooth inner and outer surface. It may also be constructed of a soft, resilient material, such as urethane, though preferably constructed of polyvinyl chloride (PVC). Cannula  310  may further include spiral wire reinforcement (not shown) disposed within the cannula wall, further cannula  310  may contain malleable material  312  disposed within wall  318  of cannula  310 . Malleable material  312  allows the cannula to be shaped into a desired form before inserting cannula  310  into the patient. Cannula  310  may be manufactured by a dip-molding process utilizing a mandrel as an inner mold.  
         [0066]     Alternatively, as illustrated in  FIG. 22 , cannula assembly  310  may contain more than one curved portion  340 ,  347  within one or more planes. Therefore, cannula assembly  310  is bent in at least two directions. Curved portions  340 ,  347  aid the user in aligning distal tip  341  with the patient&#39;s right ventricle or pulmonary artery.  
         [0067]     In use, as illustrated in  FIG. 23 , cannula assembly  210  is inserted within the patient&#39;s body through the right atrium. Distal tip  241  of cannula assembly  210  is disposed within the patient&#39;s right ventricle by advancing cannula assembly  210  through the right atrium and tricuspid valve. After cannula assembly  210  is placed within the patient&#39;s right ventricle, inner cannula  260  is inserted distally through main lumen  211  of cannula assembly  210 . Inner cannula  260  is advanced through lumen  211  of cannula assembly  210  until distal tip  261  of inner cannula  260  is placed within the patient&#39;s pulmonary artery. Curved portion  240  of cannula assembly  210  aids in placing distal tip  261  of inner cannula  260  into the patient&#39;s pulmonary artery by providing the user with a means for advancing inner cannula  260  without the need for supplemental guiding means, such as a guidewire or balloon catheter. After placing inner cannula  260  within the patient&#39;s pulmonary artery, cannula  260  is preferably clamped near the y-connector  280 , thereby restricting cannula  260  from moving independent of cannula assembly  210 .  
         [0068]     As illustrated in  FIG. 19 , cannula assembly  210  may further contain y-connector  280  disposed about proximal end  214  of cannula assembly  210 . Y-connector  280  contains hemostasis valve  285  disposed about proximal end  281  of y-connector  280 . Hemostasis valve  285  seals around inner cannula  260 , thereby allowing the inner cannula to move relative to the outer cannula and further reducing the possibility of blood leakage or emboli forming within the patient&#39;s blood stream. The y-connector  280  and hemostasis valve  285  may comprise any number of commercially available y-connectors and hemostasis valves, inclusive but not limited to the hemostasis valves of the type shown and described in U.S. patent application Ser. No. 09/163,102 and U.S. patent application Ser. No. 09/163,103, owned by the assignee of the present application, the contents of which are herein incorporated by reference.  
         [0069]     A further embodiment of the invention is illustrated in FIGS.  24  AND  25 . Cannula assembly  610  consists of a main tube  620  with a wall  618  defining a main lumen  611 , an inflow port  630 , and a curved portion  640 . Cannula assembly  610  may also be equipped with lumen  690  disposed axially through wall  618  of main tube  620 , inflow port  630 , and pre-curved portion  640 . Lumen  690  may contain stylet  691  that allows the user to adjust the curvature of curved tip  640  of cannula assembly  610 . Initially stylet  691  is inserted through lumen  690  in cannula wall  618 . After placing cannula assembly  610  within the patient&#39;s heart, stylet  691  may be removed thereby enabling curved portion  640  of cannula assembly  610  to become more flexible. Alternatively, curved tip  640  may further contain steering wire fixedly attached within lumen  690  of cannula assembly  610  adjacent to distal tip  641 . By manipulating the proximal end of steering wire, the operator may adjust the curvature of the distal tip  641  of cannula assembly  610 .  
         [0070]     As illustrated in FIGS.  26  AND  27 , another alternative embodiment of a cannula assembly  710  comprises a main tube  720  and an inflow port  730 . D Distal tip  741  may further contain wire  791  having resistive joint connections  795  forming a continuous wire. Lumen  790  disposed axially through cannula assembly  710 , having electrical wire  796  in communication with wire  791  disposed within distal tip  741  of cannula assembly  710 . Proximal end of electrical wire  796  is connected to an adjustable current source. As illustrated in  FIG. 27 , distal tip of cannula assembly  710  can be selectively curved by passing an electrical signal through electrical wire  796 . The electrical signal is passed to wire  791 , where selective resistive joints  795  will sever allowing the portion  740  to assume a pre-determined curved shape. Prior to assembly, portion  740  of cannula assembly  710  is formed having a curved portion. Portion  740  further contains lumen  790  though which wire  791  may be disposed, thereby straightening portion  740  for insertion into the patient. After inserting cannula assembly  710  into the patient&#39;s right ventricle, a current generator may be activated, thereby severing a selective joint  795 , and allowing portion  740  to curve into a pre-determined shape.  
         [0071]     An alternative method of selectively bending portion  740 , would be to use a memory shape alloy metal such as Nitinol™ shape memory wire which reacts to changes in temperatures. Therefore, portion  740  of cannula assembly  710  may be formed having an initial curvature. Before insertion into a patient the cannula is either heated or chilled, thereby activating the Nitinol wire that straightens the cannula for insertion into the patient. After insertion into the patient, the cannula warms to the temperature of the blood flowing therethrough, thus causing the tip of the cannula to return back to its pre-curved state.  
         [0072]     Alternatively, portion  740  of cannula assembly  710  containing Nitinol™ shape memory wire wire may be initially formed with a curvature adjacent to distal tip  741 . After inserting cannula assembly into the patient&#39;s heart, cannula assembly is warmed to body temperature, thereby activating the Nitinol wire which allows curved portion to become flexible. Thus, if the heart is rotated, curved portion  740  will not resist the rotation of the heart.  
         [0073]     An alternative embodiment of the pump and cannula system described above can best be understood by reference to the illustrations in  FIGS. 28-31 . Cannula assembly  510  comprises a substantially cylindrical structure having a main tube  520  having a distal tip  541  with wall  518  defining a main lumen  511 , at least one inflow port  530 , and formed curved portions  540  and  560 . As shown in  FIG. 28 , inflow port  530  contains a plurality of apertures  533 . Proximal end  534  of inflow port  530  is adapted to receive distal end  521  of tube  520  of cannula assembly  510 . Distal end  532  of inflow port  530  is adapted to receive the proximal end  543  of curved portion  540 . Curved portion  540  may further contain apertures  545  disposed adjacent inflow port  530  and along the length of curved portion  540 . As shown in  FIG. 28 , curved portion  560  extends generally from the distal end  521  of cannula body  520 . Similar to the embodiment shown in  FIGS. 24 and 25 , the assembly  510  may be equipped with a lumen  590  that contains a stylet  591  that allows the user to adjust the curvature of curved portion  560 .  
         [0074]     In use, as illustrated in  FIG. 31 , cannula assembly  510  is inserted within the patient&#39;s heart through the right atrium. Curved portion  540  is advanced through the atrial valve into the right ventricle and the inflow port  530  is disposed in the right atrium. After placing cannula assembly  510 , inner cannula  260  is advanced through lumen  511  and guided by curved portion  540  such that the distal end  261  of inner cannula  260  is disposed within the pulmonary artery. Curved portion  540  of cannula assembly  510  aids in placing distal tip  261  of inner cannula  260  into the patient&#39;s pulmonary artery by providing a guiding function for inner cannula  260 . Blood may then be withdrawn from the right atrium through port  530  by the action of blood pump  2 . Blood pump  2  then redirects the blood (withdrawn from the right atrium) through the inner cannula  260  such that it passes out the distal tip  261  for deposit into the pulmonary artery.  
         [0075]     The second curved portion  560  also serves a guiding function, that is, to guide a second inner cannula  270  through the atrial septum such that its distal tip  271  is disposed within the left atrium. This may be facilitated by first using a stylet (not shown) and a guidwire (not shown) to pierce and expand the atrial septum. In use, blood is withdrawn from the left atrium through apertures disposed adjacent to the distal tip  271  of second inner cannula  270 , into blood pump  3 , whereby the blood is expelled from blood pump  3  into the patient&#39;s aorta through cannula  580 .  
         [0076]     It will now be apparent to those skilled in the art that various modifications, variations, substitutions, and equivalents exist for various elements of the invention but which do not materially depart from the spirit and scope of the invention. Accordingly, it is expressly intended that all such modifications, variations, substitutions and equivalents which fall within the spirit and scope of the invention as defined by the appended claims be embraced thereby.