Patent Publication Number: US-6902556-B2

Title: Methods and devices for occluding the ascending aorta and maintaining circulation oxygenated blood in the patient when the patient&#39;s heart is arrested

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a division of U.S. patent application Ser. No. 09/235,043 filed on Jan. 21, 1999 now U.S. Pat. No. 6,592,547, which is a continuation-in-part of U.S. patent application Ser. No. 09/012,833, filed Jan. 23, 1998, now issued as U.S. Pat. No. 6,159,178, the full disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to methods and devices for occluding a patient&#39;s ascending aorta and maintaining circulation of oxygenated blood in the patient when the patient&#39;s heart is arrested. Such devices and methods are useful for performing various procedures on a patient&#39;s vascular system and heart such as the procedures described in U.S. Pat. Nos. 5,584,803 and 5,682,906 which describe coronary artery bypass grafting (CABG) and valve procedures, respectively. Another device and method for occluding a patient&#39;s ascending aorta is described in Re. 35,352. 
     The methods and devices described in the above-mentioned patents use an internal occlusion device to occlude the ascending aorta rather than a conventional external cross-clamp. Use of an internal occlusion device may reduce strokes as compared to conventional external cross-clamps since external cross-clamps distort and compress the aorta which may release emboli leading to strokes. 
     It is an object of the invention to provide alternative methods and devices for occluding a patient&#39;s ascending aorta and maintaining circulation of oxygenation blood when the patient&#39;s heart is arrested. 
     SUMMARY OF THE INVENTION 
     In accordance with the object of the invention, the present invention provides alternative methods and devices for occluding a patient&#39;s ascending aorta and maintaining circulation of oxygenated blood in a patient when the patient&#39;s heart is arrested. 
     In a first preferred method and device of the present invention, an aortic occlusion device having a blood delivery lumen and an occluding member is introduced into the patient&#39;s aortic arch. The occluding member has an interior in fluid communication with the blood delivery lumen so that delivery of oxygenated blood inflates the occluding member. An advantage of this method is that a separate inflation lumen is not necessary. The aortic occlusion device preferably passes through a cannula having a y-arm with the aortic occlusion catheter passing through an arm of the y-arm. The other arm of the y-arm connector is coupled to the source of oxygenated blood so that bypass support can be maintained even when the aortic occlusion device has been removed. 
     In another preferred method and device, oxygenated blood is delivered to the patient through the aortic occlusion catheter. The aortic occlusion catheter also passes through a cannula with a y-arm connector so that bypass support can be maintained when the aortic occlusion device is removed. The aortic occlusion device also preferably includes a lumen for delivering cardioplegic fluid and venting the ascending aorta and a pressure lumen for measuring pressure in the ascending aorta. If the lumens are not provided in the aortic occlusion device, delivery of cardioplegic fluid, venting of the ascending aorta and pressure monitoring may be accomplished with the cannula. 
     In another preferred device, the aortic occlusion device has not occluding member mounted to a side of the catheter. The occluding member has a pathway therethrough which is in communication with a lumen in the aortic occlusion catheter. The pathway directs cardioplegic fluid toward the coronary ostia while the aortic occlusion device directs the oxygenated blood in the direction of normal blood flow in the aorta. 
     In another aspect of the invention, the cannula has a curved or angled distal end. The distal end is straightened for introduction by the introducer. 
     In still another aspect of the present invention, the occluding member is stabilized by a mesh structure to prevent distortion of the occluding member. 
     These and other aspects and advantages of the present invention will become apparent from the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an aortic occlusion device; 
         FIG. 2  is a cross-sectional view of a first step in forming the aortic occlusion catheter of FIG.  1 : 
         FIG. 3  is a cross-sectional view of the structure of  FIG. 2  after heating; 
         FIG. 4  is a cross-sectional view of a further step in forming the aortic occlusion catheter of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of  FIG. 1  along line I—I; 
         FIG. 6  shows a cannula; 
         FIG. 7  shows an enlarged view of the distal end of the cannula of  FIG. 6 ; 
         FIG. 8  is a plan view of a ring; 
         FIG. 9  is a side view of the ring; 
         FIG. 10  shows an introducer with an incising element in a retracted position; 
         FIG. 11  shows the introducer with the incising element in an exposed position; 
         FIG. 12  shows the aortic occlusion device and cannula passing through a penetration in the ascending aorta; 
         FIG. 13  shows another aortic occlusion device passing through the cannula and into the patient&#39;s ascending aorta; 
         FIG. 14  shows yet another aortic occlusion device; 
         FIG. 15  shows still another aortic occlusion device; 
         FIG. 16  shows a final aortic occlusion device; 
         FIG. 17  illustrates a preferred method of introducing the aortic occlusion device; 
         FIG. 18  shows another preferred aortic occlusion device with the balloon occluding the ascending aorta; and 
         FIG. 19  shows the aortic occlusion device of  FIG. 18  with the balloon deflated. 
         FIG. 20  shows a cannula having an angled or curved distal portion; 
         FIG. 21  shows the distal portion of the cannula of  FIG. 20 ; 
         FIG. 22  shows the cannula of  FIG. 20  with the introducer straightening the distal portion; 
         FIG. 23  illustrates introduction of the cannula; 
         FIG. 24  shows the aortic occlusion device passed through the cannula; 
         FIG. 25  shows the cannula of  FIG. 20  including an occluding member; 
         FIG. 26  shows another cannula having a angled shaft and an angled stabilizing ring; 
         FIG. 27  shows the cannula of  FIG. 26  with the introducer straightening the shaft; 
         FIG. 28  shows a balloon having a first, smaller section stabilized by a second, larger section; 
         FIG. 29  is an end view of the balloon along line II—II of  FIG. 28 ; 
         FIG. 30  is a cross-sectional view of  FIG. 28  along line III—III; 
         FIG. 31  shows the balloon of  FIG. 28  having a different orientation on the shaft; 
         FIG. 32  shows yet another orientation for the balloon of  FIG. 28 ; 
         FIG. 33  shows a discoid occluding member supported by a stabilization having an open structure which permits blood flow to the head and neck vessels; 
         FIG. 34  shows the stabilizer of  FIG. 33  in a collapsed position; and 
         FIG. 35  shows the stabilizer of  FIG. 33  in an expanded position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1 and 5 , an aortic occlusion device  2  is shown. The aortic occlusion device  2  has an occluding member  4  configured to occlude a patient&#39;s ascending aorta. The occluding member  4  is preferably a balloon but may also be a mechanically actuated member. The aortic occlusion device  2  has an inflation lumen  6  for inflating the occluding member  4 , a pressure lumen  8  for measuring pressure in the ascending aorta, and a lumen  10  for delivering cardioplegic fluid and/or venting the ascending aorta. The aortic occlusion device  2  is preferably manufactured and used in the manner described in U.S. patent application Ser. No. 08/782,113 but may also be manufactured in any other manner such as an extrusion. 
     The aortic occlusion device  2  is preferably substantially straight in an unbiased position, however, the aortic occlusion device  2  may also have a shaped end. For example, the aortic occlusion catheter  2  can have an L-shaped end which facilitates positioning the occluding member  4  in the ascending aorta depending upon the surgical approach. The aortic occlusion device  2  is preferably flexible so that it can be bent as necessary without kinking. 
     Returning to  FIGS. 2-5 , a preferred method of forming the aortic occlusion device  2  is shown.  FIG. 2  shows a longitudinal cross-section of a tube  12 , preferably a urethane tube, mounted on a teflon-coated mandrel  14  with the elongate element  16  wound helically around the tube  12 . The elongate element  16  is preferably a wire ribbon having a thickness of 0.003 inch and a width of 0.012 inch. The elongate element  16  is preferably wrapped around the tube  12  with a spacing of 0.010 inch. Another tube  20  is positioned over the elongate member  16  and a shrink tube (not shown) is positioned over the tube  20 . The entire structure is then heated to fuse the tubes together to form a reinforced tube  22  which is shown in longitudinal cross-section in FIG.  3 . The resulting reinforced tube  22  preferably has an inner diameter of about 0.100 inch and a wall thickness of about 0.010 inch. 
     Referring to  FIG. 4 , a two-lumen member  24  is positioned against the reinforced tube  22  and a shrink tube  26  is positioned around the member  24  and reinforced tube  22 . The two lumen member  24  has the inflation lumen  6 , which is used for inflating the occluding member  4 , and the pressure lumen  8 , which is used for pressure monitoring in the ascending aorta. The two-lumen member  24  is preferably an extrusion having a D-shaped outer surface in cross-section. The member  24  and tube  22  are then heated and the shrink tube  26  is removed to obtain the egg-shaped cross-sectional shape shown in FIG.  5 . The cross-sectional shape is preferably about 0.145 inch tall and 0.125 inch wide. The inflation lumen  6  is then pierced to provide an inflation path to the occluding member  4  and the occluding member  4  is then mounted to the shaft. 
     Referring to  FIGS. 6 and 7 , a cannula  28  is shown which is used to return oxygenated blood to the patient when the patient&#39;s heart is arrested. The aortic occlusion device  2  is introduced into the patient through the cannula  28  as will be described below. The cannula  28  has a y-arm connector  30  with first and second arms  32 ,  34  with each coupled to a lumen  35 . The second arm  34  has a hemostasis valve  36  which may be any hemostasis valve and is preferably a Thouy-Borst valve. The cannula  28  has a reinforced body  38  which is preferably formed in the manner described in U.S. patent application Ser. No. 08/749,683, which is hereby incorporated by reference, however, any other method may be used including extrusion. The distal end  40  of the cannula  28  is beveled and has an open end  42  and two side ports  44  for infusing oxygenated blood into the patient. A radiopaque markers  45  are provided at the distal end for visualization as discussed below. 
     Referring to  FIGS. 6-9 , a ring  46  is attached to the distal end  40  of the cannula  28 . The ring  46  limits insertion of the cannula  28  into the vessel, stabilizes the cannula  28 , and receives purse-string sutures which provide homostasis around the cannula  28  when the cannula  28  is positioned in a vessel. Referring to  FIGS. 8 and 9 , the ring  46  has slots  48  which may receive purse-string sutures as will be described below. 
     Referring to  FIGS. 10 and 11 , an introducer  50  is positioned in the cannula  28  to introduce the cannula  28  into a vessel. The introducer  50  has a connector hub  51  which is received by the hemostasis valve  36  on the second arm  32  of the cannula  28  to seal the space between the introducer  50  and cannula  28 . The introducer  50  has an incising element  52  for incising the vessel into which the cannula  28  is introduced. The incising element  52  is attached to a shaft  54  which is coupled to a trigger  56  for moving the incising element  52  from the retracted position of  FIG. 10  to the exposed position of FIG.  11 . An o-ring seals  58  the space between an outer housing  60  and the shaft  54 . The incising element  52  is biased toward the retracted position by a spring  62  so that the incising element  52  is only exposed when the trigger  56  is actuated. When introducing the cannula  28  into the vessel, the trigger  56  is actuated to move the incising element  52  to the exposed position, the vessel is incised with the incising element  52  and the cannula  28  is inserted through the incision. As will be described below, one or more purse-string sutures are then used to form a hemostatic seal around the cannula  28 . The incising element  52  may be omitted if a separate incising device is used. 
     Referring to  FIGS. 12 , the cannula  28  is positioned in a patient&#39;s ascending aorta with the aortic occlusion device  2  passing through the hemostasis valve  36 . Placement of the cannula  28  and aortic occlusion device  2  into the position of  FIG. 12  is described below. Referring to  FIGS. 5 and 12 , the lumen  10  is coupled to a source of cardioplegic fluid  64 , the inflation lumen  6  is coupled to a source of inflation fluid  66 , and the pressure lumen  8  is coupled to the pressure monitor  68  for measuring pressure in the ascending aorta. The lumen  10  is also coupled to a vacuum source  70  for venting the ascending aorta. 
     The first arm  32  of the cannula  28  is coupled to a source of oxygenated blood  72  so that blood is delivered through the lumen  35  of the cannula  28  with the blood passing through the annular area between the cannula  28  and the aortic occlusion device  2 . The oxygenated blood passing through the open end  42  of the cannula  28  is directed at the occluding member  4  so that the oxygenated blood is not directed at the wall of the aorta. An advantage of directing the oxygenated blood at the occluding member  4  is that the fluid is dispersed radially outward by the occluding member  4  before coming into contact with the wall of the aorta. By directing the blood at the occluding member  4 , rather than at the wall of the aorta, the likelihood of releasing emboli from the wall of the aorta may be reduced. Oxygenated blood is also directed through the side ports  44  so that oxygenated blood is delivered to the patient even if the occluding member  4  blocks the open end  42  of the cannula  28 . 
     Referring to  FIGS. 13 , another aortic occlusion device  2 A is shown having a balloon  76  which is inflated with the oxygenated blood delivered to the patient. The aortic occlusion device  2 A has a blood flow lumen  78  which is fluidly coupled to the interior of the balloon  76  for inflating the balloon  76 . Oxygenated blood is then delivered to the patient through an opening  80 , preferably a number of openings, in the balloon  76 . An advantage of the aortic occlusion device  2 A is that a separate inflation lumen is not required since occlusion is accomplished by simply delivering oxygenated blood through the aortic occlusion device  2 A. The aortic occlusion device  2 A may also include a pressure lumen  82  for measuring pressure in the ascending aorta and a lumen  84  for delivering cardioplege and venting the ascending aorta. The aortic occlusion device  2 A is preferably formed in the manner described above except that the lumen  78  is sized large enough to provide sufficient flow of oxygenated blood at an acceptable pressure. Acceptable blood flow rates and pressures are disclosed in the above-mentioned patents and patent applications which have been incorporated by reference. Although it is preferred to manufacture the device in the manner described above, the aortic occlusion device  2 A may also simply be an extrusion or laminated structure. The balloon  76  is preferably made of silicone having a thickness of between 0.005 and 0.0009 inch. 
     The aortic occlusion catheter  2 A passes through the cannula  28  so that oxygenated blood can be delivered to the patient when the aortic occlusion device  2 A is removed. The cannula  28  is preferably the cannula  28  described above with the first arm  32  coupled the source of oxygenated blood  72 , pressure monitor  68 , and source of cardioplegic fluid via valve  86 . Thus, cardioplegic fluid and oxygenated blood can be directed through the lumen  35  in the cannula  28  if the lumen  84  is not  36  to seal the space between the cannula  28  and aortic occlusion device  2 A. 
     Referring to  FIG. 14 , yet another aortic occlusion device  2 B is shown. The aortic occlusion device  2 B has the occluding member  4  and the inflation lumen  6  coupled to the source of inflation fluid  66  for inflating the occluding member  4 . The aortic occlusion device  2 B also has a lumen  88  for delivering oxygenated blood to the patient from the source of oxygenated blood  72 . The shaft is preferably reinforced with a wire in the manner described above except that the lumen  88  is sized large enough to provide adequate blood flow to the patient at an acceptable pressure as discussed above. The cannula  28  is preferably the same as the cannula  28  described above and the aortic occlusion device  2 B is introduced through the cannula  28  in the manner described below. The first arm  34  of the cannula  28  has the hemostasis valve  36  for receiving the aortic occlusion device  2 B. The second arm  32  is coupled to a valve  90  which determines whether cardioplegic fluid or oxygenated blood is delivered through the lumen  35  in the cannula  28 . Valve  92  determines whether oxygenated blood is delivered through the lumen  35  in the cannula  28  or the lumen  88  in the aortic occlusion device  2 B. An advantage of the aortic occlusion device  2 B and cannula  28  is that bypass support can be provided before inflating the occluding member  4  and can also be maintained after the aortic occlusion device  2 B is removed from the cannula  28 . 
     Referring to  FIGS. 15 , another aortic occlusion device  2 C is shown. The aortic occlusion device  2 C has a balloon  94  mounted to a side of a shaft  96 . The aortic occlusion device  2 C has an inflation lumen  98  for inflating the balloon  94  through inflation outlet  100  and a lumen  102  for delivering cardioplegic fluid from the source of cardioplegic fluid  64  and venting the ascending aorta using the vacuum source  70 . The aortic occlusion device  2 C also has a blood flow lumen  104  for delivering oxygenated blood to the patient from the source of oxygenated blood  72 . A fluid path  106  passes through the balloon  94  which is in fluid communication with the lumen  102  so that cardioplegic fluid is delivered through the fluid path  106  in the balloon  94 . An advantage of the aortic occlusion device  2 C is that the cardioplegic fluid can be delivered toward the aortic valve while oxygenated blood is directed in the direction of normal blood flow in the aortic arch. The distal end of the aortic occlusion device has an open end  108  and side ports  110  through which the oxygenated blood is delivered. The aortic occlusion device  2 C also includes the ring  46  which is the same as the ring  46  described above. The aortic occlusion device  2 C may be manufactured in any manner such as the manner described above or as a simple extrusion or laminated structure. 
     Referring to  FIG. 16 , the aortic occlusion device  2  is shown passing through a side port  112  of a cannula  28 D. The side port  112  facilitates positioning the occluding member  4  in the ascending aorta. The aortic occlusion device  2  is preferably the aortic occlusion device  2  described above. The aortic occlusion device  2  passes through a lumen  114  in the cannula  28 D. The lumen  114  is coupled to the source of oxygenated blood  72  so that the oxygenated blood is delivered through the annular area between the aortic occlusion device  2  and the wall of the lumen  114 . The lumen  114  has an open end  116  with a cross-member  118  which prevents the aortic occlusion catheter  2  from passing through the open end  116 . An advantage of the side port  112  is that the aortic occlusion device  2  is directed into the ascending aorta while blood passing through the lumen  114  is directed in the direction of normal blood flow in the aorta. 
     Referring to  FIGS. 18 and 19 , another aortic occlusion device  2 E is shown. The aortic occlusion device  2 E is similar to the aortic occlusion device  2 A of  FIG. 13  in that balloon  130  is inflated with oxygenated blood delivered from the source of oxygenated blood  72 . Oxygenated blood is delivered to the patient through a lumen  132  and an open end  134  of the aortic occlusion device  2 E. As will be described below, the interior of the balloon  130  is fluidly coupled to the lumen  132  through an inflation hole  133  for inflating the balloon  130  when blood is delivered through the lumen  132 . 
     The aortic occlusion device  2 E includes a body  136  having the y-arm connector  30  described above. A sleeve  138  is positioned in the lumen  132  to control inflation and deflation of the balloon  130 . Blood passing through the lumen  132  passes through the sleeve  138  so that the sleeve  138  does not interfere with delivery of oxygenated blood to the patient. The sleeve  138  is attached to a rod  140  which is manipulated to move the sleeve  138  between the positions of  FIGS. 18 and 19 . The sleeve  138  has a hole  142  which is aligned with the inflation hole  133  as shown in  FIG. 18  to fluidly couple the interior of the balloon  130  with the lumen  132 . When the sleeve  138  is advanced to the position of  FIG. 19 , the hole  142  is not aligned with the inflation lumen  133  and the sleeve  138  covers the inflation hole  133  so that the interior of the balloon  130  is not fluidly coupled to the lumen  132 . 
     The sleeve  138  permits the surgeon to control inflation and deflation of the balloon  130 . After introduction of the aortic occlusion device  2 E, bypass support is generally initiated before inflating the balloon  130 . This can be accomplished by maintaining the sleeve  138  in the position of  FIG. 19  so that the balloon  130  is not inflated by the blood delivered through the lumen  132 . When it is desired to inflate the balloon  130  and occlude the ascending aorta, the sleeve  138  is moved to the position of  FIG. 18  so that the balloon  130  is inflated with blood. The sleeve  138  also permits the surgeon to maintain full occlusion of the ascending aorta even when blood flow is reduced to a level which would not provide sufficient pressure to inflate the balloon to maintain full occlusion of the aorta. In order to maintain occlusion at low flow rates, the sleeve  138  is moved to the position of  FIG. 19  before reducing the blood flow rate so that the balloon  130  will remain inflated when the delivery pressure drops. Finally, the sleeve  138  also permits the surgeon to maintain bypass support with a deflated balloon  130  after the surgical procedure is completed. In order to maintain deflation of the balloon while delivering blood, the blood flow rate is reduced to deflate the balloon  130 , the sleeve is moved to the position of  FIG. 19  to deflate the balloon, and the blood flow rate is then increased. The sleeve  138  prevents the balloon  130  from inflating when the blood flow rate is increased. 
     The body  136  may be made in any suitable manner and is preferably manufactured similar to the cannula  28  of  FIG. 6. A  support tube  144  is attached to the body and the balloon  130  is mounted to the support tube. A soft tip  145  is attached to the distal end of the support tube  144  to provide an atraumatic distal end to prevent injury during introduction of the device  2 E. The sleeve  138  may be made of any suitable material and is preferably a urethane tube. The rod  140  may also be made of any suitable material and is preferably urethane coated polyamide. Although it is preferred to provide the sleeve  138  between the interior of the balloon  130  and the lumen  132  any other device may be used such as a valve, balloon or plug. 
     Use of the cannula and aortic occlusion device  2  is now described in connection with  FIGS. 12 and 17 . The description below is applicable to all cannulae  28 ,  28 D and aortic occlusion devices  2 ,  2 A,  2 B,  2 C described herein. Although the method described below is for direct insertion of the cannula  28  and aortic occlusion device  2  into the aortic arch, the cannula  28  and aortic occlusion device  2  may also be introduced through a peripheral artery such as the femoral, subclavian or axillary arteries as described in U.S. Pat. No. 5,484,803. 
     Before introduction of the cannula, a rib retractor  120  or other device is used to form an opening in an intercostal space such as the 4 th  intercostal space. The opening through the intercostal space is used for access to perform a surgical procedure such as a valve repair or replacement. The opening also provides direct access to the ascending aorta for control of the ascending aorta and to place purse-string sutures in the aorta. 
     An incision is also created in the 1 st  or 2 nd  intercostal space in which an 11.5 mm trocar  122  is positioned. The cannula  28  is then introduced through the trocar  122  and advanced to the surface of the aorta with the introducer  50  (see  FIGS. 10 and 11 ) positioned in the lumen  35  of the cannula  28  to determine the appropriate orientation of the cannula  28 . The distal end of the introducer  50  is then moved into contact with the aorta about 1-2 cm below the origin of the innominate artery to identify the appropriate location for purse-string sutures  124 . The surgeon that places two purse-string sutures  124  around the site. The ends of the purse-string sutures  124  are passed through tubes  126  which are used to tension the purse-string sutures  124 . The purse-string sutures  124  are then passed through the slots  48  in the ring  46 . 
     The cannula  28  is then advanced into contact with the aorta at the site now surrounded by the purse-string sutures  124 . The surgeon then incises the aorta with the incising element  52  of the introducer  50  or with a separate incising instrument. The cannula  28  is then immediately advanced through the incision until the ring  46  engages the aorta. The radiopaque marker  45  may be viewed under fluoroscopy and the cannula  28  manipulated until the beveled tip is directed toward the aortic valve. Alternatively, the tip orientation may be determined by TEE. The purse-string  124  sutures are then tensioned to seal around the cannula  28 . The aortic occlusion device  2  is then passed through the hemostasis valve  36  and advanced until the occluding member  4  is positioned in the ascending aorta. Delivery of oxygenated blood, occlusion of the ascending aorta and delivery of cardioplegic fluid is then performed in the manner described in U.S. Pat. No. 5,484,803. 
     Referring now to  FIGS. 20-24 , a cannula  28 F is shown wherein the same or similar reference numbers refer to the same or similar structure. The cannula  28 F may be used with any of the catheters and cannulae described herein and, thus, the features of the cannula  28 F may be included in any of the cannulae or catheters described herein without departing from the invention. For example, the cannula  28 F may receive the aortic occlusion catheter  2  ( FIG. 24 ) or have the aortic occlusion member  4  (see FIG.  25 ). The cannula  28 F may also be used to simply deliver blood in conventional open-chest surgery where an external cross-clamp is used to occlude the ascending aorta. 
     The cannula  28 F is similar to the cannula  28  described above except that the cannula  28 F has a curved or angled distal portion  130  when in the natural, unbiased shape of  FIGS. 20 and 21 . An advantage of the curved or angled distal portion  130  is that fluids, such as blood, may be infused or withdrawn from a passageway with the cannula  28 F directed with or against natural flow. Another advantage of the curved or angled distal end  130  is that the cannula  28 F is centered in the vessel so that fluid infused through the cannula  28 F is not directed at a wall. The cannula also helps to center the catheter  2  extending from the distal end of the cannula  28 F. Centering the catheter  2  ensures that the distal tip of the catheter  2  is centered in the vessel rather than directed at a vessel wall to facilitate fluid infusion or venting through the catheter  2  as described above. The distal portion  130  also helps anchor the catheter  2  and occluding member  4  in the vessel to resist migration of the catheter  2  and distortion of the occluding member  4 . 
     Referring to  FIG. 22 , the introducer  50  straightens the distal portion  130  of the cannula  28 F for introduction of the cannula  28 F into a vessel. The straightened configuration facilitates introduction since the cannula  28 F is advanced into the vessel with simple linear motion from the proximal end of the device. Although it is preferred to use the introducer  50  described above, any other suitable introducer may be used including an introducer without an incising element. The cannula  28 F preferably includes the y-arm connector  30  having the first and second arms  32 ,  34  each coupled to the lumen  35 . The y-arm connector  30  has the hemostasis valve  36  for receiving a catheter such as any of the aortic occlusion catheters  2 ,  2 A,  2 B described herein. The cannula  28 F is preferably manufactured in substantially the same manner as cannula  28  described above, however, cannula  28 F may be also made in any other suitable manner such as extrusion molding. 
     Use of the cannula  28 F is now described in connection with  FIGS. 23 and 24 . As mentioned above, all features of the cannula  28 F may be included in any of the cannulae and catheters described herein and description of the method is applicable to all of the cannulae and catheters. Purse-string sutures (not shown) are sewn in the aorta to provide hemostasis around the cannula. The cannula  28 F is moved toward the aorta and the incising element  52  (see  FIG. 11 ) is extended to incise the aorta. The cannula  28 F is then advanced into the aorta, the incising element  52  is retracted and the purse-string sutures are tensioned. The introducer  50  is then removed which permits the distal portion  130  of the cannula  28 F to curve or angle in the manner shown in FIG.  24 . Catheters, such as the aortic occlusion device  2 , can then be advanced into the aorta as described above for occlusion of the aorta, delivery of cardioplegic fluid and return of oxygenated blood. Alternatively, the cannula  28 F may be oriented downstream to simply deliver blood from a bypass system. Referring to  FIG. 25 , another cannula  28 G is shown which includes the occluding member  4  and lumen  132  for venting and delivery of cardioplegic fluid. 
     Referring to  FIGS. 26 and 27 , another cannula  28 H is shown wherein the same or similar reference numbers refer to the same or similar structure. The cannula  28 H has an angled shape to move the shaft out of the surgical field and away from the surgeon so that the cannula  28 H does not interfere with the procedure. The angled shape is particularly useful when introducing the cannula  28 H through small incisions between the ribs such as an incision in the first or second intercostal space. The cannula  28 H may, of course, be introduced through a median sternotomy, thoracotomy or other surgical incision without departing from the scope of the invention. 
     The cannula  28 H has a first section  150  extending from the y-arm connector  30  to a second section  152  which is angled with respect to the first section  150 . The second section  152  extends from 2-6 cm and more preferably 3-4 cm from a distal end  154 . The first section  150  forms an angle α with the second section  152  of about 110 to 140 degrees and more preferably about 125 degrees. The stabilizing ring  46 H is mounted to the first section  150  and preferably forms an angle β of about 45 to 85 degrees and more preferably about 60-75 degrees with the first section  150 . The ring  46 H is preferably attached to the second section  152  about 3-4 cm from the distal end  154 . The cannula  28 H may be used as a substitute for any of the other cannulae  28 H described herein and, thus, the cannula  28 H may receive catheters  2 ,  2 A,  2 B, have the occluding member  4  or may be used to simply return blood to the patient from a bypass system. The cannula  28 H may be manufactured in any suitable manner and is preferably manufactured in a substantially similar manner to the cannula  28  described above. 
     Another aortic occlusion device  2 J is now described in connection with  FIGS. 28-30  wherein the same or similar reference numbers describe the same or similar structure. The aortic occlusion device  2 J includes a balloon  160  having a first, small section  162  and a second, larger section  164 . The first section  162  minimizes the amount of space that the balloon  160  occupies in the aorta to maximize space in the aorta for performing aortic valve procedures and proximal anastomoses in coronary artery bypass procedures. The second section  164  stabilizes the first section  162  so that the first section  162  remains stable in the aorta. If the balloon  160  was discoid, for example, the balloon  160  may become unstable in the aorta and partially flip to one side or the other. Flipping or distortion of the balloon  160  can prevent full occlusion of the aorta which would allow warm, oxygenated blood to reach the patient&#39;s coronary arteries and possibly start the patient&#39;s heart beating before the procedure is completed. 
     Referring to the end view of  FIG. 29 , the second section  164  expands to a semi-circular profile with a top portion  166  of the second section  164  bonded to the shaft. The second section  164  preferably extends about 180 degrees around the cannula, however, the second section  164  may extend anywhere between 90 degrees and 230 degrees around the cannula shaft. 
     A cross-sectional view of the aortic occlusion device  2 J is shown in FIG.  30 . The aortic occlusion device  2 J is preferably wire-reinforced in the manner described above, however, the aortic occlusion device  2 J may be manufactured in any other suitable manner. The aortic occlusion device  2 J includes a lumen  165  having an outlet to return oxygenated blood to the patient. The aortic occlusion device  2 J also has a lumen  166  to deliver cardioplegic fluid and vent the aorta and a lumen  167  to inflate the balloon  160 . The lumen  166  may also receive a vent catheter  168  which passes into the ascending aorta to vent blood from the ascending aorta as described above. 
     The first and second sections  162 ,  164  may be positioned around the aortic occlusion device  2 J in any orientation depending upon the angle and location that the cannula  2 J is introduced into the aorta. The second section  164  is preferably positioned diametrically opposite the head and neck vessels so that the head and neck vessels are not blocked.  FIG. 31  shows the first and second sections  162 ,  164  switched for use when the cannula is introduced from an inferior location.  FIGS. 32 and 33  show yet another embodiment where the first and second sections  162 ,  164  are on opposite sides of the cannula. The aortic occlusion device  2 J may, of course, take any of the forms described herein. For example, the orientation of the device  2 J may be reversed so that blood passes through the lumen  166  and cardioplegic fluid is delivered through the lumen  165 . The aortic occlusion device  2 J may also be configured with the separate arterial cannula  28  ( FIG. 12 ) rather than having the lumen  165  integrated into the device  2 J. 
     Referring to  FIG. 34 , another aortic occlusion device  2 K is shown wherein like or similar reference numbers refer to like or similar structure. The aortic occlusion device  2 K has a thin, discoid occluding member  4 K, which is preferably a balloon, stabilized and supported by a stabilizer  170 . As mentioned above, the discoid occluding member  4 K may be unstable in the aorta which can cause a portion of the occluding member to flip or otherwise distort thereby preventing full occlusion of the aorta. The stabilizer  170  supports and stabilizes the occluding member  4 K thereby preventing the discoid occluding member  4 K from flipping or distorting. The stabilizer  170  is positioned adjacent the occluding member to engage and contact the occluding member  4 K. 
     The stabilizer  170  is preferably an open mesh  172  when in the expanded condition which permits blood flow to the head and neck vessels. An advantage of the stabilizer  170  is that the discoid occluding member  4 K can be moved closer to the head and neck vessels to provide more room in the aorta to perform surgical procedures. Although the stabilizer  170  preferably has a woven or mesh structure, the stabilizer  170  may also be a perforated tube or an expanding basket or cone without departing from the scope of the invention. 
     The device  2 K has the arterial cannula  2 B and the aortic occlusion device  2 B described above and the system may, of course, have any of the other suitable cannula and/or catheter configuration. The aortic occlusion device  2 K includes another y-arm connector  174  having a hemostasis valve  176  which receives the stabilizer  170 . The stabilizer  170  is preferably independent of the shaft supporting the occluding member  4 K but may also be integrally formed with the shaft to which the occluding member  4 K is attached. 
     Referring to  FIGS. 35 and 36 , the stabilizer  170  includes a shaft  178  having a passageway  180  which receives a wire  182  which is pulled to move the stabilizer  170  to the expanded condition of  FIG. 36. A  proximal end  184  of the mesh  172  is attached to a distal end  186  of the shaft  178  and a distal end  188  of the mesh  172  is attached to the wire  182 . The stabilizer  170  is naturally biased to the contracted position of  FIG. 35  so that the stabilizer  170  is collapsed by simply releasing tension on the wire  182 . The mesh  172  is preferably made of stainless steel wire or a plastic braid, although any suitable material may be used. 
     Although the method described above positions the aortic occlusion device through an opening separate from the opening through which the surgeon operates, the cannula and aortic occlusion device  2  may also be introduced through the same opening through which the surgeon operates. The choice of opening location, number and size are a matter of surgical choice depending upon patient anatomy, the medical procedure being performed, surgeon preference and the particular embodiment of the invention being used. Furthermore, the devices described herein may have application in other parts of the heart and in other parts of the body. Thus, the description of the specific procedure described above is merely an example and other surgical methods may be used with the devices and methods of the present invention.