Abstract:
A system is disclosed for cannulating the vena cava of a patient during cardiopulmonary bypass procedures. Such cannulation is necessary for drainage of venous blood from the patient so that it may be oxygenated and pumped back to the patient to perfuse tissues during cardiac surgery and, more specifically, during periods of ischemic cardiac arrest or dysfunction. The device of the present invention not only provides venous drainage for cardiopulmonary bypass, but also performs the function of routing cardioplegic solution through the heart in the retrograde direction. Such cardioplegia provides protection to the heart during periods of ischemic cardiac arrest. This invention replaces a plurality of cannulae currently used for open-heart surgery, thus simplifying the surgical field and improving visibility of the heart. The device allows for the delivery of retrograde cardioplegia to the coronary circulation of both the right and the left side of the heart. The device further includes protection mechanisms to prevent overinflation or excessive pressurization of the right atrium during retrograde delivery of cardioplegia solution.

Description:
PRIORITY CLAIM  
       [0001]     This application is a continuation of U.S. application Ser. No. 10/759,310, now U.S. Pat. No. 6,821,263, filed Jan. 16, 2004, which is a continuation-in-part of U.S. application Ser. No. 09/894,564, now U.S. Pat. No. 6,682,499, filed on Jun. 28, 2001, the entirety of which are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of this invention is cardiac bypass surgery and cardiopulmonary bypass.  
       BACKGROUND OF THE INVENTION  
       [0003]     During cardiac surgery for procedures such as coronary artery bypass grafting, heart valve repair or replacement, septal defect repair, pulmonary thrombectomy, atherectomy, aneurysm repair, aortic dissection repair and correction of congenital defects, cardiopulmonary bypass and cold cardiac ischemic arrest are often required. Typically, a cooled cardioplegia solution, a solution containing elevated levels of potassium, for example, is administered in the antegrade direction (in the direction of normal blood flow) through the patient&#39;s aorta and into the coronary arteries. The cold (2 to 3 degrees centigrade) cardioplegia solution stops the heart from beating and reduces its temperature to minimize damage to the heart during surgery. The cardioplegia solution exits the coronary circulation through the coronary veins at the coronary sinus, where it empties into the right atrium. Cardiopulmonary bypass maintains the peripheral circulation of oxygenated blood to all body organs except the heart during the period of cold, cardioplegic, ischemic arrest.  
         [0004]     For some patients, such as those suffering from critical coronary artery stenosis and aortic valve disease, antegrade perfusion may be difficult, inefficient and incomplete. Retrograde (in the direction opposite of normal blood flow) cardioplegia, using current technology, may be administered via the coronary sinus into the coronary circulation using devices, which cannulate the coronary sinus. Such cannulation of the coronary sinus by prior art devices requires inserting a catheter into the coronary sinus and perfusing cardioplegia into the sinus. Drainage of cardioplegia solution is accomplished into the coronary ostea located at the base of the aorta. The problem with prior art methods is that either the right or left heart will be perfused, but not both, since the right coronary veins come off the coronary sinus at an angle and are not cannulated by current catheters that cannulate the left coronary veins. Thus, incomplete perfusion of segments of the heart muscle, primarily the right heart and septum, will occur since the right coronary veins frequently come off near the coronary sinus ostea or within the right atrial wall proper. The right coronary veins are not perfused by prior art retrograde cardioplegic catheters.  
         [0005]     Currently surgeons performing cardiac bypass surgery use one or more cannulae for venous drainage and an additional cannula for retrograde perfusion. The multiple cannulae are obstacles and restrict visibility in the surgical arena. Placement of the cardioplegia cannula into the coronary sinus is a semi-blind procedure performed through an additional purse-string suture-closed access port via the right atrium. The retrograde cannula may be improperly positioned within the coronary sinus, which results in critical coronary vessels being inadequately perfused. Typically, placement of currently available retrograde cardioplegia cannula within the coronary sinus results in retrograde perfusion of the left heart but inadequate retrograde perfusion of the right heart because of cannula obstruction of the right coronary ostea as they arise from the coronary sinus. Thus the tissue of the left heart is perfused, in a retrograde direction, with cardioplegia solution but the right heart is perfused with a diminished, or no, supply of cardioplegia solution since the right coronary veins are generally a side-branch of the left coronary veins at the coronary sinus and the right coronary veins are blocked by the cannula. Poor right heart retrograde perfusion occurs because, most-frequently, anatomic variations of the right coronary sinus and veins cannot be properly perfused with the currently available cannula.  
         [0006]     New devices and methods are needed, which facilitate cold cardioplegic arrest, yet limit the number of cannulae required to isolate the heart and coronary blood vessels from the peripheral vasculature, arrest the heart, protect all the coronary blood vessels, protect all or most of the myocardium, and drain venous blood from the inferior and superior vena cava. Furthermore, it would be advantageous to the diseased myocardium being subjected to ischemic arrest if a retrograde cardioplegia perfusion cannula could perfuse the coronary vasculature of both the right and left heart simultaneously.  
       SUMMARY OF THE INVENTION  
       [0007]     This invention relates to a balloon, or tourniqueted, catheter or cannula useful in the retrograde administration of cardioplegia through the coronary sinus and simultaneous venous drainage during cardiac bypass surgery without the need to cannulate the coronary sinus.  
         [0008]     The invention is a cannula for performing venous drainage and retrograde perfusion of the heart during cardiac bypass surgery. A single multi-lumen cannula of the present invention can perform the same function as multiple cannulae currently used. The cannula of the invention for cardioplegic administration can improve the protection of a heart during periods of ischemia such as occurs during open-heart surgery. The cannula is preferably fabricated from materials, which are biocompatible for the intended use.  
         [0009]     One embodiment of the invention is a multi-lumen cannula with occlusive structures for the superior and inferior vena cava, a protection structure, cardioplegia infusion channel, a pressure monitoring port, and venous drainage ports. Occlusion structures may include devices such as, but not limited to, balloons, umbrellas, structures that draw a vacuum against a wall of the heart, externally applied tourniquets, umbrellas with rim-seal balloons, or the like. In a preferred embodiment, the occlusion structures are balloons constructed of elastomeric materials or vacuum-assisted walled structures.  
         [0010]     In one embodiment, a first lumen of the cannula is connected to the cardioplegia infusion system and provides cardioplegia solution to arrest the heart. A second cannula lumen is connected to the venous drainage system. The drainage ports are located in the second lumen. A third lumen is connected to the balloon inflation system, which provides inflation fluids, such as water, isotonic saline or cardioplegia solution, under controlled pressure or volume to inflate the occlusion balloons. The pressure of the occlusion balloons and right atrium may also be monitored through additional lumens. The occlusion balloons isolate the heart from the peripheral vasculature by occluding the inferior and superior vena cava just proximal to the right atrium. The inferior and superior vena cava balloons utilized to direct flow into the extracorporeal circuit are optionally movable to accommodate anatomic variability. Additional lumens may be utilized for inflation of multiple balloons, pressure monitoring, flow monitoring, drainage of cardioplegia, fluid and drug infusion and the like. Since it is useful to measure cardioplegic perfusion pressure, a pressure transducer or pressure measuring lumen may, for example, be provided at or near the distal end of the cardioplegia perfusion lumen for this purpose.  
         [0011]     The cannula may be placed into the vena cava, for example, via a route through the internal jugular vein, cranial vena cava, femoral vein, or brachial vein. A smaller diameter cannula may be placed through any of the smaller venous access ports. The use of smaller venous access ports may be enabled by use of a pump or vacuum powered venous drainage system, typically external to the cannula. In one embodiment, the catheter or cannula combines the functions of several catheters currently used in cardiac surgery. A single catheter, rather than multiple catheters, facilitates the surgery and improves the surgical field because extra cannulae do not obstruct the operative field. In addition, the number of individual catheters is reduced, providing a more cost effective method for cardiac surgery. Most importantly, improved cardiac protection is achieved compared to that of standard retrograde perfusion cannulae.  
         [0012]     In yet another embodiment, a single-function venous drainage cannula comprising occlusion balloons, a cannula, a drainage lumen and ports, and a balloon inflation lumen and ports is provided for access through any percutaneous access point and is routed to the right atrium through the venous system. This embodiment would be very useful for emergency cardiac assist.  
         [0013]     The cannula of the present invention provides for venous drainage and simultaneous retrograde cardioplegia delivery into the coronary sinus of the heart so that the myocardium of both the right and left heart is perfused. In doing so, the coronary sinus is pressurized. Optionally, some or all of the right atrium is pressurized. Since such pressurization is unnatural for the thin walls of the right atrium, the catheter or cannula, in one embodiment, provides structures that protect the walls of the right atrium from the high perfusion pressures and minimize the risk of wall rupture. These protective structures include double wall balloons that inflate to approximate the interior of the right atrium. The space between the inner wall and the outer wall is ribbed or channeled so that gaps are maintained when a vacuum is drawn in the space between the outer wall and the inner wall of the balloon. The vacuum is drawn through the cannula by a vacuum applied at the proximal end of the cannula by way of a connector. The venous drainage cannula runs through the center of the balloon and allows for venous blood drainage from both the superior and inferior vena cava. The balloon further comprises a walled off region that is disposed laterally relative to the venous drainage cannula and permits pressurization of the coronary sinus with cardioplegia solution which is introduced at the proximal end of the cannula and which flows through a lumen in the cannula to reach the walled-off region. In one embodiment, the protection structure eliminates the need for the occlusive balloons in the vena cava.  
         [0014]     In yet another embodiment, the balloon does not require pulling a vacuum but simply inflates to seal off or isolate the walls of the vena cava relative to the walled-off region in which pressurized cardioplegia solution is infused. Seals or gaskets are provided to ensure that such pressure seal is optimized. In yet another embodiment, the vacuum system further comprises an external collection reservoir and plumbing that returns any blood or bodily fluids captured by the vacuum system, to the external cardiopulmonary circuit.  
         [0015]     Since the cardioplegia cannula does not cannulate the coronary sinus, it will perfuse both the left and right side of the heart. Perfusion of the right heart may be very important in obtaining optimal patient outcomes following cardiopulmonary bypass. In addition, cold cardioplegic solution will bathe the endomyocardium of the right ventricle aiding in myocardial protection of the right heart.  
         [0016]     In one embodiment, a venous cannula is adapted for retrograde administration of cardioplegia solution to a heart and simultaneous venous drainage from a vena cava during cardiopulmonary bypass comprising a cardioplegia solution infusion mechanism, wherein the cardioplegia solution infusion mechanism receives pressurized cardioplegia solution and routes the pressurized cardioplegia solution into a coronary sinus, located in a right atrium of a heart, without cannulating the coronary sinus. The venous cannula further comprises a venous blood drainage mechanism, wherein the venous blood drainage mechanism drains venous blood from a superior and an inferior vena cava. The cannula further comprises a vena cava occlusion mechanism, wherein the vena cava occlusion mechanism occludes the vena cava from the right atrium to prevent pressurized cardioplegia solution from entering the vena cava. The venous cannula further comprises a protection device, wherein the protection device limits pressurization of the right atrium by the pressurized cardioplegia solution.  
         [0017]     One aspect of the invention is a method of cannulating a patient&#39;s heart during cardiopulmonary bypass comprising the steps of inserting a cannula into a venous system of a patient and then positioning the cannula so that said cannula traverses a right atrium and extends into both a superior and an inferior vena cava. The method further comprises enabling an occlusion device in each of the superior and inferior vena cava and draining venous blood from the vena cava. The method further comprises inflating a protection balloon within the right atrium and infusing cardioplegia solution, in the retrograde direction, into a coronary sinus of the heart, without cannulating the coronary sinus, wherein the cardioplegia solution is infused through the cannula into the coronary sinus.  
         [0018]     In another embodiment of the invention, a venous cannula is adapted for retrograde administration of cardioplegia solution to a heart during cardiopulmonary bypass and comprises a length of axially elongate multi-lumen tubing with a proximal end and a distal end, wherein at least one of the lumens is a cardioplegia solution infusion lumen, and a cardioplegia solution infusion annulus located near the distal end of the multi-lumen tubing the infusion annulus being operably connected to the cardioplegia solution infusion lumen. The venous cannula further comprises an annular seal ring surrounding the cardioplegia solution infusion annulus, wherein a vacuum lumen in the multi-lumen tubing is operably connected to the annular seal ring. The venous cannula also comprises a cardioplegia solution infusion mechanism, wherein the cardioplegia solution infusion mechanism receives pressurized cardioplegia solution from an external cardioplegia solution infusion source and delivers it to the cardioplegia solution infusion lumen.  
         [0019]     For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.  
         [0020]     These and other objects and advantages of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced elements.  
         [0022]      FIG. 1  illustrates a longitudinal cross-section of the cannula of the present invention comprising a distal tip, a proximal end, and a connecting tube according to aspects of an embodiment of the invention. External systems provide for venous drainage, cardioplegia infusion, and balloon inflation;  
         [0023]      FIG. 2  illustrates a lateral cross-section of a multi-lumen axially elongate tube for construction of the cannula according to aspects of an embodiment of the invention;  
         [0024]      FIG. 3  illustrates, in detail, a longitudinal cross-section of the distal tip of the cannula of  FIG. 1  according to aspects of an embodiment of the invention;  
         [0025]      FIG. 4  illustrates, in detail, a longitudinal cross-section of the proximal end of the cannula of  FIG. 1  according to aspects of an embodiment of the invention;  
         [0026]      FIG. 5  shows the placement of the cannula of the present invention in the heart for venous drainage and retrograde perfusion according to aspects of an embodiment of the invention;  
         [0027]      FIG. 6  illustrates, in exterior view, another embodiment of the cannula comprising multiple balloons to accommodate various anatomic differences according to aspects of an embodiment of the invention. Cutouts on the balloons show features on the cannula surface that would normally be hidden by the balloons;  
         [0028]      FIG. 7  illustrates a lateral cross-section of a multi-lumen tube for construction of the cannula of  FIG. 6  according to aspects of an embodiment of the invention;  
         [0029]      FIG. 8  illustrates a longitudinal cross-section of a cannula comprising a balloon to protect the walls of the vena cava from high pressure during retrograde cardioplegia infusion, according to aspects of an embodiment of the invention;  
         [0030]      FIG. 9  illustrates a lateral cross-section of an axially elongate, multi-lumen tube for use in a cannula comprising a balloon to protect the walls of the vena cava from high pressure during retrograde cardioplegia infusion, according to aspects of an embodiment of the invention;  
         [0031]      FIG. 10  illustrates a longitudinal cross-section of the distal end of a cannula comprising a laterally directed retrograde cardioplegia delivery annulus and a seal system surrounding the cardioplegia delivery annulus, according to aspects of an embodiment of the invention; and  
         [0032]      FIG. 11  illustrates a longitudinal cross-section of a distal end of a cannula comprising a forward directed retrograde cardioplegia delivery annulus, a seal system surrounding the cardioplegia delivery annulus, and a steering mechanism, according to aspects of an embodiment of the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     As used herein the terms distal and proximal are used to clarify the location of various points along the axial length of the venous drainage and retrograde perfusion catheter or cannula. Points are defined with respect to the end grasped by the user and the end that is inserted in the patient in the same manner as would one skilled in the art of medical device catheter construction. The proximal end of the catheter or cannula is defined as that end closest to the user or operator of the catheter or cannula while the distal end of the catheter or cannula is defined as that end that is inserted into the patient.  
         [0034]      FIG. 1  illustrates a catheter, tube or cannula  10  of an embodiment of the invention connected to a cardioplegia infusion system or set  12 , a venous drainage collection system  14  and an occlusion enabling system  16 . In this preferred embodiment, the occlusion enabling system  16  is a balloon inflation system. The catheter  10  comprises a distal tip  18 , a proximal end  20 , and a length of multi-lumen connection tubing  22 . The proximal end  20  comprises a manifold or hub  23 . The manifold  23  comprises a cardioplegia infusion adapter or fitting  24 , a venous drainage collection adapter or fitting  26 , and an occlusion adapter  28 . In a preferred embodiment, the occlusion adapter  28  may be a balloon inflation adapter, quick-connect, bayonet, luer fitting, or the like. The manifold  23  is typically molded from materials such as, but not limited to, polymers such as polyvinyl chloride, polycarbonate, ABS, polyimide, poly methyl-methacrylate, or the like.  
         [0035]     The cardioplegia infusion adapter  24  is connected to the cardioplegia infusion system  12 . The cardioplegia infusion adapter  24  may be any fluid-tight fitting, such as, for example, a luer adapter, quick-connect, or other fluid-tight fitting, suitable for use with the cardioplegia infusion set  12 . The standard cardioplegia system  12  generally comprises a pressurized or non-pressurized bag of cardioplegia solution, a roller pump or similar pressurizing system, a length of tubing and a plurality of connectors. Standard cardioplegia solutions include those comprising water, electrolytes such as but not limited to potassium, crystalloid solutions, blood, and the like.  
         [0036]     The venous drainage collection adapter  26  is connected to the venous drainage collection system  14 . The drainage collection adapter  26  is typically larger in diameter than the balloon inflation fitting  28  or cardioplegia infusion fitting  24 . The drainage collection adapter  26  should be capable of being connected to the gravity fed, pump driven or vacuum fed drainage system  14  and is, for example, a ⅜ inch to ½ inch diameter hose barb but could be as small as ⅛ inch in diameter. Standard venous drainage systems  14  generally comprise a connector, a length of tubing and a venous reservoir. Optionally, a vacuum pump may be connected to the venous reservoir.  
         [0037]     The balloon inflation adapter  28  is connected to the balloon inflation system  16 . The balloon inflation adapter  28  is typically a female luer fitting but may be any fluid-tight fitting suitable for use with an inflation syringe or the like. The standard balloon inflation system  16  comprises a syringe, a volume of balloon inflation fluid such as saline or radiopaque media, and a valve or stopcock associated with each balloon inflation adapter  28 . Additionally, the balloon inflation system  16  could comprise a device, such as, for example, a jackscrew, which is a threaded rod moved longitudinally by a longitudinally affixed but rotatable nut, or a pressurized hydraulic cylinder, to advance or withdraw a plunger on the syringe using mechanical advantage.  
         [0038]      FIG. 2  shows the cross-section of the connection tubing  22 . The connection tubing  22  may be a length of multi-lumen tubing comprising an infusion lumen  30 , a venous drainage lumen  32 , an inflation lumen  34 , and a wall  31 . The connection tubing  22  is preferably made from a polymeric material such as polyvinyl chloride, polyethylene, polypropylene, polyurethane and the like. In a preferred embodiment, the tubing  22  is transparent.  
         [0039]      FIG. 3  illustrates the distal tip  18  of the catheter  10  of  FIG. 1  in detail. The distal tip  18  is an extension of the connecting tubing  22  and comprises the infusion lumen  30 , the venous drainage lumen  32  and the inflation lumen  34 . Additionally, the distal tip  18  comprises a plurality of venous drainage ports  36 , a distal or first occlusion device  39 , a plurality of cardioplegia infusion port or ports  42 , and a proximal or second occlusion device  45 . The distal tip  18  further comprises an inflation lumen plug  48  and an infusion lumen plug  50 . A cardioplegic drainage lumen may likewise be utilized to adjust cardioplegic perfusion pressures, if needed.  
         [0040]     In an embodiment, the first occlusion device  39  comprises a first balloon  38  and a plurality of first balloon inflation ports  40 . The second occlusion device  45  comprises a second balloon  44  and a plurality of second balloon inflation ports  46 .  
         [0041]     The venous drainage ports  36  are openings in the drainage lumen  32  and connect the venous drainage lumen  32  with the exterior of the cannula  10 . There is no communication between the venous drainage lumen  32  and the other cannula lumens  30  and  34 . The venous drainage ports  36  are preferably located more proximally than the second balloon  44  and/or more distally than the first balloon  38  on the cannula  10 .  
         [0042]     The balloon inflation ports  40  and  46  are located on the inflation lumen  34 . The inflation lumen  34  is isolated from the other cannula lumens  30  and  32 . The first balloon  38  and the second balloon  44  are located over the first balloon inflation ports  40  and the second balloon inflation ports  46 , respectively. When the balloon inflation fluid flows through the inflation ports  40  and  46  from the inflation lumen  34 , the balloons  38  and  44  inflate.  
         [0043]     The cardioplegia infusion port(s)  42  are openings on the infusion lumen  30 . The infusion lumen  30  is isolated from the other lumens  32  and  34 . The cardioplegia infusion ports  42  are located between the balloons  38  and  44  such that cardioplegia solution is infused between the balloons  38  and  44  and is directed into the right atrium and ventricle of the heart where it subsequently passes into the coronary arteries by way of the coronary sinus.  
         [0044]      FIG. 4  shows the proximal end  20  of the cannula  10  of  FIG. 1  in detail. The proximal end  20  is an extension of the connecting tube  22  and comprises the cardioplegic infusion lumen  30 , the venous drainage lumen  32 , and the inflation lumen  34 . The proximal end  20  additionally comprises the manifold  23 , which comprises the cardioplegia infusion adapter  24 , the venous drainage collection adapter  26  and the balloon inflation adapter  28 . The cardioplegia infusion adapter  24  connects to the infusion lumen  30 . The venous drainage collection adapter  26  connects to the drainage lumen  32  and the balloon inflation adapter  28  connects to the inflation lumen  34 .  
         [0045]      FIG. 5  illustrates the placement of the cannula  10  of the present invention in a heart  100  during retrograde perfusion. The heart  100  comprises a left ventricle  102 , a right ventricle  104 , a coronary sinus  108 , a right atrium  110 , an inferior vena cava  112 , and a superior vena cava  114 .  
         [0046]     During normal operation of the heart, or during the normal cardiac cycle, blood returning from the tissues of the body passes through peripheral veins into the superior  114  and inferior vena cava  112  and into the right atrium  110 . The coronary sinus  108  is the region of the heart  100  where blood exits the coronary vascular circuit and passes back into the right atrium  110 . The coronary sinus  108  is located in close proximity to the inferior vena cava&#39;s entry into the right atrium  110 . Blood leaving the coronary circulation by way of the coronary sinus  108  joins the venous blood from the vena cava  112  and  114  in the right atrium  110 . The venous blood flows from the right atrium  110  into the right ventricle. Venous blood is pumped by the right ventricle  104  into the lungs where it is oxygenated and where carbon dioxide is removed. The oxygen-rich blood then passes into the left atrium and left ventricle  102  where it is then pumped into the systemic circulation to nourish the organs and tissues of the body. The coronary ostea, or entrance to the coronary arteries, are located at the root of the aorta, just downstream of the aortic valve.  
         [0047]     When the heart  100  is placed on cardiopulmonary bypass, blood is removed from the venous circulation at the inferior vena cava  112  and superior vena cava  114  and is routed to an oxygenator that adds oxygen and removes carbon dioxide. The oxygenated blood is pumped back into the patient&#39;s systemic circulation so tissues can be perfused while the heart is being surgically repaired.  
         [0048]     in an embodiment, the cannula  10  serves the triple function of blocking venous blood from entering the right heart during surgery, removing the venous blood from the vena cava so that it may be extracorporeally oxygenated and pumped back to the patient, and infusing cardioplegia solution into the heart in a retrograde direction during the surgical repair procedure.  
         [0049]     Referring to  FIGS. 1, 3 ,  4 ,and  5 , the physician makes an incision in the jugular vein, for example, and inserts the distal tip  18  of the catheter or cannula  10  into the incision. The catheter  10  is threaded into the vein, advanced into the vena cava  112  and  114 , and positioned, with the aid of fluoroscopy, for example, such that the balloons  38  and  44  are located in the inferior vena cava  112  and superior vena cava  114 , respectively. The cardioplegia infusion ports  42  are located at the entrance to, or inside of, the right atrium  110  and the drainage ports  36  are located in the superior vena cava  114  and inferior vena cava  112 , proximal or upstream of the balloons  38  and  44 . In one embodiment, the superior and inferior vena cava obstructive balloons  38  and  44  can be adjusted to an appropriate position within the respective vena cava  112  or  114 .  
         [0050]     Next, the balloon inflation system  16  is activated. Balloon inflation is accomplished by driving balloon inflation fluid from the balloon inflation system  16 , through the balloon inflation adapter  28 , into the balloon inflation lumen  34 , through the balloon inflation ports  40  and  46  and into the balloons  38  and  44 . The inflation lumen plug  48  prevents the balloon inflation fluid from escaping from the distal end of the inflation lumen  34 . This infusion of balloon inflation fluid causes the balloons  38  and  44  to inflate and occlude the entrance of the right atrium  110  from the superior vena cava  114  and the inferior vena cava  112 . Because of this occlusion, blood is prevented from flowing from the superior vena cava  114  and the inferior vena cava  112  into the right atrium  110  of the heart  100 , and must exit via the drainage ports  36  of the cannula  10 . The blood passes through the cannula  10  and on into the venous reservoir of the cardiopulmonary bypass system, also known as a circuit.  
         [0051]     The cardioplegia solution flows from the cardioplegia infusion system  12 , through the cardioplegia infusion adapter  24 , into the infusion lumen  30 , through the cardioplegia infusion ports  42 , and into the right atrium  110  where, under a moderate pressure of  120  mm Hg or less, the cardioplegia solution enters the coronary sinus  108  and the right ventricle  104 . In order for cardioplegic solution to enter the coronary sinus  108  in a retrograde fashion, the right atrium  110  and ventricle  104  must be pressurized, which necessitates occlusion of the pulmonary artery root. The pulmonary artery thus is typically cross-clamped, for example, to prevent perfusion of the lungs during surgery. The infusion lumen plug  50  prevents the cardioplegia solution from escaping from the distal end of the infusion lumen  30 . The cardioplegia solution arrests the beating of the heart  100  by interfering with the sodium potassium cycle of the cardiac muscle cells.  
         [0052]     In addition, the venous drainage collection system  14  is activated. Any blood in the superior vena cava  114  and inferior vena cava  112  flows through the drainage ports  36 , into the drainage lumen  32 , through the drainage collection adapter  26 , and into the drainage collection system  14 . The drainage collection system  14  collects the venous blood. This blood is, in most cases, routed to a venous reservoir of a cardiopulmonary bypass system. The blood then passes into an oxygenator where it undergoes removal of carbon dioxide and addition of oxygen. The blood also passes through a heat exchanger where it undergoes heat transfer, either heating or cooling. The oxygenated and cooled, or warmed, blood is pumped back into the patient&#39;s systemic circulation via an arterial cannula placed in a systemic artery distal to the aortic valve.  
         [0053]     The surgeon can now perform the prescribed heart surgery. A single cannula of the present invention provides the infusion, inflation, and drainage functions, which eliminates the need for the multiple cannulae currently used for open-heart procedures.  
         [0054]     Referring to  FIG. 5 , patients have different spacing between the entrance of the inferior vena cava  112  into the right atrium  110  and the entrance of the superior vena cava  114  into the right atrium  110 . A one-size-fits-all catheter  10  may not be optimum for use in all patients.  FIG. 6  shows a more preferred embodiment of the catheter, which compensates for anatomic differences between patients. The operations of cardioplegia infusion and drainage collection are the same as that described earlier for the cannula  10 .  
         [0055]     Referring to  FIG. 6 , the catheter or cannula  52  comprises a plurality of first balloons  54 , a second balloon  56 , a plurality of first balloon inflation port sets  58 , a plurality of second balloon inflation ports  60 , and a length of connecting tubing  62 . The catheter  52  also comprises a manifold  64 , which comprises a plurality of first balloon inflation adapters  66  and a second balloon inflation adapter  68 . The catheter is connected to the cardioplegia infusion system  12 , the venous drainage collection system  14 , and the balloon inflation system  16 .  
         [0056]      FIG. 7  illustrates a cross section of multi-lumen connection tubing  62  for the construction of the catheter  52  of  FIG. 6 . The tubing  62  comprises a plurality of first balloon inflation lumens  70 , a second balloon inflation lumen  72 , the infusion lumen  30 , the drainage lumen  32 , and the wall  31 .  
         [0057]     Referring to  FIGS. 6 and 7 , the balloon inflation system  16  connects to the catheter  52  through the first balloon inflation adapters  66  and the second balloon inflation adapter  68 . Each first balloon inflation adapter  66  connects to one first balloon inflation lumen  70 . The second balloon inflation adapter  68  connects to the second balloon inflation lumen  72 . Each set of first balloon inflation ports  58  is located on one first balloon inflation lumen  66 . The second balloon inflation ports  60  are located on the second balloon inflation lumen  72 . Each first balloon  54  is positioned over one set of first balloon inflation ports  58 , such that when inflation fluid is injected through the selected first balloon inflation ports  58 , only the first balloon  54  over the selected first balloon inflation ports  58  is inflated. The second balloon  56  is positioned over the second balloon inflation ports  60  such that when balloon inflation fluid is injected through the second balloon inflation ports  60 , the second balloon  56  is inflated. Each first balloon inflation adapter  66  has a corresponding first balloon inflation lumen  70 , as shown in  FIG. 7 , a corresponding set of first balloon inflation ports  58 , and a corresponding first balloon  54 .  
         [0058]     Referring to  FIGS. 5 and 6 , the physician places the catheter  52  into the right atrium  110 . The physician places the second balloon  56  in the entrance of the superior vena cava  114  and the series of first balloons  54  line up in the right atrium  110  and into the inferior vena cava  112 . The second balloon  56  is inflated to occlude the superior vena cava  114 . Only the first balloon  54  in the plurality of first balloons  54 , which is in the entrance of the inferior vena cava  112 , corresponding to the correct spacing for the patient&#39;s heart, is inflated to occlude the inferior vena cava  112 . Balloons  54  and  56  to be inflated are connected to the balloon inflation system  16  through their balloon inflation lumen  70  and  72 . The balloon inflation lumen  70  of the balloons  54  selected for non-inflation is simply not connected to the balloon inflation system  16 . In this manner, the catheter  52  is optimized for the individual patient&#39;s anatomy. The better fit minimizes the chance of the balloons  54  and  56  slipping out of position and leaking venous blood into the heart, with potentially severe complications for the surgery patient.  
         [0059]     Preferably, the plurality of balloons are located on the distal end of the catheter&#39;s cardioplegia infusion ports  42 , although multiple balloons proximal to the cardioplegia inflation ports  42  would also be acceptable. Only the balloons that are spaced correctly to occlude the patient&#39;s superior  114  and inferior  112  vena cava are inflated.  
         [0060]     In another embodiment for multiple balloon inflation selection, a single balloon inflation lumen may be connected to all of the balloons and to a control rod that selectively opens balloon inflation ports to the correct balloon or balloons. Such a control rod would typically be an axially elongate, torqueable structure running the length of the cannula tubing. By rotating or axially moving the control rod by grasping a projection at the proximal end of the cannula, inflation ports would be selectively opened between the balloon inflation lumen and the balloon to be inflated. Markings on the control rod would indicate which balloons were being inflated or which spacing was being chosen. Again, only the balloons correctly spaced to occlude the patient&#39;s vena cava are inflated. Other balloons would not be inflated because their ports would not have been selectively opened.  
         [0061]     In yet another embodiment of the cannula  10 , the distal tip  18  comprises an accordion-like or telescoping structure between the occlusion devices  39  and  45 , and a control rod. The accordion-like or telescoping structure allows the length of the cannula  10  to be adjusted so that the occlusion devices  39  and  45  fit the spacing between the patient&#39;s superior vena cava  114  and inferior vena cava  112 . This accordion-like structure is a longitudinally flexible area of the cannula  10  with corrugations to allow for compression or expansion in length. The control rod extends from the distal tip  18  of the cannula  10  to the proximal end  20 . The control rod is linked to the cannula  10  such that pushing or pulling the control rod relative to the proximal end  20  increases or decreases the length of the cannula  10 . The control rod is locked into place with a locking device when the correct spacing between the occlusion devices  39  and  45  is achieved. A telescoping structure could be used in place of the accordion-like structure to allow for cannula length adjustment using the control rod.  
         [0062]     In yet another embodiment, the balloon inflation adapter  28  is connected to the cardioplegia infusion system  12 . In this embodiment, the cardioplegia solution is used in the cardioplegia infusion system  12  to arrest the heart and in the balloon inflation system  16  to inflate the balloons  38  and  44  or  54  and  56 . Typically, cardioplegia solution is infused at a pressure of around 20 mmHg. The balloons  38 ,  44 ,  54 , and  56  may be inflated with an internal pressure of 20 mmHg and this pressure may be derived from the pressure of the cardioplegia solution. This embodiment has the advantage of reduced complexity and simplified pressure limiting.  
         [0063]     The balloons  38  and  44  are only one way of occluding the vena cava  112  and  114 . Another embodiment of the occlusive structures  39  and  45  comprises one or more external tourniquets. One or more tourniquets may be applied external to the vena cava  112  and  114  to seal the vena cava  112  and  114  to the cannula  10  and prevent cardioplegia solution from escaping the environs of the right atrium entry  110  to the coronary sinus  108 .  
         [0064]     A further embodiment of the occlusive structures  39  and  45  comprises umbrella mechanisms, which open up to occlude the vena cava. Opening and closing of the umbrellas, optionally with toroidal edge-seal balloons, would be accomplished using a control rod extending along the length of the catheter and out the proximal end of the catheter where it could be grasped.  
         [0065]      FIG. 8  illustrates a longitudinal cross-sectional view of the distal end of a catheter or cannula  120  of the present invention, comprising a length of cannula tubing  122 , a distal occlusion balloon  124 , a proximal occlusion balloon  126 , a plurality of distal drainage ports  128 , a plurality of proximal drainage ports  130 , a protection balloon  132 , an occlusion balloon pressurization or inflation lumen  134 , a drainage lumen  136 , a vacuum lumen  138  (not shown), a plurality of vacuum ports  140 , a plurality of protection balloon perforations  142 , and a walled-off cardioplegic delivery annulus  144 . The protection balloon  132  further comprises an inner protection balloon layer  146 , a protection balloon outer layer  148 , a vacuum channel  150 , one or more occlusion balloon inflation lumens  152 , a plurality of protection balloon inflation ports  154 , one or more cardioplegia delivery ports  156 , and a cardioplegia delivery lumen  158 , a protection balloon pressurization or inflation lumen  160 , a plurality of occlusion balloon inflation ports  162 , a cardioplegia delivery annulus wall  164 , and a radiopaque marker  166 .  FIG. 8  further illustrates the cannula  120  in situ in the heart  100  further comprising the left ventricle  102 , the right ventricle  104 , a plurality of coronary veins  106 , the coronary sinus  108 , the right atrium  110 , the inferior vena cava  112 , and the superior vena cava  114 .  
         [0066]     Referring to  FIG. 8 , the protection balloon  132  may be either symmetric or asymmetrically disposed about the length of cannula tubing  122 . The protection balloon  132  is sealably affixed to the cannula tubing  122 . The protection balloon  132  is affixed to the cannula tubing such that a vacuum channel  150  exists between the inner protection balloon layer and the outer protection balloon layer  148 . The vacuum channel  150  is in fluid communication with the vacuum lumen  138  in the cannula tubing  122  by way of vacuum ports  140 . The vacuum lumen  138  is in fluid communication with a connector (not shown) on the proximal end of the cannula  120 . The walled-off cardioplegic delivery annulus  144  is a feature in the protection balloon  132  that directs cardioplegia from the cardioplegia delivery lumen  158  through cardioplegia delivery ports  156  and on into the coronary sinus. The walled-off cardioplegic delivery annulus  144  is sealed from the rest of the vena cava and right atrium by the protection balloon  132 .  
         [0067]     A vacuum being drawn through the vacuum channel  150  seals the protection balloon  132  through the protection balloon perforations  142  in the protection balloon outer layer  148 . Ridges or indentations (not shown) in the vacuum channel  150  allow the vacuum to be maintained even though the outer protection balloon wall  148  is drawn against the inner protection balloon wall  146  by the vacuum. In this way, pressurized cardioplegia solution can be directed at the coronary sinus  108  and on into the coronary veins  106  without causing excessive pressure on the walls of the right atrium  110  and vena cava  112  and  114 . The cardioplegia delivery channel or annulus  144  is directed at and is operably in fluid communication with the coronary sinus. Blood is drained through the drainage lumen  136  by way of the drainage ports  128  and  130  to the proximal end of the cannula  120  where it is routed to a collection device or cardiopulmonary bypass system. As shown in  FIG. 8 , in a preferred embodiment the protection balloon inflation lumen  160  and the occlusion balloon inflation lumen  134  are the same channel. The protection balloon  132  is inflated by the protection balloon inflation lumen  160  through protection balloon inflation ports  154  while the occlusion balloons  124  and  126  are inflated by the occlusion balloon inflation lumen  134  through the occlusion balloon inflation ports  162 . The cardioplegia delivery lumen  158  is preferably asymmetric on the cannula  120  so radiopaque markers  166  are preferred to show the asymmetry and allow correct alignment of the cannula with the heart under fluoroscopy.  
         [0068]     Referring to  FIG. 8 , the cannula tubing  122 , comprises an affixed, optional radiopaque marker  166  or plurality of radiopaque markers  122  to allow visibility under fluoroscopy of the position of key elements of the tubing and to delineate the rotational orientation of the tubing  122 . The radiopaque (RO) marker  166  is asymmetrically configured circumferentially, in a preferred embodiment, so that under fluoroscopy, the RO marker  166  orientation and the orientation of the tubing  122  can be determined under said fluoroscopic evaluation. Examples of asymmetrical RO markers include, but are not limited to, arrows, rectangles with one rounded side, triangles, and the like. In another embodiment, a plurality of radiopaque markers  166  are asymmetrically arranged to provide the user with cannula tubing  122  rotational information when viewed in two-dimensional projection as is typical with fluoroscopic visualization. An example of a preferred embodiment of multiple radiopaque markers  166  include, but are not limited to two markers  166  that are asymmetric in shape, are located 180-degrees apart on the circumference of the tubing  122  or other cannula structure, such as the protection balloon  132 , and each comprises a fenestration or hole that is aligned with a hole on the opposing radiopaque marker  166  to ensure exact rotational orientation of the cannula  120 . Such rotational orientation is complimentary to the longitudinal or axial positioning or orientation of the cannula  120 .  
         [0069]      FIG. 9  illustrates a lateral cross section of a length of cannula tubing  122 . The cannula tubing comprises a tube wall  170 , a vacuum lumen  138 , a drainage lumen  136 , one or more occlusion balloon inflation lumens  134 , a cardioplegia delivery or infusion lumen  158 , and a protection balloon inflation lumen  160 .  
         [0070]     Referring to  FIGS. 8 and 9 , the cannula tubing  122  is preferably flexible but has column strength and torqueability. The cannula tubing  122  diameter ranges from 5 mm to 20 mm. Preferably the cannula tubing  122  diameter ranges from 8 mm to 15 mm. The cannula tubing  122  is preferably fabricated by extrusion. The cannula tubing  122  may also be fabricated by winding a wire or polymer coil or a wire or polymer braid around a mandrel. The cannula tubing  122  may be poured or dipped or extruded over this braid or coil to provide additional torqueability, kink-resistance, and the like. The cannula tubing  122  is typically fabricated from polymers such as, but not limited to, PEBAX, polyurethane, silicone, poly vinyl chloride, polyethylene, polypropylene, polyimide, polyamide, and the like. The braid or coil used to reinforce the cannula tubing  122  is preferably fabricated from wire such as, but not limited to, round or rectangular cross-sections of stainless steel, nitinol, Kevlar, polyimide, polyester, and the like. The radiopaque markers  166  may be comprised of metals such as platinum, tantalum, gold, and the like or they may be additives of barium sulfate and the like, formed as attached rings, extruded stripes, or other shapes.  
         [0071]      FIG. 10  shows yet another embodiment of a venous cannula  200  adapted for retrograde administration of cardioplegia solution to a heart during cardiopulmonary bypass. The venous cannula  200  comprises a length of multi-lumen tubing  202  with a proximal end and a distal end, a cardioplegia solution infusion lumen  204 , a cardioplegia solution infusion annulus  206  affixed at or near the distal end of the cannula  200 , an annular seal ring  208  affixed to the distal end of the cannula  200  surrounding the cardioplegia solution infusion annulus  206 , a vacuum lumen  210  operably connected to the vacuum or sealing annulus  220  of the annular seal ring  208 , a cardioplegia solution infusion port  212  (not shown) affixed at the proximal end of the cannula  200 , and a vacuum port  214  (not shown) affixed at the proximal end of the cannula  200 . The annular seal ring  208  of the cannula  200  further comprises an optional inner wall  216 , an outer wall  218 , and a sealing annulus  220 . The cannula  200  further comprises an optional inflation lumen  222  and an inflation port  224  (not shown), which are affixed to each other and operably connected to the sealing annulus  220 . The outer wall of the cardioplegia solution infusion annulus  206  is, in one embodiment, the same as the inner wall of the sealing annulus  220 . Webs or attachments (not shown) connect the inner wall of the sealing annulus  220  to the outer wall  218  of the annular seal ring  208  but permit application of a vacuum to tissue where the sealing annulus  220  touches said tissue. Expansion or movement of the outer wall  218  moves the inner wall of the sealing annulus  220  correspondingly.  
         [0072]     Referring to  FIG. 10 , the cardioplegia solution infusion port  212  comprises an attachment to a cardioplegia infusion system, which preferably comprises a reservoir of cardioplegia solution and a pump. The annular seal ring  208  comprises the inner wall  216  and the outer wall  218  and the sealing annulus  220 . The annular seal ring  208  controllably seals to the right atrial wall around the coronary sinus by way of a vacuum drawn through the vacuum lumen  210  by way of the vacuum port  214 . The annular seal ring  208 , when attached to the atrial wall by vacuum, prevents or minimizes the escape of cardioplegia solution from the cardioplegia solution infusion annulus  206  into the right atrium. In a preferred embodiment, the annular seal ring  208  is an expandable structure that can be inserted endovascularly and routed to the right atrium. The annular seal ring  208  is then expanded and placed against the tissue surrounding the coronary sinus. The interior most lumen of the annular seal ring  208  is the cardioplegia solution infusion annulus  206 . Such expansion of the annular seal ring  208  is, in one embodiment, accomplished by providing an inflation lumen  222  within the tubing  202  and an inflation port  224  at the proximal end of the tubing  202 , the inflation port  224  operably connects to the inflation lumen  222 . Pressurized fluid such as air, saline, or radiopaque liquid is infused under pressure and inflates the annular seal ring, which consists of multiple walls. A vacuum is then drawn through the vacuum lumen  210  as described earlier while cardioplegia solution is infused into the coronary sinus through the cannula  200  via a retrograde approach. In one embodiment, the cannula  200  further comprises the integral venous drainage system shown in  FIG. 8 . In another embodiment, the cannula  200  does not require a venous drainage system. The materials and methods used for manufacture of this embodiment, are the same as or similar to those used to manufacture the cannula of  FIG. 8 .  
         [0073]     In one embodiment, the annular seal ring  208  and the cardioplegia solution infusion annulus  206  are affixed to the cannula tubing  202  substantially at a direction perpendicular to the longitudinal axis of the cannula tubing  202 . Thus, the annular seal ring  208  projects sideways, or is laterally directed, and toward the coronary sinus while the main axis of the cannula  200  is longitudinally located within the vena cavae. In a preferred embodiment, the annular seal ring  208  and cardioplegia solution infusion annulus  208  are controllably extendable in the direction lateral to the longitudinal axis of the cannula tubing  202 . The expansion may be controlled from the proximal end of the cannula  200  by way of pull wires running through lumens in the tubing  202  or by inflation of balloon structures through inflation lumens in the tubing  202 .  
         [0074]      FIG. 11  illustrates another embodiment of the cannula  250 , wherein the annular seal ring  258  and the cardioplegia infusion annulus  256  are disposed concentrically with the axis of the tubing  252  so that the distal tip of the cannula  250  opens to form the cardioplegia solution infusion annulus  256 . In this embodiment, steering apparatus is disposed within the cannula  250  to bend, steer, or articulate the distal end of the cannula tubing  252  and allow the annular seal ring  258  to be mated or docked with the tissue surrounding the coronary sinus  108 . The steering apparatus comprises, in one embodiment, one or more pull-wires  260  slidably disposed within lumens  264  in the tubing  252 . The pull-wire lumens  264  are preferably located at  90 -degree or  120 -degree interval spacing about the cannula tubing  252 . For clarity,  FIG. 11  shows only one pull-wire lumen  264 . The pull-wire  260  associated with the illustrated pull-wire lumen  264  is also shown exiting the cannula tubing  260  cutaway. Additional pull-wires  260 , whose pull-wire lumens  264  are not shown, are shown exiting the tubing  252  cutaway more proximally. The pull-wires  260  are terminated at the proximal end of the cannula  250  with grips or knobs (not shown) that allow manual or power-assisted tension to be applied to the pull-wires. The pull-wires  260  are terminated and affixed at the distal tip of the cannula  250  into attachment points  262  on the distal end of the tubing  252 . The pull-wires  260  are preferably disposed on opposite circumferential sides of the tubing  252  so that tension on one pull-wire  260  causes the tubing  252  to bend to that side on which the pull-wire  260  is located. A minimum of one pull-wire  260  is required but more pull-wires  260  are desirable. In a preferred embodiment, three or more pull-wires  260  are comprised by the cannula  250  to provide full X-Y orientation and articulation. The pull-wires  260  are fabricated from polyimide, polyester, stainless steel, nitinol, or other material with suitable tensile strength and biocompatibility. The pull-wire  260  may be either monofilament or multifilament with a braided structure. The pull-wire  260  may further be coated with polytetrafluoroethylene or other fluoropolymers to minimize friction. In yet another embodiment, the pull-wire  260  is shape-memory nitinol and is selectively or controllably heated by application of electrical energy across its length to achieve contraction of the pull-wire  260 . Such electrical energy is applied to electrical leads (not shown) that run longitudinally through the cannula tubing  252  from the proximal end to the distal end and can provide a complete circuit to any component comprised by the cannula  250 .  
         [0075]     Referring to  FIG. 11 , in one embodiment, the tubing  252  is more flexible in a region  262  just proximal to the distal tip of the cannula  250 . This region of increased flexibility  268  allows the cannula tubing  252  to bend preferentially at that flexible region  268  upon application of tension in the pull-wires  260 . In yet another embodiment, the steering apparatus comprises microactuators such as those fabricated from shape memory metals and Ohmic heating elements or from electromechanical actuators. Exemplary shape-memory microactuators include those described in U.S. Pat. No. 6,447,478 to Ronald Maynard, entitled Thin-Film Shape Memory Alloy Actuators and Processing Methods, the entirety of which is included herein by reference. Electrical energy, provided at the proximal end of the cannula  250  and transmitted by electrical cabling within lumens in the tubing  252 , provide the power and control for the microactuators. The control unit, which supplies the electrical energy to the microactuators minimally comprises a power supply and an on-off switch for each microactuator. The control unit may, in other embodiments, comprise computer systems or other types of logic circuitry to control the power to the microactuators. The microactuators are preferably affixed longitudinally across the area of increased flexibility near the distal end of the cannula  250  and are disposed on opposing sides of the tubing to provide counter-motion since these actuators generally only work in tension, not expansion.  
         [0076]     Referring to  FIG. 11 , the lateral cross-sectional shape of the annular seal ring  258  is generally or substantially circular but may be oval or any other appropriate shape. The annular seal ring  258  is, in a preferred embodiment, a double wall structure that permits a vacuum to be applied to a vacuum annulus  254  between the walls to hold the annular seal ring  258  against the cardiac tissue with a high level of force. Vacuum is drawn at the proximal end of the cannula  250  and is transmitted to the vacuum annulus  254  by way of vacuum lumens in the cannula tubing  252  which are operably connected to the vacuum annulus  254  and the applied vacuum at the proximal end of the cannula  250 . The cardioplegia infusion annulus  256  is a region interior to the inner wall of the annular seal ring  258 , which further permits and guides the infusion of cardioplegia solution, in a non-cannulating fashion, to the coronary sinus  108 . In one embodiment, the annular seal ring  258  is of constant, non-tapering cross-section. In a preferred embodiment, the annular seal ring  258  comprises an elastomeric wall and an inflatable or expandable structure  266  at the distal tip to provide for diametric or radial expansion to a size greater than that of the cannula  250 . In one embodiment, the expandable structure  266  comprises a ring of shape-memory nitinol that expands under application of electricity which results in Ohmic heating of the nitinol to a temperature above its austenite finish temperature (A f ). The nitinol expandable ring  266  may be a simple split ring or it may be a pattern of diamonds, “W” s or “Z” s or other typical cardiovascular stent shapes known in the art that are capable of diametric expansion. The cannula  250  may further comprise a plurality of slats or longitudinal elastomeric elements  272 , which serve as a strain relief and permit smooth tapering of the tip when the expandable ring  266  is activated. These separated longitudinal elastomeric elements  272  are fabricated from stainless steel, nitinol, polyester, cobalt nickel alloys or other materials with high strength in the form of leaf springs. In a preferred embodiment, the longitudinal elastomeric elements  272  are fabricated from shape-memory nitinol and, upon application of electrical energy, are heated to above their austenitic finish temperature and expand to a pre-determined shape. In all embodiments, electrical energy is supplied at the proximal end of the cannula  250  and is routed to the distal tip of the cannula  250  by electrical leads (not shown) longitudinally disposed within lumens or co-extruded within the tubing  252 . These electrical leads are electrically connected to both ends of the nitinol itself or to high resistance heating elements disposed in proximity of the shape-memory nitinol. Removal of the electrical energy results in cooling and restoration of the non-expanded configuration of the longitudinal elastomeric elements  272 . In another embodiment, the annular seal ring  258  further comprises an expandable structure  266 , which is a toroidal or annular balloon that expands under pressure applied at the proximal end of the cannula  250  and transmitted through the length of the cannula tubing  252  by a pressurization lumen to the balloon, the interior of which is in fluid communication with the pressurization lumen. The balloon may be either an elastomeric balloon or an inelastic angioplasty type balloon and is pressurized with water, saline, radiopaque contrast media, gas, or other material. The annular seal ring  258  preferably has a smooth distal edge that is capable of sealing to cardiac tissue without causing damage or trauma. Radiopaque markers  166  are, in a preferred embodiment, affixed to the distal end of the cannula  250  to assist with visualization and orientation of the cannula  250  distal tip under fluoroscopy. The radiopaque markers  166  are fabricated from material such as, but not limited to, platinum, gold, iridium, tantalum, and the like.  
         [0077]     The device or apparatus for such retrograde cardioplegia delivery is directed to a method for retrograde delivery of cardioplegia without cannulating the coronary sinus. Embodiments of the apparatus of the present invention permit the entire coronary sinus and coronary venous circuit to be perfused, and therefore, both the right and left coronary veins are perfused. Referring to  FIG. 11 , perfusion is, in a preferred embodiment, performed by sealing the catheter around the entrance to the coronary sinus  108  but not inserting a catheter into the coronary sinus  108 . In one embodiment, the preferred method comprises inserting a catheter into the right atrium and inflating a protection balloon, which seals to the region around the coronary sinus. The protection balloon prevents high-pressure cardioplegia solution from over-inflating the right atrium or surrounding structures. Once the catheter or cannula seals to the region around the coronary sinus, any air or gas is removed from the perfusion lumen and infusion of cardioplegic solution is initiated. At the conclusion of the procedure, cardioplegia solution infusion terminates, the vacuum terminates, and the surgeon, robot, or operator withdraws the cannula from the patient with any access sites being sealed by appropriate surgical, least invasive, or minimally invasive techniques.  
         [0078]     The catheter, cannula, device, or apparatus, all of which are used herein interchangeably, further comprises a cardioplegia delivery channel that is oriented toward the coronary sinus and sealed against the tissue around the coronary sinus. Such guiding or orientation is done either under direct visualization or by fluoroscopic, MRI, or ultrasonic guidance. Fiuoroscopic orientation and guidance is accomplished by visualizing radiopaque markers or structures on the catheter. The radiopaque markers or structures permit evaluation of orientation of the cannula since they are, in a preferred embodiment, asymmetrically placed about the cannula. The step of sealing is performed by drawing a vacuum on the protection device or balloon to pull surrounding tissue against the balloon or protection device, thus sealing the region around the coronary sinus. In another embodiment, the sealing is performed by inflating a sealing structure into the right atrium or by opening an umbrella-type structure, optionally comprising an inflatable toroidal edge sealing balloon, to occlude and seal off parts of the right atrium. Cardioplegia solution is then infused into the coronary sinus through infusion ports on the cannula. With this method, the use of occluding balloons is optional and may not be needed since the protection balloon seals the coronary sinus from the rest of the circulation. Venous drainage is optionally performed by the same cannula as that used for the cardioplegia delivery and the drainage ports are preferably positioned within the superior and inferior vena cava. In another embodiment, cardioplegia is infused through a catheter that is inserted into the coronary sinus  108 , but which is perforated so that cardioplegia solution can flow into the coronary veins  106  of both the right heart and the left heart. This system does not cannulate the coronary sinus  108  at the region of the coronary veins  106 . In yet another embodiment, the cannula is inserted surgically into the right atrium through an opening in the right atrium or vena cava, rather than being routed endovascularly to the right atrium from a remote access site.  
         [0079]     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is therefore indicated by the appended claims rather than the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.