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.

Description:
FIELD OF THE INVENTION  
         [0001]    The field of this invention is cardiac bypass surgery.  
         BACKGROUND OF THE INVENTION  
         [0002]    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. Cardiopulmonary bypass maintains the peripheral circulation of oxygenated blood to all body organs except the heart during the period of cold, cardioplegic, ischemic arrest.  
           [0003]    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.  
           [0004]    Currently surgeons performing cardiac bypass surgery use one or more cannulae for venous drainage and additional cannulae 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.  
           [0005]    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, and drain venous blood from the inferior and superior vena cava.  
         SUMMARY OF THE INVENTION  
         [0006]    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.  
           [0007]    The present 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. 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.  
           [0008]    The present invention is a multi-lumen cannula with superior and inferior vena cava occlusion structures, cardioplegia infusion and drainage ports, a pressure monitoring port, and venous drainage ports. Typical occlusion structures may include balloons, umbrellas, or externally applied tourniquets. The preferred occlusion structures are balloons constructed of elastomeric materials.  
           [0009]    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 balloons. The pressure of the balloons and right atrium may also be monitored through additional lumens. The balloons isolate the heart from the peripheral vasculature by occluding the inferior and superior vena cava just proximal to the right atrium. 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 be provided at or near the distal end of the cardioplegia perfusion lumen for this purpose.  
           [0010]    The cannula is placed into the vena cava via a route through the internal jugular vein, cranial vena cava or brachial vein. A smaller diameter cannula could be placed through smaller venous access ports. The use of smaller venous access ports could be enabled by use of a pump or vacuum powered venous drainage system, typically external to the cannula. The catheter of the present invention combines the functions of several catheters currently used in cardiac surgery. This facilitates the surgery and improves the surgical field because extra cannulae do not obstruct the operative field. 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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]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. External systems provide for venous drainage, cardioplegia infusion, and balloon inflation.  
         [0012]    [0012]FIG. 2 illustrates a lateral cross-section of a multi-lumen tube for construction of the cannula.  
         [0013]    [0013]FIG. 3 illustrates, in detail, a longitudinal cross-section of the distal tip of the cannula of FIG. 1.  
         [0014]    [0014]FIG. 4 illustrates, in detail, a longitudinal cross-section of the proximal end of the cannula of FIG. 1.  
         [0015]    [0015]FIG. 5 shows the placement of the cannula of the present invention in the heart for venous drainage and retrograde perfusion.  
         [0016]    [0016]FIG. 6 illustrates, in exterior view, another embodiment of the cannula comprising multiple balloons to accommodate various anatomic differences. Cutouts on the balloons show features on the cannula surface that would normally be hidden by the balloons.  
         [0017]    [0017]FIG. 7 illustrates a lateral cross-section of a multi-lumen tubing for construction of the cannula of FIG. 6. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    [0018]FIG. 1 illustrates a catheter, tube or cannula  10  of the present 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 this preferred embodiment, the occlusion adapter  28  is a balloon inflation adapter or luer fitting. The manifold  23  is typically molded from polymer, such as polyvinyl chloride, polycarbonate, or the like.  
         [0019]    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 a luer 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, a length of tubing and a plurality of connectors. Standard cardioplegia solutions include water, electrolytes such as but not limited to potassium, crystalloid solutions, and blood.  
         [0020]    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 most typically a ⅜ inch to ½ inch diameter hose barb. 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.  
         [0021]    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 a jackscrew, to advance or withdraw a plunger on the syringe using mechanical advantage.  
         [0022]    [0022]FIG. 2 shows the cross-section of the connection tubing  22 . The connection tubing  22  is multi-lumen tubing and comprises, at minimum, 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. Preferably, the tubing  22  is transparent.  
         [0023]    [0023]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.  
         [0024]    In this preferred 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 .  
         [0025]    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 .  
         [0026]    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.  
         [0027]    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 of the heart where it subsequently passes into the coronary arteries by way of the coronary sinus.  
         [0028]    [0028]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 .  
         [0029]    [0029]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 tricuspid valve  106 , a coronary sinus  108 , a right atrium  110 , an inferior vena cava  112 , and a superior vena cava  114 .  
         [0030]    During normal operation of the heart, 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 through the right atrium  110  and is pumped by the right ventricle  104  into the lungs where it is oxygenated and 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.  
         [0031]    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 patients systemic circulation so tissues can be perfused while the heart is being surgically repaired.  
         [0032]    The cannula  10  of the present invention 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.  
         [0033]    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 .  
         [0034]    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.  
         [0035]    The cardioplegia infusion system  12  is next activated. 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 moderate pressure, 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 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.  
         [0036]    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 where it then passes into an oxygenator and heat exchanger where it, respectively, undergoes removal of carbon dioxide and addition of oxygen and undergoes heat transfer. The oxygenated 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.  
         [0037]    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.  
         [0038]    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 operation of cardioplegia infusion and drainage collection are the same as that described earlier for the cannula  10 .  
         [0039]    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 .  
         [0040]    [0040]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 lumen  70 , a second balloon inflation lumen  72 , the infusion lumen  30 , the drainage lumen  32 , and the wall  31 .  
         [0041]    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 , a corresponding set of first balloon inflation ports  58 , and a corresponding first balloon  54 .  
         [0042]    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 are 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.  
         [0043]    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.  
         [0044]    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.  
         [0045]    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.  
         [0046]    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.  
         [0047]    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 .  
         [0048]    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 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.  
         [0049]    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.