Patent Publication Number: US-2023157275-A1

Title: Endovascular apparatus for perfusing organs in a body

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/397,704, filed Apr. 29, 2019, which is a continuation of U.S. National Stage application Ser. No. 15/115,623, filed Jul. 29, 2016, issued as U.S. Pat. No. 10,278,384 on May 7, 2019, which is the U.S. National Stage of International Application No. PCT/US2014/068116, filed Dec. 2, 2014, which claims the benefit of and priority to U.S. Provisional Application No. 61/935,729, filed Feb. 4, 2014; each of the prior applications are incorporated by reference herein in their entirety. 
    
    
     FIELD 
     The present application concerns embodiments of an endovascular apparatus for perfusing organs in a patient, such as an organ donor patient until the organs can be removed for transplant. 
     BACKGROUND 
     In the U.S., over 120,000 patients are in need of an organ transplant. It has been reported that only about 28,000 people received organ transplants organs in 2012 in the U.S. As a result, an average of 18 patients will die each day awaiting an organ transplant. Furthermore, the economic burden of kidney dialysis while awaiting transplant is significant, costing nearly S40 billion dollars a year in the U.S. alone. 
     Organs recovered from living donors and those donated after brain death (DBD) (also referred to as “heartbeating donation” (HBD)) represent controlled situations where organs can be carefully exposed and cooled immediately at the time of recovery. This rapid cooling allows the highest preservation of function. Donation after cardiac death (DCD) (also referred to as “non-heartbeating donation” (NHBD)) represents a growing source of organs but presents unique challenges with regard to adequately preserving organ function just prior to transplant. 
     Organs (e.g., kidneys) from all donor types are susceptible to warm ischemia, which is caused by reduced blood flow or the cessation of blood flow to organs and can result in significant loss of organ function. DCD donors are particularly susceptible to rather long warm ischemia times compared to DBD donors because DCD donors can experience relatively long periods of low blood pressure that is inadequate for organ perfusion prior to actual cardiac death, such as after the DCD donor is removed from life support. Needless to say, maneuvers that expedite cardiac death are prohibited. Moreover, in order to ensure that brain damage after cardiac arrest is irreversible, transplant teams must wait a predetermined time period prior to commencing the procedure for removing an organ from the DCD donor. This time period typically is referred to as a “no-touch” time period and on average is at least five minutes from the time of pronounced cardiac death. Consequently, warm ischemia times of about 10-40 minutes have been documented for DCD donors. As a result of these delays, warm ischemia can result in significant loss of organ function. 
     SUMMARY 
     The present disclosure concerns embodiments of an endovascular apparatus that can be used to perfuse the organs of a patient, for example, the organs of a donor patient until the organs can be explanted, thereby minimizing warm ischemia times. In particular embodiments, the endovascular apparatus is configured to isolate blood circulating through the heart from flowing through the visceral arteries and veins while perfusing the organs within the abdomen with a separate perfusion liquid that helps preserve organ function until explant. As such, the endovascular apparatus is particularly suited for maintaining adequate perfusion of organs in DCD donors, in which there may not be adequate blood flow to the abdominal organs prior to cardiac arrest and during the so called “no-touch” time period following cardiac arrest. The disclosed methods and apparatuses therefore can significantly increase the number of viable organs that can be made available for transplant. In alternative embodiments, the disclosed methods and apparatuses can also be used to perfuse organs in survival surgery, such as cardiac or proximal aortic repairs where prolonged cessation of blood flow poses a risk of organ damage. 
     In one representative embodiment, a method of perfusing organs in a patient&#39;s body is provided. The method comprises isolating the visceral arteries and the visceral veins from blood circulating through the patient&#39;s heart. The visceral arteries, the visceral veins, and the abdominal organs are perfused with a perfusion fluid that is fluidly separated from the blood circulating through the patient&#39;s heart. While the visceral arteries and the visceral veins are isolated and being perfused with a perfusion fluid, the patient&#39;s blood continues to circulate through the heart and other parts of the body. 
     In another representative embodiment, a method of perfusing organs in a patient&#39;s body comprises deploying a first perfusion stent in the patient&#39;s aorta and a second perfusion stent in the patient&#39;s vena cava, the first perfusion stent allowing blood from the heart to flow in a downstream direction from a location upstream of the abdominal organs to a location downstream of the abdominal organs without flowing into the visceral arteries, the second perfusion stent allowing blood to flow in a downstream direction from a location upstream of the abdominal organs to a location downstream of the abdominal organs without flowing into the visceral veins. The first perfusion stent has enlarged end portions that seal against the inner wall of the aorta and an intermediate portion defining an arterial perfusion space between the inner wall of the aorta and the outer surface of the intermediate portion, and the second perfusion stent has enlarged end portions that seal against the inner wall of the vena cava and an intermediate portion defining a venous perfusion space between the inner wall of the vena cava and the outer surface of the intermediate portion. The first perfusion conduit has an end portion that extends through one of the enlarged end portions of the first perfusion stent; and the second perfusion conduit has an end portion that extends through one of the enlarged end portions of the second perfusion stent. The perfusion fluid flows through the first perfusion conduit, through the arterial perfusion space, through the visceral arteries, through the abdominal organs, through the visceral veins, through the venous perfusion space, and into the second perfusion conduit. 
     In another representative embodiment, a method of perfusing organs in a patient&#39;s body comprises inserting an arterial catheter into the patient&#39;s aorta and inserting a venous catheter into the patient&#39;s vena cava. The arterial catheter has a first lumen, a second lumen, and first and second balloons spaced apart along the length of the arterial catheter. The venous catheter has a first lumen, a second lumen, and first and second balloons spaced apart along the length of the venous catheter. The method further comprises positioning the arterial catheter in the aorta such that the first balloon is upstream of the visceral arteries and the second balloon is downstream of the visceral arteries, and positioning the venous catheter in the vena cava such that the first balloon is upstream of the visceral veins and the second balloon is downstream of the visceral veins. The first and second balloons of the arterial and venous catheters are inflated, thereby isolating the visceral arteries and visceral veins from blood circulating through the patient&#39;s heart. A flow of a perfusion fluid flows into and through the second lumen of the arterial catheter, into and through the visceral arteries, the abdominal organs, and the visceral veins, and into and through the second lumen of venous catheter while blood from the heart is allowed to flow into and through the first lumen of the arterial catheter, and back into and through the first lumen of the venous catheter. 
     In another representative embodiment, an assembly for perfusing organs in a patient&#39;s body comprises a first perfusion stent, a second perfusion stent, a source of a perfusion fluid, a first perfusion conduit, and a second perfusion conduit. The first perfusion stent is configured to be deployed within the aorta of a patient, the first perfusion stent allowing blood from the heart to flow in a downstream direction from a location upstream of the abdominal organs to a location downstream of the abdominal organs without flowing into the visceral arteries. The second perfusion stent is configured to be deployed within the vena cava of the patient, the second perfusion stent allowing blood to flow in a downstream direction from a location upstream of the abdominal organs to a location downstream of the abdominal organs without flowing into the visceral veins. The first perfusion conduit has an inlet in fluid communication with the source of the perfusion fluid and an outlet that is configured to be in fluid communication with the visceral arteries when the first perfusion stent is deployed within the aorta. The second perfusion conduit has an inlet that is configured to be in fluid communication with the visceral veins when the second perfusion stent is deployed within the vena cava. Using the assembly, perfusion fluid can flow through the first perfusion conduit, through the arterial perfusion space, through the visceral arteries, through the abdominal organs, through the visceral veins, through the venous perfusion space, and into the second perfusion conduit. 
     In another representative embodiment, an assembly for perfusing organs in a patient&#39;s body comprises an arterial catheter configured to be inserted into the aorta of a patient. The arterial catheter comprises a first lumen, a second lumen, and first and second balloons spaced apart along the length of the arterial catheter. The balloons are configured to seal against the inner wall of the aorta upstream and downstream of the visceral arteries to isolate the visceral arteries from blood circulating through the patient&#39;s heart. The assembly further comprises a venous catheter configured to be inserted into the vena cava of a patient. The venous catheter comprises a first lumen, a second lumen, and first and second balloons spaced apart along the length of the venous catheter. The balloons are configured to seal against the inner wall of the vena cava upstream and downstream of the visceral veins to isolate the visceral veins from blood circulating through the patient&#39;s heart. A source of a perfusion fluid is in fluid communication with the second lumen of the arterial catheter. The first lumen of the arterial catheter is in fluid communication with the first lumen of the venous catheter to allow blood from the heart to flow into and through the first lumen of the arterial catheter, and back into and through the first lumen of the venous catheter. 
     In another representative embodiment, a perfusion stent implantable within a body lumen is provided. The perfusion stent comprises a radially compressible and expandable, elongated body comprising first and second end portions and an intermediate portion extending from the first end portion to the second end portion. The first and second end portions have an outer diameter greater than an outer diameter of the intermediate portion when the body is in a radially expanded state, thereby defining an annular perfusion space between the first and second end portions and around the intermediate portion. The perfusion stent also comprises a central lumen extending through the first end portion, the intermediate portion, and the second end portion, and a perfusion lumen extending at least partially through the first end portion and having a distal opening in communication with the perfusion space. When the elongated body is in the radially expanded state within the body lumen, and the first and second end portions are engaged with an inner wall of the body lumen, the central lumen is fluidly separated from the perfusion space. In another representative embodiment, the perfusion fluid being circulated through the isolated visceral arteries, visceral veins and abdominal organs is the patient&#39;s own blood. This blood is in a fluidly separate circuit from the blood being circulated by the heart. The blood perfusing the isolated visceral arteries, visceral veins and abdominal organs can flow into and through the second lumen of the arterial catheter, into and through the visceral arteries, the abdominal organs, and the visceral veins, and into and through the second lumen of venous catheter. The venous effluent (blood from the venous catheter) can be warmed, oxygenated and/or pressurized by an external device and returned to the second lumen of the arterial catheter to repeat the cycle. Meanwhile, blood from the heart is allowed to flow into and through the first lumen of the arterial catheter, and back into and through the first lumen of the venous catheter. This provides the abdominal organs with warmed, pulsatile, oxygenated blood independent of the blood being circulated by the heart. 
     The foregoing and other features and advantages of this disclosure will become more apparent from the following detailed description of several embodiments which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an exemplary embodiment of an endovascular apparatus for perfusing organs of a patient. 
         FIG.  2    is an enlarged view of the apparatus of  FIG.  1   , showing the apparatus deployed within the body of a patient. 
         FIG.  3    is a cross-section view of the apparatus of  FIG.  2    taken along line  3 - 3  of  FIG.  2   . 
         FIG.  4    is a cross-section view of the apparatus of  FIG.  2    taken along line  4 - 4  of  FIG.  2   . 
         FIG.  5    illustrates another exemplary embodiment of an endovascular apparatus for perfusing organs of a patient. 
         FIG.  6    is a side view of an arterial catheter of an endovascular apparatus, according to another embodiment. 
         FIG.  7    is a cross-section view of the apparatus of  FIG.  6    taken along line  7 - 7  of  FIG.  6   . 
         FIG.  8    is a cross-section view of the apparatus of  FIG.  6    taken along line  8 - 8  of  FIG.  6   . 
         FIG.  9    illustrates another exemplary embodiment of an endovascular apparatus for perfusing organs of a patient. 
         FIG.  10    illustrates an endovascular apparatus for perfusing organs of a patient, according to another embodiment. 
         FIG.  11    is an enlarged view of the apparatus of  FIG.  10   , showing the apparatus deployed within the body of a patient. 
         FIG.  12    is a side view of an annular frame of a perfusion stent, according to one embodiment. 
         FIG.  13    is a side view of a perfusion stent, according to one embodiment. 
         FIG.  14    is a cross-section view of the perfusion stent of  FIG.  13    taken along line  13 - 13  of  FIG.  14   . 
         FIG.  15    is a cross-section view of the perfusion stent of  FIG.  13    taken along line  14 - 14  of  FIG.  15   . 
         FIG.  16    is a cross-section view of the perfusion stent of  FIG.  13    taken along line  15 - 15  of  FIG.  16   . 
         FIG.  17    shows a delivery apparatus being used to deliver a perfusion stent within the aorta of a patient. 
         FIG.  18    illustrates an exemplary embodiment of an endovascular apparatus for perfusing organs of a patient, according to another embodiment, 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure concerns embodiments of an endovascular apparatus that can be used to perfuse the organs of a patient, such as an organ donor patient until the organs can be removed, thereby minimizing warm ischemia times. In particular embodiments, the endovascular apparatus is configured to isolate blood from the heart from flowing through the visceral arteries and veins while perfusing the organs within the abdomen with a separate perfusion liquid that helps preserve organ function until explant. As such, the endovascular apparatus is particularly suited for maintaining adequate perfusion of organs in DCD donors, in which there may not be adequate blood flow to the abdominal organs prior to cardiac arrest and during the so called “no-touch” time period following cardiac arrest. 
     Referring first to  FIGS.  1  and  2   , there is shown an endovascular apparatus  10  for isolating and perfusing the organs of a patient (e.g., an organ donor patient), according to one embodiment. The apparatus  10  in the illustrated embodiment comprises a first, arterial catheter  12  and a second, venous catheter  14 . The arterial catheter  12  is configured to isolate the visceral arteries  80  and divert blood from the aorta  82  to a location outside the body while the venous catheter  14  is configured to isolate the visceral veins  84  and introduce the blood back into the inferior vena cava  86  of the patient. The arterial catheter  12  also is configured to introduce a perfusion fluid (e.g., a cold perfusion solution) into the visceral arteries  80  for the purpose of perfusing donor organs (e.g., kidneys  114  or liver  116 ) in the abdominal cavity until such time the organs can be explanted. The venous catheter  14  also is configured to be placed into fluid communication with the visceral veins  84  in order to remove the perfusion fluid from the body. 
     The arterial catheter  12  in the illustrated embodiment comprises a first shaft  16  defining a first lumen  54  ( FIG.  3   ) and a second shaft  18  defining a second lumen  60  ( FIG.  3   ). Mounted on the shafts  16 ,  18  is a distal balloon  20  and a proximal balloon  22  spaced from the distal balloon  20 . As shown in  FIGS.  1  and  2   , the first and second shafts  16 ,  18  extend through the proximal balloon  22 . The first shaft  16  can extend through the distal balloon  20  and has a distal opening  24  that is in fluid communication with the aorta upstream of the distal balloon. The second shaft  18  can terminate at a location proximal to the distal balloon  20  and can have a closed end  26 . The second shaft  18  also can have one or more side openings, or apertures,  28  along the length of the shaft between the distal and proximal balloons  20 ,  22 , respectively. As best shown in  FIG.  2   , a proximal end portion  30  of the second shaft  18  can be fluidly connected to a source  32  of a perfusion fluid. A proximal end portion  33  of the first shaft  16  can be fluidly connected to an inlet port of a blood warmer  34 . 
     The venous catheter  14  in the illustrated embodiment comprises a first shaft  36  defining a first lumen  62  ( FIG.  4   ) and a second shaft  38  defining a second lumen  68  ( FIG.  4   ). Mounted on the shafts  36 ,  38  is a distal balloon  40  and a proximal balloon  42  spaced from the distal balloon  40 . As shown in  FIGS.  1  and  2   , the first and second shafts  36 ,  38  extend through the proximal balloon  42 . The first shaft  36  can extend through the distal balloon  40  and has a distal opening  44  that is in fluid communication with the inferior vena cava downstream of the distal balloon. The second shaft  38  can terminate at a location proximal to the distal balloon  40  and can have a closed end  46 . The second shaft  38  also can have one or more side openings, or apertures,  48  along the length of the shaft between the distal and proximal balloons  40 ,  42 , respectively. As best shown in  FIG.  2   , a proximal end portion  50  of the second shaft  38  can extend outside the body for draining perfusion fluid away from the body. A proximal end portion  52  of the first shaft  36  can be fluidly connected to an outlet port of the blood warmer  34 . 
     As shown in  FIG.  3   , the first shaft  16  of the arterial catheter  12  can have a first lumen  54  for diverting blood from the aorta to the blood warmer  34  and second and third lumens,  56 ,  58 , respectively, for introducing an inflation fluid to the distal and proximal balloons  20 ,  22 , respectively. The second lumen  56  can have a distal end in fluid communication with the inside of the distal balloon  20  and a proximal end in fluid communication with a source of an inflation fluid (not shown). The third lumen  58  can have a distal end in fluid communication with the inside of the proximal balloon  22  and a proximal end in fluid communication with the source of the inflation fluid. Thus, in use, an inflation fluid (e.g., saline) can be introduced under pressure into the balloons to inflate the balloons and cause them to engage and form a seal with the inner wall of the aorta. The second shaft  18  can have a lumen  60  that allows a perfusion fluid from the source  32  to be introduced into the visceral arteries  80 . In an alternative embodiment, the inflation lumens  56 ,  58  can be provided in the second shaft  18  rather than in the first shaft  16 . In another embodiment, one of the inflation lumens can be provided in the first shaft  16  and the other inflation lumen can be provided in the second shaft  18 . 
     As shown in  FIG.  4   , the first shaft  36  of the venous catheter  14  can have a first lumen  62  for introducing blood from the blood warmer  34  back into the body and second and third lumens,  64 ,  66 , respectively, for introducing an inflation fluid to the distal and proximal balloons  40 ,  42 , respectively. The second lumen  64  can have a distal end in fluid communication with the inside of the distal balloon  40  and a proximal end in fluid communication with the inflation fluid source. The third lumen  66  can have a distal end in fluid communication with the inside of the proximal balloon  42  and a proximal end in fluid communication with the inflation fluid source. Thus, in use, an inflation fluid (e.g., saline) can be introduced under pressure into the balloons  40 ,  42  to inflate the balloons and cause them to engage and form a seal with the inner wall of the inferior vena cava. The second shaft  38  can have a lumen  68  that allows the perfusion fluid returning from the visceral veins  84  to flow outside the body, where it can be collected and disposed of as waste. In an alternative embodiment, the inflation lumens  64 ,  66  can be provided in the second shaft  38  rather than in the first shaft  36 . In another embodiment, one of the inflation lumens can be provided in the first shaft  36  and the other inflation lumen can be provided in the second shaft  38 . 
     Each of the catheters  12 ,  14  can include suitable positioning markers and/or sensors at convenient locations to assist in locating the balloons of each catheter at the desired locations within the aorta and the inferior vena cava. In the illustrated embodiment, for example, the first shaft  16  of the arterial catheter  12  includes a pair of radiopaque markers  68  aligned with the distal and proximal balloons  20 ,  22 , respectively. Similarly, the first shaft  36  of the venous catheter  14  includes a pair of radiopaque markers  68  aligned with the distal and proximal balloons  40 ,  42 , respectively. In alternative embodiments, the markers  68  can be provided on the second shafts  18 ,  38  or on both the first and second shafts of each catheter  12 ,  14 . Also, although the illustrated embodiment includes a pair of markers  68  for each catheter, a greater or fewer number of markers can be provided for each catheter  12 ,  14 . 
     In alternative embodiments, the positioning markers can comprise passive or active emitters that can emit electromagnetic waves through the body and a corresponding detector or monitor can be used to receive the electromagnetic waves from the emitters and provide visual and/or audible feedback to a user indicating the position of the markers inside the body relative to external landmarks on the body. In particular embodiments, for example, the positioning markers can be emitters that can emit radiofrequency waves, such as radiofrequency identification (RFID) tags. Further details of the use of RFID tags as positioning marks are disclosed in co-pending Application No. 61/845,896, filed Jul. 12, 2013, and PCT/US2014/046224, filed Jul. 10, 2014, which are incorporated herein by reference. 
     In use, as depicted in  FIG.  1   , the first catheter  12  can be inserted into the aorta via an incision in a femoral artery in a minimally invasive manner using known techniques. Similarly, the second catheter  14  can be inserted into the inferior vena cava via an incision in a femoral vein in a minimally invasive manner Guidewires, dilators and/or introducers can be used to help introduce and advance the catheters through the patient&#39;s vasculature, as known in the art. As best shown in  FIG.  2   , the arterial catheter  12  is positioned such that the distal balloon  20  is upstream of the visceral arteries  80  and the proximal balloon  22  is downstream of the visceral arteries  80 . Similarly, the venous catheter  14  is positioned such that the distal balloon  40  is downstream of the visceral veins  84  and the proximal balloon  42  is upstream of the visceral veins  84 . The proper positioning of the catheter  12 ,  14  can be accomplished by viewing the markers  68  under fluoroscopy. 
     Once the catheters are in place, each pair of balloons can be inflated against the inner walls of the aorta and inferior vena cava, thereby isolating the visceral arteries and veins. This causes oxygenated blood from the heart to flow through the first shaft  16  of the arterial catheter, through the blood warmer, through the first catheter  36  of the venous catheter and into the inferior vena cava where blood can flow back into the right atrium of the heart, as indicated by arrows  90 . At the same time, a cold perfusion fluid from source  32  is introduced into the visceral arteries  80  via the side openings  28  in the second shaft  18  of the arterial catheter, as indicated by arrows  92 . The perfusion fluid can flow through the abdominal organs, the visceral veins  84  and into the isolated region of the inferior vena cava, where it can then flow inwardly through the side openings  48  of the second catheter  38 , as indicated by arrows  94 . The perfusion fluid can then be removed from the body via the second catheter  38  for proper disposal. 
     In particular embodiments, the perfusion fluid can be similar to the University of Wisconsin solution and can comprise, without limitation, one or more of the following compounds: heparin, pentastarch, steroids, lactobionic acid, magnesium sulfate, raffinose, adenosine, allopurinol, glutathione, and potassium hydroxide. The perfusion fluid can be cooled to a temperature of about 0 degree C. to about 10 degrees C. for introduction into the body and more preferably to a temperature of about 4 degrees C. to about 6 degrees C. As an alternative perfusion fluid, blood separate from the circuit of blood being circulated by the heart can be propelled, oxygenated and warmed before being cycled continuously through the catheters, as further described below. 
     As noted above, the apparatus is particularly suited for use with DCD donors. In this regard, the catheters  12 ,  14  can be inserted and deployed (i.e., the balloons inflated to isolate the visceral arteries and veins) in the vasculature of a DCD donor as soon as possible prior to cardiac death. For example, the catheters  12 ,  14  can be inserted and deployed in a DCD donor just prior to or at the same time as removing the patient from life support or when the donor is experiencing unstable vital signs for normal organ blood flow. The blood flow circuit allows for normal blood flow through the body, except for those isolated regions, while awaiting expected cardiac death and during the predetermined waiting period before explant can occur. In another implementation, the catheters  12 ,  14  can be inserted into the DCD donor prior to cardiac death and then are deployed at the time of cardiac death. In yet another implementation, the apparatus can be inserted and deployed in a donor who expires prematurely before a donor team is ready to perform the explant procedure. In any case, during the period of time before explant can be performed, the perfusion fluid reduces warm ischemia time and preserves organ function. 
     In another embodiment, the catheters  12 ,  14  can be inserted into the aorta and the vena cava of a donor (e.g., a DCD donor) but not deployed (i.e., the balloons are not inflated) until after cardiac death or until after the predetermined waiting period. This allows for normal blood flow throughout the body until the balloons are deployed. At the prescribed time (e.g., after confirmed cardiac death), the balloons can be rapidly deployed to isolate the visceral arteries and veins and a perfusion fluid (e.g., a cold solution or blood) can be circulated through the isolated regions until explant. 
     In the embodiment of  FIGS.  1  and  2   , the catheters  12 ,  14  also isolate the lower extremities from the flow of blood. It has been found that humans can tolerate lower extremity ischemia for several hours. If desired, however, the apparatus  10  can be adapted to permit blood from the heart to circulate through the lower extremities. 
     For example,  FIG.  5    shows the apparatus  10  of  FIGS.  1  and  2    with additional components to permit blood from the heart to circulate through the lower extremities. In the embodiment of  FIG.  5   , the apparatus  10  further includes an arterial extension portion or conduit  100  that has a first end portion  102  that is in fluid communication with the proximal end portion  33  of the first shaft  16  of the arterial catheter  12 . A second end portion  104  of the extension portion  100  can be inserted into a femoral artery, which can be the same femoral artery through which the arterial catheter  12  has been inserted or the other femoral artery. If the extension portion  100  is inserted into the same femoral artery as the arterial catheter  12 , the extension portion  100  would be inserted downstream of the insertion point of the arterial catheter  12 . The conduit  100  diverts a portion of blood from shaft  16  to flow into the vasculature of the lower extremities. 
     In the embodiment of  FIG.  5   , the apparatus  10  also includes a lower extremity return line or conduit  106  having a first end portion  108  inserted into a femoral vein, which can be the same femoral vein through which the venous catheter  14  has been inserted or the other femoral vein. If the return conduit  106  is inserted into the same femoral vein as the venous catheter  14 , the return line would be inserted upstream of the insertion point of the venous catheter  14 . A second end portion  110  of the return conduit  106  is in fluid communication with an inlet port of a blood pump  112 . As shown in  FIG.  5   , the proximal end portion  33  of shaft  16  is also in fluid communication with a respective inlet port of the blood pump  112 . In this manner, the blood flowing through the vasculature of the lower extremities is returned to pump  112  via the return conduit  106 . 
     The blood pump  112  is configured to allow higher pressure blood from shaft  16  and lower pressure blood from return conduit  106  to mix and equalize before it is pumped under pressure into shaft  36  of the venous catheter  14 . For example, the blood pump can have an internal storage chamber that receives blood from the return conduit  106  and shaft  16  at static pressure. Blood from the storage chamber can then be pumped under pressure into shaft  36 . In this manner, blood from the heart can be diverted to flow through the lower extremities and back into the vena cava. Blood from shaft  16  and return conduit  106  can also flow through a blood warmer, which can be an integral or separate component from the blood pump  112 . 
       FIG.  6    shows an arterial catheter  200  for an endovascular apparatus, according to another embodiment. The arterial catheter  200  performs the same function as the arterial catheter  12  of  FIGS.  1  and  2    but has a different construction. The arterial catheter  200  comprises an outer shaft  202 , an inner shaft  204  spaced radially inwardly from the outer shaft  202 , an annular lumen  206  defined between shafts  202 ,  204 , and an inner lumen  208  defined by the inner shaft  204 . Mounted on the outer shaft  202  are two spaced apart inflatable balloons  210 ,  212 . A plurality of side openings or apertures  214  are formed along the length of the outer shaft  202  between the balloons  210 ,  212 . First and second inflation conduits  216 ,  218 , respectively, extend through the annular lumen  206 . The first inflation  216  conduit has a distal end that is fluid communication with the proximal balloon  212  and a proximal end that is in fluid communication with a source of an inflation fluid. The second inflation conduit  218  has a distal end that is fluid communication with the distal balloon  214  and a proximal end that is in fluid communication with the inflation fluid source. 
     The proximal end of the outer shaft  202  can terminate at a proximal hub  220  that extends outside the body and is fluidly connectable to a source of a perfusion fluid. The inner shaft  204  has a proximal end portion  222  that extends outside the body and is fluidly connectable to a blood warmer and/or pump (not shown in  FIG.  6   ). The annular lumen  206  is closed at the distal end of the outer shaft  202 . 
     The arterial catheter  200  can be inserted and deployed within a patient&#39;s aorta in the same manner described above in connection with the arterial catheter  12 . A venous catheter (not shown) having the same construction as the arterial catheter  200  can be inserted into the vena cava in the same manner described above in connection with the venous catheter  14 . In use, the inner shaft of the venous catheter is fluidly connected to the outlet of the blood pump/warmer and the outer shaft of the venous catheter can be fluidly connected to a drain outside the body. Upon deployment of the arterial catheter  200  and the similarly constructed venous catheter, the visceral arteries and veins are isolated and blood from the heart flows proximally through the inner lumen  208  and exits the body where it can be routed through the blood pump/warmer, as indicated by arrows  224 . Blood from the blood pump/warmer can be returned to the vena cava via the inner lumen of the venous catheter where returning blood can flow back to the heart. The abdominal organs can be perfused by introducing a pressurized perfusion fluid into the annular lumen  206  of the catheter  200 , which then flows outwardly through side openings  214  into the visceral arteries. The perfusion fluid can then flow through the abdominal organs, the visceral veins, and back into and through the annular lumen of the venous catheter via side openings in the venous catheter. 
       FIG.  9    shows an endovascular apparatus  300 , according to another embodiment. The apparatus  300  is similar in many respects to the apparatus  10  of  FIGS.  1  and  2   . Thus, components in  FIG.  9    that are the same as components in  FIGS.  1  and  2    are given the same respective reference numbers and are not described further. 
     In the embodiment of  FIG.  9   , the isolated regions of the patient&#39;s vasculature can be perfused with the patient&#39;s own blood rather than a cold perfusion solution. The apparatus  300  comprises a cardiopulmonary bypass machine  302  or equivalent device that can warm, oxygenate and pressurize blood. The machine  302  has an inlet port fluidly connected to the second shaft  38  of the venous catheter  14  and an outlet port fluidly connected to the second shaft  18  of the arterial catheter. In use, blood can be drawn from the patient and introduced into a blood flow circuit that is fluidly separated from the blood being circulated by the heart. The blood being used as the perfusion fluid is circulated outwardly from the body via the second shaft  38  of the venous catheter  14 , and through the cardiopulmonary bypass machine  302 , which can oxygenate and warm the blood, and pump the blood back into the body via the second shaft  18  of the arterial catheter  12 , in the direction indicated by arrows  304 . Maintaining blood circulation through the isolated regions that is fluidly separated from the circulation of blood through the patient&#39;s heart allows for adequate perfusion of the organs while awaiting cardiac death. 
     The embodiments disclosed herein can be used for procedures other than procedures for preserving organ function for explant surgery. For example, in another implementation, an endovascular apparatus (e.g., an apparatus of  FIG.  1 ,  5  or  6   ) can be used to perfuse organs during survival surgery, such as cardiac or proximal aortic repairs where prolonged cessation of blood flow poses a risk of organ damage. 
     Referring to  FIGS.  10  and  11   , there is shown another embodiment of an endovascular apparatus that can be used for isolating and perfusing the organs of a patient (e.g., an organ donor patient), indicated generally at  400 . The apparatus  400  in the illustrated embodiment comprises an arterial perfusion stent  402  and a venous perfusion stent  404 . The arterial perfusion stent  402  is configured to isolate blood flow to the visceral arteries  80 , while allowing blood from the aorta  82  to continue to flow to the lower extremities. The venous perfusion stent  404  is configured to isolate blood flow from the visceral veins  84 , while allowing blood from the lower extremities to continue to flow to the heart via the inferior vena cava  86  of the patient. Thus, when deployed in a patient, the endovascular apparatus allows blood from the heart to pass uninterrupted through a central lumen of the arterial perfusion stent  402  to perfuse the lower body and then flow through a central lumen of the venous perfusion stent  404  to return to the heart. 
     Additionally, the arterial perfusion stent  402  of endovascular apparatus  400  is configured to introduce a perfusion fluid (e.g., a cold perfusion solution, or re-oxygenated and/or warmed blood) into the visceral arteries  80  for the purpose of perfusing donor organs (e.g., kidneys  114  or liver  116 ) in the abdominal cavity until such time the organs can be explanted. The venous perfusion stent  404  is configured to receive the perfusion fluid from the visceral veins  84  that was introduced into the body from the arterial perfusion stent  402 . As discussed in more detail below, the arterial and venous perfusion stents  402 ,  404  can each comprise a perfusion lumen (such as defined by an arterial perfusion conduit or sleeve  446  and a venous perfusion conduit or sleeve  448 , see  FIG.  11   ) that facilitates perfusion of blood or fluid through the abdominal organs, while allowing normal blood flow between the heart and lower extremities. Additionally, the arterial and venous perfusion stents  402 ,  404  include a non-porous liner  466  (best shown in  FIG.  13   ) that prevents or substantially reduces mixing of blood or other fluids flowing through the aorta or inferior vena cava and the visceral arteries and veins. 
     The arterial perfusion stent  402  comprises an elongated body that includes a radially compressible and expandable annular frame  430  supporting the liner  466 . In  FIG.  13    the frame  430  comprise a metal mesh, although the frame can have other configurations in other embodiments. Referring to  FIGS.  13 - 16   , in the illustrated embodiment, the stent  402  defines a central lumen  403  that extends from a proximal end  408  to a distal end  406  of the perfusion stent. The central lumen  403  allows passage of fluid (e.g., blood) through the body of the perfusion stent, thus maintaining blood flow through the artery in which the perfusion stent is deployed. The perfusion stent  402  can be radially compressible to a compressed state for delivery through the body to a deployment site and expandable to its functional size shown in  FIG.  11    at the deployment site. In certain embodiments, the perfusion stent  402  is self-expanding; that is, the stent can radially expand to its functional size when advanced from the distal end of a delivery sheath. Apparatuses particularly suited for percutaneous delivery and implantation of a self-expanding stent in the vessels of the body are well known and described briefly below. In other embodiments, the perfusion stent can be a plastically-expandable perfusion stent that can be adapted to be mounted in a compressed state on the balloon of a delivery catheter or another type of expansion device configured to expand the stent radially from a compressed delivery state to a radially expanded state. The perfusion stent can be expanded to its functional size at a deployment site by inflating the balloon of a balloon catheter, as known in the art. 
     The elongated body of the arterial perfusion stent  402  comprises a distal end portion  410 , a generally cylindrical intermediate portion  412 , and a proximal end portion  414 . The distal end portion  410  can comprise a generally cylindrical first section  411   a  and a tapered second section  411   b  positioned proximal to the first section  411   a . Likewise, the proximal end portion  414  can comprise a generally cylindrical first section  415   a  and a tapered second section  415   b  proximal to the first section  415   a . In the radially expanded state of the perfusion stent, the distal and proximal end portions  410 ,  414  have an outer diameter that is larger than the outer diameter of the intermediate portion  412 , thereby defining an annular perfusion space  416  (best shown in  FIG.  11   ) between the end portions and around the intermediate portion. Central lumen  403  extends through body of the arterial perfusion stent, allowing flow of fluid (e.g., blood) through from the distal end  406  to the proximal end  408  of the arterial perfusion stent, in the direction of arrows  415  shown in  FIG.  11   . 
     The outer surfaces of the distal and proximal end portions  410 ,  414  form a seal against the inner wall of the aorta when the arterial perfusion stent is in the radially expanded state. Thus, the outer surface of the distal and proximal end portions  410 ,  414  of the stent in the radially expanded state can have a diameter that is about the diameter of the inner surface in the region of the aorta where the stent will be placed. For example, for a perfusion stent to be placed in an adult, the outer surface of the distal and proximal end portions  410 ,  414  of the stent in the radially expanded state can have a diameter ranging from 12 mm to 3 cm. Smaller stents can be used in pediatric patients. 
     The venous perfusion stent  404  can have the same construction as the arterial perfusion stent  402 . Thus, in the illustrated embodiments, the venous perfusion stent  404  has a distal end  418  and a proximal end  420 . The stent  404  can comprise a distal end portion  422 , a generally cylindrical intermediate portion  424 , and a proximal end portion  426 . The distal end portion  422  can comprise a generally cylindrical first section  423   a  and a tapered section  423   b  positioned proximal to the first section  423   a . Likewise, the proximal end portion can comprise a generally cylindrical first section  427   a  and a tapered second section  472   b  positioned proximal to the first section  427   a . In the radially expanded state of the venous perfusion stent, the distal and proximal end portions  422 ,  426  have an outer diameter that is larger than the outer diameter of the intermediate portion  424 , thereby defining an annular perfusion space  428  (best shown in  FIG.  11   ) between the end portions and around the intermediate portion. A central lumen extends through body of the venous perfusion stent, allowing flow of fluid (e.g., blood) through from the proximal to distal end of the venous perfusion stent, in the direction of arrows  427  shown in  FIG.  11   . 
     The outer surfaces of the distal and proximal end portions  422 ,  426  form seals against the inner wall of the inferior vena cava when the venous perfusion stent is in the radially expanded state. Thus, the outer surface of the distal and proximal end portions  422 ,  426  of the stent in the radially expanded state can have a diameter that is about the diameter of the inner surface in the region of the inferior vena cava where the stent will be placed. For example, for a perfusion stent to be placed in an adult, the outer surface of the distal and proximal end portions  422 ,  426  of the stent in the radially expanded state can have a diameter ranging from 15 mm to 3 cm. Smaller stents can be used in pediatric patients. 
       FIG.  12    shows an alternate embodiment of an expandable annular frame indicated generally at  500  that can be used for the perfusion stent  402  or the perfusion stent  404 . As shown, the frame  500  has a distal end  502  and a proximal end  504 . The frame  500  can comprise an enlarged distal end portion  506 , a generally cylindrical intermediate portion  508 , and an enlarged proximal end portion  510 . In the radially expanded state of the perfusion stent, the distal and proximal end portions  506 ,  510  have an outer diameter that is larger than the outer diameter of the intermediate portion  508 . The intermediate portion  508  can be formed from a plurality of longitudinally extending frame members, or struts,  512 . The distal and proximal end portions  506 ,  510  can be formed from angled struts  514  that are welded or otherwise secured to each other at nodes  516  formed from the vertices of adjacent bends so as to form a mesh structure. 
     The struts  512 ,  514  of the distal, intermediate, and proximal portions of the perfusion stent can be made of a suitable shape memory material, such as the nickel titanium alloy known as Nitinol, that allows the prosthetic valve to be compressed to a reduced diameter for delivery in a delivery apparatus (such as described below) and then causes the perfusion stent to expand to its functional size inside the patient&#39;s body when deployed from the delivery apparatus. If the perfusion stent is a balloon-expandable perfusion stent that is adapted to be crimped onto an inflatable balloon of a delivery apparatus and expanded to its functional size by inflation of the balloon, the perfusion stent  402  can be made of a suitable plastically expandable material, such as stainless steel. 
     The distal, intermediate, and proximal portions  506 ,  508 ,  510  can be constructed as a single unit, such as by machining (e.g., laser cutting). Alternatively, the frame can be constructed of separate segments each comprising respective struts or frame members, and each segment can be welded or otherwise secured together using means known in the art. In one example, the distal, intermediate, and proximal portions  506 ,  508 ,  510  are each constructed separately and secured together. 
     As shown in  FIG.  12   , the distal end portion  506  of the frame  500  in its radially expanded state can have a cylindrical shape at its distal aspect and can gradually decrease in diameter to the diameter of the intermediate portion  508 . The proximal end of the distal end portion of the frame  500  is secured to the distal end of the intermediate portion  508  of the frame  430 . The intermediate portion  508  of the frame in its radially expanded state generally has a uniform cylindrical shape having a diameter that is narrower than the outermost diameter of the distal and proximal end portions  436 ,  440  of the frame  500 . The proximal end of the intermediate portion of the frame  500  is secured to the proximal end portion  510  of the frame  500 . The proximal portion  510  of the frame  500  in its radially expanded state can have a cylindrical shape at its distal aspect and can gradually decrease to a narrower diameter at its proximal end, for example, to the diameter of the intermediate portion  508 . The tapered proximal sections of the distal end portion  506  and the proximal end portion  510  can facilitate re-sheathing and recapture of the stent, as further discussed below. 
     Although a particular shape for the frame  500  is shown in  FIG.  12   , any shape that allows for delivery of the perfusion stent to appropriate vessel location in the patient and for formation of a seal against the inner wall of the aorta and isolation of blood flow from the aorta to the visceral arties can be used. 
     The venous perfusion stent  404  can also include an expandable annular frame, which can be substantially identical to frame  500  of the arterial perfusion stent. However, the frames of the arterial and venous perfusion stents  402 ,  404  can include minor structural differences (for example in the diameter or length of the perfusion stent) as needed for the placement and fit of the stents when implanted in to the aorta or inferior vena cava of the patient, respectfully. 
     Referring to  FIG.  11   , the arterial perfusion stent  402  comprises a perfusion conduit  446  that facilitates perfusion of blood or other perfusion fluid to the abdominal organs in the direction of arrows  452 . The arterial perfusion conduit  446  comprises an outlet  447  that opens into the arterial perfusion space  416 . The perfusion fluid can flow through a perfusion lumen  450  ( FIG.  16   ) of the arterial perfusion conduit  446  into the arterial perfusion space  416 . The arterial perfusion conduit  446  can extend at least partially through the proximal end portion  414  of the stent body and has a proximal end that can extend beyond the proximal end portion  414 , where it can be fluidly connected to a catheter  456  that extends outside of the body of the patient. Desirably, the catheter  456  can be connected to an oxygenator and/or blood warmer  458  and/or a blood pump  460 . The oxygenator can add oxygen to the blood or other fluid flowing through the catheter, and the pulsatile pump can push blood flow in the direction of arrow  461  through the endovascular apparatus  400  and the abdominal organs of the patient. 
     The arterial perfusion conduit  446  can be placed anywhere in the stent body that allows the perfusion lumen  450  to be in fluid communication with the arterial perfusion space  416 . In the illustrated embodiment, the arterial perfusion conduit extends from the interior of the proximal end portion  414  of the stent body to the arterial perfusion space  416 , thereby allowing such access. 
     The venous perfusion stent  404  comprises a perfusion conduit  448  that facilitates perfusion of the perfusion fluid from the abdominal organs in the direction of arrows  462 . The venous perfusion conduit  448  comprises an inlet  449  at its distal end that opens into the venous perfusion space  428 . The perfusion fluid can flow from the venous perfusion space  428  and into a perfusion lumen of the venous perfusion conduit  448 . The venous perfusion conduit  448  can extend at least partially through the proximal end portion  426  of the stent body and has a proximal end that can extend beyond the proximal end portion  426 , where it can be connected to a catheter  464  that extends outside of the body of the patient and connects to the blood pump  460  (as shown) and/or the oxygenator and/or blood warmer  458 . 
     The venous perfusion conduit  448  can be placed anywhere in the stent body that allows the perfusion lumen of the venous perfusion conduit  448  to be in fluid communication with the venous perfusion space  428 . In the illustrated embodiment, the venous perfusion conduit extends from the interior of the proximal end portion  4426  of the arterial perfusion stent  404  to the venous perfusion space  428 , thereby allowing such access. 
     Referring again to  FIG.  13   , as noted above the arterial perfusion stent  402  can include a liner  466  that is non-porous to the perfusion fluid (blood, in the illustrated embodiment). The liner can be secured to the frame  430  by any suitable means, for example an adhesive or suturing. The liner covers the frame  430  of the arterial perfusion stent and prevents or substantially reduces mixing of blood flowing through the aorta and the central lumen  403  with the perfusion fluid flowing through the perfusion space  416 . The venous perfusion stent  404  includes a non-porous liner that can be substantially identical to the liner used for the arterial perfusion stent, and that prevents or substantially reduces mixing of blood flowing through the inferior vena cava with the perfusion fluid flowing through the perfusion space  428 . However, the liners of the arterial and venous perfusion stents  402 ,  404  can include minor structural differences (for example in diameter or length) as needed for sufficient coverage of the arterial and venous perfusion stents. In the illustrated embodiment, the liner is located on the outside of the frame of the perfusion stent. However, the liner can be located on the stent in any way that provides a non-porous barrier to blood. For example, the liner can be located on the inside of the frame of the stent, or on both the outside and the inside of the stent. 
     In several embodiments, the liner  466  can be made of any suitable bio-compatible synthetic or biological material, such as those described in U.S. Pat. No. 6,730,118, which is incorporated herein by reference. The liner  466  desirably can be substantially impermeable to aqueous solutions, such as blood or plasma. In some embodiments, the liner  466  can be a polymer or composite membrane or layer, for example, polytetrafluoroethylene (PTFE); or a woven, knit, or non-woven fabric material (e.g., a ripstop fabric) manufactured from natural and/or synthetic yarns or fibers, such as woven polyester (e.g., polyethylene terephthalate, PET, such as Dacron®), or cellulose (such as cotton or linen), silk, nylon, polyolefin, carbon fiber, and/or metal fibers. In additional embodiments, the liner  466  can be made of a synthetic and/or natural material that is coated with a sealant (such as ePTFE, fluoropolymer, or gelatin (Vasutek® Gelatin Sealant, Terumo, UK); see, e.g., International Publication No. WO 2001/080918, which is incorporated by reference herein in its entirety). In more embodiments, the liner  466  can be made of a bio-synthetic materials and composites (e.g., collagen-polyester composites, Omniflow®, Bio Nova, Melbourne, AU). Other embodiments use natural tissue, including intestinal submucosa, natural blood vessels (arteries or veins, e.g., from animal sources), pericardial tissue and the like, which may be fixed (for example, using gluteraldehyde and/or formaldehyde). Other embodiments include artificial collagen or cellulose tubes. 
     In some embodiments, the liner  466  is manufactured from sheet stock, two edges of which are brought together, for example, overlapped and/or abutted, and sealed or closed to form a tube comprising a seam. In some embodiments, the seam is linear, for example, extending along a longitudinal axis. In other embodiments, the seam has a different shape, for example, zig-zag or helical. The edges are closed using any suitable method, for example, suturing, welding, gluing, laminating, and/or bonding. In other embodiments, the liner  466  does not comprise a seam, for example, when the tubular sealing member comprises a portion of a blood vessel, intestinal submucosa, or certain artificial tubular structures. 
     In additional embodiments, the liner  466  can desirably be made of an electrospun polyurethane fabric (see, e.g., Amoroso et al., Elastomeric electrospun polyurethane scaffolds: The interrelationship between fabrication conditions, fiber topology, and mechanical properties.  Advanced materials.  23:106-111, 2011, which is incorporated by reference herein in its entirety). In particular embodiments, the frame  430  of the stent can comprise a micro-pattered thin Nitinol film (see, e.g., WO2004/028340; Chun et al., Thin film nitinol microstent for aneurysm occlusion,  J. Biomechanical Engineering,  131(5):051014, 8 pages, 2009; Chun et al., Novel micro-patterning processes for thin film niti vascular devices  Smart Materials and Structures,  19:105021, 2010; Chun et al., Modeling and experimental analysis of the hyperelastic thin film nitinol,  Journal of Intelligent Material Systems and Structures.  22, 2045-2051, 2011; Rigberg et al., Thin-film nitinol (niti): A feasibility study for a novel aortic stent graft material  Journal of vascular surgery,  50:375-380, 2009; each of which is incorporated by reference herein in its entirety). Micro-fabrication techniques can be used to form a plurality of micro-openings or apertures in a thin sheet of Nitinol (about 6 μM) so as to form a thin film lattice or mesh. A layer of non-porous material, such as polyurethane or ePTFE, can be applied to and secured to the metal film to provide the liner  466 . 
       FIG.  17    depicts the stent  402  being deployed from a sheath  472  of a delivery apparatus. As shown, each of the perfusion stents  402 ,  404  can include suitable positioning markers and/or sensors at convenient locations to assist in locating the proximal and distal end portions of each perfusion stent at the desired locations within the aorta or the inferior vena cava. For example, each of the distal end portion  410  and proximal end portion  414  of the arterial perfusion stent  402  can include a respective positioning marker  468  (see  FIG.  17   ). In some embodiments, the positioning markers  468  can be radiopaque markers that can be used to locate the position of the stent during deployment in a patient by radiography. For example, an x-ray image of the stent within the body of the patient can be obtained using a bed-side x-ray machine to determine the position of the stent within the aorta or inferior vena cava. Certain bones or other tissue visible under x-ray can be used as landmarks to help position the stent relative to the visceral arteries. For example, the radiopaque markers  468  can be positioned above and below the T12 and L2 vertebrae. Although the illustrated embodiment includes a pair of positioning markers for the arterial perfusion stent, a greater or fewer number of markers can be provided as needed for the surgeon to properly position the stent in the aorta of the patient. The distal end portion  422  and proximal end portion  426  of the venous perfusion stent  404  similarly can include a corresponding pair of radiopaque markers that can be used to position the venous perfusion stent in a patient by radiography. 
     In an alternative embodiment, positioning markers  468  can be provided on the sheath  472 . When the stent  402  is located in the sheath, one marker is aligned with the distal end portion  410  of the stent and the other marker is aligned with the proximal end portion  414 . 
     In alternative embodiments, the positioning markers can comprise passive or active emitters that can emit electromagnetic waves through the body and a corresponding detector or monitor can be used to receive the electromagnetic waves from the emitters and provide visual and/or audible feedback to a user indicating the position of the markers inside the body relative to external landmarks on the body. In particular embodiments, for example, the positioning markers can be emitters that can emit radiofrequency waves, such as radiofrequency identification (RFID) tags. Further details of the use of RFID tags as positioning marks are disclosed in co-pending Application No. 61/845,896, filed Jul. 12, 2013, which is incorporated herein by reference. 
     Referring to  FIG.  11   , the arterial and venous perfusion stents can be secured to respective one or more recovery wires  470 . The recovery wires  470  can be secured to the proximal end of the frame of the perfusion stents and can extend proximally from the perfusion stents to outside the patient&#39;s body via the artery or vein through which the perfusion stent was deployed. If it is desired to re-position or remove the arterial and/or venous perfusion stents from the patient (for example, if the patient recovers), then tension can be applied to the recovery wires to retract the perfusion stents in the proximal direction into respective sheaths  472 . Once the stents are retracted into the sheaths  472 , the sheaths can be withdrawn from the body. The tapered sections  411   b ,  415   b  of the end portion of the stent facilitate recapture of the stent back into the sheath  472 . 
     In use, as depicted in  FIG.  10   , the arterial perfusion stent  402  can be inserted into the aorta via an incision in a femoral artery in a minimally invasive manner using known techniques. Similarly, the venous perfusion stent  404  can be inserted into the inferior vena cava via an incision in a femoral vein in a minimally invasive manner Guidewires, dilators and/or introducers can be used to help introduce and advance the perfusion stents through the patient&#39;s vasculature, as known in the art. As best shown in  FIG.  11   , the arterial perfusion stent is positioned such that the distal end portion  410  is upstream of the visceral arteries  80  and the proximal end portion  414  is positioned downstream of the visceral arteries  80 . Similarly, the venous perfusion stent  404  is positioned such that the distal end portion  422  is positioned downstream of the visceral veins  84  and the proximal end portion  426  is positioned upstream of the visceral veins  84 . The proper positioning of the perfusion stent  402 ,  404  can be accomplished by viewing the markers  468  by x-ray or under fluoroscopy, for example. 
     Once the arterial and venous perfusion stents are in place, the proximal and distal end portions of each stent form a seal against the inner walls of the aorta and inferior vena cava, respectively, thereby isolating blood flow from the aorta  82  to the visceral arteries  80  and from the visceral veins  84  to the inferior vena cava  86 . Thus, blood from the heart can flow through the arterial stent  402  (bypassing the visceral arteries), through the vasculature of the lower extremities, through the venous stent  404  (bypassing the visceral veins), and back to the heart. The blood flow to and from the visceral organs is redirected from the venous perfusion space  428  around the venous perfusion stent  404  through the venous perfusion conduit  448  and via the catheter  464  to the blood pump  460 , blood oxygenator and/or warmer  458  that are outside the patient&#39;s body. The blood is then redirected back into the patient via the catheter  456  connected to the arterial perfusion conduit  446  and into the arterial perfusion space  416  around the arterial perfusion stent  402 . The blood flows through the visceral arteries  80  to the abdominal organs, and back to venous perfusion space  428  via the visceral veins  84 . 
     Although perfusion with the patient&#39;s blood is discussed above, use of a cold perfusion fluid is also available. The cold perfusion fluid can be introduced into the arterial perfusion space  416  via the arterial perfusion conduit  446 , and retrieved from the venous perfusion space via the venous perfusion conduit  448  similar to that shown in  FIG.  2   . 
     In particular embodiments, the perfusion fluid can be similar to the University of Wisconsin solution and can comprise, without limitation, one or more of the following compounds: heparin, pentastarch, steroids, lactobionic acid, magnesium sulfate, raffinose, adenosine, allopurinol, glutathione, and potassium hydroxide. The perfusion fluid can be cooled to a temperature of about 0 degree C. to about 10 degrees C. for introduction into the body and more preferably to a temperature of about 4 degrees C. to about 6 degrees C. As an alternative perfusion fluid, blood separate from the circuit of blood being circulated by the heart can be propelled, oxygenated and warmed before being cycled continuously through the catheters, as further described below. 
     The apparatus  400  is particularly suited for use with DCD donors. In this regard, the perfusion stent  402 ,  404  can be inserted and deployed in the vasculature of a DCD donor as soon as possible prior to cardiac death. For example, the perfusion stent  402 ,  404  can be inserted and deployed in a DCD donor just prior to or at the same time as removing the patient from life support or when the donor is experiencing unstable vital signs for normal organ blood flow. The blood flow circuit allows for normal blood flow through the body, except for those isolated regions, while awaiting expected cardiac death and during the predetermined waiting period before explant can occur. In another implementation, the perfusion stents  402 ,  404  can be inserted into the DCD donor prior to cardiac death and then are deployed at the time of cardiac death. In yet another implementation, the apparatus can be inserted and deployed in a donor who expires prematurely before a donor team is ready to perform the explant procedure. In any case, during the period of time before explant can be performed, the perfusion fluid reduces warm ischemia time and preserves organ function. 
       FIG.  18    shows an endovascular apparatus  600 , according to another embodiment. The endovascular apparatus  600  is similar in many respects to the apparatus  400  of  FIGS.  10  and  11   , but has been modified for deployment in the aortic arch and superior vena cava to isolate and perfuse the head and arms of a patient with a perfusion fluid. 
     The apparatus  600  in the illustrated embodiment comprises an arterial perfusion stent  602  and a venous perfusion stent (not pictured). The arterial perfusion stent  602  is configured for deployment in the aortic arch and to isolate blood to the head and arms via carotid and subclavian arteries  601 . When deployed in a patient, the endovascular apparatus  600  allows blood from the heart to pass uninterrupted through a central lumen of the arterial perfusion stent  602  and flow via the aorta  82  to perfuse the abdomen and lower body and then flow uninterrupted through the inferior vena cava to return to the heart. Further, the arterial perfusion stent  602  of endovascular apparatus  600  is configured to introduce a perfusion fluid (e.g., re-oxygenated and/or warmed blood) into the carotid and subclavian arteries  601  for the purpose of perfusing the head and arms with the perfusion fluid. For example, the apparatus  600  can be used to maintain blood flow to the brain or spinal cord during a surgical procedure that restricts such flow in order to reduce or prevent brain ischemia or spinal cord ischemia during the procedure. 
     The arterial perfusion stent  602  can have a similar construction as that of the arterial perfusion stent  402 . The size and shape of the arterial perfusion stent  602  can be generally similar to the size and shape of the arterial perfusion stent  402 , with modifications as needed to allow for deployment of the arterial perfusion stent  602  in the aortic arch. For example, similar to arterial perfusion stent  402 , the arterial perfusion stent  602  comprises an elongated body that includes an annular frame supporting a non-porous liner that can be radially compressible to a compressed state for delivery through the body to a deployment site and expandable to its functional size shown in  FIG.  18    at the deployment site. Similar to perfusion stent  402 , the perfusion stent  602  can be self-expanding, or, in other embodiments, can be a plastically-expandable perfusion stent. The frame and the non-porous liner of the arterial perfusion stent  602  can be made of the same materials as those used for the arterial perfusion stent  402 . 
     The stent  602  defines a central lumen that extends from a proximal end  608  to a distal end  606  of the perfusion stent. The central lumen allows passage of fluid (e.g., blood) through the body of the perfusion stent, thus maintaining blood flow through the artery in which the perfusion stent is deployed. In the radially expanded state of the perfusion stent, distal and proximal end portions  610 ,  614  have an outer diameter that is larger than the outer diameter of an intermediate portion  612 , thereby defining an annular perfusion space  616  between the end portions and around the intermediate portion. The outer surfaces of the distal and proximal end portions  610 ,  614  form a seal against the inner wall of the aorta when the arterial perfusion stent is in the radially expanded state. 
     Similar to the arterial perfusion stent  402 , the arterial stent  602  can comprise a perfusion lumen (such as defined by an arterial perfusion conduit or sleeve  646 ) that is in fluid communication with the arterial perfusion space  616  and facilitates perfusion of blood or fluid through the head and arms, while allowing normal blood flow between the heart and lower extremities. The perfusion fluid can flow through the perfusion lumen and into the arterial perfusion space  416 . The arterial perfusion conduit  646  can extend at least partially through the proximal end portion  614  of the stent body and has a proximal end that can extend beyond the proximal end portion  614 , where it can be fluidly connected to a catheter that extends outside of the body of the patient. Desirably, the catheter can be connected to an oxygenator and/or blood warmer and/or a blood pump to treat and pump the blood of the patient as needed. 
     The venous perfusion stent included in the apparatus  600  can be configured for deployment in the superior vena cava to isolate blood flow returning from the head and arms to the heart via the superior vena cava. The venous perfusion stent is configured to receive the perfusion fluid from the superior vena cava that was introduced into the body from the arterial perfusion stent  602 . The venous perfusion stent of apparatus  600  can have a structure similar to the venous perfusion stent of apparatus  400 , and can be configured for placement in the superior vena cava in any way so as to collect fluid returning via the superior vena cava to the heart. In some non-limiting embodiments the venous stent can include a configuration such that a perfusion space of the stent collects fluid (e.g., blood) from the right brachiocephalic vein, the left internal jugular, or the right brachiocephalic vein and the left internal jugular. 
     Once the arterial and venous perfusion stents of the apparatus  600  are in place, the proximal and distal end portions of each stent form a seal against the inner walls of the aortic arch and superior vena cava, respectively, thereby isolating blood flow from the aorta to the carotid and subclavian arteries  601  and from the veins of the head and arms to the superior vena cava. Thus, blood flow to and from the head and arms is redirected from the superior vena cava through a venous perfusion conduit to a blood pump, blood oxygenator and/or warmer that are outside the patient&#39;s body. The blood is then redirected back into the patient via the catheter  646  connected to the arterial perfusion conduit  646  and into the arterial perfusion space  616  around the arterial perfusion stent  602 . The blood flows through the carotid and subclavian arteries  601  to the head and arms, and back to superior vena cava. 
     The embodiments disclosed herein can be used for procedures other than procedures for preserving organ function for explant surgery. For example, in another implementation, an endovascular apparatus (e.g., an apparatus of  FIG.  1 ,  5 ,  6 ,  10 ,  11 ,  12   , or  18 ) can be used to perfuse organs during survival surgery, such as cardiac or proximal aortic repairs where prolonged cessation of blood flow poses a risk of organ damage. In another implementation, an endovascular apparatus (e.g., an apparatus of  FIG.  1 ,  5 ,  6 ,  10 ,  11 ,  12   , or  18 ) can be used to selectively perfuse organs, but not other body regions, with a therapeutic agent. For example, if a particular therapeutic agent has therapeutic effect on the organs, but is toxic to other body regions (for example, the central nervous system), the agent can be selectively administered to the organs using a disclosed endovascular apparatus. In one non-limiting example, a chemotherapeutic agent can be delivered to the visceral organs using a disclosed endovascular apparatus (e.g., an apparatus of  FIG.  1 ,  5 ,  6 ,  10 ,  11   , or  12 ) to selectively perfusion the visceral organs of the body with a solution (e.g., blood) that includes the chemotherapeutic agent. 
     GENERAL CONSIDERATIONS 
     For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. 
     Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. As used herein, the terms “a”, “an” and “at least one” encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus “an” element is present. The terms “a plurality of” and “plural” mean two or more of the specified element. 
     As used herein, the term “and/or” used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase “A, B, and/or C” means “A,” “B,” “C,” “A and B,” “A and C,” “B and C” or “A, B and C.” 
     As used herein, the term “coupled” generally means physically coupled or linked and does not exclude the presence of intermediate elements between the coupled items absent specific contrary language. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.