Abstract:
The present invention relates to a catheter or cannula system that facilitates cardiopulmonary bypass surgeries and enables prolonged circulatory support of the heart. More specifically, the present invention provides an aortic catheter system including a porous aortic root balloon capable of occluding the aorta, delivering cardioplegia and providing tactile feedback and helping to maintain the competency of regurgitant aortic valves.

Description:
This application claims benefit of Prov. No. 60/084,939 filed May 11, 1998. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to a system and methods for inducing cardioplegic arrest and for performing cardiopulmonary bypass procedures. More particularly, the invention relates to an aortic catheter having a porous aortic root balloon for controlling flow through the coronary arteries and the aortic lumen, and for inducing cardiac arrest. The invention further relates to devices for maintaining the competence of a patient&#39;s aortic valve and for preventing unwanted flow through the aortic valve. 
     BACKGROUND OF THE INVENTION 
     Recent advances in the field of minimally invasive cardiac surgery have included the development of aortic catheters and methods for inducing cardiac arrest without the necessity of opening the patient&#39;s chest with a sternotomy or other major thoracotomy. For example, U.S. Pat. No. RE 35,352 to Peters describes a single balloon catheter for occluding a patient&#39;s ascending aorta and a method for inducing cardioplegic arrest. A perfusion lumen or contralateral arterial cannula is provided for supplying oxygenated blood during cardiopulmonary bypass. U.S. Pat. No. 5,584,803 to Stevens et al. describes a single balloon catheter for inducing cardioplegic arrest and a system for providing cardiopulmonary support during closed chest cardiac surgery. A coaxial arterial cannula is provided for supplying oxygenated blood during cardiopulmonary bypass. The occlusion balloon of these catheters must be very carefully placed in the ascending aorta between the coronary arteries and the brachiocephalic artery, therefore the position of the catheter must be continuously monitored to avoid complications. 
     In clinical use, in patients with incompetent or regurgitant aortic valves, antegrade infusion of cardioplegia by aortic root injection is contraindicated because the pressure generated by infusion of cardioplegia overcomes the reduced competence of the valve, causing cardioplegia to enter the ventricle rather than entering the coronary arteries. In some cases the left ventricle may become distended. In patients with incompetent or regurgitant aortic valves, it is recommended that cardioplegia be administered by direct coronary cannulation or by retrograde perfusion through the coronary sinus. Direct coronary cannulation can be difficult and can dislodge plaques from ostial lesions in the coronary arteries. Retrograde perfusion of cardioplegia through the venous system has been used successfully, however, there is debate as to the effectiveness of this procedure, and correct placement of the catheters can be difficult. Furthermore, even in patients with normal aortic valves, pressures generated during surgery may cause the valve to become temporarily incompetent, leading to problems similar to those discussed above. 
     Another difficulty encountered with prior art aortic catheters is the tendency of the single balloon catheters to migrate or drift in the direction of the pressure gradient within the aorta. Specifically, during infusion of cardioplegia, the balloon catheter will tend to drift downstream away from the heart and toward the aortic arch and, while the cardiopulmonary bypass pump is on during the procedure and after completion of infusion of cardioplegia, the balloon catheter will tend to drift upstream in the opposite direction toward the heart into the aortic root. This migration can be problematic if the balloon drifts downstream far enough to occlude the brachiocephalic artery, or upstream enough to occlude the coronary arteries, or to pass through the aortic valve into the ventricle. 
     What is needed is a peripheral or central access catheter configuration that maintains the competence of weakened aortic valves, and does not challenge the competence of healthy aortic valves, during infusion of cardioplegia, and is more resistant than prior apparatus to migration due to pressure gradients within the patient&#39;s aorta. 
     The following patents are hereby incorporated herein in their entirety: U.S. Pat. Nos. 5,383,854, 5,308,320, 5,820,593 and 5,879,316 by Safar et al.; U.S. patent applications Ser. No. 08/909,293 filed Aug. 11, 1997, Ser. No. 08/909,380 filed Aug. 11, 1997 and Ser. No. 09/152,589 filed Sep. 11, 1998, by Safar et al.; U.S. Pat. No. 5,738,649 by John A. Macoviak; U.S. Pat. Nos. 5,827,237 and 5,833,671 by John A. Macoviak and Michael Ross; and U.S. patent application Ser. No. 08/665,635, filed Jun. 17, 1996, by John A. Macoviak and Michael Ross; U.S. patent application 09/205,753, filed Dec. 8, 1997, by Bresnahan et al. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides an aortic catheter or cannula having a distal flow control member located at or near a distal end of the cannula. The distal flow control member is positioned within the aortic root and is intended to fulfill at least one and preferably all five of the following functions: occluding the aorta at the aortic root, perfusing the coronary arteries with a selected fluid, maintaining the competence of the aortic valve when perfusing the coronary arteries, resisting migration of the distal flow control member or cannula, and providing a bumper for tactile feedback when placing the catheter. Preferably, the distal flow control member may be an inflatable balloon that is inflated using a cardioplegia fluid, and which will occlude the aorta and deliver an effective volume of cardioplegia fluid to the coronary arteries. The distal flow control member may be shaped to conform to the shape of the aortic root and may also be shaped to conform to the cusps of the aortic valve. The material or materials used in the inflatable distal flow control member should have properties that allow an internal pressure within the distal flow control member to be maintained at a sufficient level to occlude the aorta, while also allowing a controlled volume of fluid to seep or otherwise escape from the balloon for perfusing the coronary arteries. Thus, the surface of the balloon may be porous, or have one or more porous regions, or include apertures that allow cardioplegia to seep or flow when a specific pressure is attained, and/or to prevent flow of cardioplegia when the pressure is higher or lower than ideal for coronary perfusion. 
     The catheter may further include one or more additional flow control members located downstream from the distal flow control member to segment the aorta for selective perfusion to different organ systems within the body. These flow control members may be inflatable balloons or selectively deployable external catheter valves. The catheter may further include one or more anchoring members located downstream from the distal flow control member. The downstream anchoring member may be a larger inflatable balloon or other anchoring structure that provides sufficient force or friction to prevent the catheter from drifting from a selected position within the aorta. Useable flow control members include, but are not limited to, expandable or inflatable members such as inflatable balloons and valves including collapsible/expandable valves of various configurations including retrograde valves, antegrade valves, and various central flow and peripheral flow valves. 
     A combination of valves and inflatable members may be used as appropriate for a given procedure, thus in some embodiments, the catheter body can include one or more antegrade and retrograde valves, as well as one or more inflatable balloons. Inflatable balloons and collapsible/deployable valves suitable for this application have been previously described in the patents incorporated by reference above and any desirable or practical inflatable balloon or deployable valve may be used. Inflatable balloons typically include an interior chamber that is in fluid communication with an inflation lumen extending within the catheter shaft a location from within the respective flow control member to a location in the proximal portion which is adapted to extend out of the patient. 
     A first embodiment of the aortic catheter system of the present invention is configured for retrograde deployment via a peripheral artery, such as the femoral artery. The aortic catheter has an elongated catheter shaft having a proximal end and a distal end. A distal flow control member, preferably in the form of an inflatable balloon, is mounted on the catheter shaft near the distal end of the catheter shaft so that it may be positioned within the aortic root when deployed. An inflation and cardioplegia lumen extends through the catheter shaft to one or more inflation ports within the distal flow control member. In the preferred embodiment, a guide wire lumen extends from the proximal end of the catheter shaft to the distal end of the shaft, and may have a hydrophilic or lubricious coating. Generally, the distal flow control member comprises an impermeable portion and a permeable portion. More exemplary embodiments will now be discussed. 
     In a second embodiment, the distal flow control member is a three-lobed balloon to conform to the shape of the aortic valve. In a third embodiment the distal flow control member is comprised of a balloon formed of a non-porous material, but having two or more porous windows that align with the coronary ostia for delivery of cardioplegia. In a fourth embodiment, the distal flow control member comprises a balloon comprising both a non-porous material portion, and a porous portion that extends circumferentially around the diameter of the balloon. In a fifth embodiment, bistable nipples or pressure valves are used. In a sixth embodiment, the distal flow control member comprises three adjacent balloons on the catheter shaft, with the most distal balloon conforming to the shape of the aortic valve, the middle balloon being porous, and the most proximal balloon being non-porous. In a seventh embodiment, a second balloon is positioned within a first outer balloon. When the inner balloon is fully inflated, the outer surface of the inner balloon contacts the inner surface of the outer balloon preventing escape of cardioplegia through the porous portions, nipples, or pressure valves located on the outer balloon. When the inner balloon is deflated, cardioplegia is allowed to flow. In an eighth embodiment, the distal flow control member comprises two adjacent balloons on the catheter shaft having porous surfaces facing each other. 
     In each embodiment discussed above, the distal flow control member preferably resists migration because the distal flow control member comprises a diameter larger than the diameter of the sinotubular ridge and the aortic valve annulus. In alternate embodiments, the surface of the flow control member may include a sticky polymer coating to further resist migration. 
     In a ninth embodiment of the invention, describes a catheter system for retrograde deployment that includes an additional occluding/anchoring member is described. In this configuration, the aortic catheter has an elongated catheter shaft having a proximal end and a distal end. Any of the previously described porous root balloons may be implemented. The porous aortic root balloon is mounted on the catheter shaft near the distal end of the catheter shaft so that it may be positioned within the aortic root when deployed and is capable of occlusion and cardioplegia delivery. An occluding/anchoring member, hereafter referred to as the anchoring member, in the form of an inflatable balloon, is mounted on the catheter shaft proximal to the porous root balloon and at a position located in the descending aorta when deployed. Preferably, an arch perfusion lumen extends through the catheter shaft from the proximal end to one or more arch perfusion ports on the exterior of the catheter shaft between the porous root balloon and the downstream anchoring member, to perfuse the aortic arch. An arch pressure lumen preferably extends through the catheter shaft from the proximal end to an arch pressure port located between the distal flow control member and the anchoring member to monitor pressure in the aortic arch. At least one inflation lumen extends through the catheter shaft from the proximal end to one or more balloon inflation ports located on the catheter shaft within the distal flow control member and the anchoring member. In other embodiments, each flow control member may be deployed using a separate lumen. A guide wire lumen extends from the proximal end of the catheter shaft to the distal end of the shaft. The distal flow control member used in this embodiment would be similar to the distal flow control member and alternative embodiments described previously. Occlusion of the aorta by the anchoring balloon may also be used to partition the aorta for differential perfusion of the partitioned portions. 
     In a tenth embodiment, otherwise similar to the ninth embodiment described above, the system performs the partitioning function of the anchoring balloon with a valve, which enables the partitioning of the aorta for differential perfusion. 
     Furthermore, methods according to the invention are described using the aortic catheter for occluding the ascending aorta at the aortic root and for perfusing a selected fluid to the coronary arteries and/or inducing cardioplegic arrest, for supporting the patient&#39;s circulation on cardiopulmonary bypass, for partitioning the patient&#39;s aorta and for performing selective aortic perfusion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a shaft portion of a first embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for insertion into a peripheral artery and configured to occlude the ascending aorta and deliver cardioplegia to the coronary ostia. 
     FIG. 2 illustrates a magnified lateral cross portion of the aortic catheter of FIG. 1 taken along line  2 - 2 . 
     FIG. 3 shows a side view of an aortic catheter according to the present invention with a catheter shaft configured for retrograde deployment via femoral artery access. 
     FIG. 4 is a schematic diagram showing an aortic catheter according to the present invention deployed within a patient&#39;s aorta via femoral artery access. 
     FIG. 5 illustrates is a second embodiment of the present invention illustrating a three-lobed porous aortic root balloon positioned within an aortic root, configured to conform to the shape of the cusps of the aortic valve when deployed. 
     FIG. 6 is a distal end view of the porous aortic root balloon of FIG. 5 illustrating the three-lobed configuration. 
     FIG. 7 illustrates a third embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. 
     FIG. 8 illustrates a fourth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. 
     FIG. 9 illustrate a fifth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia having a circumferential region covered with bistable nipples. 
     FIG. 10 illustrates a magnified view of an exemplary design of a single bistable nipple in an inverted low pressure configuration wherein low or no flow of cardioplegia is permitted. 
     FIG. 11 illustrates a magnified view of an exemplary design of a single bistable nipple in the everted high pressure configuration wherein flow of cardioplegia is permitted. 
     FIG. 12 illustrates a sixth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. 
     FIG. 13 illustrates a seventh embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. 
     FIGS. 14 and 14 a  illustrate an eighth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. 
     FIG. 15 illustrates a shaft portion of the catheter system configured for insertion into a peripheral artery, such as the femoral artery, capable of occluding the ascending aorta, delivering cardioplegia to the coronary ostia and providing differential perfusion. 
     FIG. 16 illustrates a magnified lateral cross portion of the aortic catheter of FIG. 15 taken along line  16 — 16  illustrating the multilumen arrangement of the catheter shaft. 
     FIG. 17 shows a side view of an aortic catheter according to the present invention with a catheter shaft configured for retrograde deployment via femoral artery access. 
     FIG. 18 is a schematic diagram showing an aortic catheter according to the present invention deployed within a patient&#39;s aorta via femoral artery access. 
     FIG. 19 is a schematic diagram showing a tenth embodiment of the aortic catheter system of the present invention deployed within a patient&#39;s aorta having a flow control valve positioned in the descending aorta rather than an anchoring balloon. 
    
    
     DETAILED DESCRIPTION 
     The porous aortic root balloon perfusion catheter of the present invention generally comprises a catheter shaft configured for peripheral artery access or central artery access, having sufficient length to reach from an insertion site to the ascending aorta and a distal flow control member, in the form of a porous aortic root member, which is configured to deliver cardioplegia to the coronary ostia and is also capable of substantially occluding the ascending aorta. With the aforementioned general features in mind, the following illustrative embodiments will show in greater detail the specific aspects of the present invention. 
     FIGS. 1-4 are marked with parallel series of reference numbers. Like features are identified by a two-digit reference number preceded by a prefix identifying the drawings figure where the feature appears. Features that are not explicitly described in the specification can be identified by reference to the other figure descriptions in this grouping. 
     FIG. 1 illustrates a shaft portion of a first embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for insertion into a peripheral artery, such as the femoral artery, and capable of both occluding the ascending aorta and delivering cardioplegia to the coronary ostia. The porous aortic root balloon catheter  100  has an elongated catheter shaft  102  having a proximal end  104  and a distal end  106 . Preferably, the elongated catheter shaft  102  has an outer diameter which is from approximately 9 to 22 French (3.0-7.3 mm diameter), more preferably from approximately 12 to 18 French (4.0-6.0 mm diameter), and an overall length from approximately 60 to 120 cm, more preferably 70 to 90 cm, for femoral artery deployment in adult human patients. The catheter shaft  102  is preferably formed of a flexible thermoplastic material, a thermoplastic elastomer, or a thermoset elastomer. Suitable materials for use in the elongated catheter include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers thereof, as well as braided, coiled or counterwound wire or filament reinforced composites. 
     A distal flow control member  116 , in this illustrative embodiment in the form of an inflatable porous root balloon, is mounted on the catheter shaft  102  near the distal end  106  by heat welding or with an adhesive. The inflatable porous root balloon  116  has a deflated state in which the diameter of the porous root balloon  116  is, preferably, not substantially larger than the diameter of the catheter shaft  102 , and an inflated state in which the porous root balloon  116  expands to a diameter sufficient to occlude blood flow in the aortic root of the patient. For use in adult humans, the distal flow control member  116  preferably has an inflated outer diameter of approximately 2 to 5 cm. The catheter shaft  102  is navigated transluminally into the ascending aorta until the porous root balloon  116  is capable of delivering cardioplegia through a porous material  126  to the coronary ostia and is also capable of substantially occluding the ascending aorta when deployed. The material or materials used in the porous root balloon  116  are preferably characterized by properties that allow an internal pressure within the distal flow control member to be maintained at a sufficient level to occlude the aorta, while also allowing a controlled volume of fluid to escape from the flow control member for perfusing the coronary arteries. Thus, the surface of the balloon may be porous, or have porous regions, or include apertures that allow cardioplegia to seep or flow at a known rate when a specific pressure is attained. 
     As shown in FIG. 2, which is a magnified lateral cross portion of the aortic catheter  100  of FIG. 1 taken along line  2 — 2 , the catheter shaft  102  has four lumens: a perfusion lumen  108 , a pressure lumen  112 , an inflation cardioplegia lumen  110 , and a guide wire lumen  114 . The configuration of the lumens shown is for illustrative purposes only, and other configurations could be used. For example, in alternate embodiments the catheter shaft  102  may not include a perfusion lumen  108  and a separate arterial perfusion cannula would be provided which would simplify the overall construction of the aortic catheter  100 . In these alternative embodiments, which can be used for all embodiments described herein, a separate integral or nonintegral slidably disposed coaxial arterial cannula may be used. Alternatively, a contralateral or collateral arterial cannula can be provided. In the case of a contralateral arterial cannula insertion into the other femoral artery may necessary. Referring now to FIGS. 1 and 2 the perfusion lumen  108  extends through the catheter shaft  102  from the proximal end  104  to one or more perfusion ports  120  on the exterior of the catheter shaft  102  proximal to the distal flow control member  116 . The pressure lumen  112  extends through the catheter shaft  102  from the proximal end  104  to a pressure port  122  located proximal to the distal flow control member  116  to monitor pressure near the aortic arch. The inflation/cardioplegia lumen  110  extends through the catheter shaft  102  from the proximal end  104  to an inflation/cardioplegia port  130  for inflation and deflation of the distal flow control member  116  with cardioplegia fluid. The guide wire lumen  114  extends from the proximal end  104  of the catheter shaft  102  to a guide wire port  136  at the distal end  106  of the catheter shaft  102 , distal to the distal flow control member  116 . Attached to the proximal end  104  of the catheter shaft  102  is a manifold  350  with fittings for each of the catheter lumens, which shall be described in more detail below in connection with FIG.  3 . The aortic catheter  100  includes a distal radiopaque marker  118  positioned near the distal end  106  of the catheter shaft  102 , and a proximal radiopaque marker  140  positioned near the proximal edge of the distal flow control member  116 . 
     FIG. 3 shows a side view of an aortic catheter  300  according to the present invention with a catheter shaft  302  configured for retrograde deployment via femoral artery access. In order to facilitate placement of the aortic catheter  300  and to improve the stability of the catheter  300  in the proper position in the patient&#39;s aorta, a distal region  344  of the catheter shaft  302  may be preshaped with a curve to match the internal curvature of the patient&#39;s aortic arch. The curved distal region  344  represents a J-shaped curve of approximately 180 degrees of arc with a radius of curvature of approximately 2 to 4 cm to match the typical curvature of the aortic arch in an adult human patient. In addition, the distal end  306  of the catheter may be skewed slightly up out of the plane of the curve to accommodate the forward angulation of the patient&#39;s ascending aorta. Additionally, the catheter shaft  302  may be reinforced, particularly in the curved distal region  344 , for example with braided or coiled wire, to further improve the stability of the catheter  300  in the proper position in the patient&#39;s aorta. The elongated catheter shaft  302  is preferably formed of a flexible thermoplastic material, a thermoplastic elastomer, or a thermoset elastomer. Suitable materials for use in the elongated catheter include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers thereof, as well as braided, coiled or counterwound wire or filament reinforced composites. 
     As mentioned above, the proximal end  304  of the catheter shaft  302  is connected to a manifold  350  with fittings for each of the catheter lumens. The corporeal perfusion lumen  308  is connected to a Y-fitting  370  that has a barb connector  372  for connection to a perfusion pump or the like and a luer connector  374 , which may be used for monitoring perfusion pressure, for withdrawing fluid samples or for injecting medications or other fluids. The pressure lumen  312  is connected to a luer connector  371  or other fitting suitable for connection to a pressure monitor. The inflation/cardioplegia lumen  310  is connected to a luer connector  376  or other fitting suitable for connection to a cardioplegia source. The guide wire lumen  314  is connected to a Y-fitting  373  that has a luer connector  375  and a guide wire port  378  with a Touhy-Borst adapter or other hemostasis valve. Alternatively, a second perfusion lumen may be added with perfusion ports located downstream from the perfusion ports  320  for separately perfusing the corporeal body. In addition, a separate coaxial, collateral or contralateral arterial cannula may be implemented to perfuse the corporeal body in a retrograde direction separate from the perfusion lumen  308  to minimize the catheter shaft outer diameter. 
     FIG. 4 is a schematic diagram showing an aortic catheter  400  according to the present invention deployed within a patient&#39;s aorta via femoral artery access. The aortic catheter  400  is introduced into the patient&#39;s circulatory system through a peripheral artery access, such as the femoral artery, by using the percutaneous Seldinger technique, through an introducer sheath or via an arterial cutdown. The catheter  400  may optionally be introduced into the femoral artery through a coaxial arterial perfusion cannula (not shown). Meanwhile, one or more venous cannulae are introduced into the vena cava via the femoral vein or the jugular vein. The aortic catheter  400  is advanced up the descending aorta and across the aortic arch under fluoroscopic or ultrasound guidance with the aid of a guide wire within the guide wire lumen  414 . The aortic catheter  400  is advanced until the distal flow control member  416 , in this illustrative embodiment in the form of a porous aortic root balloon, is positioned within the ascending aorta within the aortic root. The distal flow control member  416  may be partially inflated enabling the distal flow control member  416  to serve as an atraumatic bumper giving tactile feedback when the catheter has touched the aortic valve. In addition, the radiopaque markers  418  and  440  can be referenced to establish proper placement of the distal flow control member  416 . Once proper placement is established, the guide wire is withdrawn. 
     Using a multihead cardiopulmonary bypass pump or the like, perfusion of oxygenated blood is started through the perfusion ports  420  (or arterial cannula). The distal flow control member  416  is totally inflated with a cardioplegia solution to partition the aorta, whereupon a cardioplegic agent, such an cold crystalloid cardioplegia or blood cardioplegia, is infused through the distal flow control member  416  to induce cardioplegic arrest. Generally, the distal flow control member  416  will have an inflated diameter sufficient to occlude blood flow through the aortic root. Since the diameter of the aortic root is typically somewhat larger than the diameter of the ascending aorta, the fully inflated distal flow control member  416  is prevented from leaving the aortic root by the sinotubular ridge and the aortic valve annulus. 
     Typically, during surgery, approximately 500 ml to 1,000 ml of cardioplegia is infused to the heart at an initial rate of 250 ml to 350 ml/minute to induce cardioplegic arrest. The flow is then typically continued intermittently, alternating between no flow of cardioplegia and a low flow of cardioplegia ranging from 25 to 250 ml/minute, to prevent the heart from resuming a sinus rhythm until the operation is complete. Therefore, it is preferable that the flow rate of cardioplegia be controllable within a range from 0 ml to 500 ml/minute, and more preferably within a range from 0 ml to 350 ml/minute. Alternatively, an initial bolus of cardioplegia may be delivered by other known means such as direct injection into the aortic root or into the coronary arteries, a separate coronary sinus catheter, or other known means for infusing cardioplegia, then a lower maintaining quantity of cardioplegia is infused using the aortic catheter of the invention. 
     In one illustrative embodiment, the distal flow control member  416  is shaped to conform somewhat to the shape of the aortic root, and may further conform to the shape of the aortic valve. Illustrated in FIG. 5 is a second embodiment of the present invention illustrating a three-lobed porous aortic root balloon  516  positioned within an aortic root, configured to conform to the shape of the cusps of the aortic valve when deployed. The lengths of the lobes  599  of the porous aortic root balloon  516  are aligned longitudinally with respect to the catheter shaft  502  and the aortic valve. FIG. 6 is a distal end view of the porous aortic root balloon  516  of FIG. 5 taken along line  6 — 6  illustrating the three-lobed configuration. The lobes  599  are configured to support the cusps of the aortic valve and maintain the competence of the aortic valve against pressure in the aortic lumen. The three-lobed balloon embodiment can be easily incorporated into this or any embodiment disclosed herein. Alternatively, the distal flow control member  416  may be compliant, or formed of a compliant material so that the inflated balloon conforms to the shape of the aortic valve when inflated. 
     Referring back to FIG. 4, the distal flow control member  416  is comprised of a non-porous portion  431  where cardioplegic fluid is not allowed to seep therethrough and a porous portion  432  where cardioplegic solution is allowed to seep therethrough. The size, shape, and position of the porous portion  432 , as shown, is for illustrative purposes only, any other desired sizes, shapes, or positions may be used. The porous portion  432  and non-porous portion  431  of the porous aortic root balloon  416  may be formed from the same or separate materials. Suitable materials for the non-porous portions  431  of the distal flow control member  416  include, but are not limited to, elastomers, thermoplastic elastomers, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers and reinforced composites thereof. In addition, the outer surface of the distal flow control member  416  may include a force or friction increasing means such as a friction increasing coating or texture to increase friction between the distal flow control member  416  and the aortic wall when deployed. Suitable materials for the porous portion  432  include, but are not limited to, a perforated polymer film, porous or microporous membranes, TYVEK (spun-bonded polyethylene), expanded PTFE (GORTEX), woven or knit mesh or fabric, or the like. 
     A selected fluid, such as a cardioplegia fluid, is introduced into the distal flow control member  416  by way of the inflation/cardioplegia lumen  410 . Any acceptable cardioplegia fluid may be used, such as cold crystalloid cardioplegia, normothermic blood cardioplegia, or hypothermic blood cardioplegia. In an alternate embodiment, it may be preferable to prime the balloon with a more viscous solution, for example a radiopaque contrast agent mixed with saline solution or with cardioplegic solution to initially inflate the balloon with a solution that will leak from the balloon at a rate slower than the cardioplegia solution will leak. When the distal flow control member  416  is fully inflated, the porous portion  432  should be positioned over the coronary ostia. It is possible, but uncommon, for a heart to have more than two coronary ostia. The number and positioning of the porous portion  432  may be selected to compensate for this or other unusual anatomical arrangements. When the correct pressure is attained, the member  416  occludes blood flow through the aortic lumen. The cardioplegia fluid used to inflate the distal flow control member  416  seeps through the porous portion  432  at a known rate into the coronary arteries. The flow rate may be adjustable by adjusting the pressure within the distal flow control member  416 . The competence of the aortic valve is not challenged because the cardioplegic fluid is delivered directly to the coronary arteries, thus preferably; the aortic valve does not experience significant retrograde fluid pressure. The distal flow control member  416  prevents seepage of cardioplegia fluid through the porous portion  432  by contacting the aortic wall with portions of porous windows  432  not aligned with the coronary ostia. Preferably, only the areas in contact with the coronary ostia are capable of delivering cardioplegia since this is the only area with an open space for the fluid to travel. 
     Perfusion of the patient is maintained through the perfusion ports  420  (and/or arterial cannula) and cardioplegic arrest is maintained by continued infusion of the cardioplegic agent through the distal flow control member  416  for as long as necessary for completion of the surgical procedure using minimally invasive or standard open-chest techniques. At the completion of the surgical procedure, the distal flow control member  416  is deflated to allow oxygenated blood to flow into the patient&#39;s coronary arteries, whereupon the heart should spontaneously resume normal sinus rhythm. If necessary, cardioversion or defibrillation shocks may be applied to restart the heart. The patient is then weaned off of bypass and the aortic catheter  400  and any other cannulae are withdrawn. 
     FIG. 7 illustrates a third embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. The distal flow control member in this third embodiment is in the form of a porous aortic root balloon  716  having a non-porous material portion  733  surrounding one or more porous windows  730 . The size, shape, and position of the porous windows  730  are shown for illustrative purposes, and any other desired sizes, shapes, or positions may be used. The porous windows  730  and non-porous  733  portions may be formed from the same or separate materials. Suitable materials for the non-porous  733  portion of the porous aortic root balloon  716  include, but are not limited to, elastomers, thermoplastic elastomers, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers and reinforced composites thereof. In addition, the outer surface of the porous aortic root balloon  716  may include a force or friction increasing means such as a friction increasing coating or texture to increase friction between the porous aortic root balloon  716  and the aortic wall when deployed. Suitable materials for the porous windows  730  include, but are not limited to, a perforated polymer film, porous or microporous membranes, TYVEK (spun-bonded polyethylene), expanded PTFE (GORTEX), woven or knit mesh or fabric, or the like. 
     In use, the porous aortic root balloon  716  is positioned within the aortic root. A selected fluid, such as a cardioplegia fluid, is introduced through the inflation/cardioplegia lumen  710  into the inflatable distal flow control member  716 . Any acceptable cardioplegia fluid may be used, such as cold crystalloid cardioplegia, normothermic blood cardioplegia, or hypothermic blood cardioplegia. Some cardioplegia fluid may seep out through the porous windows  730  during inflation, but at a rate less than the rate at which the cardioplegia enters porous aortic root balloon  716 . In an alternate embodiment, it may be preferable to prime the balloon with a more viscous solution, for example a radiopaque contrast agent mixed with saline solution or with cardioplegic solution, that is, to initially inflate the balloon with a solution that will leak from the balloon at a rate slower than the cardioplegia solution will leak. When the porous aortic root balloon  716  is fully inflated, at least one porous window  730  should be positioned over the opening of each coronary ostium. It is possible, but uncommon, for a heart to have more than two coronary ostia. The number and positioning of the porous windows  730  may be selected to compensate for this or other unusual anatomical arrangements. 
     When the correct pressure is attained, the porous aortic root balloon  716  occludes blood flow through the aortic lumen. Concurrently the cardioplegia fluid used to inflate the porous aortic root balloon  716  escapes through the porous windows  730  at certain predetermined pressures and at a known rate of flow into the coronary arteries. The flow rate may be adjustable by adjusting the pressure within the porous aortic root balloon  716 . The competence of the aortic valve is not challenged because the cardioplegic fluid is delivered directly to the coronary arteries, thus preferably, the aortic valve does not experience significant retrograde fluid pressure. The contact of the wall of the porous aortic root balloon  716  against the aortic wall prevents seepage of cardioplegia fluid through the porous windows  730  or the portions of porous windows  730  not aligned with the coronary ostia. 
     FIG. 8 illustrates a fourth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. However, rather than separate porous windows, a large, preferably circumferential, porous strip or patch  832  is used instead of the porous windows of the previous embodiment. The size and position of the porous strip  832  is shown in FIG. 8 for illustrative purposes only, and other configurations may be used. The width and position of the porous strip  832  is preferably chosen to cover the coronary ostia of the typical patient. One advantage to the larger porous area is that the porous root balloon  816  need not be as carefully positioned to assure the alignment of the porous portion with each coronary ostium. The porous  832  and non-porous  833  portions of the distal flow control member  816  may be made from the same or different materials. Suitable materials for the non-porous portions  833  of the porous aortic root balloon  816  include, but are not limited to, elastomers, thermoplastic elastomers, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers and reinforced composites thereof. In addition, the outer surface of the distal flow control member  816  may include a friction increasing means such as a friction increasing coating or texture to increase friction between the porous aortic root balloon  816  and the aortic wall when deployed. Suitable materials for the porous strip  832  include but are not limited to a perforated polymer film, porous or microporous membranes, TYVEK (spun-bonded polyethylene), expanded PTFE (GORTEX), woven or knit mesh or fabric, or the like. 
     In use, the porous aortic root balloon  816  is positioned within the aortic root. A cardioplegia fluid is introduced to the porous aortic root balloon  816  through the inflation/cardioplegia lumen  810  into the porous aortic root balloon  816 . As previously described, any acceptable cardioplegia fluid may be used. Some cardioplegia fluid may seep from the porous strip  832  during inflation, but at a rate less than the rate at which the cardioplegia enters the porous aortic root balloon  816 . When the porous aortic root balloon  816  is fully inflated, the porous strip  832  should be positioned so that some portion of the porous strip  832  covers each coronary ostium. When the correct pressure is attained, the porous aortic root balloon  816  occludes blood flow through the aortic lumen. The cardioplegia fluid used to inflate the distal flow control member escapes through the porous strip  832  where the porous strip  832  covers the coronary ostia, at a known rate. Contact between the wall of the porous aortic root balloon  816  and the aortic wall prevents seepage of cardioplegia fluid through portions of the porous strip  832  not aligned with a coronary ostium. The flow rate may be adjustable by adjusting the pressure within the porous aortic root balloon  816 . The competence of the aortic valve is not challenged because the cardioplegic fluid is delivered directly to the coronary arteries. 
     FIGS. 9 through 11 collectively illustrate a fifth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronay ostia having a circumferential region  1034  covered with bistable nipples  1036 . In any of the embodiments described above, the porous portions may be replaced by portions having bistable nipples, pressure valves, micropores, micro-nipples or the like. FIG. 10 illustrates a magnified view of an exemplary design of a single bistable nipple  1036  in an inverted low pressure configuration wherein low or no flow of cardioplegia is permitted. FIG. 11 illustrates a magnified view of an exemplary design of a single bistable nipple  1036  in the everted high pressure configuration wherein flow of cardioplegia is permitted. The nipple  1036  comprises a cylinder  1040  resting in a cylindrical fold, and a top surface  1042  having a pressure valve aperture  1044  located in the center of the top surface  1042 . The nipple  1036  may be formed so that, in the low pressure configuration, forces exerted around the circumference of the top surface  1042  by the cylindrical fold tend to compress the top surface  1042 , closing the pressure valve aperture  1044 . The valve aperture  1044  may be in the form of a hole, a slit, or a cross slit in the top surface  1042 . Preferably, the nipple  1036  will maintain this configuration at pressures existing in the porous aortic root balloon  1016  when inflated for occlusion of the aortic root. However, when the pressure is increased beyond a pre-determined level, the nipple everts, as seen in FIG.  11 . The folded portion unfolds as the nipple top  1042  moves outward from the distal flow control member  1216  outer surface. The pressure around the nipple top  1042  caused by the circumferential fold is released, and the aperture  1044  opens, allowing cardioplegia fluid flow. Contact of the nipple top  1042  with the aortic root wall at portions of the balloon not over the coronary ostia prevents the bistable nipples  1036  from everting and allowing significant cardioplegia fluid flow. In alternate embodiments, other known pressure valves or nipples may be used. 
     The porous aortic root balloon  1016  having nipple or pressure valves may be fabricated from a single material, or different materials may be used in the portions containing nipples or pressure valves and those regions which do not contain nipples or pressure valves. Suitable materials include, but are not limited to, elastomers, thermoplastic elastomers, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers and reinforced composites thereof. 
     In any of the embodiments described above, the porous aortic root balloon  1016  may be configured as shown in FIGS. 5 and 6, which discloses a three-lobed balloon embodiment of the distal flow control member  516  positioned within an aortic root, shaped to conform to the shape of the cusps of the aortic valve when properly deployed. The lobes are configured to support the cusps of the aortic valve and maintain the competence of the aortic valve against pressure in the aortic lumen. The three-lobed balloon embodiment works in the same manner as any of the previously described embodiments including porous membranes or nipples. The same materials used in previous embodiments may be used in construction of this embodiment. 
     FIG. 12 illustrates a sixth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. In this illustrative embodiment, the distal flow control member is comprised of a first occlusion balloon  1250 , a second porous balloon  1252 , and a third occlusion balloon  1254 . The first occlusion balloon  1250 , located nearest the distal end  1206  of the aortic catheter shaft  1202 , is preferably comprised of a non-porous material, and is preferably configured to conform to the cusps of the aortic valve. The first occlusion balloon  1250  is intended to prevent cardioplegia from entering the ventricle through the aortic valve. The second porous balloon  1252  is positioned adjacent the proximal side of the first occlusion balloon  1250 . The second porous balloon  1252  is preferably formed of a porous material, or includes other means for allowing a controlled amount of cardioplegia to escape. The third occlusion balloon  1254  is located adjacent the second porous balloon  1252 . The purpose of this balloon is primarily for occluding the aorta to prevent cardioplegia from entering the aortic arch. The third occlusion balloon  1254  is preferably comprised of a non-porous material, and is shaped to conform to the top of the aortic root. 
     FIG. 13 illustrates a seventh embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. In this illustrative embodiment, the distal flow control member on catheter shaft  1302  is comprised of a first outer balloon  1356  and a second inner balloon  1358  is positioned therein. The first outer balloon  1356  includes porous portions comprising porous material, nipples, or valves, to allow a controlled flow of cardioplegia. The second inner balloon  1358  is preferably nonporous. When the second inner balloon  1358  is fully inflated, the outer surface of the second inner balloon  1358  contacts the inner surface of the first outer balloon  1356 , preventing escape of cardioplegia through the porous portions, nipples, or pressure valves located on the first outer balloon  1356 . When the first inner balloon  1358  is fully or partially deflated, cardioplegia flow is allowed to resume. Separate lumens connecting to the outer balloon port  1380  and the inner balloon ports  1364  and  1362  are required for independently inflating the first outer balloon  1356  and the second inner balloon  1358 . 
     FIGS. 14 and 14 a  illustrate an eighth embodiment of the porous aortic root balloon perfusion catheter of the present invention configured for occluding the ascending aorta and delivering cardioplegia to the coronary ostia. In this illustrative embodiment, the distal flow control member is comprised of two adjacent occlusion balloons  1403  and  1404 . The first occlusion balloon  1404 , located nearest the distal end  1406  of the aortic catheter shaft  1402 , preferably comprises a hemispherical nonporous portion  1411 , and a hemispherical porous portion  1408  located on the proximal side of the first occlusion balloon  1404 . As shown in FIGS. 14 and 14 a  the first occlusion balloon  1404  may have at least one lobe for biasing an aortic valve leaflet. The second balloon  1403  is positioned adjacent the proximal side of the first occlusion balloon  1404 , and preferably comprises a hemispherical non-porous portion  1412  and a hemispherical porous portion  1407  located on the proximal side of the second occlusion balloon  1403 . Alternatively, only one of the balloons  1403  or  1404  may include a porous portion. 
     FIGS. 15-19 are marked with parallel series of reference numbers. Like features are identified by a two-digit reference number preceded by a prefix identifying the drawing figure where the feature appears. Features that are not explicitly described in the specification can be identified by reference to the other figure description in this grouping. 
     FIGS. 15 and 16 illustrate a ninth embodiment of the porous aortic root balloon perfusion catheter system of the present invention configured for insertion into a peripheral artery and having a downstream anchoring member to stabilize the catheter shaft. FIG. 15 illustrates a shaft portion of the catheter system configured for insertion into a peripheral artery, such as the femoral artery, capable of occluding the ascending aorta, delivering cardioplegia to the coronary ostia and providing differential perfusion. A porous aortic root balloon catheter  1500  has an elongated catheter shaft  1502  having a proximal end  1504  and a distal end  1506 . Preferably, the elongated catheter shaft  1502  has an outer diameter which is from approximately 9 to 22 French (3.0-7.3 mm diameter), more preferably from approximately 12 to 18 French (4.0-6.0 mm diameter), and an overall length from approximately 60 to 120 cm, more preferably 70 to 90 cm, for femoral artery deployment in adult human patients. The catheter shaft  1502  is preferably formed of a flexible thermoplastic material, a thermoplastic elastomer, or a thermoset elastomer. Suitable materials for use in the elongated catheter include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers thereof, as well as braided, coiled or counterwound wire or filament reinforced composites. 
     An upstream distal flow control member  1516 , in this illustrative embodiment in the form of an inflatable porous root balloon, is mounted on the catheter shaft  1502  near the distal end  1506  by heat welding or with an adhesive. The porous root balloon  1516  has a deflated state in which the diameter of the porous root balloon is, preferably, not substantially larger than the diameter of the catheter shaft  1502 . And, an inflated state in which the porous root balloon  1516  expands to a diameter sufficient to occlude blood flow in the aortic root of the patient. For use in adult humans, the porous root balloon  1516  preferably has an inflated outer diameter of approximately 2 to 5 cm. The catheter shaft  1502  is navigated transluminally into the ascending aorta until the porous root balloon  1516  is positioned in the aortic root. Thereafter, the delivery of cardioplegia to the coronary ostia is performed through a porous material  1532  while a non-porous material  1531  substantially occludes the ascending aorta. The material or materials used in the porous root balloon  1516  are preferably characterized by properties that allow an internal pressure within the porous root balloon  1516  to be maintained at a sufficient level to occlude the aorta, while also allowing a controlled volume of fluid to escape from the porous root balloon  1516  for perfusing the coronary arteries. Thus, the surface of the balloon may be porous, or have porous regions, or include apertures that allow cardioplegia to seep or flow at a known rate when a specific pressure is attained. 
     A downstream anchoring member  1518  is mounted proximal to the porous root balloon  1516  on the catheter shaft  1502 . The distance between the porous root balloon  1516  and the downstream anchoring member  1518  is preferably between 3 and 20 cm, more preferably between 8 and 15 cm, and is chosen so that when the aortic catheter  1500  is deployed and the porous root balloon  1516  is positioned in the aortic root, the downstream anchoring member  1518  will be positioned in the descending aorta downstream of the left subclavian artery. The downstream anchoring member  1518  in this embodiment is in the form of an expandable, inflatable balloon bonded to the catheter shaft  1502  by heat welding or with an adhesive. The downstream anchoring member  1518  may be larger, the same size or smaller than the porous root balloon  1516 . Of primary importance is the downstream anchoring member configuration that stabilizes the shaft  1502  and allows for the separation of the aorta for differential perfusion. Suitable materials for the inflatable balloon downstream anchoring member  1518  include flexible polymers and elastomers, which include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polypropylene, polyamides (nylons), polyesters, latex, silicone, and alloys, copolymers and reinforced composites thereof. In addition, the outer surface of the downstream anchoring member  1518  may include a friction increasing coating or texture to increase friction with the aortic wall when deployed. 
     The inflatable balloon downstream anchoring member  1518  has a deflated state, in which the diameter of the anchoring member  1518  is preferably not much larger than the diameter of the catheter shaft  1502 , and an inflated state, in which the anchoring member  1518  expands to a diameter sufficient to regulate blood flow in the descending aorta of the patient. For use in adult human patients, the inflatable balloon downstream anchoring member  1518  preferably has an inflated outer diameter of approximately 1.5 cm to 5.0 cm and a length of approximately 3.5 cm to 7.5 cm. The more elongated form of the inflatable balloon downstream anchoring member  1518  creates greater anchoring friction against the wall of the descending aorta when the downstream anchoring member  1518  is inflated in order to prevent migration of the aortic catheter  1500  due to pressure gradients within the aorta during perfusion. 
     As shown in FIG. 16, which is a magnified lateral cross portion of the aortic catheter  1500  of FIG. 15 taken along line  16 — 16 , the catheter shaft  1502  has five lumens: a corporeal perfusion lumen  1508 , an arch perfusion lumen  1511 , a pressure lumen  1512 , a common cardioplegia/inflation lumen  1510 , and a guide wire lumen  1514 . The configuration of the lumens shown is for illustrative purposes only, and other configurations could be used. For example, in alternate embodiments the catheter shaft  1502  may not include a corporeal perfusion lumen  1508 . In embodiments where a corporeal perfusion lumen is not provided corporeal flow can be accomplished by through an integral or nonintegral slidably disposed coaxial cannula or through a contralateral or collateral cannula. In addition, the catheter shaft may be configured to provide separate inflation lumens to provide individual inflation pressures in the balloons. 
     Referring now to FIGS. 15 and 16 the corporeal perfusion lumen  1508  extends through the catheter shaft  1502  from the proximal end  1504  to one or more perfusion ports  1536  on the exterior of the catheter shaft  1502  proximal to the porous root balloon  1516 . The pressure lumen  1512  extends through the catheter shaft  1502  from the proximal end  1504  to a pressure port  1526  located proximal to the porous root balloon  1516  to monitor pressure near the aortic arch. The inflation/cardioplegia lumen  1510  extends through the catheter shaft  1502  from the proximal end  1504  to inflation/cardioplegia ports  1522  for inflation and deflation of the porous root balloon  1516  and the anchoring member  1518  with cardioplegia fluid. The guide wire lumen  1514  extends from the proximal end  1504  of the catheter shaft  1502  to a guide wire port  1536  at the distal end  1506  of the catheter shaft  1502 , distal to the porous root balloon  1516 . Attached to the proximal end  1504  of the catheter shaft  1502  is a manifold  1750  with fittings for each of the catheter lumens, which shall be described in more detail below with reference to FIG.  17 . 
     The aortic catheter  1500  includes a distal radiopaque marker  1540  positioned near the distal end  1506  of the catheter shaft  1502 , and an intermediate radiopaque marker  1542  positioned near the proximal edge of the porous root balloon  1516  and a proximal radiopaque marker  1544  located on the distal edge of the anchoring member  1518 . 
     FIG. 17 shows a side view of an aortic catheter  1700  according to the present invention with a catheter shaft  1702  configured for retrograde deployment via femoral artery access. In order to facilitate placement of the aortic catheter  1700  and to improve the stability of the catheter  1700  in the proper position in the patient&#39;s aorta, a distal region  1744  of the catheter shaft  1702  may be preshaped with a curve to match the internal curvature of the patient&#39;s aortic arch. The curved distal region  1744  represents a J-shaped curve of approximately 180 degrees of arc with a radius of curvature of approximately 2 to 4 cm to match the typical curvature of the aortic arch in an adult human patient. In addition, the distal end  1706  of the catheter may be skewed slightly up out of the plane of the curve to accommodate the forward angulation of the patient&#39;s ascending aorta. Additionally, the catheter shaft  1702  may be reinforced, particularly in the curved distal region  1744 , for example with braided or coiled wire, to further improve the stability of the catheter  1700  in the proper position in the patient&#39;s aorta. The elongated catheter shaft  1702  is preferably formed of a flexible thermoplastic material, a thermoplastic elastomer, or a thermoset elastomer. Suitable materials for use in the elongated catheter include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers thereof, as well as braided, coiled or counterwound wire or filament reinforced composites. 
     As mentioned above, the proximal end  1704  of the catheter shaft  1702  is connected to a manifold  1750  with fittings for each of the catheter lumens. The corporeal perfusion lumen  1708  is connected to a Y-fitting  1770  that has a barb connector  1772  for connection to a perfusion pump or the like and a luer connector  1774 , which may be used for monitoring perfusion pressure, for withdrawing fluid samples or for injecting medications or other fluids. The pressure lumen  1712  is connected to a luer connector  1771  or other fitting suitable for connection to a pressure monitor. The inflation/cardioplegia lumen  1710  is connected to a luer connector  1776  or other fitting suitable for connection to a cardioplegia source. The guide wire lumen  1714  is connected to a Y-fitting  1773  that has a luer connector  1775  and a guide wire port  1778  with a Touhy-Borst adapter or other hemostasis valve. An arch perfusion lumen  1711  is connected to a Y-fitting  1709  having a barb connector  1777  for connection to a perfusion pump or the like and a luer connector  1780  which may be used for monitoring perfusion pressure, for withdrawing fluid samples or for injecting medications or other fluids. In addition, a separate coaxial arterial cannula may be implemented to perfuse the corporeal body in a retrograde direction eliminating the need for a corporeal perfusion lumen  1708  to minimize the catheter shaft outer diameter and simplifying the overall catheter design. 
     FIG. 18 is a schematic diagram showing an aortic catheter  1800  according to the present invention deployed within a patient&#39;s aorta via femoral artery access. The aortic catheter  1800  is introduced into the patient&#39;s circulatory system through a peripheral artery access, such as the femoral artery, by using the percutaneous Seldinger technique, through an introducer sheath or via an arterial cutdown. The catheter  1800  may optionally be introduced into the femoral artery through a coaxial arterial perfusion cannula (not shown). Meanwhile, one or more venous cannulae are introduced into the vena cavae via the femoral vein or the jugular vein. The aortic catheter  1800  is advanced up the descending aorta and across the aortic arch under fluoroscopic or ultrasound guidance with the aid of a guide wire within the guide wire lumen  1814 . The aortic catheter  1800  is advanced until the distal flow control member  1816 , in this illustrative embodiment in the form of a porous aortic root balloon, is positioned within the ascending aorta within the aortic root. The porous root balloon  1816  may be partially inflated enabling the porous root balloon to serve as an atraumatic bumper giving tactile feedback when the catheter has touched the aortic valve. In addition, the radiopaque markers can be referenced to establish proper placement of the porous root balloon  1816 . Once proper placement is established, the guide wire is withdrawn. 
     Using a multihead cardiopulmonary bypass pump or the like, perfusion of oxygenated blood is started through the perfusion ports  1820  and  1836  (or separate arterial cannula). The porous root balloon  1816  and anchoring member  1818  are totally inflated with a cardioplegia solution to partition the aorta, whereupon a cardioplegic agent, such cold crystalloid cardioplegia or blood cardioplegia, is infused through the porous aortic root balloon  1816  to induce cardioplegic arrest. Generally, the porous root balloon  1816  will have an inflated diameter sufficient to occlude blood flow through the aortic root and the anchoring member will have sufficient diameter to engage the descending aortic wall to stabilize the catheter shaft  1802  in the aorta. Since the diameter of the aortic root is typically somewhat larger than the diameter of the ascending aorta, the fully inflated porous root balloon  1816  may thus be prevented from leaving the aorta by the sinotubular ridge and the aortic valve annulus. 
     Typically, during surgery, approximately 500 ml to 1,000 ml of cardioplegia is infused to the heart at an initial rate of 250 ml to 350 ml/minute to induce cardioplegic arrest. The flow is then typically continued intermittently, alternating between no flow of cardioplegia and a low flow of cardioplegia ranging from 25 to 250 ml/minute to prevent the heart from resuming a sinus rhythm until the operation is complete. Therefore, it is preferable that the flow rate of cardioplegia be controllable within a range from 0 ml to 500 ml/minute, and more preferably within a range from 0 ml to 350 ml/minute. Alternatively, an initial bolus of cardioplegia may be delivered by other known means such as a retrograde coronary sinus catheter, direct injection into the aortic root, injection into the coronary arteries, or other known means for infusing cardioplegia. 
     In one illustrative embodiment, the porous root balloon  1816  is shaped to conform somewhat to the shape of the aortic root, and may further conform to the shape of the aortic valve. As previously illustrated in FIG. 5 a three-lobed porous aortic root balloon  516  can be implemented. The lobes  599  are configured to support the cusps of the aortic valve and maintain the competence of the aortic valve against pressure in the aortic lumen. The three-lobed balloon embodiment can be easily incorporated into this or any embodiment disclosed herein. Alternatively, the porous root balloon  1816  may be compliant, or formed of a compliant material so that the inflated balloon conforms to the shape of the aortic valve when inflated. 
     The porous aortic root balloon  1816  is comprised of a non-porous portion  1831  where cardioplegic fluid is not allowed to seep therethrough and a porous portion  1832  where cardioplegic solution is allowed to seep therethrough. The size, shape, and position of the porous portion  1832  is for illustrative purposes only, any other desired sizes, shapes, or positions may be used. The porous portion  1832  and non-porous portion  1831  of the porous aortic root balloon  1816  may be formed from the same or separate materials. Suitable materials for the non-porous portions  1831  of the porous aortic root balloon  1816  include, but are not limited to, elastomers, thermoplastic elastomers, polyvinylchloride, polyurethane, polyethylene, polyamides, polyesters, silicone, latex, and alloys or copolymers and reinforced composites thereof. In addition, the outer surface of the porous aortic root balloon  1816  may include a force or friction increasing means such as a friction increasing coating or texture to increase friction between the porous aortic root balloon  1816  and the aortic wall when deployed. Suitable materials for the porous portion  1832  include, but are not limited to, a perforated polymer film, porous or microporous membranes, TYVEK (spun-bonded polyethylene), expanded PTFE (GORTEX), woven or knit mesh or fabric, or the like. 
     A selected fluid, such as a cardioplegia fluid, is introduced into the porous aortic root balloon  1816  by way of the inflation/cardioplegia lumen  1810 . Any acceptable cardioplegia fluid may be used, such as cold crystalloid cardioplegia, normothermic blood cardioplegia, or hypothermic blood cardioplegia. In an alternate embodiment, it may be preferable to prime the balloon with a more viscous solution, for example a radiopaque contrast agent mixed with saline solution or with cardioplegic solution, that is, to initially inflate the balloon with a solution that will leak from the balloon at a rate slower than the cardioplegia solution will leak. When the porous root balloon  1816  is fully inflated, the porous portion  1832  should be positioned over the coronary ostia. It is possible, but uncommon, for a heart to have more than two coronary ostia. The number and positioning of the porous portion  1832  may be selected to compensate for this or other unusual anatomical arrangements. When the correct pressure is attained, the porous aortic root balloon  1816  occludes blood flow through the aortic lumen. The cardioplegia fluid used to inflate the porous aortic root balloon  1816  seeps through the porous portion  1832  at a known rate into the coronary arteries. The flow rate may be adjustable by adjusting the pressure within the porous aortic root balloon  1816 . The competence of the aortic valve is not challenged because the cardioplegic fluid is delivered directly to the coronary arteries, thus preferably the aortic valve does not experience significant retrograde fluid pressure. The porous aortic root balloon  1816  prevents seepage of cardioplegia fluid through the porous portion  1832  by contact between the aortic wall and the portions of porous windows  1832  not aligned with the coronary ostia. Preferably, only the areas in contact with the coronary ostia are capable of delivering cardioplegia since this is the only area with an open space for the fluid to travel. 
     Perfusion of the patient is maintained through the perfusion ports  1820  and  1836  (and/or arterial cannula) and cardioplegic arrest is maintained by continued infusion of the cardioplegic agent through the porous aortic root balloon  1816  for as long as necessary for completion of the surgical procedure using minimally invasive or standard open-chest techniques. Perfusion temperatures, perfusate compositions and flow rates may be optimized to each of the segmented regions of the patient&#39;s circulation for optimal organ preservation while on cardiopulmonary bypass. While the aortic catheter  1800  is deployed, the anchoring member  1818  stabilizes and anchors the catheter shaft  1802  and prevents upstream or downstream migration of the catheter  1800  or the porous root balloon  1816  due to differential pressures within the aorta. At the completion of the surgical procedure, the porous aortic root balloon  1816  is deflated to allow oxygenated blood to flow into the patient&#39;s coronary arteries, whereupon the heart should spontaneously resume normal sinus rhythm. If necessary, cardioversion or defibrillation shocks may be applied to restart the heart. The patient is then weaned off of bypass and the aortic catheter  1800  and any other cannulae are withdrawn. 
     FIG. 19 is a schematic diagram showing a tenth embodiment of the aortic catheter system of the present invention deployed within a patient&#39;s aorta, in a configuration similar to that explained above relating to FIG. 18, but having a flow control valve  1990  positioned in the descending aorta rather than an anchoring balloon. The valve  1990  performs the function of partitioning the aorta providing the possibility of differential perfusion of the partitioned circulatory system. Any desirable or practical collapsible/deployable valve may be used. Examples of useable collapsible/deployable valves have been previously described in U.S. Pat. Nos. 5,827,237 and 5,833,671 and U.S. patent application Ser. No. 08/665,635, by John A. Macoviak and Michael Ross all previously incorporated herein by reference. 
     The embodiments of the porous aortic root balloon described above have focused on the perfusion of cardioplegia to the coronary arteries. However, other selected fluids may be perfused to the coronary arteries including streptokinase, tPA, or urokinase for thrombolysis, blood and blood substitutes such as PERFLUBRON or other perfluorocarbon compounds, and radiopaque dyes for angiography.