Abstract:
An aortic shunt apparatus and methods for cerebral embolic protection are described for isolating the aortic arch vessels from the aortic lumen, for selectively perfusing the arch vessels with a fluid and for redirecting blood flow within the aortic lumen and any potential embolic materials carried in the blood through a shunt past the isolated arch vessels. The perfusion shunt apparatus may be mounted on a catheter or cannula for percutaneous introduction or for direct insertion into the aorta. The perfusion shunt apparatus has application for protecting a patient from embolic stroke and hypoperfusion during cardiopulmonary bypass or cardiac surgery and also for selectively perfusing the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids in the presence of risk factors, such as head trauma or cardiac insufficiency. The perfusion shunt apparatus will also find application for selective perfusion of other organ systems within the body.

Description:
CROSS REFERENCE TO OTHER PATENT APPLICATIONS 
     This application is a continuation of application Ser. No. 09/532,660, filed Mar. 20, 2000, now U.S. Pat. No. 6,254,563, which is a continuation of application Ser. No. 09/212,580, filed Dec. 14, 1998, now U.S. Pat. No. 6,139,517, which claims the benefit of U.S. Provisional application Ser. No. 60/069,470, filed Dec. 15, 1997, which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an aortic shunt apparatus and methods for cerebral embolic protection by isolating the aortic arch vessels from the aortic lumen, selectively perfusing the arch vessels with a fluid and directing blood flow within the aortic lumen and any potential embolic materials carried in the blood through a shunt past the isolated arch vessels. 
     The perfusion shunt apparatus of the present invention may be mounted on a catheter or cannula for percutaneous introduction or for direct insertion into a circulatory vessel, such as the aorta. The perfusion shunt apparatus has application for protecting a patient from embolic stroke or hypoperfusion during cardiopulmonary bypass or cardiac surgery and also for selectively perfusing the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids in the presence of risk factors, such as head trauma or cardiac insufficiency. The perfusion shunt apparatus will also find application for selective perfusion of other organ systems within the body. 
     BACKGROUND OF THE INVENTION 
     Over the past decades tremendous advances have been made in the area of heart surgery, including such life saving surgical procedures as coronary artery bypass grafting (CABG) and cardiac valve repair or replacement surgery. Cardiopulmonary bypass (CPB) is an important enabling technology that has helped to make these advances possible. Recently, however, there has been a growing awareness within the medical community and among the patient population of the potential sequelae or adverse affects of heart surgery and of cardiopulmonary bypass. Chief among these concerns is the potential for stroke or neurologic deficit associated with heart surgery and with cardiopulmonary bypass. One of the likely causes of stroke and of neurologic deficit is the release of emboli into the blood stream during heart surgery. Potential embolic materials include atherosclerotic plaques or calcific plaques from within the ascending aorta or cardiac valves and thrombus or clots from within the chambers of the heart. These potential emboli may be dislodged during surgical manipulation of the heart and the ascending aorta or due to high velocity jetting (sometimes called the “sandblasting effect”) from the aortic perfusion cannula. Air that enters the heart chambers or the blood stream during surgery through open incisions or through the aortic perfusion cannula is another source of potential emboli. Emboli that lodge in the brain may cause a stroke or other neurologic deficit. Clinical studies have shown a correlation between the number and size of emboli passing through the carotid arteries and the frequency and severity of neurologic damage. At least one study has found that frank strokes seem to be associated with macroemboli larger than approximately 100 micrometers in size, whereas more subtle neurologic deficits seem to be associated with multiple microemboli smaller than approximately 100 micrometers in size. In order to improve the outcome of cardiac surgery and to avoid adverse neurological effects it would be very beneficial to eliminate or reduce the potential of such cerebral embolic events. 
     Several medical journal articles have been published relating to cerebral embolization and adverse cerebral outcomes associated with cardiac surgery, e.g.: Determination or Size of Aortic Emboli and Embolic Load During Coronary Artery Bypass Grafting; Barbut et al.; Ann Thorac Surg 1997; 63; 1262-7; Aortic Atheromatosis and Risks of Cerebral Embolization; Barbut et al.; J Card &amp; Vasc Anesth, Vol 10, No 1, 1996; pp 24-30; Aortic Atheroma is Related to Outcome but not Numbers of Emboli During Coronary Bypass; Barbut et al.; Ann Thorac Surg 1997; 64; 454-9; Adverse Cerebral Outcomes After Coronary Artery Bypass Surgery; Roach et al.; New England J of Med, Vol 335, No 25, 1996; pp 1857-1863; Signs of Brain Cell Injury During Open Heart Operations; Past and Present; .ANG.berg; Ann Thorac Surg 1995; 59; 1312-5; The Role of CPB Management in Neurobehavioral Outcomes After Cardiac Surgery; Murkin; Ann Thorac Surg 1995; 59; 1308-11; Risk Factors for Cerebral Injury and Cardiac Surgery; Mills; Ann Thorac Surg 1995; 59; 1296-9; Brain Microemboli Associated with Cardiopulmonary Bypass; A Histologic and Magnetic Resonance Imaging Study; Moody et al.; Ann Thorac Surg 1995; 59; 1304-7; CNS Dysfunction After Cardiac Surgery; Defining the Problem; Murkin; Ann Thorac Surg 1995; 59; 1287+; Statement of Consensus on Assessment of Neurobehavioral Outcomes After Cardiac Surgery; Murkin et al.; Ann Thorac Surg 1995; 59; 1289-95; Heart-Brain Interactions; Neurocardiology Comes of Age; Sherman et al.; Mayo Clin Proc 62: 1158-1160, 1987; Cerebral Hemodynamics After Low-Flow Versus No-Flow Procedures; van der Linden; Ann Thorac Surg 1995; 59; 1321-5; Predictors of Cognitive Decline After Cardiac Operation; Newman et al.; Ann Thorac Surg 1995; 59; 1326-30; Cardiopulmonary Bypass; Perioperative Cerebral Blood Flow and Postoperative Cognitive Deficit; Venn et al.; Ann Thorac Surg 1995; 59; 1331-5; Long-Term Neurologic Outcome After Cardiac Operations; Sotaniemi; Ann Thorac Surg 1995; 59; 1336-9; Macroemboli and Microemboli During Cardiopulmonary Bypass; Blauth; Ann Thorac Surg 1995; 59; 1300-3. 
     Commonly owned, co-pending U.S. provision application No. 60/060,117, and corresponding U.S. patent application Ser. No. 09/158,405, which are hereby incorporated by reference, describe an aortic perfusion filter catheter for prevention of cerebral embolization and embolic stroke during cardiopulmonary bypass or cardiac surgery. The patent literature also includes several other references relating to vascular filter devices for reducing or eliminating the potential of embolization. These and all other patents and patent applications referred to herein are hereby incorporated by reference in their entirety. The following U.S. patents relates to vena cava filters; U.S. Pat. Nos. 5,549,626, 5,415,630, 5,152,777, 5,375,612, 4,793,348, 4,817,600, 4,969,891, 5,059,205, 5,324,304, 5,108,418, 4,494,531. The following U.S. patents relate to vascular filter devices: U.S. Pat. Nos. 5,496,277, 5,108,419, 4,723,549, 3,996,938. The following U.S. patents relate to aortic filters or aortic filters associated with atherectomy devices: U.S. Pat. Nos. 5,662,671, 5,769,816. The following international patent applications relate to aortic filters or aortic filters associated with atherectomy devices: WO 97/17100, WO 97/42879, WO 98/02084. The following international patent application relates to a carotid artery filter; WO 98/24377. The patent literature also includes the following U.S. patents related to vascular shunts and associated catheters: U.S. Pat. Nos. 3,991,767, 5,129,883, 5,613,948. None of these patents related to vascular shunts provides an apparatus or method suitable for preventing of cerebral embolization and embolic stroke or for performing selective perfusion of the aortic arch vessels to prevent hypoperfusion during cardiopulmonary bypass or cardiac surgery. 
     While some of these previous devices and systems represent advances in the prevention of some causes of neurologic damage, there continues to be a tremendous need for improved apparatus and methods to prevent cerebral embolization, embolic stroke and cerebral hypoperfusion during cardiopulmonary bypass and cardiac surgery. Similarly, there continues to be a tremendous need for apparatus and methods for selective perfusion of the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids in the presence of risk factors, such as head trauma or cardiac insufficiency and also for selective perfusion of other organ systems within the body. 
     SUMMARY OF THE INVENTION 
     In keeping with the foregoing discussion, the present invention takes the form of a perfusion shunt apparatus and methods for isolating and selectively perfusing a segment of a patient&#39;s cardiovascular system and for directing circulatory flow around the isolated segment. In a particularly preferred embodiment of the invention, the perfusion shunt apparatus is configured as an aortic perfusion shunt apparatus for deployment within a patient&#39;s aortic arch and methods are described for isolating the aortic arch vessels from the aortic lumen, for selectively perfusing the arch vessels with a fluid and for directing blood flow within the aortic lumen through a shunt conduit past the isolated arch vessels. The perfusion shunt apparatus may be mounted on a catheter or cannula for percutaneous introduction via peripheral artery access or for direct insertion into a circulatory vessel, such as the aorta. The perfusion shunt apparatus protects the patient from cerebral embolization and embolic stroke during cardiopulmonary bypass or cardiac surgery by directing potential emboli downstream from the aortic arch vessels where they will be better tolerated by the body. The perfusion shunt apparatus further protects the patient from cerebral hypoperfusion by providing selective perfusion of the aortic arch vessels and the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids. The perfusion shunt apparatus also finds application for selective perfusion of the cerebrovascular circulation in the presence of risk factors, such as head trauma or cardiac insufficiency. The perfusion shunt apparatus will also find application for selective perfusion of other organ systems within the body. 
     The perfusion shunt apparatus of the present invention includes an expandable shunt conduit with an upstream end, a downstream end and an internal lumen. The expandable shunt conduit is mounted on a catheter or cannula for percutaneous introduction via peripheral artery access or for direct insertion into the aorta. The expandable shunt conduit is a generally cylindrical tube of a flexible polymeric material or fabric that may be impermeable or porous to blood. Located at the upstream end of the expandable shunt conduit is an upstream sealing member. A downstream sealing member is located at the downstream end of the expandable shunt conduit. Optionally, the expandable shunt conduit may also include a plurality of support members that bridge between the upstream sealing member and the downstream sealing member. When deployed, the upstream sealing member and the downstream sealing member support the expandable shunt conduit in an open, deployed configuration and create a seal between the expandable shunt conduit and the vessel wall. An annular chamber is created between the vessel wall and the shunt conduit. A perfusion lumen within the catheter shaft communicates with the annular chamber external to the shunt conduit. 
     In one particularly preferred embodiment, the upstream sealing member and the downstream sealing member are inflatable toroidal balloon cuffs, which are sealingly attached to the upstream end and the downstream end of the expandable shunt conduit. In another embodiment, the upstream sealing member and the downstream sealing member are in the form of selectively deployable external flow valves. In yet another embodiment, the upstream sealing member and the downstream sealing member include extendible and retractable elongated expansion members to expand the upstream and downstream ends of the expandable shunt conduit until they contact and create a seal against the inner surface of the aorta. 
     Optionally, an outer tube may be provided to cover the shunt conduit when it is in the collapsed state in order to create a smooth outer surface for insertion and withdrawal of the perfusion shunt apparatus and to prevent premature deployment of the shunt conduit. Optionally, each embodiment of the perfusion shunt apparatus may also include an occlusion device, such as an inflatable balloon, to selectively occlude and seal the lumen of the expandable shunt conduit. Each embodiment of the perfusion shunt apparatus may also include an embolic filter for filtering potential emboli from the blood passing through the internal lumen of the expandable shunt conduit. Each embodiment of the perfusion shunt apparatus may include one or more radiopaque markers, sonoreflective markers or light emitting devices to enhance imaging of the apparatus using fluoroscopy, ultrasonic imaging or aortic transillumination. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-3 show a perfusion shunt apparatus according to the present invention configured for retrograde deployment in a patient&#39;s aortic arch via a peripheral arterial access point. FIG. 1 is a cutaway perspective view of the perfusion shunt apparatus deployed within the aortic arch via femoral artery access. FIG. 2 is a cross section of the perfusion shunt apparatus taken along line  2 — 2  in FIG.  1 . FIG. 3 shows the apparatus with the shunt in a collapsed state for insertion or withdrawal of the device from the patient. 
     FIG. 4 shows an alternate embodiment of the perfusion shunt apparatus using external flow control valves as sealing members. 
     FIGS. 5 and 6 show an aortic perfusion shunt apparatus configured for retrograde deployment via subclavian artery access. FIG. 5 is a cutaway perspective view of the perfusion shunt apparatus deployed within the aorta. FIG. 6 shows the apparatus with the perfusion shunt conduit in a collapsed state for insertion or withdrawal of the device from the patient. 
     FIGS. 7 and 8 show an aortic perfusion shunt apparatus configured for antegrade deployment via direct aortic insertion. FIG. 7 is a cutaway perspective view of the perfusion shunt apparatus deployed within the aorta. FIG. 8 shows the apparatus with the perfusion shunt in a collapsed state for insertion or withdrawal of the device from the aorta. 
     FIGS. 9 a - 9   b  and  10   a - 10   b  shows an embodiment of an aortic perfusion shunt apparatus with an aortic occlusion mechanism at the upstream end of the shunt conduit. 
     FIGS. 11 a - 11   b  and  12   a - 12   b  show an alternate embodiment of an aortic perfusion shunt apparatus with an aortic occlusion mechanism at the upstream end of the shunt conduit. 
     FIG. 13 shows an alternate construction of an aortic perfusion shunt apparatus according to the present invention. 
     FIG. 14 a  is an end view of the aortic perfusion shunt apparatus of FIG.  13 . FIG. 14 b  is a cross section of the aortic perfusion shunt apparatus of FIG.  13 . 
     FIG. 15 shows another alternate construction of an aortic perfusion shunt apparatus according to the present invention. 
     FIG. 16 is a cross section of the aortic perfusion shunt apparatus of FIG.  15 . 
     FIG. 17 shows an aortic perfusion filter shunt apparatus according to the present invention. 
     FIG. 18 shows a combined aortic perfusion shunt apparatus with an embolic filter mechanism positioned at the downstream end of the shunt conduit. 
     FIG. 19 shows an alternate embodiment of an aortic perfusion shunt apparatus combined with an embolic filter mechanism positioned within the shunt conduit. 
     FIGS. 20 and 21 show an aortic perfusion shunt apparatus configured for retrograde deployment via femoral artery access and having upstream and downstream sealing members operated by extendible and retractable elongated expansion members. FIG. 20 is a cutaway perspective view of the perfusion shunt apparatus deployed within the aorta. FIG. 21 shows the apparatus with the perfusion shunt conduit in a collapsed state for insertion or withdrawal of the device from the patient. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1-3 show a perfusion shunt apparatus  100  according to the present invention configured for retrograde deployment in a patient&#39;s aortic arch via a peripheral arterial access point. FIG. 1 is a cutaway perspective view of the perfusion shunt apparatus  100  deployed within the aortic arch via femoral artery access. FIG. 2 is a cross section of the perfusion shunt apparatus  100  taken along line  2 — 2  in FIG.  1 . FIG. 3 shows the distal end of the apparatus with the shunt conduit  102  in a collapsed state for insertion or withdrawal of the device from the patient. 
     Referring now to FIG. 1, the perfusion shunt apparatus  100  is shown in an expanded or deployed state within a patient&#39;s aortic arch. The perfusion shunt apparatus  100  includes an expandable shunt conduit  102 , which has an upstream end  104 , a downstream end  106  and an internal lumen  112 . Preferably, the expandable shunt conduit  102  is constructed as a generally cylindrical tube of a flexible polymeric material or fabric that is substantially impermeable to blood or fluid flow. Suitable materials for the expandable shunt conduit  102  include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polypropylene, polyamides (nylons), polyesters and alloys of copolymers thereof, as well as knitted, woven or nonwoven fabrics. Located at the upstream end  104  of the expandable shunt conduit  102  is an upstream shunt conduit support and sealing member  108 . A downstream shunt conduit support and sealing member  110  is located at the downstream end  106  of the expandable shunt conduit  102 . When deployed, the upstream sealing member  108  and the downstream sealing member  110  support the expandable shunt conduit  102  in an open, deployed configuration and create a seal between the expandable shunt conduit  102  and the vessel wall, as shown in FIG.  1 . An annular chamber  130  is thus created between the vessel wall and the shunt conduit  102 . The annular chamber  130  is delimited on the upstream end by the upstream sealing member  108  and on the downstream end by the downstream sealing member  110  and is isolated from the internal lumen  112  by the cylindrical wall of the shunt conduit  102 . In one particularly preferred embodiment, the upstream shunt conduit support and sealing member  108  and the downstream shunt conduit support and sealing member  110  are configured as inflatable annular balloon cuffs, which are sealingly attached to the upstream end  104  and the downstream end  106  of the expandable shunt conduit  102 , respectively. Suitable materials for the inflatable annular balloon cuffs  108 ,  110  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. 
     Optionally, the expandable shunt conduit  102  may also include a plurality of support members  136 , which bridge between the upstream sealing member  108  and the downstream sealing member  110 . The support members  136  strengthen the expandable shunt conduit  102  and help to hold the internal lumen  112  open when the perfusion shunt apparatus  100  is deployed. The support members  136  may be made of a semi-rigid, resilient wire or polymer material joined to or formed integrally with the wall of the shunt conduit  102 . The support members  136  may be longitudinally oriented with respect to the shunt conduit  102 , as shown, or they may be configured as one or more circumferential hoops or helical support members. The expandable shunt conduit  102  and the support members  136  may be made in a straight, but somewhat flexible, configuration so that they conform naturally to the internal curvature of the patient&#39;s aortic arch when deployed. Alternatively, the expandable shunt conduit  102  and the support members  136  may be preshaped with a curve to match the internal curvature of the patient&#39;s aortic arch. 
     Preferably, the expandable shunt conduit  102  between the upstream member  108  and the downstream sealing member  110  will have a length sufficient to bridge across the target branch vessels without occluding them. In various embodiments configured for different clinical applications, the expandable shunt conduit  102  is preferably from 1 cm to 40 cm in length, more preferably from 5 cm to 15 cm in length. In one particularly preferred embodiment configured for perfusing the aortic arch vessels in adult human patients, the expandable shunt conduit  102  is preferably approximately 8 cm to 12 cm in length. Likewise, the diameter of the expandable shunt conduit  102  is also adaptable for a variety of different clinical applications. The expandable shunt conduit  102  should have a large enough diameter, when expanded, to allow sufficient blood flow through the expandable shunt conduit  102  to adequately perfuse the organs and tissues downstream of the deployed perfusion shunt apparatus  100 . Preferably, the expandable shunt conduit  102  is of a diameter slightly smaller than the host vessel into which it is intended to be introduced so that the wall of the expandable shunt conduit  102  is separated from the vessel wall creating an annular chamber  130  between the upstream sealing member  108  and the downstream sealing member  110 , as described above. This arrangement also prevents the wall of the expandable shunt conduit  102  from occluding or restricting flow of perfusate into the target branch vessels. In various embodiments configured for different clinical applications, the expandable shunt conduit  102  is preferably from 0.2 cm to 10 cm in diameter, more preferably from 1 cm to 5 cm in diameter. For deployment in the aortic arch and perfusing the aortic arch vessels in adult human patients, the expandable shunt conduit  102  is preferably approximately 1.0 cm to 2.5 cm in diameter. With these dimensions, the internal lumen  112  of the expandable shunt conduit  102  will be capable of delivering approximately 2 to 4 liters of oxygenated blood per minute from the heart, which are necessary to adequately perfuse the organs and tissues downstream of the aortic arch. When deployed, the upstream sealing member  108  and the downstream sealing member  110  preferably have an inner diameter approximately equal to the diameter of the expandable shunt conduit  102  and an outer diameter sufficient to seal against the interior wall of the host vessel. In various embodiments configured for different clinical applications, the upstream sealing member  108  and the downstream sealing member  110  preferably have an outer diameter of 0.3 cm to 15 cm, more preferably 1 cm to 7 cm. For deployment in the aortic arch in adult human patients, the upstream sealing member  108  and the downstream sealing member  110  preferably have an outer diameter of approximately 1.5 cm to 3.5 cm. 
     Preferably, the expandable shunt conduit  102  is mounted on an elongated catheter shaft or cannula  102  for introduction into the patient&#39;s circulatory system. In this exemplary embodiment of the perfusion shunt apparatus  100 , the elongated catheter shaft  120  is configured for retrograde deployment of the expandable shunt conduit  102  in a patient&#39;s aortic arch via a peripheral arterial access point, such as the femoral artery. The elongated catheter shaft  120  should have a length sufficient to reach from the arterial access point where it is inserted into the patient to the aortic arch. For femoral artery deployment, the elongated catheter shaft  120  preferably has a length from approximately 60 to 120 cm, more preferably 70 to 90 cm. The elongated catheter shaft  120  is preferably extruded of a flexible thermoplastic material or a thermoplastic elastomer. Suitable materials for the elongated catheter shaft  120  include, but are not limited to, polyvinylchloride, polyurethane, polyethylene, polypropylene, polyamides (nylons), polyesters, and alloys or copolymers thereof, as well as braided, coiled or counterwound wire or filament reinforced composites. Optionally, the distal end of the catheter shaft  120  may be preshaped with a curve to match the internal curvature of the patient&#39;s aortic arch. 
     As seen in the cross section of the apparatus in FIG. 2, the elongated catheter shaft  120  has a perfusion lumen  122 , a first inflation lumen  124  and a second inflation lumen  126 . The catheter shaft  120  has one or more perfusion ports  118  that connect the perfusion lumen  122  with the annular chamber  130  on the exterior of the shunt conduit  102  between the upstream sealing member  108  and the downstream sealing member  110 . The proximal end  128  of the elongated catheter shaft  120  is adapted for connecting the perfusion lumen  122  to a cardiopulmonary bypass pump or other source of oxygenated blood or other fluid using standard barb connectors or other connectors, such as a standard luer fitting (not shown). The perfusion lumen  122  should be configured to allow sufficient fluid flow to preserve organ and tissue function of the organs and tissues supplied by the target branch vessels. For cerebral perfusion, the perfusion lumen  122  should be configured to allow sufficient fluid flow to preserve organ function of the brain and other tissues supplied by the arch vessels. For normothermic perfusion with oxygenated blood, the perfusion lumen  122  should have sufficient cross-sectional area to allow 0.5 to 1.5 liters per minute, and more preferably 0.75 to 1.0 liters per minute, of blood flow without significant hemolysis or other damage to the blood. For hypothermic perfusion with cooled oxygenated blood, the flow rate can be reduced to 0.25 to 0.75 liters per minute, permitting a reduction in the cross-sectional area of the perfusion lumen  122 . For perfusion with blood substitutes, such as perfluorocarbons, or with neuroplegic solutions, the cross-sectional area of the perfusion lumen  122  should be designed to allow sufficient flow rate to preserve organ function given the viscosity, pressure susceptibility and the oxygen and metabolite transport capabilities of the chosen perfusate fluid. 
     Optionally, the perfusion shunt apparatus  100  may be configured for introduction over a guidewire. For example, the perfusion lumen  122  of the elongated catheter shaft  120  may be adapted for accepting a guidewire. The perfusion lumen  122  may be provided with a distal opening at the distal end of the elongated catheter shaft  120  for passing a guidewire, such as an 0.035 or 0.038 inch diameter guidewire. Optionally, a valve, such as the catheter valve described in U.S. Pat. No. 5,085,635, which is hereby incorporated by reference, may be included at the distal end of the perfusion lumen  122  to prevent perfusate from passing through the distal opening during perfusion. Alternatively, the elongated catheter shaft  120  may include an addition lumen (not shown) for introducing the perfusion shunt apparatus  100  over a guidewire. 
     In various embodiments of the perfusion shunt apparatus  100  configured for different clinical applications, the elongated catheter shaft  120  preferably has an external diameter from 3 to 24 French size (1 to 8 mm diameter), more preferably from 8 to 16 French size (2.7 to 5.3 mm diameter). In one particularly preferred embodiment configured for perfusing the aortic arch vessels with normothermic blood in adult human patients, the elongated catheter shaft  120  preferably has a length of approximately 70 to 90 cm and an external diameter from approximately 10 to 14 French size (3.3 to 4.6 mm diameter), which allows a flow rate of approximately 0.75 to 1.0 liters per minute. In another preferred embodiment configured for perfusing the aortic arch vessels with hypothermic blood in adult human patients, the elongated catheter shaft  120  preferably has a length of approximately 70 to 90 cm and an external diameter from approximately 8 to 12 French size (2.6 to 4.0 mm diameter), which allows a flow rate of approximately 0.25 to 0.75 liters per minute. 
     Preferably, the perfusion shunt apparatus  100  includes one or more markers, which may include radiopaque markers and/or sonoreflective markers, to enhance imaging of the perfusion shunt apparatus  100  using fluoroscopy or ultrasound, such as transesophageal echography (TEE). By way of example, FIGS. 1 and 3 show a perfusion shunt apparatus  100  having a first, upstream radiopaque and/or sonoreflective marker ring  140  on the catheter shaft  120  just proximal to the upstream sealing member  108  and a second, downstream radiopaque and/or sonoreflective marker ring  142  on the catheter shaft  120  just distal to the downstream sealing member  110 . Alternatively or additionally, radiopaque markers and/or sonoreflective markers may be placed on the sealing members  108 ,  110  and/or the shunt conduit  102  to show the position and/or the deployment state of the perfusion shunt apparatus  100 . 
     A first inflation port  114  connects the first inflation lumen  124  with the interior of the inflatable annular balloon cuff that forms the upstream sealing member  108 . The proximal end of the first inflation lumen  124  is connected to a first luer fitting  132  or other suitable inflation connector. A second inflation port  114  connects the second inflation lumen  126  with the interior of the inflatable annular balloon cuff of the downstream sealing member  110 . The proximal end of the second inflation lumen  126  is connected to a second luer fitting  134  or other suitable inflation connector. This configuration allows individual inflation and deflation control of the upstream sealing member  108  and the downstream sealing member  110 . In an alternate configuration of the perfusion shunt apparatus  100 , the elongated catheter shaft  120  may be made with a single inflation lumen connected to both the first inflation port  114  and the second inflation port  114  and connected at the proximal end to a single luer fitting. In this alternate configuration, the upstream sealing member  108  and the downstream sealing member  110  would be simultaneously inflated and deflated through the single inflation lumen. Such a configuration could be used to reduce the overall diameter of the elongated catheter shaft  120 . 
     Referring now to FIG. 3, the perfusion shunt apparatus  100  is shown in an undeployed or collapsed state for insertion or withdrawal of the device from the patient. To place the perfusion shunt apparatus  100  in the collapsed state, the upstream sealing member  108  and the downstream sealing member  110 ′ are deflated and the shunt conduit  102 ′ is wrapped or folded around the catheter shaft  120  to reduce its overall diameter. Optionally, an outer tube  138  may be provided to cover the shunt conduit  102  when it is in the collapsed state in order to create a smooth outer surface for insertion and withdrawal of the perfusion shunt apparatus  100  and to prevent premature deployment of the shunt conduit  102 . 
     The perfusion shunt apparatus  100  is prepared for use by folding or compressing the shunt conduit  102 ′ into a collapsed state within the outer tube  138 , as shown in FIG.  3 . The distal end of the perfusion shunt apparatus  100  is then inserted into the aorta in a retrograde fashion. Preferably, this is done through a peripheral arterial access, such as the femoral artery or subclavian artery, using the Seldinger technique or an arterial cutdown. Alternatively, the perfusion shunt apparatus  100  may be introduced directly through an incision into the descending aorta after the aorta has been surgically exposed. The perfusion shunt apparatus  100  is advanced up the descending aorta and across the aortic arch while in the collapsed state. The position of the perfusion shunt apparatus  100  may be monitored using fluoroscopy or ultrasound, such as transesophageal echography (TEE), with the help of the radiopaque markers and/or sonoreflective markers  140 ,  142  on the catheter shaft  120 . When the upstream marker ring  140  is positioned in the ascending aorta between the aortic valve and the brachiocephalic artery and the downstream marker ring  142  is positioned downstream of the left subclavian artery, the outer tube  124  is withdrawn and the shunt conduit  102  is expanded by inflating the upstream sealing member  108  and the downstream sealing member  110 , as shown in FIG.  1 . To encourage the upstream sealing member  108  and the downstream sealing member  110  to seal with the inner surface of the aorta, they may be made with differential wall compliance that encourages the toroidal balloons to expand outward, away from the expandable shunt conduit  102 . For example, the upstream sealing member  108  and the downstream sealing member  110  may be made with a thicker balloon wall  109  near the inner surface of the toroidal balloon and a thinner balloon wall  111  near the outer surface of the toroidal balloon, as indicated in FIG.  2 . Differential wall compliance can also be accomplished by combining different balloon materials of varying elasticity. The annular chamber  130  surrounding the shunt conduit  102  created by inflation of the upstream sealing member  108  and the downstream sealing member  110  is fluidly connected to the arch vessels and is isolated from the lumen of the aorta. Once the perfusion shunt apparatus  100  is deployed, oxygenated blood or another chosen perfusate may be infused through the perfusion lumen  122  to selectively perfuse the arch vessels that deliver blood to the brain and the upper extremities. 
     If the perfusion shunt apparatus  100  is to be used in conjunction with cardiopulmonary bypass, an arterial return cannula  146  may be placed in the ascending aorta upstream of the shunt conduit  102  using known methods. Blood flow the aortic lumen from the beating heart and/or from the arterial return cannula  146  is shunted past the arch vessels through the internal lumen  112  of the shunt conduit  102 . If desired, a standard cross clamp and a cardioplegia needle or an intra-aortic occlusion catheter, such as described in U.S. Pat. Nos. 5,308,320 and 5,383,854, by Peter Safar, S. William Stezoski, and Miroslav Klain, which are hereby incorporated by reference may be applied upstream of the arterial cannula  146  for isolating the coronary arteries and inducing cardioplegic arrest. After use, the shunt conduit  102  is returned to the collapsed position by deflating the upstream sealing member  108  and the downstream sealing member  110  and advancing the outer tube  138  distally over the shunt conduit  102 , then the apparatus  100  is withdrawn from the patient. 
     Selective perfusion of the arch vessels provides protection from embolization or hypoperfusion of the brain. Any potential emboli from the cardiopulmonary bypass circuit or from surgical manipulation of the heart or the aorta are prevented from entering the neurovascular through the arch vessels. After use, the perfusion shunt assembly  102  is returned to the collapsed position and the catheter  100  is withdrawn from the patient. 
     In an alternate method for use with this and other embodiments of the perfusion shunt apparatus described herein, the perfusion shunt apparatus  100  may be deployed by inflating the upstream sealing member  108  only to expand the shunt conduit  102  and leaving the downstream sealing member  110  uninflated. Aortic blood flow from the heart or from an arterial return cannula  146  will hold the shunt conduit  102  in the open position. Potential emboli are prevented from entering the arch vessels and the cerebral circulation by pumping perfusate through the perfusion lumen  122  at a sufficient rate to create a pressure gradient that prevents blood flowing through the shunt conduit  102  from entering the annular chamber  130  surrounding the shunt conduit  102 . When using this alternate method, the perfusion shunt apparatus  100  may be simplified by eliminating the downstream sealing member  110  from the shunt conduit  102 . 
     In an alternate embodiment of the perfusion shunt apparatus  150 , shown deployed within a patient&#39;s aortic arch in FIG. 4, the upstream sealing member  152  and the downstream sealing member  154  may take the form of external flow control valves, as described in commonly owned, copending U.S. patent application Ser. Nos. 08/665,635, 08/664,361, now U.S. Pat. Nos. 5,827,237, and Ser. No. 08/664,360, now U.S. Pat. No. 5,833,671, which are hereby incorporated by reference. In this alternate embodiment, the upstream sealing member  152  would preferably be in the form of an antegrade, peripheral flow valve and the downstream sealing member  154  would preferably be in the form of a retrograde, peripheral flow vale. In such a configuration, positive perfusion pressure within the annular chamber  156  surrounding the shunt conduit  160  would tend to seal the upstream sealing member  152  and the downstream sealing member  154  against the vessel wall. However, in the event that the perfusion pressure within the annular chamber  156  dropped below aortic pressure, the upstream sealing member  152  would open so that aortic blood flow could augment the cerebral blood flow delivered through the perfusion lumen  162 . Alternatively or in addition to this passive valve action, the upstream sealing member  152  and the downstream sealing member  154  may be actively deployed by one or more actuation wires  158  extending through the elongated shaft  166  of apparatus. The actuation wires  158  would be attached at their distal ends to one or more of the valve leaflets of the upstream sealing member  152  and the downstream sealing member  154  and at their proximal ends to one or more slide buttons  164  or other actuation means for independent or simultaneous deployment. 
     The foregoing examples of the perfusion shunt apparatus of the present invention show retrograde deployment of the device within the aorta via femoral artery access. Each of the described embodiments of the perfusion shunt apparatus can also be adapted for retrograde deployment via subclavian artery access or for antegrade or retrograde deployment via direct aortic puncture. 
     Retrograde deployment of the perfusion shunt apparatus  100  via direct aortic puncture is quite similar to introduction via femoral artery access, except that the perfusion shunt apparatus  100  is introduced directly into the descending aorta after it has been surgically exposed, for example during open-chest or minimally invasive cardiac surgery. Because of the direct aortic insertion, the length and the diameter of the catheter shaft  120  may be significantly reduced. 
     FIGS. 5 and 6 show an aortic perfusion shunt apparatus  170  configured for retrograde deployment via subclavian artery access. FIG. 5 is a cutaway perspective view of the perfusion shunt apparatus  170  deployed within the aorta. FIG. 6 shows the distal end of the apparatus  170  with the perfusion shunt in a collapsed state for insertion or withdrawal of the device from the patient. Because it is intended for subclavian artery access, the perfusion shunt apparatus  170  has a catheter shaft  172  with a length of approximately 45 to 90 cm. Because of the shorter length, as compared to the femoral version of the catheter, the outside diameter of the catheter shaft  172  can be reduced to 6 to 12 French size (2 to 4 mm outside diameter) for delivering the 0.25 to 1.5 liters per minute of oxygenated blood needed to perfuse the arch vessels to preserve organ function. The reduced diameter of the catheter shaft  172  is especially advantageous for subclavian artery delivery of the perfusion shunt apparatus  170 . To further reduce the size of the catheter system for subclavian or femoral artery delivery, the outer tube  174  may be adapted for use as an introducer sheath by the addition of an optional hemostasis valve  176  at the proximal end of the outer tube  174 . This eliminates the need for a separate introducer sheath for introducing the perfusion shunt apparatus  170  into the circulatory system. 
     In use, the perfusion shunt apparatus  170  is introduced into the subclavian artery, using the Seldinger technique or an arterial cutdown, with the perfusion shunt conduit  178 ′ in a collapsed state within the outer tube  176 , as shown in FIG.  6 . The perfusion shunt apparatus  170  is advanced across the aortic arch while in the collapsed state. The position of the perfusion shunt apparatus  170  may be monitored using fluoroscopy or ultrasound, such as transesophageal echography (TEE) with the help of upstream and downstream radiopaque markers and/or sonoreflective markers  180 ,  182 , located on the catheter shaft  172  and/or the perfusion shunt conduit  178 . When the upstream marker  180  is positioned in the ascending aorta between the aortic valve and the brachiocephalic artery and the downstream marker  182  is positioned at the ostium of the left subclavian artery, the outer tube  174  is withdrawn and the shunt conduit  102  is expanded by inflating the upstream sealing member  184  and the downstream sealing member  186 , as shown in FIG.  5 . In a preferred embodiment of the apparatus, the catheter shaft  172  has a preformed bend  188  at the point where it passes through the downstream sealing member  186  and where it makes the transition from the left subclavian artery into the aortic arch to assist seating the apparatus  170  in the correct position. The downstream sealing member  186  is configured so that when it is inflated it also occludes the left subclavian artery. The annular chamber  190  surrounding the shunt conduit  178  created by inflation of the upstream sealing member  184  and the downstream sealing member  186  is fluidly connected to the arch vessels and is isolated from the lumen of the aorta. 
     Once the perfusion shunt apparatus  170  is deployed, oxygenated blood or another chosen perfusate may be infused through a first perfusion lumen  192  and out through one or more perfusion ports  194  to selectively perfuse the arch vessels that deliver blood to the brain and the upper extremities. Because the left subclavian artery is occluded by the downstream sealing member  186  when it is inflated, a second perfusion lumen  196  is provided in the catheter shaft  172  to perfuse the left upper extremity through a perfusion port  198  located on the catheter shaft  172  proximal to the downstream sealing member  186 . Additionally or alternatively, the arch vessels may be perfused through a cannula placed in a branch of one of the arch vessels, such as the patient&#39;s right subclavian artery. Such an arrangement would allow the perfusion lumen  192  to be reduced in size or even eliminated from the apparatus  170 . Again, if the perfusion shunt apparatus  170  is to be used in conjunction with cardiopulmonary bypass, an arterial return cannula  146  may be placed in the ascending aorta upstream of the shunt conduit  178  using known methods. Blood flow through the aortic lumen from the beating heart and/or from the arterial return cannula  146  is shunted past the arch vessels through the internal lumen of the shunt conduit  178 . After use, the shunt conduit  178  is returned to the collapsed position by deflating the upstream sealing member  184  and the downstream sealing member  186  and advancing the outer tube  176  distally over the shunt conduit  178 , then the apparatus  170  is withdrawn from the patient. 
     FIGS. 7 and 8 show an aortic perfusion shunt apparatus  200  configured for antegrade deployment via direct aortic insertion. FIG. 7 is a cutaway perspective view of the perfusion shunt apparatus  200  deployed with the perfusion shunt conduit  202  in an expanded state within the aorta. FIG. 8 shows the apparatus  200  with the perfusion shunt conduit  202 ′ in a collapsed state for insertion or withdrawal of the device from the aorta. 
     The perfusion shunt conduit  202  is mounted on an elongated catheter shaft  208 . The perfusion shunt conduit  202  is similar to the embodiments previously described except that, because the aortic perfusion shunt apparatus  200  is introduced into the ascending aorta in the antegrade direction, the upstream sealing member  206  is positioned proximally to the downstream sealing member  204  on the elongated catheter shaft  208 . The elongated catheter shaft  208  has a perfusion lumen  214  which is fluidly connected to one or more perfusion ports  216  located on the catheter shaft  208  between the upstream sealing member  206  and the downstream sealing member  204 . The proximal end of the elongated catheter shaft  208  is adapted for connecting the perfusion lumen  214  to a cardiopulmonary bypass pump or other source of oxygenated blood or other fluid using standard barb connectors or other connectors. A first inflation lumen  218  fluidly connects a first luer fitting  220  with a first inflation port  222  located on the interior of the upstream sealing member  206 . A second inflation lumen  224  fluidly connects a second luer fitting  226  with a second inflation port  228  located on the interior of the downstream sealing member  204 . Optionally, the elongated catheter shaft  208  may also include a second perfusion lumen (not shown), which would be connected to one or more perfusion ports located upstream of the upstream sealing member  206 . 
     The perfusion lumen  214  should be configured to allow sufficient fluid flow to preserve organ and tissue function of the organs and tissues supplied by the target branch vessels. Because the perfusion shunt apparatus  200  is introduced directly into the ascending aorta, the elongated catheter shaft  208  can be reduced to a length of approximately 20 to 60 cm and an outside diameter of approximately 6 to 12 French size (2 to 4 mm outside diameter) for delivering the 0.25 to 1.5 liters per minute of oxygenated blood needed to perfuse the arch vessels to preserve organ function. 
     Preferably, the perfusion shunt apparatus  200  includes a first, upstream radiopaque and/or sonoreflective marker ring  210  on the catheter shaft  208  just distal to the upstream sealing member  206  and a second, downstream radiopaque and/or sonoreflective marker ring  212  on the catheter shaft  208  just proximal to the downstream sealing member  204 . Visual markers may also be placed on the catheter shaft  208  to assist placement under direct or thoracoscopic visualization. 
     In use, a purse string suture is placed in the wall of the ascending aorta and an aortotomy incision is made. The perfusion shunt apparatus  200  is introduced into the ascending aorta through the aortotomy incision, with the perfusion shunt conduit  202 ′, upstream sealing member  206 ′ and the downstream sealing member  204 ′ in a collapsed state, as shown in FIG.  8 . Optionally, the collapsed perfusion shunt conduit  202 ′ may be covered with an outer tube  230  to ease insertion of the device and to prevent premature deployment. The perfusion shunt apparatus  200  is advanced across the aortic arch in an antegrade fashion. The position of the perfusion shunt apparatus  200  may be monitored using fluoroscopy or ultrasound, such as transesophageal echography (TEE). When the upstream marker  210  is positioned in the ascending aorta between the aortic valve and the brachiocephalic artery and the downstream marker  212  is positioned downstream of the left subclavian artery, the outer tube  230  is withdrawn and the shunt conduit  202  is expanded by inflating the upstream sealing member  206  and the downstream sealing member  204 , as shown in FIG.  7 . In one preferred embodiment, the catheter shaft  208  has a preformed bend  232  proximal to the perfusion shunt conduit  202  where the catheter shaft  208  passes through the aortic wall to assist seating the apparatus  200  in the correct position. Once the perfusion shunt apparatus  200  is deployed, oxygenated blood or another chosen perfusate may be infused through a perfusion lumen  214  and out thorough the perfusion ports  216  to selectively perfuse the arch vessels. If the perfusion shunt apparatus  200  is to be used in conjunction with cardiopulmonary bypass, an arterial return cannula (not shown) may be placed in the ascending aorta upstream of the shunt conduit  202  using known methods or the aorta may be perfused through the optional second perfusion lumen discussed above. Blood flow through the aortic lumen from the beating heart and/or from the arterial return cannula is shunted past the arch vessels through the internal lumen of the shunt conduit  202 . For complete cardiopulmonary bypass with cardioplegic arrest, the perfusion shunt apparatus  200  may be used in combination with a standard aortic cross clamp or with an intra aortic balloon clamp. After use, the shunt conduit  202  is returned to the collapsed position by deflating the upstream sealing member  206  and the downstream sealing member  204  and advancing the outer tube  230  distally over the shunt conduit  202 , then the apparatus  200  is withdrawn from the patient. 
     FIGS. 9 a - 9   b  and  10   a - 10   b  show an embodiment of an aortic perfusion shunt apparatus  240  with an aortic occlusion mechanism at the upstream end of the expandable shunt conduit  242 . FIG. 9 a  shows the aortic perfusion shunt apparatus  240  with the expandable shunt conduit  242  deployed within a patient&#39;s aortic arch. FIG. 9 b  is a distal end view of the expandable shunt conduit  242  of the aortic perfusion shunt apparatus  240  of FIG. 9 a . FIG. 10 a  shows the aortic perfusion shunt apparatus  240  of FIG. 9 a  with the aortic occlusion mechanism  244 ′ activated to block flow through the expandable shunt conduit  242 . FIG. 10 b  is a distal end view of the expandable shunt conduit  242  and activated aortic occlusion mechanism  244 ′ of FIG. 10 a.    
     This embodiment of the aortic perfusion shunt apparatus  240  may be adapted for retrograde deployment via peripheral arterial access, as shown, or it may be adapted for antegrade deployment via direct aortic insertion. In most aspects, the aortic perfusion shunt apparatus  240  and the expandable shunt conduit  242  are similar in construction to the embodiments previously described. However, the upstream sealing member  244  is adapted so that it also serves as an aortic occlusion mechanism. The upstream sealing member  244  is expandable from a collapsed position for insertion to an expanded position for sealing between the expandable shunt conduit  242  and the aortic wall, as shown in FIGS. 9 a  and  9   b . As shown in FIGS. 10 a  and  10   b , the upstream sealing member  244 ′ is further expandable to an occluding position in which the inner diameter of the toroidal upstream sealing member  244 ′ decreases to occlude the inner lumen  246  of the expandable shunt conduit  242 . To encourage the upstream sealing member  244 ′ to expand inward to occlude the inner lumen  246  of the expandable shunt conduit  242 , the toroidal balloon  244  may be made with differential wall compliance. For example, the toroidal upstream sealing member  144  may be made with a thinner balloon wall  243  near the inner surface of the toroidal balloon and a thicker balloon wall  245  near the outer surface of the toroidal balloon, as indicated in FIG. 10 b . Differential wall compliance can also be accomplished by combining different balloon materials of varying elasticity. This integral aortic occlusion mechanism obviates the need for a separate aortic cross clamp or intra aortic balloon clamp when the aortic perfusion shunt apparatus  240  is used for complete cardiopulmonary bypass with cardioplegic arrest. Preferably, the aortic perfusion shunt apparatus  240  also includes a cardioplegia lumen  248 , which extends from the distal end of the elongated catheter shaft  252  to a luer fitting  250  on the proximal end. The cardioplegia lumen  248  may also be used as a guidewire lumen to assist introduction of the device into the vasculature. 
     After the upstream sealing member  244 ′ has been inflated to its occluding position, cardioplegic solution may be infused through the cardioplegia lumen  248  into the aortic root and hence into the coronary arteries to induce cardioplegic arrest. The arch vessels may be selectively perfused through the perfusion lumen  254 , which connects to one or more perfusion ports  256  located on the exterior of the catheter shaft  252  between the upstream sealing member  244  and the downstream sealing member  252 . The descending aorta downstream of the perfusion shunt apparatus  240  may be perfused through a separate arterial cannula, which may be placed in the contralateral femoral artery or which may be coaxial to the elongated catheter shaft  252 . Alternatively, the elongated catheter shaft  252  of the perfusion shunt apparatus  240  may be provided with a second perfusion lumen (not shown) connecting to perfusion ports located downstream of the downstream sealing member  252 . 
     The patient can be converted from cardioplegic arrest to a beating heart condition, while maintaining selective perfusion of the arch vessels, by partially deflating the upstream sealing member from the occluding position  244 ′ to the expanded position  244 . This allows oxygenated blood to flow retrograde through the inner lumen  246  of the expandable shunt conduit  242  and into the coronary arteries to revive the arrested heart. Once the heart has resumed beating, blood flow from the heart will flow antegrade through the expandable shunt conduit  242  to the rest of the body. Selective perfusion of the arch vessels through the perfusion lumen  254  may be maintained as long as necessary. After use, the shunt conduit  242  is returned to the collapsed position by deflating the upstream sealing member  244  and the downstream sealing member  252  and the apparatus  240  is withdrawn from the patient. 
     FIGS. 11 a - 11   b  and  12   a - 12   b  show an alternate embodiment of an aortic perfusion shunt apparatus  260  with an aortic occlusion mechanism  280  at the upstream end of the expandable shunt conduit  262 . FIG. 11 a  shows the aortic perfusion shunt apparatus  260  with the expandable shunt conduit  262  deployed within a patient&#39;s aortic arch. FIG. 11 b  is a distal end view of the expandable shunt conduit  262  of the aortic perfusion shunt apparatus  260  of FIG. 11 a . FIG. 12 a  shows the aortic perfusion shunt apparatus  260  of FIG. 11 a  with the aortic occlusion mechanism  280 ′ activated to block flow through the expandable shunt conduit  262 . FIG. 12 b  is a distal end view of the expandable shunt conduit  262  and activated aortic occlusion mechanism  280 ′ of FIG. 12 a.    
     Again, most aspects of the aortic perfusion shunt apparatus  260  and the expandable shunt conduit  262  are similar in construction to the embodiments previously described. In addition, however, the aortic perfusion shunt apparatus  260  includes an occlusion member  280  within the inner lumen  266  of the expandable shunt conduit  262 . In one preferred embodiment, the occlusion member  280  is an expandable balloon, which may be generally spherical in shape and may be made of a flexible polymer or elastomer, such as polyvinylchloride, polyurethane, polyethylene, polypropylene, polyamides (nylons), polyester, latex, silicon, or alloys, copolymers and reinforced composites thereof. The occlusion member  280  is fluidly connected by an inflation lumen  282  to a luer fitting  284  or other connector on the proximal end of the perfusion shunt apparatus  260 . The occlusion member  280  is inflatable from a collapsed position  280 , shown in FIG. 11 b , to an occluding position  280 ′, shown in FIG. 12 b , to occlude the inner lumen  266  of the expandable shunt conduit  262 . Alternatively, the occlusion member  280  may be a flap or valve, which is selectively actuatable to occlude the inner lumen  266  of the expandable shunt conduit  262 . This integral aortic occlusion mechanism obviates the need for a separate aortic cross clamp or intra aortic balloon clamp when the aortic perfusion shunt apparatus  260  is used for complete cardiopulmonary bypass with cardioplegic arrest. Preferably, the aortic perfusion shunt apparatus  260  also includes a cardioplegia lumen  268 , which extends from the distal end of the elongated catheter shaft  272  to a luer fitting  270  on the proximal end. The cardioplegia lumen  268  may also be used as a guidewire lumen to assist introduction of the device into the vasculature. 
     After the occlusion member  280 ′ has been inflated to its occluding position, cardioplegic solution may be infused through the cardioplegia lumen  268  into the aortic root and hence into the coronary arteries to induce cardioplegic arrest. The arch vessels may be selectively perfused through the perfusion lumen  274 , which connects to one or more perfusion ports  276  located on the exterior of the catheter shaft  272  between the upstream sealing member  264  and the downstream sealing member  272 . The descending aorta downstream of the perfusion shunt apparatus  260  may be perfused through a separate arterial cannula, which may be placed in the contralateral femoral artery or which may be coaxial to the elongated catheter shaft  272 . Alternatively, the elongated catheter shaft  272  of the perfusion shunt apparatus  260  may be provided with a second perfusion lumen (not shown) connecting to perfusion ports located downstream of the downstream sealing member  272 . 
     The patient can be converted from cardioplegic arrest to a beating heart condition, while maintaining selective perfusion of the arch vessels, by partially or completely deflating the occlusion member  280  from the occluding position  280 ′ to the collapsed position  280 . This allows oxygenated blood to flow retrograde through the inner lumen  266  of the expandable shunt conduit  262  and into the coronary arteries to revive the arrested heart. Once the heart has resumed beating, blood flow from the heart will flow antegrade through the expandable shunt conduit  262  to the rest of the body. Selective perfusion of the arch vessels through the perfusion lumen  274  may be maintained as long as necessary. After use, the shunt conduit  262  is returned to the collapsed position by deflating the upstream sealing member  264  and the downstream sealing member  272  and the apparatus  260  is withdrawn from the patient. 
     FIGS. 13,  14   a  and  14   b  show an alternate construction of an aortic perfusion shunt apparatus  290  according to the present invention. FIG. 13 shows the aortic perfusion shunt apparatus  290  deployed within a patient&#39;s aorta. FIG. 14 a  is an end view of the aortic perfusion shunt apparatus  290  of FIG.  13 . FIG. 14 b  is a cross section of the aortic perfusion shunt apparatus  290  of FIG.  13 . This alternate construction may be used with any of the embodiments of the perfusion shunt apparatus described herein. In most respects, the aortic perfusion shunt apparatus  290  and the expandable shunt conduit  292  are similar in construction to the embodiments previously described. However, in this embodiment a distal portion of the elongated catheter shaft  294  passes through the inner lumen  296  of the expandable shunt conduit  292 . One or more perfusion ports connect to the catheter shaft  294  through the wall of the expandable shunt conduit  292 . This construction of the aortic perfusion shunt apparatus  290  allows the expandable shunt conduit  292  to be made in a larger diameter, more closely approximating the luminal diameter of the host vessel, in this case the aortic arch. It also allows a clear unobstructed flow of perfusate around the exterior of the expandable shunt conduit  292 . This aspect may be important for other clinical applications where the target branch vessels are distributed around the host vessel rather than lined up along one side of the host vessel, such as in the descending aorta. 
     FIGS. 15 and 16 show another alternate construction of an aortic perfusion shunt apparatus  300  according to the present invention. FIG. 15 shows the aortic perfusion shunt apparatus  300  deployed within a patient&#39;s aorta. FIG. 16 is a cross section of the aortic perfusion shunt apparatus  300  of FIG.  15 . Once again, this alternate construction may be used with any of the embodiments of the perfusion shunt apparatus described herein. In most respects, the aortic perfusion shunt apparatus  300  and the expandable shunt conduit  302  are similar in construction to the embodiments previously described. However, in this embodiment the upstream sealing member  304  and the downstream sealing member  306  are eccentric toroidal balloon cuffs with the larger side of the eccentric toroidal balloon cuffs positioned toward the arch vessels on the superior side of the aortic arch. This displaces the expandable shunt conduit  302  and the elongated catheter shaft  308  toward the inferior side of the aortic arch and away from the arch vessels. The expandable shunt conduit  302  and the elongated catheter shaft  308  are thus less likely to interfere with blood flow into the arch vessels when the aortic perfusion shunt apparatus  300  is deployed. 
     FIG. 17 shows an aortic perfusion filter shunt apparatus  310  according to the present invention. In most respects, the aortic perfusion shunt apparatus  310  and the expandable shunt conduit  312  are similar in construction to the embodiments previously described. However, in this embodiment, rather than being made of a relatively impermeable material, the expandable shunt conduit  312  is made of a porous filter mesh material. Optionally the downstream end of the expandable shunt conduit  312  may have an end wall  318  of filter mesh material across the inner lumen  320  of the expandable shunt conduit  312 , as well. The filter mesh material of the expandable shunt conduit  312  may be a woven or knitted fabric, such as Dacron or nylon mesh, or other fabrics, or it may be a nonwoven fabric, such as a spun bonded polyolefin or expanded polytetrafluoroethylene or other nonwoven material. Alternatively, the filter mesh material of the expandable shunt conduit  312  may be an open cell foam material. The filter mesh material of the expandable shunt conduit  312  must be nontoxic and hemocompatible, that is, non-thrombogenic and non-hemolytic. Preferably, the filter mesh material of the expandable shunt conduit  312  has a high percentage of open space, with a uniform pore size. The pore size of the filter mesh material can be chosen to capture macroemboli only or to capture macroemboli and microemboli. In most cases the pore size of the filter mesh material will preferably be in the range of 1-200 micrometers. For capturing macroemboli only, the pore size of the filter mesh material will preferably be in the range of 50-200 micrometers, more preferably in the range of 80-100 micrometers. For capturing macroemboli and microemboli, the pore size of the filter mesh material will preferably be in the range of 1-100 micrometers, more preferably in the range of 5-20 micrometers. In other applications, such as for treating thromboemolic disease, a larger pore size, e.g. up to 1000 micrometers (1 mm) or larger, would also be useful. In some embodiments, a combination of filter materials having different pore sizes may be used. The expandable shunt conduit  312  and the end wall  318  may be made of filter mesh materials having different pore sizes. For example, the expandable shunt conduit  312  may be made with a very fine filter mesh material for capturing both macroemboli and microemboli, and the end wall  318  may be made of a coarser filter mesh material for capturing macroemboli only. 
     When the aortic perfusion filter shunt apparatus  310  is deployed within the aortic arch, the filter mesh material of the expandable shunt conduit  312  will protect the arch vessels and prevent emboli from entering the cerebral vasculature. Potential emboli that are stopped by the filter mesh material of the expandable shunt conduit  312  will either pass through the inner lumen  320  of the expandable shunt conduit  312  and flow downstream where they will be better tolerated or they will be stopped by the filter mesh material of the end wall  318 . Undesirable embolic events can be avoided without stopping the heart or otherwise interfering with the normal function of the circulatory system. In addition, selective perfusion of the arch vessels with a perfusate of preselected temperature or chemical composition can be performed through the perfusion lumen  314  of the aortic perfusion filter shunt apparatus  310 . The perfusate that exits the perfusion ports  316  will be concentrated in the arch vessels by the presence of the filter mesh material of the expandable shunt conduit  312 . 
     In addition, the aortic perfusion filter shunt apparatus  310  of FIG. 17 may be combined with the aortic occlusion mechanism of FIGS. 9 a - 9   b  and  10   a - 10   b  or  11   a - 11   b  and  12   a - 12   b  for performing complete cardiopulmonary bypass with cardioplegic arrest. With this arrangement, one catheter will provide a motionless stopped heart environment for intricate cardiac surgery while on bypass and cerebrovascular protection by filtration an selective perfusion while on or off bypass. 
     Additionally or alternatively, the aortic perfusion filter shunt apparatus  310  of FIG. 17 may be operated in the alternate method of use described above in connection with FIGS. 1-3 by inflating the upstream sealing member  322  only to expand the shunt conduit  312  and leaving the downstream sealing member  324  uninflated. The annular space around the expandable shunt conduit  312  is perfused through the perfusion ports  316  of the perfusion lumen  314 . When using this alternate method, the aortic perfusion filter shunt apparatus  310  may be simplified by eliminating the downstream sealing member  324  from the shunt conduit  312 . 
     FIG. 18 shows a combined aortic perfusion shunt apparatus  330  with an embolic filter mechanism  332  positioned at the downstream end of the shunt conduit. The elongated catheter shaft  336  and the expandable shunt conduit  312  of the apparatus  330  may be built according to any of the previously described embodiments. Attached to the apparatus  330  at the downstream end of the expandable shunt conduit  312  is an embolic filter mechanism  332  made of a filter mesh material. The filter mesh material of the embolic filter mechanism  332 , which may be made of any of the filter materials described above, can be chosen to capture macroemboli only or to capture macroemboli and microemboli. The embolic filter mechanism  332  may be roughly conical in shape as shown or any other convenient geometry. Other examples of suitable geometries and constructions for the embolic filter mechanism  332  may be found in commonly owned, copending U.S. provisional application No. 60/060,117, and corresponding U.S. patent application Ser. No. 09/158,405, which has previously been incorporated by reference. 
     When the aortic perfusion shunt apparatus  330  is deployed within the aortic arch, the arch vessels and thus the cerebral vasculature, are protected from embolization or hypoperfusion by selective perfusion through the perfusion lumen  338  of the elongated catheter shaft  336 , while the organs and tissues downstream of the apparatus  330  are protected from embolization by the embolic filter mechanism  332 . In addition, the aortic perfusion shunt apparatus  330  of FIG. 18 may be combined with the aortic occlusion mechanism of FIGS. 9 a - 9   b  and  10   a - 10   b  or  11   a - 11   b  and  12   a - 12   b  for performing complete cardiopulmonary bypass with cardioplegic arrest. Thus, one catheter will provide a motionless stopped heart environment for intricate cardiac surgery while on bypass and cerebrovascular protection by filtration and selective perfusion while on or off bypass. 
     FIG. 19 shows an alternate embodiment of an aortic perfusion shunt apparatus  340  combined with an embolic filter mechanism  342  positioned within the expandable shunt conduit  344 . This embodiment is similar in construction and materials to the combined aortic perfusion shunt apparatus and embolic filter mechanism of FIG. 16, except that the embolic filter mechanism  342  is positioned within the inner lumen  346  of the expandable shunt conduit  344 . This arrangement provides a more compact construction of the apparatus  340 . The arrangement also provides additional protection and support for the embolic filter mechanism  342 , which can thus be made of very delicate or intricately arranged fine filter mesh material. The additional protection also provides more positive capture of embolic materials within the embolic filter mechanism  342 , particularly upon withdrawal of the device after use, because the filter mesh material of the embolic filter mechanism  342  is surrounded with the relatively impermeable material of the expandable shunt conduit  344 . The apparatus of FIG. 19 can also be combined with any of the embodiments or constructions previously described in conjunction with other embodiments of the present invention, including the aortic occlusion mechanisms of FIGS. 9 a - 9   b  and  10   a - 10   b  or  11   a - 11   b  and  12   a - 12   b . Likewise, all operable combinations and subcombinations of the features of the present invention described herein, or incorporated by reference, are considered to be within the scope of the present invention whether or not they have been explicitly described. 
     FIGS. 20 and 21 show an aortic perfusion shunt apparatus  400  configured for retrograde deployment via femoral artery access and having upstream and downstream sealing members  402 ,  404  operated by extendible and retractable elongated expansion members  406 ,  408 . FIG. 20 is a cutaway perspective view of the perfusion shunt apparatus  400  deployed within the aorta. FIG. 21 shows the apparatus with the perfusion shunt conduit  410  in a collapsed state for insertion or withdrawal of the device from the patient. 
     Similar to the previously described embodiments, the aortic perfusion shunt apparatus  400  has an elongated catheter or cannula shaft  412  that may be configured for introduction via peripheral artery access, as shown, or for central aortic access. An expandable shunt conduit  410  is mounted near the distal end of the catheter shaft  412 . The expandable shunt conduit  410  is a tubular structure of either porous or impermeable fabric. An upstream elongated expansion member  406  extends out of a port or ports  414  on the catheter shaft  412  and encircles the shunt conduit  410  near its upstream end  416 . The fabric of the shunt conduit  410  is folded back over the upstream elongated expansion member  406  and sewn with a seam  418  to enclose the upstream elongated expansion member  406 . A downstream elongated expansion member  408  extends out of another port or ports  420  on the catheter shaft  412  and encircles the shunt conduit  410  near its downstream end  422 . The fabric of the shunt conduit  410  is folded back over the downstream elongated expansion member  408  and sewn with a seam  424  to enclose the downstream elongated expansion member  408 . 
     The upstream elongated expansion member  406  is a flexible wire, rod, fiber or cable made from a polymer or metal, such as stainless steel or a nickel-titanium alloy. A first actuation member  426  extends through the catheter shaft  412  and connects the upstream elongated expansion member  406  to a first actuator button  430  on the proximal end of the perfusion shunt apparatus  400 . The first actuation member  426  may be an extension of the upstream elongated expansion member  406  or it may be a separate wire or rod attached to the upstream elongated expansion member  406 . Similarly, the downstream elongated expansion member  408  is a flexible wire, rod, fiber or cable made from a polymer or metal, such as stainless steel or a nickel-titanium alloy. A second actuation member  428  extends through the catheter shaft  412  and connects the downstream elongated expansion member  408  to a second actuator button (not visible in this view) on the proximal end of the perfusion shunt apparatus  400 . The second actuation member  428  may be an extension of the downstream elongated expansion member  408  or it may be a separate wire or rod attached to the downstream elongated expansion member  408 . Alternatively, the upstream elongated expansion member  406  and the downstream elongated expansion member  408  may be actuated by a single actuation member  426  and actuator button  430 . 
     To prepare the aortic perfusion shunt apparatus  400  for use, the actuator button or buttons  430  are moved proximally to retract the upstream elongated expansion member  406  and the downstream elongated expansion member  408  into the catheter shaft  412  through the ports  414 ,  420 . This gathers the upstream end  416  and the downstream end  422  of the shunt conduit  410  and collapses the shunt conduit  410  toward the catheter shaft  412 , as shown in FIG.  21 . Optionally, an outer tube (not shown) may be placed over the collapsed shunt conduit  410 . 
     The aortic perfusion shunt apparatus  400  is inserted and positioned as previously described. Once the aortic perfusion shunt apparatus  400  is in the proper position, the process is reversed to deploy the expandable shunt conduit  410 . The actuator button or buttons  430  are moved distally to extend the upstream elongated expansion member  406  and the downstream elongated expansion member  408  from the ports  414 ,  420  in the catheter shaft  412 . This expands the upstream end  416  and the downstream end  422  of the shunt conduit  410  until they contact and create a seal against the inner surface of the aorta, as shown in FIG.  20 . Advantageously, the shunt conduit  410  maybe made of a somewhat elastic film or fabric to easily accommodate variations in the sizes of patient&#39;s aortas. 
     As in previously described embodiments, the aortic perfusion shunt apparatus  400  of FIGS. 20 and 21 may optionally include one or more radiopaque and/or sonoreflective markers on the apparatus for enhanced imaging by fluoroscopic or ultrasonic imaging techniques. Another feature that can be combined with each of the embodiments of the present invention is an aortic transillumination system for locating and monitoring the position of the catheter, the shunt and the optional occlusion devices without fluoroscopy by transillumination of the aortic wall. Aortic transillumination systems using optical fibers and/or light emitting diodes or lasers suitable for this application are described in commonly owned, copending U.S. patent application Ser. No. 60/088,652, filed Jun. 9, 1998, which is hereby incorporated by reference in its entirety. By way of example, the aortic perfusion shunt apparatus  400  of FIGS. 20 and 21 is easily adaptable for use with a fiberoptic system for aortic transillumination. For this purpose, the upstream elongated expansion member  406  and the first actuation member  426  may be made of a first optical fiber, preferably a flexible polymeric optical fiber. Similarly, the downstream elongated expansion member  408  and the second actuation member  428  may be made of a second optical fiber, also preferably a flexible polymeric optical fiber. An optical coupling (not shown) would be provided at the proximal end of the perfusion shunt apparatus  400  to connect the optical fibers to a light source. The fiberoptic upstream elongated expansion member  406  and the fiberoptic downstream elongated expansion member  408  can be made lossy by abrading the optical fibers or their cladding so that light escapes through the walls of the fibers. The light emitted by the fiberoptic upstream elongated expansion member  406  and the fiberoptic downstream elongated expansion member  408  is visible through the aortic wall and can be used to locate and monitor the position and the deployment state of the expandable shunt conduit  410 . Similarly, in embodiments of the perfusion shunt apparatus utilizing an aortic occlusion device, one or more optical fibers or other light emitting devices may be positioned on the aortic occlusion device to locate and monitor its position and state of deployment. 
     Likewise, the features and embodiments of the present invention may also be combined with a bumper location device for facilitating catheter insertion and positioning by providing tactile feedback when the catheter device contacts the aortic valve. Bumper location devices suitable for this application are described in commonly owned, copending U.S. provisional patent application Ser. No. 60/060,158, filed Sep. 26, 1997, and Ser. No. 60/073,681, filed Feb. 4, 1998, and corresponding U.S. patent application Ser. No. 09/161,207, which are hereby incorporated by reference in their entirety. 
     While the present invention has been described herein with respect to the exemplary embodiments and the best mode for practicing the invention, it will be apparent to one of ordinary skill in the art that many modifications, improvements and subcombinations of the various embodiments, adaptations and variations can be made to the invention without departing from the spirit and scope thereof.