Abstract:
Modular systems comprising a cannula and at least one access port adjacent to a distal end of the cannula provide insertion of one or more therapeutic or diagnostic devices into a vessel or cardiac tissue through a single incision site. Other embodiments include a vessel introducer or multi-port introducer. The devices can be operated in combination or independently. The systems can be employed to provide multiple therapies, including blood perfusion, filtration, aspiration, vessel occlusion, atherectomy, and endoscopic devices. Methods of using the system for vessel cannulation are also disclosed herein.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a modular system for introducing therapeutic or diagnostic devices, such as a blood filter, occluder, atherectomy device, stents, angiographic catheters, and pressure monitors to a vessel or cardiac tissue. More particularly, the system delivers the devices independently or in combination through a single incision on the vessel or cardiac tissue via one or more access ports and lumens. 
     BACKGROUND OF THE INVENTION 
     During various cardiothoracic, pulmonary, and vascular surgeries, including coronary artery bypass grafting, heart valve repair or replacement, atrial or ventricular septal defect repair, angioplasty, atherectomy, aneurysm repair, and pulmonary thrombectomy, cannulation of a patient&#39;s vessel(s) are often required to provide vascular access for delivery of various diagnostic and therapeutic devices. In a conventional approach, separate incisions are needed for introduction of each medical device. For example, during coronary artery bypass grafting (CABG) surgeries, cardiopulmonary bypass is established by cannulation of the aorta to provide circulatory isolation of the heart and coronary blood vessels. Two incisions on the aorta may be required, i.e., one for insertion of the arterial cannula and another for insertion of a balloon occluder to provide coronary isolation from the peripheral vascular system. When cardiac arrest is desired, a third incision may be required on the aorta to introduce a catheter for delivering cardioplegic solution to the coronary arteries. Additional incisions may be required for insertion of other devices, such as a blood filter, pressure monitor, or atherectomy device. Once the incisions are made on the aorta, the devices often remain in the aorta throughout the entire procedure despite only being used intermittently, e.g., the cardioplegia catheter. 
     Due to significant mortality and morbidity associated with the conventional CABG surgeries from the use of cardiopulmonary bypass for circulatory support and the traditional method of access by median sternotomy, minimally invasive concepts recently have been adopted to make cardiothoracic procedures less invasive. Minimally invasive alternatives include the minimally invasive direct CABG procedure in which the operation is performed through minimal access incisions, eliminating cardiopulmonary bypass. The second alternative is to perform the procedure through minimal access incisions, and cardiopulmonary support is instituted through an extra thoracic approach, i.e., the port access approach. The third alternative is to perform the procedure on a beating heart which allows greater access for more extensive revascularization, i.e., the “off pump” sternotomy approach. In any of the minimally invasive alternatives, the space allowed for multiple instrumentation and device insertion is limited. 
     The disadvantages associated with the conventional or minimally invasive approach are that (1) by having multiple devices inserted in the aorta, the space available for the surgeon to perform procedures is limited, and (2) the aorta is traumatized as a result of multiple incisions, which may result in aortic dissection, aortic wall hematoma, and/or embolization of calcium plaque from the aortic wall. The greater the aortic trauma, the higher the perioperative morbidity a patient will endure. 
     New devices or systems are therefore needed which provide access to a patient&#39;s vessel and introduction of multiple diagnostic and therapeutic devices during cardiovascular procedures, thereby minimizing crowding caused by the multiple device insertions and trauma to the vessel wall. 
     SUMMARY OF THE INVENTION 
     The methods and systems of the present invention provide means of introducing a combination of multiple devices or instruments into a vessel through a single incision site, thereby reducing the number of incisions on the vessel and minimizing space crowding during vascular surgeries. More particularly, various devices and instruments can be inserted into the vessel through one or multiple lumens and access ports included in the modular access port systems, thereby minimizing the trauma of exchanging devices against the vessel wall. The methods and systems can be used in conventional or minimally invasive surgeries to provide any combination of the following functions: perfusion, drug delivery, fluid infusion, vessel occlusion, filtration, aspiration, venting, fluid diversion, venous return in cardiopulmonary bypass, atherectomy, fluid pumping, suturing, stapling, collagen or fibrin delivery, placement of pacing leads, use of angiographic catheters, angioplasty catheters, valvuoplasty catheters, electrode catheters, sizing tools, internal vessel segregating or isolating dams, endoscopic cameras, pressure monitors, shunts, stents, grafts, stent/grafts, vessel surfacing modalities, radioactive isotopes, graft delivery, and endoscopic devices. For example, devices traditionally introduced through the femoral artery (i.e., stents, atherectomy catheters, or angioplasty catheters) can also be introduced directly into the aorta, if deemed advantageous or beneficial to the patient. 
     In a first embodiment, the systems comprise a cannula having a distal end, a first access port adjacent to the distal end of the cannula, and a second access port adjacent to the first port. The ports and the distal end of the cannula are arranged substantially in a line. The distal end of the cannula is adapted for perfusion of blood, i.e. for use as an arterial cannula or venous return cannula in cardiopulmonary bypass. The cannula also has a proximal end adapted for attachment to a bypass-oxygenator machine, and a lumen adapted for perfusion of oxygenated or deoxygenated blood. Each of the first and the second access ports has a lumen extending from a proximal end to a distal end. The proximal ends of the ports are adapted to receive medical devices. 
     In another embodiment, the second port is adjacent to the distal end of the cannula and to the first port, such that the ports are arranged at the vertices of a triangle. Having the triangular arrangement may be preferred in minimally invasive procedures where surgical space is limited. A hemostatic valve may be included in the lumen of either or both of the access ports. The distal ends of the cannula and/or the access ports may include a suture flange for securing the system onto the vessel. 
     In still another embodiment, the systems comprise an elongate cannula having a distal end and an access port adjacent to the distal end of the cannula. The port has a lumen communicating with a distal end and a proximal end of the port. The proximal end and the lumen are adapted to receive at least one medical device, e.g., a blood filter and/or an occlusion catheter. 
     In still another embodiment, the systems comprise a vessel introducer having a tubular member and an obturator. The tubular member has a proximal end, a distal end, and a lumen, which may include a hemostatic valve in some embodiments. The obturator is removably insertable into the lumen of the tubular member. Medical devices, e.g., a blood filter, can be introduced through the proximal end and lumen of the tubular member. 
     In still another embodiment, the systems comprise a multi-port introducer having a first tubular member and a second tubular member mounted adjacent to the first member. Each of the first and second tubular members has a proximal end, a distal end and a lumen, which may include a hemostatic valve in some embodiments. The blood filter, for example, is removably insertable into the proximal port of either the first or the second member, allowing the other member to receive another medical device. 
     In a first method to provide insertion of medical devices and cannulation of a vessel or cardiac tissue, the distal ends of the cannula and the access ports described in the first embodiment are inserted through an incision on the vascular or cardiac tissue. For example, to provide arterial cannulation for cardiopulmonary bypass, the cannula is inserted through an incision on the aorta. A blood filter may be inserted through the first port, and an occlusion catheter having a balloon occluder may be inserted through the second port into the aorta. The blood filter is expanded to entrap embolic materials, calcium, myocardial tissue debris, or atheromatous plague, which arise as a result of introducing instrumentation or due to surgery. The occluder, e.g., a balloon occluder is expanded to provide circulatory isolation of the coronary vessels from the peripheral vascular system. The proximal end of the cannula is attached to a bypass-oxygenator machine to deliver oxygenated blood to the aorta. After the cardiopulmonary bypass is established, a surgical procedure can be performed on the heart and/or aorta. 
     In another method to provide insertion of medical devices and cannulation of a vessel or cardiac tissue, the distal ends of the cannula and the access port are inserted into a vessel or cardiac tissue. One or more medical devices are then inserted through an access port. For example, during arterial cannulation for cardiopulmonary bypass as described above, the blood filter and the occlusion catheter can be inserted sequentially through one access port into the aorta. After completion of the surgical procedure, one or both devices are removed from the access port. In situations where continuation of the cardiopulmonary bypass is desired post-operatively due to a patient&#39;s low cardiac output state, the blood filter may be removed, leaving the occlusion catheter and the cannula in the aorta. In this manner, multiple therapies and procedures are employed in combination or independently of each other. 
     The present invention also provides methods for introducing medical devices into a vessel without cannulation of the vessel. Using the vessel introducer described above, the distal end of the introducer is first inserted into the vessel. The obturator is removed and a medical device, e.g., blood filter, is inserted through the proximal end of the introducer into the vessel. It should be noted that the medical device can be removed from the introducer and replaced with another device without altering the incision site or requiring another incision. 
     In still another method for introducing multiple devices into a vessel, the distal end of the multi-port introducer is inserted into the vessel. A medical device, such as a blood filter, is inserted into the proximal end of the first tubular member and advanced into the vessel. Another medical device is then inserted into the proximal end of the second tubular member and advanced into the vessel. Certain medical devices, such as a cardioplegia catheter, which are often used intermittently can remain in the introducer for the entire length of the procedure or be removed during part of the surgical procedure (to reduce space crowding), and then be reinserted into the introducer without altering the incision site. 
     It will be understood that there are several advantages to using the systems and methods disclosed herein for delivering medical therapies. For example, the systems (1) permit a combination of therapies to be employed through only one incision site, thereby minimizing trauma to the vessel wall, (2) allow multiple devices to be operated in combination or independently, (3) reduce the number of devices used concomitantly, thereby minimizing crowding in the surgical field, (4) can be employed in a variety of cardiac or vascular surgeries, and (5) can be used in minimally invasive procedures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a lateral view of a cannula system for introduction of medical devices according to the present invention. 
     FIG. 2 depicts a lateral view of the cannula system of FIG.  1 . 
     FIG. 3A depicts a frontal cross-sectional view of the cannula system of FIG.  1 . 
     FIG. 3B depicts a frontal cross-sectional view of an alternative cannula system. 
     FIG. 4 depicts the cannula system of FIG. 1 inserted in an ascending aorta. 
     FIG. 5 depicts a medical device attached to the proximal end of the first access port of the cannula system of FIG.  1 . 
     FIG. 6A depicts the medical device of FIG. 5 carrying a blood filter. 
     FIG. 6B depicts the deployment of the blood filter of FIG.  6 B. 
     FIG. 7A depicts a cross-sectional view of an elongate tube housing a filter. 
     FIG. 7B depicts a cross-sectional view of an elongate tube housing a windsock. 
     FIG. 7C depicts a cross-sectional view of an elongate tube housing an aspiration catheter. 
     FIG. 7D depicts a cross-sectional view of an elongate tube housing a needle. 
     FIG. 7E depicts a cross-sectional view of an elongate tube housing a suction catheter. 
     FIG. 8 depicts another embodiment of a cannula system for introduction of medical devices having two hemostatic valves. 
     FIG. 9 depicts an embodiment of an occlusion catheter for isolating blood flow within a vessel. 
     FIG. 10 depicts the cannula system of FIG. 8 having the devices of FIG.  6 A and FIG. 9 deployed in the aorta through the access ports. 
     FIG. 10A depicts the cannula system of FIG. 8 having the devices of FIG.  6 A and FIG. 9 attached to the proximal ends of the access ports. 
     FIG. 11A depicts another embodiment of the medical device carrying an occluder and a filter having the balloon occluder mounted in the center of the filter. 
     FIG. 11B depicts another embodiment of the medical device carrying an occluder and a filter having an occlusion catheter and the filter independently operable relative to each other. 
     FIG. 12A depicts another embodiment of the medical device carrying an occluder and a filter, where both the occluder and the filter are mounted on a catheter. 
     FIG. 12B depicts the device of FIG. 12A deployed in the aorta with expanded balloon occluder. 
     FIG. 12C depicts the device of FIG. 12A deployed in the aorta with deflated balloon occluder. 
     FIG. 12D depicts the filter in the device of FIG. 12A, the filter in a compressed state. 
     FIG. 12E depicts the filter of FIG. 12D in an expanded state. 
     FIG. 13 depicts a multi-port introducer having two lumens. 
     FIG. 14A depicts a vessel introducer. 
     FIG. 14B depicts a lateral view of the introducer of FIG.  14 A. 
     FIG. 14C depicts a cross-sectional view of the introducer through section line C—C of the introducer depicted in FIG.  14 B. 
     FIG. 15A depicts a lateral view of the tubular member shown in FIG.  14 B. 
     FIG. 15B depicts a proximal view of the tubular member of FIG.  15 A. 
     FIG. 15C depicts a distal view of the tubular member of FIG.  15 A. 
     FIG. 15D depicts a cross-sectional view of the tubular member through section line D—D of the tubular member depicted in FIG.  15 A. 
     FIG. 16A depicts a lateral view of the obturator shown in FIG.  14 B. 
     FIG. 16B depicts another lateral view of a proximal region of the obturator of FIG.  16 A. 
     FIG. 16C depicts a cross-sectional view of a proximal region of the obturator through section line C—C of the obturator depicted in FIG.  16 A. 
     FIG. 16D depicts a distal view of the obturator shown in FIG.  16 A. 
     FIG. 17A depicts another embodiment of the tubular member of the vessel introducer. 
     FIG. 17B depicts another embodiment of the obturator of the vessel introducer. 
     FIG. 17C depicts the vessel introducer of FIG.  17 A and obturator of FIG. 17B inserted in the aorta. 
     FIG. 17D depicts the tubular member of FIG. 17A inserted in the aorta. 
     FIG. 17E depicts the filter of FIG. 6A inserted in the tubular member of FIG.  17 D. 
     FIG. 18 depicts another embodiment of the cannula system having a side-port on the cannula. 
    
    
     DETAILED DESCRIPTION 
     An embodiment of the cannula system for introducing medical devices into a patient&#39;s vessel or cardiac tissue is shown in FIGS. 1 and 2. In this embodiment, cannula  1  comprises elongate tubular member  2  having proximal end  3 , distal end  4 , and lumen  6 . The lumen communicates with proximal end  3  and distal port  5  at the distal end. When used as an arterial cannula, the distal port is adapted to deliver oxygenated blood. When used as a venous return cannula, the distal port is adapted to receive deoxygenated blood. In FIG. 1, distal port  5  is shown angled relative to proximal end  3  for directing blood flow downstream the aorta more effectively, thereby reducing turbulent flow. The proximal end is adapted for attachment to a bypass-oxygenator machine. The wall of tubular member  2  further includes one or more helical wires  7  running the entire length of lumen  6  to prevent kinking while bending the cannula. First access port  10  is mounted adjacent to distal end  4  of the cannula, and second access port  20  is mounted adjacent to the first port. Each of the first and second access ports has, respectively, proximal end  11  and  21 , distal end  12  and  22 , and lumen  13  and  23 . The proximal ends of the first and second access ports are adapted to receive therapeutic and/or diagnostic medical devices. It will be understood that, in use, the first and second access ports will be occupied by an obturator (e.g., as depicted in FIG. 16A) to prevent blood leakage prior to insertion of a medical device. Lumen  13  of the first access port further includes hemostatic valve  15 . Suture flange  25  is included in distal end  4  of the cannula for suture placement. 
     Proximal end  11  of the first port, proximal end  21  of the second port, and proximal end  3  of the cannula are arranged substantially in a line as in FIG. 3A which shows a frontal cross-sectional view of the cannula system of FIG.  1 . Alternatively, proximal end  11  of the first port, proximal end  21  of the second port, and proximal end  3  of the cannula are arranged at the vertices of a triangle as shown in FIG.  3 B. The access ports may be integral with the blood cannula. 
     FIGS. 6A and 6B depict a blood filter which can be inserted into and removed from the proximal end of an access port. The blood filter has outer elongate tube  31  and inner elongate tube  32  which is slidably engaged within the outer tube. Outer tube  31  has distal end  33  and proximal end  34  which include proximal housing  35  connected proximally to collar handle  36 . 
     The cannula system of FIG. 1 can be used to cannulate, for example, a patient&#39;s aorta or right atrium for establishing cardiopulmonary bypass and to provide introduction of other medical devices in cardiovascular surgeries. In FIG. 4, the cannula system of FIG. 1 is shown inserted into a patient&#39;s ascending aorta. Distal end  4  of cannula  1  is first inserted through an incision on ascending aorta  100 . Sutures can be placed on suture flange  25  to secure the cannula system onto the aorta. Medical devices can then be inserted into proximal ends  11  and  21  of ports  10  and  20 , respectively, to carry out the following diagnostic or therapeutic functions: perfusion, drug delivery, fluid infusion, vessel occlusion, filtration, aspiration, venting, fluid diversion, venous return in cardiopulmonary bypass, atherectomy, fluid pumping, suturing, staples, collagen or fibrin delivery, pacing leads, angiographic catheters, angioplasty catheters, valvuloplasty catheters, electrode catheters, internal vessel segregating or isolating dams, endoscopic cameras, pressure monitors, shunts, stents, grafts, stent/grafts, vessel surfacing modalities, radioactive isotopes, and graft delivery. 
     In FIG. 5, medical device  60  is shown attached to proximal end  11  of first port  10 . The medical device is adapted for deployment of medical therapies, such as a blood filter, which is illustrated in FIGS. 6A and 6B. According to FIG. 6A, the device has housing  30 , elongate tube  31  partially included in the housing, and elongate member  41 . The tube has proximal end  32 , distal end  33 , and lumen  38 . Distal region  42  of the elongate member, having blood filter  50  mounted distally, is slidably inserted within lumen  38  of the tube. The filter frame can be made of nitinol or other biocompatible material, such as stainless steel or plastic. The construction of the filter is described in more details in Barbut et al., U.S. Pat. No. 5,769,816, incorporated herein by reference. Porous plug  44 , which is permeable to air but not to blood or fluid, is mounted on proximal end  43  of the elongate member. Collar handle  34  is attached to the proximal end of housing  30  and tube  31 . Distal end  35  of the housing includes releasable engaging mechanism  36 , such as a latch or fastener, and gripping members  37  for operating mechanism  36 . The gripping members are mounted on opposite sides of the housing and can be constructed to have 1,2,3,4, or any other number on each side. 
     In use, the device is attached to a cannula system as shown in FIG. 5 by depressing members  37  on opposite sides of the housing so that mechanism  36  engages the proximal end of an access port. Elongate member  41  is advanced distally by exerting force on proximal end  43  while holding collar handle  34 . As a result, filter  50  is advanced distal of opening  33  of tube  31  to be deployed in the aorta. 
     Other embodiments of device  60  depicted in FIG. 5 can be used to deploy other medical therapies as shown in FIGS. 7A,  7 B,  7 C,  7 D, and  7 E. Filter  50  is shown carried within elongate tube  31  of the device in FIG.  7 A. When deployed in a vessel, the filter entraps embolic materials, such as calcium, myocardial tissue debris, or atheromatous plagues which are generated upstream in the vessel. In FIG. 7B, windsock  51  is shown carried within tube  31 . The design and use of a windsock is described in McKenzie et al., U.S. application Ser. No. 08/996,532, filed Dec. 23, 1997, incorporated herein by reference in its entirety. When the windsock is deployed in a vessel, blood flow downstream from the windsock is reduced. In FIG. 7C, aspiration catheter  52  is shown carried within tube  31 . The aspirator can be used to remove vascular debris, for example, during coronary angioplasty or stent placement. In FIG. 7D, needle  53  is shown carried within tube  31  to provide for delivery of pharmaceutical agents, e.g., administering cardioplegia for cardiac arrest. In FIG. 7E, suction catheter  54  is carried within tube  31  to remove blood, fluid, air, or tissue debris during surgeries. 
     FIG. 8 depicts another embodiment of the cannula system having two ports and two hemostatic valves. The cannula system of FIG. 8 is similar to that of FIG. 1 except that each of first access port  10  and second access port  20  communicates, respectively, with lumen  13  and  23  which include hemostatic valves  15 . A distal region of port  20  also includes ridges  24  which minimize slippage of the cannula system from a surgeon&#39;s hand. 
     FIG. 9 depicts an embodiment of an occlusion catheter for providing isolation of blood flow within a vessel. Catheter  60  has lumen  61  communicating with proximal port  62  and distal port  63  at distal end  64 . Occluder  65 , which may comprise an elastomeric balloon, is mounted on distal end  64  proximal to port  63 . The occluder communicates with inflation lumen  66  and inflation port  67 . Lumen  61  and proximal end  62  of the catheter are adapted for delivering fluid or a pharmaceutical agent, e.g., cardioplegia solution. Lumen  61  of the catheter also communicates with port  71  and port  72  at proximal region  68  of the catheter for infusing fluid or a pharmaceutical agent. 
     In FIGS. 10A and 10, the device carrying a blood filter of FIG.  6 A and the occlusion catheter of FIG. 9 are shown attached to the cannula system of FIG.  8 . In FIG. 10A, occlusion catheter  60  is inserted through proximal end  21  and the lumen of access port  20 . The distal end of the blood filter device is inserted through proximal end  11  and the lumen of access port  10 . The releasable engaging mechanism mounted on distal end  35  of housing  30  is operated to lock the filter device onto proximal end  11  of the access port, thereby securing the device during deployment of the filter. 
     In using the cannula system of FIG. 10A, the distal end of the system is inserted through an incision on the vessel, e.g., ascending aorta  100 , as shown in FIG.  10 . The cannula system may be secured onto the aorta by placing sutures between suture flange  25  and the aortic wall. The proximal end  3  of cannula  1  is attached to a bypass-oxygenator machine. To establish cardiopulmonary bypass during cardiothoracic surgeries, for example, occlusion catheter  60  is advanced distally to deploy balloon occluder  65  in the aorta. Hemostatic valve  15  included in the lumen of the access port prevents blood loss through proximal end  21 . The occluder is expanded by infusing air or fluid through inflation port  67  and lumen  66  to completely occlude the aortic lumen, thereby isolating the coronary circulation from the peripheral vascular system. 
     Cardioplegia solution can be delivered through port  63  upstream the aorta to the heart to achieve cardiac arrest. Simultaneous with infusion of cardioplegia, oxygenated blood is delivered through lumen  6  and port  5  of the cannula downstream in the aorta to perfuse the body organs. Blood filter  50  may be deployed prior to or during cardiopulmonary bypass by advancing proximal end  43  distally. Any blood that enters the distal end of the filter device will flow proximally toward porous plug  44 , which allows air to escape but not blood. In this manner, the filter device is purged of gas and avoids introducing air emboli in the aorta. 
     After the surgeon has performed the cardiovascular procedures, cardiopulmonary bypass is discontinued by deflating balloon occluder  63  and stopping oxygenated blood infusion through cannula  1 . As the occluder is deflated, embolic materials upstream the occluder, including calcium, atheromatous plaque, myocardial tissue debris, and thrombi, are trapped by filter  50 . The filter is removed by retracting proximal end  43  of the device proximally, thereby removing vascular emboli. 
     FIGS. 11A and 11B depict other embodiments of medical devices carrying an occluder and blood filter for cardiopulmonary bypass. In FIG. 11A, the device carrying both balloon occluder  65  and filter  50  is inserted through proximal end  11  of access port  10 . Occluder  65  is mounted inside the filter. When deployed in aorta  100 , the occluder is expanded to occlude the aortic lumen during bypass and is deflated after cardiopulmonary bypass to allow embolic material upstream in the aorta to be captured in filter  50 . After the surgeon has performed the cardiovascular procedure, occluder  65  and filter  50  are removed as a unit. 
     In FIG. 11B, another embodiment of the device carrying both balloon occluder  65  and filter  50  is shown inserted through proximal end  11  of access port  10 . Filter  50  is deployed in aorta  100  by advancing filter shaft  55  distal to access port  10 . Expandable balloon occluder  65  is mounted proximal to port  63  on catheter  56 . Port  63  communicates with a lumen which is adapted for infusion of cardioplegia solution. The occluder and the filter are operated independent of each other. Other embodiments of the device carrying an occlusion member and a filter include the following: (1) having a dam covering the opening of the filter, (2) having two filters, one of which functions as an occluder, (3) having a balloon occluder mounted on the center of the filter shaft, (4) having a balloon surrounded by an inflatable seal as the occlusion member, (5) having a dam and an inflatable seal, and (6) having the occlusion member and filter constructed as a colander which can be operated to completely or partially occlude the aortic lumen. 
     FIGS. 12A,  12 B, and  12 C depict another embodiment of the device carrying an occlusion member and a blood filter. In FIG. 12A, elongate tube  70  is housed within lumen  34  of the medical device. The tube has lumen  71  which communicates with balloon occluder  65  at a distal end. Filter  50  is mounted at distal region  72  of the tube proximal to the occluder and is in a compressed state inside lumen  34 . The distal region includes bendable region  74 . Distal region  72  assumes a linear configuration relative to its proximal end when housed within the lumen of the device, and assumes a preformed angled configuration relative to its proximal end when protruding distal to port  33  of the device. 
     In use, the device is inserted through proximal end  11  of access port  10  included in the cannula system of FIG. 1, which is inserted in aorta  100 . As catheter  70  is advanced distally through port  33  of the device and access port  10 , the distal region of the catheter assumes its preformed angled configuration relative to its proximal end. The frame for filter  50 , which may be constructed of elastic material, e.g., plastic or nitinol, is expanded from its compressed state to contact the aortic wail. Balloon occluder  65  is expanded to occlude the aortic lumen by infusing air or fluid through lumen  71  of the catheter. Oxygenated blood can then be infused through lumen  6  and port  5  of cannula  1  downstream in the aorta to establish cardiopulmonary bypass. 
     After the surgeon has performed the procedure and cardiac arrest is reversed, balloon occluder  65  is deflated as depicted in FIG.  12 C. Embolic material generated during the procedure is captured by filter  50 , thereby preventing distal embolization to peripheral organs causing tissue ischemia or death. The entrapped emboli are removed from the aorta by retracting catheter  70  proximally and compressing filter  50  within the lumen of the device. One embodiment of filter  50  in a compressed state is shown in FIG.  12 D. The filter device comprises a compliant expandable framework having proximal opening  75  and distal opening  76 . The framework is mounted on the distal end of a catheter at the proximal opening. The framework includes struts  77 , which are made of flexible materials, e.g., plastic or shape memory materials, such as nitinol, and blood filter  50 . FIG. 12E depicts the filter of FIG. 12D in an expanded state when the compliant framework is not under any external compressing force. 
     FIG. 13 depicts one embodiment of a multi-port introducer for introducing medical devices into a vessel. The introducer comprises first tubular member  80  and second tubular member  81  mounted adjacent the first member. The first tubular member has lumen  13  communicating with proximal end  11  and distal port  10 . The second member has lumen  23  communicating with proximal end  21  and distal port  20 . In some embodiments, lumens  13  and  23  of the respective first and second tubular member may merge and communicate at their distal ends. Hemostatic valves  15  are disposed within the lumen of each tubular member to prevent blood escaping from the proximal ends after insertion in a vessel. Other embodiments of the multi-port introducer may include 3, 4, 5, or more lumens and ports for introduction of medical devices, including a blood filter, an occlusion catheter, an aspirator, an angioplasty catheter, a valvuoplasty catheter, an electrode catheter, internal vessel segregating or isolating dams, an endoscopic camera, a pressure monitor, a stent, a graft, a shunt, a perfusion catheter, and endoscopic devices. 
     FIGS. 14A,  14 B, and  14 C depict one embodiment of a vessel introducer comprising tubular member  85  and obturator  90 . The tubular member has lumen  86  communicating with proximal end  87  and distal end  88 . Obturator  90  which includes proximal end  91  is removably inserted in lumen  86  of the tubular member as depicted in FIG.  14 C. 
     FIGS. 15A,  15 B,  15 C, and  15 D depict further details of tubular member  85  of the vessel introducer. Lumen  86  communicates with port  89  at distal end  88 . When the obturator is inserted in the tubular member, a distal end of the obturator protrudes distal to port  89 . FIGS. 15B and 15C provide, respectively, proximal and distal views of the tubular member shown in FIG.  15 A. 
     FIG. 16A depicts a lateral view of the obturator of FIG.  14 B. Proximal end  91 , connected to body  92  of the obturator, includes releasable engaging mechanism  36 , depicted as a latch in FIG.  16 B. Gripping members  37  are mounted proximal to the engaging mechanism  36  on opposite sides of the obturator. The engaging mechanism is operated by depressing the gripping members radially inward for insertion into the tubular introducer. FIG. 16C depicts a cross-sectional view of the obturator through section line C—C of the obturator in FIG.  16 A. FIG. 16D depicts a distal view of the obturator of FIG.  16 A. In certain embodiments the obturator is equipped with porous plug  38  which communicates with hollow channel  93 . In this embodiment gas is vented from the port of the access cannula through hollow channel  93  and plug  38 , thereby purging the port of gas and making the port ready for introduction of therapeutic instruments. 
     FIG. 17A depicts another embodiment of the tubular member having suture flange  25 . Lumen  86 , communicating with port  89  and proximal end  87 , includes hemostatic valve  15 . FIG. 17B depicts another embodiment of the obturator having an elongate body  92  connected to distal end  93  and proximal end  91 . The obturator has releasable engaging mechanism  36  similar to that of FIG.  16 B. 
     In use, the obturator is inserted through proximal end  87  and lumen  86  of the tubular member, where distal end  93  of the obturator protrudes from distal port  89  of the tubular member. The assembled vessel introducer is inserted through an incision on aorta  100  as depicted in FIG.  17 C. Sutures can be placed between suture flange  25  and the aortic wall to stabilize the introducer. The obturator is then removed from the tubular member, leaving proximal end  87 , lumen  86 , and port  89  ready to receive a medical device as shown in FIG.  17 D. In FIG. 17E, the device of FIG. 6A carrying blood filter  50  is shown inserted through the proximal end and lumen of the tubular member, where the filter protrudes distal of port  89  to deploy in the aortic lumen. The filter can be temporarily removed by pulling proximal end  43  of the device proximally when surgical space within the aortic lumen is limited, e.g., during aortic valve replacement surgery. The filter can then be redeployed to entrap embolic materials generated during the procedure. 
     FIG. 18 depicts another embodiment of the cannula system inserted in aorta  100 . The system includes access port  10  mounted adjacent to cannula  1 . The cannula comprises elongate member  2  having lumen  6  and lumen  106 . Lumen  6  communicates with distal port  5 . Lumen  106  communicates proximally with proximal end  101  and distally either with side-port  105  or lumen  6 . Lumen  106  and port  105  are adapted for deployment of medical therapies, such as the blood filter of FIGS. 6A and 6B, shown here inserted through proximal end  101 . Catheter  60 , having expandable occlusion balloon  65  mounted on the distal end, is inserted through proximal end  11  and lumen  13  of access port  10 . 
     In using the cannula system for cardiopulmonary bypass, cannula  1  and access port  10  are inserted into ascending aorta  100 . Balloon  65  is inflated to occlude the aortic lumen. Port  63 , which communicates with lumen  61  of catheter  60 , can be used to deliver cardioplegia solution upstream to the coronary arteries to arrest the heart. Oxygenated blood can be delivered to the aorta downstream to perfuse the peripheral organs through lumen  6  and port  5  of cannula  1 . The blood filter can be inserted through proximal end  101 , lumen  106 , and port  105  to deploy in the aorta to capture embolic material generated during cardiac procedures. In this way, the cannula system allows delivery of multiple medical therapies to the aorta through one incision, thereby minimizing trauma to the aortic wall. 
     The length of the cannula will generally be between 10 and 60 centimeters, more preferably approximately 20 to 35 centimeters, more preferably approximately 30 centimeters. The inner diameter of the cannula will generally be between 0.5 and 1.5 centimeters, preferably approximately 1.0 centimeters. The length of the modular access port will generally be between 2.0 and 10.0 centimeters, preferably approximately 6.0 centimeters. The inner diameter of the lumen of the access port will generally be between 0.2 and 1.2 centimeters, preferably approximately 0.6 centimeters. The length of the vessel introducer will generally be between 6 and 14 centimeters, preferably approximately 9 centimeters. The inner diameter of the lumen of vessel introducer will generally be between 0.2 and 1.2 centimeters, preferably approximately 0.5 centimeters. The foregoing ranges are set forth solely for the purpose of illustrating typical device dimensions. The actual dimensions of a device constructed according to the principles of the present invention may obviously vary outside of the listed ranges without departing from those basic principles. 
     Although the foregoing invention has, for purposes of clarity of understanding, been described in some detail by way of illustration and example, it will be obvious that certain changes and modifications may be practiced which will still fall within the scope of the appended claim.