Abstract:
A bifurcated catheter having a branched distal shaft section and one or more porous or nonporous balloons, and combinations thereof, which is configured for delivery of an agent to a patient&#39;s bifurcated body lumen. Another aspect of the invention is directed to a method of delivering an agent to a patient&#39;s body lumen which facilitates maximizing the efficiency of drug uptake into the tissue at the desired site within the patient&#39;s body lumen.

Description:
FIELD  
       [0001]     The present invention relates generally to medical devices, and more particularly to a catheter for delivery of an agent to the coronary or peripheral vasculature.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the treatment of diseased vasculature, therapeutic agents have commonly been administered, typically as part of other interventional therapies such as angioplasty or stent delivery. Local, as opposed to systemic delivery is a preferred method of treatment in that smaller total levels of medication are administered in comparison to systemic dosages, yet are concentrated at a specific site. As a result, local delivery produces fewer side effects and achieves more effective results.  
         [0003]     A variety of methods and devices have been proposed for percutaneous drug delivery to a diseased region of the vasculature. For example, catheters having porous balloons can be used to deliver a therapeutic agent infused into the inflatable interior of the porous balloon and through the porous wall of the balloon. Alternatively, prostheses such as stents or other implantable devices provide for local drug delivery when coated or otherwise made to include a therapeutic agent which elutes from the implanted prosthesis. Another suggested method involves the use of one or more catheters having multiple balloons. The diseased region is isolated by inflating the balloons on either side of the diseased region, and the therapeutic agent is infused through a lumen of the catheter shaft and into the isolated diseased region from a delivery port on the catheter shaft located between the balloons.  
         [0004]     One difficulty has been maximizing the amount of drug taken-up and retained at the diseased site, while minimizing the wash out of large amounts of drug downstream of the treatment site. Drug wash out reduces the efficiency of local intravascular drug delivery, in addition to causing potentially harmful systemic exposure to the drug. Therefore, it would be a significant advance to provide an improved device and method for providing therapy to a desired location within a patient&#39;s body lumen.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention is directed to a bifurcated catheter having a branched distal shaft section and one or more porous or nonporous balloons, and combinations thereof, which is configured for delivery of an agent to a patient&#39;s bifurcated body lumen. Another aspect of the invention is directed to a method of delivering an agent to a patient&#39;s body lumen which facilitates maximizing the efficiency of drug uptake into the tissue at the desired site within the patient&#39;s body lumen.  
         [0006]     In a first embodiment, a multi-balloon bifurcated catheter of the invention generally comprises an elongated shaft having an inflation lumen, a guidewire lumen, a proximal shaft section with a proximal section of the inflation lumen therein, a branched distal shaft section having a first branch with a first distal section of the inflation lumen and a second branch with a second distal section of the inflation lumen, the first and second distal sections of the inflation lumen being in fluid communication with the proximal section of the inflation lumen, and having an agent delivery lumen extending in the proximal shaft section to one or more distal ports which is/are preferably located adjacent to a proximal end(s) of the branched distal shaft section. A proximal balloon is on the proximal shaft section located proximal to the distal port of the agent delivery lumen, a first distal balloon is on the first branch, and a second distal balloon is on the second branch. The proximal balloon and first and second distal balloons each have an interior in fluid communication with the shaft inflation lumen. In one embodiment, the balloons are in fluid communication with the same inflation lumen and are therefore configured for simultaneous inflation. In alternative embodiments, the shaft has multiple (two or more), separate inflation lumens allowing the balloons to be inflated independently of one another.  
         [0007]     The first and second distal balloons are solid-walled occlusion balloons with fluid tight interiors configured to inflate into contact with the body lumen wall, so that agent introduced into the body lumen via the agent delivery lumen of the catheter is prevented from flowing across the inflated first and second distal balloons. In a presently preferred embodiment, the proximal balloon is also a solid-walled occlusion balloon. With the proximal occlusion balloon and the first and second distal occlusion balloons inflated at a bifurcation of the patient&#39;s body lumen, agent delivered out the distal port of the agent delivery lumen into the bifurcated body lumen is confined within both the main and side branch of the bifurcated body lumen, between the inflated balloons. The first and second distal balloons are sealingly secured to the separate branches of the distal shaft, at locations spaced a sufficient distance distally apart from the proximal balloon such that the first and second distal balloons can be inflated without contacting oneanother and without contacting the bifurcation apex or crux (i.e., at the edge of the ostium defining the opening into the side branch vessel from the main branch vessel of the body lumen). Thus, in a method of using the multi-balloon bifurcated catheter, the first distal balloon is inflated in a side branch of the bifurcation and the second distal balloon is inflated in a main branch of the bifurcation with the inflated balloons typically longitudinally displaced from the crux of the bifurcation of the body lumen, so that diseased tissue at the crux of the bifurcation is exposed to a therapeutic agent contained in both the main and side branches of the body lumen, to thereby treat the diseased tissue. In contrast, methods of dilating a lesion or implanting a prosthesis at a bifurcation as previously described, such as a “kissing balloon” technique, are typically configured to inflate one or more balloons against the crux of the bifurcation.  
         [0008]     In a presently preferred embodiment, the multi-balloon bifurcated catheter is a rapid-exchange catheter having a guidewire lumen which extends from a distal port at a distal end of the first branch of the catheter to a proximal port in the proximal shaft section. The rapid exchange guidewire lumen extends from the proximal port located proximal to the proximal balloon to the distal port located distal to one of the distal balloons. As a result, agent delivered to the treatment region isolated between the proximal balloon and the first and second distal balloons is prevented from washing out of the desired region through the rapid exchange guidewire lumen. In contrast, wash out of the agent can occur through the guidewire lumen in catheter systems as previously described having the guidewire lumen port located between a proximal balloon and one or more distal occlusion balloons.  
         [0009]     In an embodiment in which the agent delivery lumen distal port (providing access to within the catheter shaft) is the only shaft port which is located between the proximal balloon and the first and second distal balloons, the treatment region between the inflated balloons is fully isolated, except for agent delivery port. Consequently, agent flowing from the agent delivery port does not leave the treatment region by flowing into or through additional accessible lumen(s) of the catheter. As a result, wash out is minimized or prevented and tissue uptake of the agent is enhanced. Additionally, by minimizing the number of lumens in the catheter shaft, the catheter has an improved low profile and maximizes the size of the inflation and agent delivery lumens, for improved catheter performance (e.g., shorter procedure time, enhanced track/distal small vessel access, and the like).  
         [0010]     An alternative embodiment of the invention is directed to a porous balloon bifurcated catheter, generally comprising an elongated shaft having an inflation lumen, a guidewire lumen, a proximal shaft section, and a branched distal shaft section having a first branch and a second branch, and a first balloon portion on the first branch of the distal shaft section and a second balloon portion on the second branch of the distal shaft section, the balloon portions being porous and each having an interior in fluid communication with the inflation lumen, so that fluid agent from the inflation lumen inflates the porous balloon portions and exits the catheter through the porous balloon portions. The porous balloon portions are either the branched distal section of a single, forked balloon (e.g., a Y or V-shaped balloon), or two separate balloons mounted on a branched distal shaft section. In one embodiment, the catheter includes one or more occlusion balloons in addition to the porous balloon portions located distal or proximal thereto and configured to occlude the body lumen and thereby prevent or inhibit wash out of an agent delivered through the porous balloon(s).  
         [0011]     In a method of using the porous balloon bifurcated catheter, the first porous balloon portion is inflated in a side branch vessel of the bifurcation and the second porous balloon portion is inflated in a main branch vessel of the bifurcation with the inflated porous balloon portions typically at the crux of the bifurcation of the body lumen, so that diseased tissue at the crux is exposed to a therapeutic agent exiting the catheter though the porous balloon portions, to thereby treat the diseased tissue.  
         [0012]     In one embodiment, a balloon catheter of the invention is provided with a perfusion lumen, which extends, in part, in both the first and second branches of the distal shaft section, to provide for perfusion during the duration that the catheter balloon(s) are inflated in the body lumen. Thus, due to the branched nature of the catheter, the perfusion lumen has a branched distal section with first and second distal ports in fluid communication with a proximal port, in one embodiment.  
         [0013]     Another embodiment of the invention is directed to a method of delivering an agent to a patient&#39;s body lumen, generally comprising delivering agent through an agent delivery lumen of an infusion catheter into a region of the body lumen isolated between two or more occlusion balloons of the catheter, such that fluid (e.g., blood, saline, and the like) in the isolated treatment region is purged by being displaced by the agent into a purging lumen of the catheter. Thus, with the infusion catheter balloons inflated, the increasing pressure caused by the infusion of the agent into the treatment region of the body lumen forces the trapped blood therein to flow back through the purging lumen and exit the catheter at a proximal purging port. The method therefore effectively increases the local drug concentration by preventing or minimizing dilution of the drug within the body lumen.  
         [0014]     The purging method preferably involves the use of an infusion catheter having separate agent delivery and purging lumens extending from the proximal end of the catheter to a distal location between two or more occlusion balloons. As a result, the preferred method minimizes agent wash out within the body lumen, unlike methods as previously described in which the region is purged by infusing agent that displaces the blood distally past a partially inflated/noninflated distal occlusion balloon, and then isolated by fully inflating the distal occlusion balloon. In addition, in one embodiment the method includes purging any unpenetrated agent remaining in the treatment region prior to deflation of the balloons by infusing a displacing fluid (e.g., blood, saline, contrast, and the like) into the isolated treatment region of the body lumen, and thus effectively increases the drug delivery efficiency by minimizing systemic wash out.  
         [0015]     The purging method provides for purging the isolated treatment region of the body lumen without aspirating the region. As a result, the method of the invention does not expose the treatment region to suction force, and therefore avoids the potential disadvantageous affects caused thereby. For example, the vacuum force of an aspirator can potentially flex or otherwise act upon the diseased vessel wall during aspiration, which is particularly to be avoided in certain disease states such as vulnerable plaque where destabilization of the plaque cap can result its rupture.  
         [0016]     A variety of suitable agents can be delivered using the catheter(s) and method(s) of the invention, including therapeutic and diagnostic agents. The agents are typically intended for treatment and/or diagnosis of coronary, neurovascular, and/or other vascular disease, and may be useful as a primary treatment of the diseased vessel, or alternatively, as a secondary treatment in conjunction with other interventional therapies such as angioplasty or stent delivery. A variety of suitable therapeutic agents can be used including but not limited to thrombolytic drugs, anti-inflammatory drugs, anti-proliferative drugs, drugs restoring and/or preserving endothelial function, and the like. A variety of bioactive agents can be used including but not limited to peptides, proteins, oligonucleotides, cells, and the like. A variety of diagnostic agents that can be used according to the present invention. According to the present invention, agents described herein may be provided in a variety of suitable formulations and carriers including liposomes, polymerosomes, nanoparticles, microparticles, lipid/polymer micelles, complexes of agents with lipid and/or polymer, and the like.  
         [0017]     A balloon catheter of the invention can be used as part of a variety of interventional procedures, including to deliver conventional or bifurcated stents (drug eluting or bare metal), pre or post dilatation, especially at the bifurcation, and the like.  
         [0018]     The invention facilitates delivery of agents to complex regions of the body, providing for therapy thereof. A catheter of invention enhances tissue uptake and retention of drugs to enable treatment of vascular regions, including bifurcations, and preferably minimizes agent wash out. These and other advantages of the invention will become more apparent from the following detailed description of the invention and accompanying exemplary drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is an elevational view, partially in section, of a multi-balloon bifurcated catheter embodying features of the invention.  
         [0020]      FIGS. 2-4  are transverse cross sectional views of the catheter of  FIG. 1 , taken along lines  2 - 2 ,  3 - 3 , and  4 - 4 , respectively.  
         [0021]      FIG. 5  illustrates the catheter of  FIG. 1  with the balloons inflated within a bifurcated body lumen.  
         [0022]      FIGS. 5A and 5B  are transverse cross-sectional views of the catheter of  FIG. 5 , taken along line  5 A- 5 A and  5 B- 5 B respectively.  
         [0023]      FIG. 6  illustrates an alternative embodiment of a multi-balloon bifurcated catheter embodying features of the invention, having a purging lumen.  
         [0024]      FIGS. 6A and 6B  are a transverse cross sectional views of the catheter of  FIG. 6 , taken along lines  6 A- 6 A and  6 B- 6 B, respectively.  
         [0025]      FIG. 7  is an elevational view, partially in section, of a porous balloon bifurcated catheter embodying features of the invention.  
         [0026]      FIGS. 8-10  are transverse cross sectional views of the catheter of  FIG. 7 , taken along lines  8 - 8 ,  9 - 9 , and  10 - 10 , respectively.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]      FIG. 1  illustrates an elevational view, partially in section, of a multi-balloon bifurcated catheter  10 , embodying features of the invention, generally comprising an elongated catheter shaft  11  having a proximal end, a distal end, a proximal shaft section  12 , a branched distal shaft section  13  with a first branch  14  and a second branch  15 , an inflation lumen  16 , a guidewire lumen  17 , and an agent delivery lumen  18 , and a proximal balloon  20  on the proximal shaft section, a first distal balloon  21  on the first branch, and a second distal balloon  22  on the second branch.  FIG. 1  illustrates the balloons in a noninflated configuration, although the space between the inner surface of the noninflated balloons and the underlying section of the shaft may be somewhat exaggerated in  FIG. 1  for ease of illustration.  
         [0028]     In the embodiment of  FIG. 1 , the proximal shaft section  12  comprises a proximal outer tubular member  23  with a proximal section of the inflation lumen  16  therein, and the first branch  14  of the bifurcated distal shaft section  13  is formed in part by a first distal outer tubular member  24 , and the second branch  15  is formed in part by a second distal outer tubular member  25 . In the illustrated embodiment, the transition from the proximal shaft section to the distal shaft section comprises an intermediate outer tubular member  26  having a proximal end bonded to the distal end of the proximal tubular member  23 , and a distal end bonded to the first and second distal outer tubular members  24 ,  25 . However, a variety of suitable configurations can be used to transition from the proximal shaft section to the bifurcated distal shaft section, including alternative embodiments (not shown) in which the distal end of the proximal tubular member  23  is secured to the proximal end of the branched distal section, such that an intermediate section of the shaft is formed as an integral, one piece unit of a proximal tubular member.  
         [0029]     A joining wire lumen  27  (see  FIG. 2 ), with a joining wire  28  slidably disposed therein, extends within the proximal section and the first branch  14  of the distal section to a distal end of the first branch. In the illustrated embodiment, the guidewire lumen  17 , with guidewire  35  slidably disposed therein, is configured for rapid exchange and extends from a guidewire distal port at the distal end of the second branch  15  to a guidewire proximal port  34  in the proximal shaft section (through a side wall of the intermediate outer tubular member  26 ). A proximal adapter  31  is secured to the proximal end of the catheter shaft, which provides access to joining wire lumen  27 , and which has a first arm  32  configured for connecting to a source of inflation fluid for inflating the balloons, and a second arm  33  configured for connecting to a source of agent.  
         [0030]     In the illustrated embodiment, the first branch  14  comprises a first inner tubular member  36  defining the joining wire lumen  27  and first outer tubular member  24  defining, together with the outer surface of the inner tubular member  36  therein, the portion of the inflation lumen  16  in the annular space between the inner tubular member  36  and the outer tubular member  24  (see  FIG. 4 ). The second branch  15  similarly comprises a second inner tubular member  37  defining the guidewire lumen  17  and outer tubular member  25  defining, together with the outer surface of the inner tubular member  37  therein, the portion of the inflation lumen  16  in the annular space therebetween.  
         [0031]     The first and second branches  14 ,  15  of the branched distal shaft section  13  are preferably configured for releasably coupling together for introduction and advancement within a patient&#39;s body lumen. For example, in the embodiment of  FIG. 1 , the branches are in a coupled configuration with the distal end of the joining wire  28  slidably disposed in a coupler on the distal end of the second branch, and are uncoupled by sliding the joining wire  28  proximally out of the coupler. Typically, a connector (not shown) is provided on the proximal end of the adapter  31 , facilitating proximally withdrawing the joining wire  28 . Details regarding bifurcated catheter construction and use, and the coupling and uncoupling of the branches of a bifurcated catheter branched distal shaft section can be found in U.S. Pat. No. 6,017,324, incorporated by reference herein in its entirety.  FIG. 1  illustrates the bifurcated catheter  10  in the coupled configuration.  
         [0032]     The agent delivery lumen  18  is defined by an inner surface of a tubular member  40  extending within, and at least in part surrounded by, the inflation lumen  16  in the proximal shaft section  12 . The agent delivery lumen  18  extends to a distal port  41  which is located adjacent to a proximal end of the branched distal shaft section  13 , to thereby provide for delivery of an agent from the lumen  18 , through port  41  and into a patient&#39;s body lumen (i.e., the distal agent port  41  opens to outside of the catheter). In the illustrated embodiment, the agent delivery lumen  18  extends to a single distal port (i.e., port  41 ). However, in alternative embodiments (not shown), the agent delivery lumen has multiple distal ports. For example, in one embodiment, the agent delivery lumen  18  is in fluid communication with multiple distal ports around the circumference and/or along a length (through the sidewall) of the distal end section of the tubular member  40 , either in addition to the distal end port  41  in the distal end of tubular member  40 , or instead of the distal end port  41  (such that the distal end port  41  of the tubular member  40  is optionally plugged). Although not illustrated, in one embodiment, the catheter  10  has one or more additional agent delivery lumens in addition to lumen  18 , for example for the delivery of multiple component formulations.  
         [0033]     A distal portion of the tubular member  40  extends in side-by-side relation with a proximal end of the first and second distal outer tubular members  24 ,  25 . In one embodiment, an outer surface of the tubular member  40  is in contact with and typically bonded to an outer surface of the tubular members  24 ,  25  (see  FIG. 5B ), although they may alternatively be radially spaced apart. The tubular member  40  and the first inner tubular member  36  are preferably eccentric, i.e., not coaxial, relative the inflation lumen in the proximal shaft section proximal to the branched distal section, see  FIGS. 2 and 3 , illustrating transverse cross sections of the catheter of  FIG. 1 , taken along lines  2 - 2  and  3 - 3 , respectively. However, one or both of the tubular members  36  and  40  can be coaxial relative to the inflation lumen  16  in alternative embodiments (not shown).  
         [0034]     In the illustrated embodiment, a proximal portion of the proximal shaft section, located proximally adjacent to the guidewire proximal port  34 , has three lumens therein, namely, the inflation lumen  16 , the agent delivery lumen  18 , and the joining wire lumen  27 . By limiting the number of lumens in the proximal portion of the proximal shaft section to, in one preferred embodiment, no more than three lumens, the catheter has a low profile with improved deliverability.  
         [0035]     The first distal balloon  21  has a proximal end sealingly secured to a distal end of the first distal outer tubular member  24  and a distal end sealingly secured to a distal end of the first inner tubular member  36 , and second distal balloon  22  has a proximal end sealingly secured to a distal end of the second distal outer tubular member  25  and a distal end sealingly secured to a distal end of the second inner tubular member  37 , so that interiors of balloon  21  and balloon  22  are in fluid communication with the inflation lumen  16 . In the illustrated embodiment, a port  39  in the side wall of intermediate tubular member  26  places the interior of proximal balloon  20  in fluid communication with the inflation lumen  16 . Thus, the balloons  20 ,  21 ,  22  are in fluid communication with a common inflation lumen  16  for simultaneous inflation in the illustrated embodiment. However, in an alternative embodiment (not shown), the shaft has separate multiple inflation lumens providing for independent inflation of one or more of the balloons.  
         [0036]     In a presently preferred embodiment, balloons  20 ,  21 ,  22  are solid walled occlusion balloons with fluid tight interiors, so that inflating the balloons occludes the body lumen. The occlusion balloons  20 ,  21 ,  22  can be formed of a variety of suitable materials commonly used to form catheter balloons, and are typically formed of elastomers such as Latex to provide high compliant balloons or non elastomers such as Nylon/Pebax to provide low compliant balloons which inflate into contact with the vessel wall to occlude the body lumen.  
         [0037]      FIG. 5  illustrates the balloon catheter  10  of  FIG. 1  with the balloons inflated in a patient&#39;s bifurcated body lumen - 50 . In  FIG. 5 , the first branch  14  of the catheter has been uncoupled from the second branch  15  and positioned within a side branch vessel  51  of the bifurcation. With the first distal balloon  21  inflated in the side branch vessel  51 , and the second distal balloon  22  and the proximal balloon  20  inflated in the main branch vessel  52  of the bifurcation, the balloons occlude the body lumen  50  and isolate a region of the body lumen therebetween. Although not illustrated, in one embodiment, the catheter  10  includes one or more perfusion lumens extending from proximal of balloon  20  to distal of at least one and typically both distal balloons  21 ,  22 , to prevent ischemia during the duration that the inflated balloons are occluding the body lumen.  
         [0038]     The isolated region includes part of the side branch vessel  51  and main branch vessel  52 , so that agent delivered through the agent delivery lumen  18  and out the distal port  41  to the body lumen  50  at the bifurcation is contained within both the main and side branch vessels  51 ,  52 . As a result, the crux  53  of the bifurcation is exposed to the delivered agent. For example, in the illustrated embodiment, the crux  53  of the bifurcation is diseased, so that the balloons  20 ,  21 ,  22  are positioned proximal and distal to the crux  53  of the bifurcation such that they do not cover up all or part of the diseased tissue at the crux  53 . Thus, the first and second distal balloons  21 ,  22  are preferably spaced distally a sufficient distance from the proximal end of the branched distal shaft section  13  such that the first and second distal balloons  21 ,  22  inflate without contacting one another and without contacting the crux  53  of the bifurcation. A method of the invention thereby exposes the crux  53  of the bifurcation to a delivered agent, without covering up or otherwise restricting the agent from accessing the tissue at the crux  53 . After a sufficient treatment duration (e.g., typically about 0.1 to about 30 minutes, more typically about 1 to 10 minutes), the balloons are deflated and the catheter repositioned within or removed from the body lumen.  
         [0039]     In the embodiment of  FIG. 1 , the distal port  41  of the agent delivery lumen  18  is the only shaft port (i.e., providing access from inside to outside of the catheter) located between the proximal balloon  20  and the first and second distal balloons  21 ,  22 .  FIG. 6  illustrates the distal end section of an alternative embodiment, in which a purging lumen  60  extends from the proximal end of the catheter to a distal port  61  located adjacent to the proximal end of the branched distal shaft section  13 . The catheter of  FIG. 6  is otherwise similar to the catheter of  FIG. 1 , with corresponding elements having the same reference numerals.  
         [0040]     In a method of performing a medical procedure using a catheter having a distal port  61  of a purging lumen  60  adjacent to a distal port  41  of an agent delivery lumen  18 , with the balloons inflated to isolate a treatment region therebetween, agent flows from the distal port  41  into the isolated treatment region. The purging lumen distal port  61  is preferably the only other shaft port located between the balloons, so that any fluid such as blood, saline, or contrast within the isolated treatment region is displaced by the agent and back-flows through the port  61  and out the catheter at the proximal end of the purging lumen  60 . Although not illustrated, another proximal port is typically provided at the proximal adapter for collecting the fluid from the purging lumen  60 . The fluid exiting from the proximal end of the purging lumen  60  will transition from being substantially fluid from the body lumen (e.g., blood, saline, and the like) to being substantially agent (i.e., substantially the solution/dispersion which contains the agent). At that point, the agent has displaced substantially all the fluid initially trapped between the catheter balloons, and the isolated region in now full of concentrated agent (i.e., agent which is not significantly diluted by the other fluid in the body lumen). In this way, the purging lumen allows for displacing of fluid from within the isolated treatment region without subjecting the region to the suctioning/vacuum force of an aspirator. After a sufficient treatment duration, the agent remaining within the isolated treatment region, which has not penetrated/adhered to the arterial wall tissue, can similarly be removed by flowing another fluid such as saline or contrast from the agent delivery lumen (or the purging lumen), so that the remaining agent is displaced and caused to back-flow through the purging lumen (or the agent delivery lumen). Flushing the remaining agent from the treatment region at the end of the treatment prevents the agent from flowing out of the treatment region after the balloons are deflated, and thus minimizes systemic wash out.  
         [0041]     The distal ports  41 ,  61  are typically longitudinally staggered, with the purging lumen distal port  61  typically being longitudinally spaced from the agent delivery lumen distal port  41  by about  2  mm to about  5  cm. Although illustrated with the purging lumen distal port  61  as the more distal port, the agent delivery distal port  41  can alternatively be distal thereto in alternative embodiments (not shown). The staggered distal ports  41 ,  61  preferably prevent or minimize clogging of the lumens  40 ,  60  caused by biological or other clotting matter during agent infusion or flushing. For example, if both ports are very close to each other, one large clot or particulate could block both ports. Also a shear force could occur between in-flow and out-flow at the ports that could impact the flow rate of agent delivery or purging process.  
         [0042]     Although discussed in terms of the embodiment of  FIG. 6  having a proximal balloon proximal to first and second distal balloons on a branched distal section of the catheter shaft, it should be understood that a variety of suitable infusion catheters can be used for the purging method of the invention. For example, in one embodiment, an infusion catheter (not shown) has two balloons (i.e., a proximal and a distal balloon) which alone are sufficient for isolating a treatment region of the body lumen therebetween, for delivering an agent to a treatment region that is not bifurcated. Additionally, a catheter of the invention can be configured for performing procedures such as dilatation and stent delivery.  
         [0043]     In a presently preferred embodiment, the purging method is performed using a catheter having multiple balloons in fluid communication with a common inflation lumen for simultaneous inflation of the balloons. Thus, the purging method of the invention allows for use of a lower profile, easier to manufacture catheter by avoiding the need for independent inflation of multiple balloons, resulting in improved, effective purging of an isolated treatment region. In contrast, prior purging methods require independent inflation of the proximal and distal balloons because blood in a partially isolated treatment region is displaced past a partially inflated/noninflated distal balloon until the treatment region appears under fluoroscopy to be filled with the infused agent (mixed with contrast), and the distal balloon is then fully inflated to isolate the treatment region.  
         [0044]      FIG. 7  illustrates an alternative embodiment of the invention, directed to a porous balloon bifurcated catheter  70 , generally comprising an elongated catheter shaft  71  having a proximal shaft section  72 , a bifurcated distal shaft section  73 , an inflation lumen  76 , and a guidewire lumen  77 , and a forked balloon  80  with a branched distal section on the bifurcated distal shaft section. In the illustrated embodiment, the shaft has a first inner tubular member  81  defining a joining wire lumen  82  which is configured for wire  78 , and a second inner tubular member  83  defining guidewire lumen  77 , although a variety of suitable shaft designs can be used including a shaft having a bifurcated inner member (not shown). The first and second branches  87 ,  88  of the balloon  80  each have distal ends sealingly secured to the respective inner tubular members  81 ,  83  of the shaft, and come together to meet at a common proximal section  86  having a proximal end sealingly secured to the distal end of an outer tubular member  84  of the shaft, so that the interior of the balloon  80  is in fluid communication with the inflation lumen  76  of the shaft.  
         [0045]     The balloon  80  is a porous balloon, so that fluid can be caused to flow across the balloon wall and into the body lumen  50 .  FIG. 7  illustrates the balloon  80  with the first branch  87  of the balloon distal section in a side branch vessel, and the second branch  88  of the balloon and the proximal section  86  of the balloon in a main branch of the body lumen. The balloon  80  is positioned so that the first and second branches  87 ,  88  of the balloon inflate into contact with the crux of the bifurcation of the body lumen. As a result, agent delivered from the porous balloon is delivered directly to the crux of the bifurcation and the, tissue of the vessel wall adjacent thereto at the bifurcation. In an alternative embodiment (not shown), a porous balloon bifurcated catheter of the invention has at least two separate porous balloons, namely a first porous balloon on the first branch of the distal shaft section and a second porous balloon on the second branch of the distal shaft section. The two balloons are preferably positioned on the catheter shaft such that proximal end sections of the two balloons inflate into contact with one another with the distal ends of the two balloons positioned in the side and main branch vessels of the body lumen. In the illustrated embodiment, agent in the balloon interior delivered from the inflation lumen flows through the porous balloon wall. However, a variety of suitable porous balloon configurations can be used including balloons having separate infusion lumens, and/or a porous outer layer allowing agent contained in a reservoir or otherwise delivered to the porous outer layer to flow through the porous outer layer. Although not illustrated, in one embodiment at least one of the first and second branch is provided with an occlusion balloon proximal or distal to the porous balloon portion, for occluding the body lumen during delivery of the agent from the porous balloon. For example, in one embodiment (not shown), a first distal occlusion balloon is provided on a distal extension of the first branch and a second distal occlusion balloon is provided on a distal extension of the second branch of the shaft, and are located distal to the porous balloon. Additionally, a porous balloon bifurcated catheter of the invention can be provided with one or more perfusion lumens configured to prevent ischemic conditions caused by inflation of the balloon(s) in the body lumen.  
         [0046]     The dimensions of catheters 10/70 are determined largely by the size of the balloon and guidewire to be employed, the catheter type, and the size of the artery or other body lumen through which the catheter must pass or the size of a stent being delivered. By way of example, the proximal outer tubular member  23  typically has an outer diameter of about 0.025 to about 0.60 inch (0.064 to 0.15 cm), usually about 0.037 inch (0.094 cm), and a wall thickness of about 0.002 to about 0.008 inch (0.0051 to 0.02 cm), typically about 0.003 to 0.005 inch (0.0076 to 0.013 cm). The inner tubular member  36  typically has an inner diameter of about 0.01 to about 0.018 inch (0.025 to 0.046 cm), usually about 0.016 inch (0.04 cm), and a wall thickness of about 0.002 to about 0.004 inch (0.005 to 0.01 cm). The overall length of the catheter 10/70 may range from about 100 to about 150 cm, and is typically about 143 cm. Preferably, balloons  20 ,  21 ,  22  have a length about 0.8 cm to about 6 cm, and an inflated working (nominal) outer diameter of about 2 to about 5 mm.  
         [0047]     The shaft tubular members can be formed by conventional techniques, for example by extruding and necking materials already found useful in intravascular catheters such a polyethylene, polyvinyl chloride, polyesters, polyamides, polyimides, polyurethanes, and composite materials. The various components may be joined using conventional bonding methods such as by fusion bonding or use of adhesives. Although the shaft is illustrated as having inner and outer tubular members, a variety of suitable shaft configurations may be used including a dual/multi-lumen extruded shaft having side-by-side lumens extruded therein. Similarly, although the embodiment illustrated in  FIG. 1  is a rapid-exchange balloon catheter, the catheter of this invention may comprise a variety of intravascular catheters, such as an over-the-wire type balloon catheter having the guidewire lumen  17  extending the full length of the catheter  10 .  
         [0048]     While the present invention is described herein in terms of certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements may be made to the invention without departing from the scope thereof. For example, although discussed primarily in terms of an embodiment in which a joining wire releasably couples the distal branches of the catheter together for delivery, a variety of suitable catheter configurations can be used including coupling the distal branches with releasable sheaths, and the like, as are conventionally known. Moreover, although individual features of one embodiment of the invention may be discussed herein or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment may be combined with one or more features of another embodiment or features from a plurality of embodiments.