Abstract:
A catheter having a perfusion section encapsulated by a porous membrane. The catheter can include a shaft to accommodate a radiation source. A spiraled balloon can be positioned about the shaft for centering within a body lumen. Additionally, a longitudinal balloon or mechanical expansion can be provided about the shaft for positioning within a body lumen. A radiotherapy system can be included with a radiation source and a catheter having a perfusion section encapsulated by a porous membrane. A method is provided where a catheter with a perfusion section encapsulated by a porous membrane is advanced through a body lumen. The body lumen is treated by the catheter while a body fluid is perfused past the perfusion section.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to intravascular therapy. In particular, the present invention relates to a perfusion catheter.  
         BACKGROUND OF THE PRIOR ART  
         [0002]    For patients with arterial blockage, such as coronary or peripheral stenotic lesions, angioplasty is often used. Through angioplasty, an angioplasty catheter is delivered to a vessel region which has been narrowed by a stenosis (atherosclerotic plaque build-up). A balloon of the angioplasty catheter is inflated to compress the stenosis against the vessel wall. The balloon is then deflated and the angioplasty catheter removed. This procedure widens an inner diameter of the arterial lumen, allowing for increased blood flow through the vessel region formerly narrowed by the stenosis. Often, a stent is placed at the vessel region in conjunction with the angioplasty procedure.  
           [0003]    However, restenosis, in which the senotic narrowing of the vessel returns, is common after angioplasty procedures. To prevent restenosis, radiotherapy procedures are used to impair cell growth by exposing potential restenosis sites to radiation.  
           [0004]    To deliver radiation to the potential restenosis sites, a variety of radiotherapy procedures may be used. Source wire radiotherapy, for example, utilizes a source wire positioned by a radiotherapy catheter. A balloon rests about a shaft of the radiotherapy catheter at a distal portion thereof. The balloon is inflated once it has been positioned adjacent the site of a former stenosis. A source wire, having a radioactive distal tip, is then advanced through the catheter to the aforementioned distal portion of the shaft, where radiation is emitted from the radioactive distal tip toward the site of the former stenosis. After a predetermined radiation exposure time, the source wire is retracted, the balloon deflated and the radiotherapy catheter removed.  
           [0005]    During such a radiotherapy procedure a balloon shaped to avoid occlusion of the vessel being treated is often used. For example, if a longitudinal and cylindrically shaped balloon is inflated within the vessel, it will occlude blood flow during the radiotherapy procedure. The effects of such an occlusion reach beyond the particular vessel which is being treated. For example, a primary vessel being directly treated with the angioplasty balloon likely services other side branch vessels which branch out from the primary vessel. If the primary vessel is occluded proximal of (i.e., upstream), or in the area of, a side branch, the side branch can also be occluded as a direct result.  
           [0006]    Where radiotherapy is used, it may result in vessel occlusions requiring parameters to be limited to short and intense radiotherapy treatments to limit ischemic episodes. Additionally, in order to alleviate an occlusion caused by the radiotherapy device, the radiotherapy may need to be periodically interrupted to allow perfusion of blood past the balloon in preventing ischemic episodes.  
           [0007]    Alternatively, to avoid occlusions of the vessel during radiotherapy, the radiotherapy catheter may be designed to permit perfusion of blood past the balloon even where the balloon is inflated. Such “perfusion balloons” may include balloons which are multi-lobed or spiraled about a distal portion of the catheter shaft. In this way blood is allowed to perfuse past the balloon via channels between balloon lobes or between spiral threading of the balloon.  
           [0008]    The perfusion channels of perfusion balloons, however, are susceptible to being blocked by vessel imperfections. That is, following an angioplasty procedure, it is unlikely that the vessel will include no more than a smooth tubular interior. Rather, the wall of the vessel will likely be rough and fairly non-uniform with obtrusive features likely present. These obtrusive vessel imperfections can interfere with perfusion of blood through a perfusion channel. A single obtrusive feature can potentially occlude all blood flow through a perfusion channel, even where the remainder of the channel remains un-occluded. Therefore, what is needed is a catheter configured to allow perfusion without allowing occlusion of a perfusion channel.  
         SUMMARY OF THE INVENTION  
         [0009]    An embodiment of the invention includes a catheter with a perfusion section and a membrane encapsulating a portion of the perfusion section. The membrane has pores.  
           [0010]    Another embodiment of the invention includes a catheter with a shaft to accommodate a radiation source. A spiraled perfusion balloon to center the shaft within a body lumen is provided with a membrane encapsulating a portion of the balloon.  
           [0011]    In another embodiment a catheter includes a shaft to accommodate a radiation source. A longitudinal balloon is included about the shaft for positioning within a body lumen. A membrane encapsulating a portion of the balloon is also provided.  
           [0012]    In yet another embodiment a catheter includes a shaft to accommodate a radiation source. A mechanical expansion coupled to the shaft is provided to position the shaft within a body lumen. A membrane encapsulating a portion of the balloon is also provided.  
           [0013]    Another embodiment of the invention includes a radiotherapy system with a radiation source. A catheter with a perfusion section and a membrane thereabout is also provided.  
           [0014]    In a method of the invention a catheter is advanced through a body lumen. The catheter includes a perfusion section with a membrane. A portion of the body lumen is treated by the catheter while a body fluid is perfused past the perfusion section. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a pictorial view of an embodiment of the present invention.  
         [0016]    [0016]FIG. 2 is a sectional view of a lobed embodiment of the present invention inserted within a vessel.  
         [0017]    [0017]FIG. 3 is a front cross sectional view of an embodiment of the present invention, taken from line  3 - 3  of FIG. 2.  
         [0018]    [0018]FIG. 4 is a side sectional view of an alternate embodiment of the present invention.  
         [0019]    [0019]FIG. 5 is a side sectional view of an alternate embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    The following description makes reference to numerous specific details in order to provide a thorough understanding of the present invention. However, each and every specific detail need not be employed to practice the present invention. Additionally, well-known details, such as particular materials or methods, have not been described in order to avoid obscuring the present invention.  
         [0021]    Referring to FIG. 1 an embodiment of a perfusion catheter  2  with a perfusion balloon  1  at a distal end thereof is shown. In FIG. 2 the perfusion balloon  1  is shown within a primary vessel  4  as partially sectioned to reveal interior features. FIG. 3 shows a cross sectional view of the perfusion balloon  1  of FIG. 2.  
         [0022]    The perfusion balloon  1  of the embodiment shown is constructed to allow perfusion of a body fluid past a shaft  3 . In the embodiment shown, the perfusion balloon  1  is also constructed to center the distal portion of the shaft  3  within a body lumen, such as the primary vessel  4 . For example, in a method of the invention, centering of the distal portion of the shaft  3  is provided where the shaft  3  is to accommodate a source wire having a radioactive distal tip during a radiotherapy procedure. In this manner, an even distribution of radiation, emanating from the distal portion of the shaft  3 , which houses the radioactive source wire via a source wire lumen  33 , is delivered to the primary vessel  4  to be treated (see also FIG. 3).  
         [0023]    The perfusion balloon  1  is configured to allow a primary flow of blood (arrows  5 ) to move past the perfusion balloon  1  even though the perfusion balloon  1  rests within the primary vessel  4 . That is, the perfusion balloon  1  is configured to allow perfusion. The natural flow of blood through the primary vessel  4  of FIG. 2 would be from right to left as shown. In order to allow perfusion, the perfusion balloon  1  is equipped with perfusion channels  7  (also shown in FIG. 3). Each perfusion channel  7  is located between individual balloon lobes  8  of the perfusion balloon  1 . The embodiment shown includes a perfusion balloon  1  having three lobes  8  (i.e., a “tri-lobed” balloon). Therefore, three perfusion channels  7 , one between each lobe  8 , are provided.  
         [0024]    The perfusion balloon  1 , having lobes  8 , runs longitudinally along the shaft  3  throughout a perfusion section of the catheter. Perfusion channels  7  prevent the perfusion balloon  1  from resting flush against the vessel wall  14  which could occlude the primary flow of blood (arrows  5 ). As a result, the perfusion balloon  1  can remain within a lumen  10  of the primary vessel  4  for a significant period of time without inducing an ischemic condition. For example, due to the perfusion channels  7 , the perfusion balloon  1  can remain within the primary vessel  4  throughout the duration of a radiotherapy procedure without obstructing the primary flow of blood (arrows  5 ).  
         [0025]    While the lobes  8  and perfusion channels  7  avoid complete occlusion of the lumen  10 , the perfusion channels  7  would be susceptible to partial blockage by irregularities  11  present in the vessel wall  14  if not for a membrane  13  discussed further below. That is, the vessel wall  14  is not generally smooth. This is especially true in portions of the primary vessel  4  which have experienced injury, such as the site of a former stenotic lesion which is likely to have thrombus projections. So, for example, if the perfusion balloon  1  is being used during a radiotherapy procedure following PTCA, there is a high probability that the vessel wall  14  includes a large number of irregularities  11  in the area that is being treated (i.e. adjacent the perfusion balloon  1 ). These irregularities  11  often include flaps or other protruding shapes which can extend into a portion of a perfusion channel  7 . Such a partial blockage of a perfusion channel  7  decreases the overall efficiency of perfusion.  
         [0026]    In order to ensure effective perfusion, the perfusion balloon  1  is surrounded by a membrane  13 . Once the catheter has been positioned, with the perfusion balloon  1  adjacent a vessel wall  14  having irregularities, the perfusion balloon  1  is inflated (as shown in FIG. 2). Upon inflation, the membrane  13  is forced against the vessel wall  14  preventing the irregularities  11  from protruding into the perfusion channels  7 . The previously protruding irregularities  11  are forced to fold up against other portions of the vessel wall  14  by the expanded membrane  13 . Thus, the irregularities are forced away from the perfusion channels  7  allowing the perfusion channels to remain open and unobstructed. A more efficient primary flow of blood (arrows  5 ) is maintained.  
         [0027]    The membrane  13  is expandable and responsive to the inflatable characteristics of the perfusion balloon  1 . When the lobes  8  are inflated, the membrane  13  expands outward. In the embodiment shown, the membrane  13  is made of an elastic biocompatible material such as polysiloxane or polysiloxane related substances or derivatives capable of expansion.  
         [0028]    Of note is the fact that, while a membrane  13  is provided, it does not prevent the primary flow of blood (arrows  5 ) from entering or exiting the perfusion channels  7 . Rather, blood is allowed access to the perfusion channels  7  at a proximal end  37  and an exit at the distal end  17  of the perfusion balloon  1 .  
         [0029]    In one embodiment, the entry and exit of the primary flow of blood (arrows  5 ) via perfusion channels  7  is provided by using a membrane  13  which surrounds the perfusion balloon  1  circumferentially only. Such a membrane  13  is secured directly to the perfusion balloon  1 . Thus, the proximal end  37  and the distal end  17  of the perfusion balloon  1  would be left open allowing the perfusion channels  7  to be directly open to the lumen  10  of the primary vessel  4 .  
         [0030]    Alternatively, as shown in the embodiment of FIGS. 1 and 2, the membrane  13  is attached to the shaft  3  distal of the perfusion balloon  1  and proximal of the perfusion balloon  1 . A distal portion  27  and a proximal portion  47  of the membrane  13  are equipped with access pores  19  to allow entry and exit of the primary flow of blood (arrows  5 ) through the perfusion channels  7 . When the perfusion balloon  1  and the membrane  13  are in an expanded state the access pores  19  have a diameter of between about 0.01 and about 0.05 inches and occupy between about 10 and about 50 percent of the surface area of the membrane  13  at its proximal and distal portion  27 . In one embodiment the access pores have a diameter of about 0.028 inches and occupy about 25 percent of the surface area of the membrane  13  in an expanded state. In one embodiment, the membrane  13  is securely attached to the shaft  3  and circumferentially surrounds the perfusion balloon  1  without inhibiting perfusion. This optimizes security of the membrane  13  and ensures that no portion of the perfusion channel  7  is susceptible to occlusion by protruding irregularities  11 .  
         [0031]    Referring specifically to FIG. 2, while the membrane  13  is configured to avoid inhibition of perfusion through the primary vessel  4 , a side branch vessel  44  branches off of the primary vessel  4 . Ideally, the side branch vessel  44  also remains un-occluded. An un-occluded side branch vessel  44  would require a side branch blood flow (arrows  55 ) emanating from the primary flow of blood (arrows  5 ). However, as shown, the portion of the primary vessel  4  being treated with the perfusion balloon  1  includes an intersection with a side branch vessel  44 . Therefore, the perfusion balloon  1  and membrane  13  rest across the entryway  30  to the side branch vessel  44 .  
         [0032]    In order to prevent occlusion of the side branch vessel  44  by the membrane  13 , the membrane  13  is equipped with perfusion pores  29 . That is, the primary flow of blood (arrows  5 ) through the perfusion channels  7  is able to exit corresponding perfusion channels  7  at the entryway  30  through the perfusion pores  29  as side branch blood flow (arrows  55 ). The embodiment shown has perfusion pores  29  throughout the body  35  of the membrane  13  to ensure that the side branch vessel  44  is not occluded by the body  35  of the membrane  13 .  
         [0033]    As shown in the embodiment of FIG. 2, access pores  19  are provided to ensure a continued primary flow of blood (arrows  5 ) past the perfusion balloon  1 . Likewise, the perfusion pores  29  are provided to ensure a continued side branch blood flow (arrows  55 ). The perfusion pores  29  take up between about 10 and about 50 percent of the surface area of the body  35  of the membrane  13 . The perfusion pores  29  are between about 0.01 and about 0.05 inches in diameter when the perfusion balloon  1  and the membrane  13  are in an expanded state (as shown in FIG. 2). In one embodiment the perfusion pores  29  take up about 25 percent of the surface area of the body  35  and are about 0.014 inches in diameter when the perfusion balloon  1  is expanded.  
         [0034]    Referring to FIG. 3, a cross section taken from line  3 - 3  of FIG. 2 is shown. From a new perspective, the perfusion balloon  1  is shown within a lumen  10  of the primary vessel  4 . All three perfusion channels  7  can be seen between the three lobes  8 . Again, the lobes  8  are provided about a shaft  3  and surrounded by the membrane  13 . The shaft  3  is equipped with a now visible source wire lumen  33  to accommodate a radiotherapy mechanism such as a source wire with a radioactive distal tip (not shown). In another embodiment the lumen  33  accommodates radiation pellets to deliver radiotherapy. In other embodiments additional forms of radiotherapy are provided via the shaft  3  and perfusion balloon  1 .  
         [0035]    In FIG. 3, the extent to which the membrane  13  holds irregularities  11  against other portions of the vessel wall  14  and away from the perfusion channels  7  leaving the perfusion channels  7  un-occluded can be seen. While keeping irregularities  11  from occluding the perfusion channels  7 , the membrane  13  also accounts for the intersection of a side branch vessel  44 . That is, perfusion pores  29  have been provided in the membrane  13  which allow a side branch blood flow (arrows  55 ) to cross the membrane from a perfusion channel  7  and into the side branch vessel  44 . Thus, the membrane  13  has prevented occlusion of the perfusion channels  7  without causing occlusion of the side branch vessel  44 .  
         [0036]    Referring to FIG. 4 an alternate embodiment of the invention is shown, again making use of a perfusion catheter. Likewise, the primary vessel  4  having irregularities  11  is to be treated. Where treatment includes radiation delivery, the catheter also provides centering capability for delivery of a uniform level of radiation from a shaft  300 . During such a treatment irregularities  11  are restrained from interfering with features of the adjacent catheter. A side branch vessel  44  is shown intersecting the primary vessel  4  in an area where the primary vessel  4  is accommodating the catheter. Therefore, embodiments of the invention are able to restrain the irregularities  11  in a manner which does not cause occlusion of the side branch vessel  44 .  
         [0037]    In order to force the irregularities against the primary vessel wall  14 , a membrane  130  is provided surrounding a perfusion section of the catheter. The membrane  130  is configured to allow a side branch blood flow (arrows  55 ) to the side branch vessel  44 . Thus, perfusion pores  290  are provided in the membrane  130 .  
         [0038]    The perfusion section of the catheter includes a spiraled perfusion balloon  21  about the shaft  300  of the catheter. The spiraled perfusion balloon  21  provides a perfusion channel  70  between adjacent threads of the spiraled perfusion balloon  21 . The perfusion channel  70  allows perfusion through the primary vessel  4 . The spiraled perfusion balloon  21  is a balloon which spirals around the shaft  300 . By spiraling around the shaft  300  interaction between the spiraled perfusion balloon  21  and the membrane  130  is maximized. The spiral shape of the spiraled perfusion balloon  21  forces the membrane  130  open in a circumferential manner. The spiraled perfusion balloon  21  is therefore, particularly adept at keeping the membrane  130  circumferentially expanded against the primary vessel wall  14 .  
         [0039]    Referring to FIG. 5 another embodiment of the invention is shown. Again, a perfusion catheter is provided within a primary vessel  4  having irregularities  11 . Where treatment includes radiation delivery, the catheter also provides centering capability for delivery of a uniform level of radiation from shaft  333 .  
         [0040]    In the embodiment of FIG. 5, the perfusion section of the catheter includes mechanical expansions  31  which arise from the shaft  333 . The mechanical expansions  31  may be ribbons of metal, plastic, or other material designed to expand out into a hump-like shape to hold open the membrane  133  and the primary vessel  4 . That is, rather than providing an inflatable balloon configured to allow a particularly shaped perfusion channel  77 , a mechanical mechanism is provided to allow perfusion (and centering capability). The mechanical expansions  31  leave all other portions of the catheter free to allow a primary flow of blood (arrows  5 ) there through within the primary vessel  4 . That is, the perfusion channel  77  is defined by the shaft  333  and the membrane  133  (where present) with the only interruption being the narrow mechanical expansions  31 . This allows for efficient perfusion through the primary vessel  4  and to the side branch  44 .  
         [0041]    Embodiments of the present invention include a perfusion balloon with perfusion channels having an ability to avoid occlusion of the perfusion channels. Additionally, embodiments of the invention also include configurations that avoid occlusion of side branch vessels emanating from a more primary vessel being treated. Although an exemplary embodiment of the invention has been shown and described in the form of particular membranes with pores, many changes, modifications, and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.