Patent Publication Number: US-2003230313-A1

Title: Imaging of the vasa vasorum to navigate through an occlusion

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
     [0001] This application is cross-referenced to and claims priority from U.S. Provisional application No. 60/364,284 filed Mar. 13, 2002, which is hereby incorporated by reference.  
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates generally to medical devices and methods. More particularly, the present invention relates to a device and method to aid in the percutaneous navigation through chronic total occlusions by imaging of the vasa vasorum.  
       BACKGROUND  
       [0003] In coronary artery disease, stenosis of arteries can become tighter over time. Eventually, it is possible for a lesion to completely block an artery. When an artery becomes totally blocked over time, the blockage is called a Chronic Total Occlusion (CTO). Opening of a CTO can restore myocardial function to a portion of the heart, and relieve associated angina.  
       [0004] CTOs are generally tough and fibrous, in contrast to the soft blockages caused by acute vulnerable plaque rupture and clotting. Percutaneous devices capable of penetrating, debulking, or dissecting a pathway through the tough matter of CTOs are currently available. However, a principal mode of failure for these devices arises secondary to an inability to safely navigate the device through the occlusion while remaining inside the vessel lumen.  
       [0005] Patients whose occlusions cannot be opened percutaneously must be referred for open heart surgery, with its heightened morbidity and mortality. Accordingly, there is a need for new devices and methods that permit the reliable and safe navigation of percutaneous devices through chronic total occlusions.  
       SUMMARY OF THE INVENTION  
       [0006] The present invention provides an aid in the percutaneous navigation through occlusions. In particular, the present invention provides an aid in the percutaneous navigation through CTOs, by imaging of the vasa vasorum. In one aspect of the invention a cavity is established in a vessel proximal to the occlusion of interest. Once the cavity is established, fluid is introduced into the cavity. The fluid is introduced under a pressure that is sufficient to drive the fluid into the vasa vasorum that are accessible from the cavity. The fluid is preferably a contrast agent that is visible to an imaging means. Examples of imaging means are for instance a fluoroscopic image means using a fluoroscopic contrast agent, a Magnetic Resonance Image (MRI) using an MRI contrast agent or an ultrasonic imaging means and using an ultrasound contrast agent. An image is taken with imaging means of at least the fluid filled cavity and vasa vasorum. This image is then used as a visual aid for a physician or interventionist to visualize the path and/or curvature of the occluded vessel. With this visualization, the physician would be able to navigate a medical instrument through the occlusion. In addition, this visualization would aid the physician to open the occlusion and therewith promote blood flow in the vessel, for instance, by expanding open, stenting open, or cutting away part of occlusion. Examples of medical instruments for such interventions that could be used are known in the art and include stents, (laser) guidewires, dissection devices, debulking devices, penetration devices, or the like.  
       [0007] In one embodiment of the invention the means to establish a cavity includes a balloon, which is preferably conformational and capable of creating a circumferential seal with the inner wall of the vessel once the balloon is inflated. Other examples of a means to establish a cavity include means to deploy a diaphragm, a collapsible wedge, or a barrier to retrograde the fluid flow.  
       [0008] In another aspect of the invention a device is provided that includes a first lumen that extends through the means to establish a cavity. In a preferred embodiment, the first lumen extends through the balloon. The first lumen is used to introduce fluid using a fluid delivery means. The fluid delivery means is located outside the body of the patient. The first lumen could also be used to introduce a medical instrument into the cavity for purposes of occlusion intervention. In another embodiment, the device includes a second lumen, which provides an additional channel that could be designated for the delivery of additional medical instruments, as a specifically dedicated channel for medical instruments, or in an additional embodiment as a channel for an extraction means. Extraction means could be used to extract a substance from the cavity such as fluid (contrast agent), blood or occlusion material.  
       [0009] In another embodiment, feedback means could be included to provide feedback of the pressure in the balloon. In yet another embodiment, feedback means could be included to provide feedback of the fluid pressure in the cavity. For instance, a pressure sensor could be used to regulate the pressure in the balloon and cavity, respectively. In still another embodiment each lumen could include a valve, which could also aid in the regulation of fluid flow through the lumen and the fluid pressure in the cavity.  
       [0010] In an alternative embodiment, a device is provided to establish both proximal and distal boundaries of a cavity in a vessel in a patient. This device includes two balloons. A first balloon contains a first lumen which extends through the first balloon, and a second balloon contains a second lumen which extends through the second balloon. A hollow element, such as a tube, is extended from outside the body of the patient and extends through the first lumen as well as through the second lumen. The part of the hollow element situated in between the first balloon and the second balloon has one or more openings. This device includes an inflation means that could inflate the first and second balloon simultaneously or separately. The balloons are also conformational and capable of creating a circumferential seal with the vessel. The device also includes a fluid injection means that is connected to the hollow element to introduce fluid through one or more openings into the cavity. 
     
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
     [0011] The objectives and advantages of the present invention will be understood by reading the following detailed description in conjunction with the drawings, in which:  
     [0012]FIG. 1 shows a vessel with a chronic total occlusion;  
     [0013]FIG. 2 shows a vessel with a chronic total occlusion and a device according to the present invention;  
     [0014]FIG. 3 shows a cavity and vasa vasorum filled with a fluid according to the present invention;  
     [0015]FIG. 4 shows an example of a navigation of a medical instrument across a chronic total occlusion using the image of the vasa vasorum as shown in FIG. 3 according to the present invention;  
     [0016]FIG. 5 shows an example of a device with two lumens according to the present invention; and  
     [0017]FIG. 6 shows an alternative embodiment of a device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0018] Although the following detailed description contains many specifics for the purposes of illustration, anyone of ordinary skill in the art will readily appreciate that many variations and alterations to the following exemplary details are within the scope of the invention. Accordingly, the following preferred embodiment of the invention is set forth without any loss of generality to, and without imposing limitations upon, the claimed invention.  
     [0019]FIG. 1 shows a vessel  100  with a vessel wall  102 , a vessel lumen  105  and an occlusion  110 , such a chronic total occlusion. The occluded vessel is shown straight in this schematic, but may be bent or convoluted in vivo. Vessel  100  also shows its vasa vasorum  120  at the outside part and through vessel  100 , which provides a signature of the path of vessel  100 . The key idea of the present invention is to utilize the network of small vessels of vasa vasorum  120  that is situated around occlusion  110  for imaging. This image is then used as a visual aid for a physician or interventionist to visualize the path and/or curvature of vessel  100 . With this visualization, the physician would be able to navigate a medical instrument through occlusion  110 . In addition, this visualization would aid the physician to open occlusion  110  and therewith promote blood flow in vessel  100 , for instance, by expanding open, stenting open, or cutting away part of occlusion  110 . Examples of medical instruments for such interventions that could be used are known in the art and include stents, (laser) guidewires, dissection devices, debulking devices, penetration devices, or the like.  
     [0020] In one aspect of the invention a catheter-based device  200  is entered in vessel  100  as shown in FIG. 2. Device  200  includes a means to establish a cavity  210 , such as an inflatable balloon. The balloon could be inflated using an air pump  230  that is positioned outside the body of the patient as is common in the art. The balloon is preferably made of pliable material, conformational (silastic), and capable of creating a circumferential seal with the inner wall of vessel  100  once the balloon is inflated. Device  200  also includes a lumen  220  that is used to introduce a fluid into vessel  100 . Lumen  220  is channeled within a flexible intravascular tubing as is common in the art. One end of the tubing and its lumen will remain positioned outside the body of the patient as it is also common in the art. Lumen  220  extends through the balloon or in general terms the means to establish the cavity. The size of lumen  220  is preferably large enough to allow fluid injection and delivery of a medical instrument necessary for interventional procedures of occlusions.  
     [0021] In a preferred aspect of the invention, device  200  is positioned in vessel  100  proximal to occlusion  110  in such a way that a cavity is created in between device  200  and occlusion  110 . FIG. 2 shows the balloon in a deflated position, which is preferred to position device  200  in vessel  100  proximal to occlusion  110  (proximal is defined by the direction of blood flow which is also referred to as anterograde movement). FIG. 3 shows the balloon in an inflated position  300  whereby it creates a seal with the inner wall of vessel  100  and a cavity  310  proximal to occlusion  100 . The inflation of the balloon could be controlled by a physician or in an automatic fashion by means that are common in the art. FIG. 3 shows an example of a pump  302  to inflate the balloon with for instance saline or air (shown as  304 ). In one embodiment of the invention, a feedback means (such as a pressure sensor positioned inside the balloon) could be provided to inform the physician or automatic inflation means about the pressure that is building up in the balloon as well as enabling regulation over the pressure in the balloon.  
     [0022] Lumen  220  is connected to a means to introduce fluid  320  in cavity  310  as shown in FIG. 3. Such a means  320  is preferably positioned outside the body of the patient. A physician controls the amount of fluid  325  that needs to be introduced in cavity  310 , however this could also be controlled in an automatic fashion. In one embodiment of the invention, a feedback means (such as a pressure sensor positioned at the cavity site of the catheter) could be provided to inform the physician or automatic fluid injection means about the pressure that is building up in cavity  310  as well as enabling regulation over the pressure in cavity  310 . The key idea of introducing fluid in cavity  310  is to build up enough pressure so that at least cavity  310  and vasa vasorum  120  receive fluid as shown in FIG. 3. The pressure should be sufficient enough to drive or diffuse an anterograde movement of the fluid through vasa vasorum  120 . In some cases, the fluid may re-enter the vessel lumen distal  330  to the occlusion or perfuse the tissue of the occlusion itself, as well as other adjacent structures which may communicate with the vasa vasorum.  
     [0023] The fluid is preferably a contrast fluid that could be used in conjunction with an imaging device (not shown). In one aspect of the invention a fluoroscopic imaging means is used and the fluid is a fluoroscopic contrast agent. However, the present invention is not restricted to the use of fluoroscopic imaging means and a fluoroscopic contrast agent as one could also use Magnetic Resonance Imaging (MRI) and MRI contrast agents, ultrasound and ultrasound contrast agents, or other techniques that are common in the medical art. Imaging means should be capable of making an image of at least the vasa vasorum and cavity both filled with the fluid irrespective of the skin and other subcutaneous tissue and/or organs that are located in between the imaging device and area of the vasa vasorum and cavity. The image could also include structures that are in communication with the vasa vasorum such as the capillary structures within the occluding lesion, adjacent areas of normal and pathological vessel wall, as well as vessel lumen distal to the site of occlusion.  
     [0024]FIG. 4 shows an example of a navigation of a medical instrument across an occlusion using an image based on the vasa vasorum that has been filled with, for example, a fluoroscopic, MRI contrast agent or ultrasound contrast agent. Medical instruments that are suitable are typically the ones that are used for occlusion intervention and small enough to fit through the lumen of the balloon. The example of FIG. 4 shows the navigation of a guidewire  400  across occlusion  110  by a physician guided by an image of the vasa vasorum as shown in FIG. 4. This could either be accomplished alone or in conjunction with another device such as a dissection device, laser guidewire, rotablator, or the like. With guidewire  400  in place, the physician can place a stent  410  to open occlusion  110 , thereby restoring blood flow to vessel  100 .  
     [0025] The present invention has now been described in accordance with several exemplary embodiments, which are intended to be illustrative in all aspects, rather than restrictive. Thus, the present invention is capable of many variations in detailed implementation, which may be derived from the description contained herein by a person of ordinary skill in the art. For instance, the medical instrument could be entered through the same lumen as used for injecting the fluid. However, in another embodiment of the invention a second lumen  500  could be used for introducing or delivering a medical instrument that is also extended through the balloon  510  (i.e. means to establish a cavity) as shown in FIG. 5. In yet another embodiment of the invention, the first or second lumen could be used to extract fluid, blood or material from the occlusion using an extraction means (not shown). An example of an extraction means is, for instance, a suction device positioned outside the body of the patient, as it is common in the art. In yet another aspect of the invention, each lumen could include a valve (one-way or two-way valve, not shown) to prevent pressure drop through leakage of the injected fluid as well as to provide control over flow direction. In the exemplary embodiments described supra, a balloon was used as a means to create a cavity. However, the present invention is not limited to a balloon and could also include a diaphragm, collapsible wedge, deployable barriers, or the like.  
     [0026] An alternative embodiment includes a catheter-based device with a first balloon  600  and a second balloon  610  as shown in FIG. 6. Each balloon can be inflated at the same time with a shared inflation means or inflated independently each with its own inflation means. The inflation of balloons  600  and  610  occurs in a similar fashion as described supra. The second balloon  610  is positioned at a proximal position along, for instance, a percutaneous tubing  620 . The present invention is not limited to percutaneous tubing since various kinds of cylinders or hollow elements could be used that are able to deliver a fluid. In this example the second balloon  610  is used to create a cavity in between both balloons in a similar fashion as described supra. This would be useful in circumstances where a total occlusion is not present or not convenient for utilization as one boundary of the cavity. Fluid can be introduced in the established cavity in a similar fashion as discussed supra whereby the fluid is delivered through percutaneous tubing  620  and through holes  630  into the established cavity. All such variations are considered to be within the scope and spirit of the present invention as defined by the following claims and their legal equivalents.