Abstract:
The present invention is directed to a Flow Maintaining Stent Delivery System, FMSDS, which can be used in many cardiovascular and surgical procedures, especially for placing stents into patients having stenosed and occluded arteries and other vascular lumens. It can also be used as an examination tool for the vascular surgical operations and to examine small orifice internal or external to the body. Most important, the advantage of the present stent delivery system is that it allows antegrade downstream blood flow to be maximally maintained during stenting procedures, angioplasty procedures or in any other vascular surgical operations that can use this system. The present invention also allows for uniform placement of the stent onto the artery.

Description:
PRIORITY  
       [0001]    This patent application claims priority to a U.S. Provisional Application filed on Mar. 19, 2002 and assigned U.S. Provisional Application Serial No. 60/365,504 and to a United States Provisional Application filed on Feb. 4, 2002 and assigned U.S. Provisional Application Serial No. 60/354,188, the contents of both applications are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a medical/surgical angioplasty and stent delivery system, and also its multi-purpose use as a small retractor to virtually keep open any small orifice of the body.  
           [0004]    2. Description of the Related Art  
           [0005]    Many balloon stent delivery systems occlude blood flow during stenting operations. For laminar flow the equation of flow in an artery is: Q (Flow)=ΔP/R f =ΔP/8ηl/πR 4 =πR 4 ΔP/8ηl (where ΔP is change in pressure; R f  is resistance; η is viscosity of fluid like blood; l is length of the artery; and R is radius of the artery). Most important, in the above equation for flow, Q, derived from physical principles is proportional to R 4  (R being the radius of an artery). Thus any incremental decrease or increase in the radial length R of the artery has tremendous effect on blood flow Q. So, stent delivery systems that allow for an incremental decrease in the radial lumen length of an artery will substantially impede blood flow. In particular the interruption of blood flow to the heart is so critical to patients during angioplasty and stenting operations, that the system of using balloons as delivery system may not be efficient.  
           [0006]    In fact during angioplasty and stenting procedures, cardiologists have only seconds to inflate then deflate the balloon and take it out. However, the current embodiment of the stent delivery system allows for the maximal maintenance of downstream antegrade blood flow while the stent is being placed and/or when angioplasty is performed. This improvement is considerably important to patients and offers cardiologists an efficient way to deliver stents and do angioplasty without worrying about inflating and deflating the balloon quickly in matter of seconds. The balloon angioplasty and stent delivery devices offer uniformity and better custom fit of stents, which may be lacking in self-deploying stents. And this advantage of uniformity and better custom fit is preserved in this current embodiment. The current invention can be made entirely of smooth metal or flexible plastic plates that conveniently allows for complete sterilization, so it can be used again and again. Or else the FMSDS can be made entirely from plastics, making it disposable.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to a flow maintaining stent delivery system, FMSDS, which has multiple uses. The stent delivery system can be used to introduce a stent within a blood vessel, and for other surgical procedures, such as to perform angioplasty or to be used as a retractor during a surgical operation. A preferred embodiment is made from smooth metal plates or smooth flexible plastic plates, springs, hinges, and strings/wires; and which are able to withstand high temperatures. Essentially, the FMSDS can go from a very small diameter cylindrical structure to a very large diameter. Any small opening can be enlarged in this manner. It can produce adequate force to keep any surgical orifice, artery, or vascular structure open steadily and in a stable manner without rupture of the vessel. More importantly, as mentioned above, FMSDS can be used to place a stent in cases of coronary artery artherosclerosed plaque obstruction or for peripheral vascular diseases. After use FMSDS can be made to collapse and contract easily and completely, and taken out of the body within seconds.  
           [0008]    FMSDS operates on the principle that the springs exert adequate force to keep the apparatus fully expanded and opened into a bigger diameter hollow cylindrical structure. Counteracting the effect of the springs are the string/wire that prevents the embodiment from opening and expanding. But when the string/wire is slowly released and unwound the embodiment opens completely into a larger diameter structure from an initial smaller diameter hollow cylindrical structure, and when the string/wire is wound up the apparatus collapses and contracts into a smaller diameter configuration from a larger diameter structure. Note that the cylindrical configuration depicted in this embodiment is just one of many different types of configurations, sizes, and shapes that can be constructed based on the same thematic design.  
           [0009]    Initially, the non-expanded stent stably rests within the smooth elliptical groove of FMSDS, and the stent will expand in circumference with the expanding apparatus. Eventually the stent will be pressed against the arterial wall retracting the artherosclerotic plaque of the coronary artery onto the artery itself. In this current embodiment the advantage is that the stent is placed uniformly onto the arterial wall with a perfect custom fit, just as is the case with the balloon delivery system, however, this may not be the case with self-deploying stents. But the most significant advantage of this embodiment over other stent delivery system is that FMSDS allows the downstream antegrade blood flow to be maximally maintained throughout stenting or angioplasty procedure. At no time is the blood flow obstructed or hindered during the stenting or angioplasty operation. Since flow Q is proportional to R 4  (where R is the radius of the artery), then any incremental decrease in the lumen diameter of an artery as with a balloon inflating devices will cause tremendous decrease in blood flow. Decreased blood flow in coronary artery poses great danger to patients, which this current embodiment circumvents. Furthermore, this embodiment of the FMSDS is heparinized; it has no sharp edges, with all areas of FMSDS made smooth, and flexible to prevent coagulation and lacerations of the artery that may occur during the stenting or angioplasty procedure. And if the FMSDS is made from metal then it can be sterilized and used again and again, or it can be made completely from non-allergic disposable plastics. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0010]    The invention will be described in greater detail with reference to the accompanying drawings in which like elements bear like reference numerals, and wherein:  
         [0011]    [0011]FIG. 1 is a schematic showing the assembly of the metal plates or flexible plastic plates, hinges, springs, tubes and string/wire into a cylindrical configuration of the present invention;  
         [0012]    [0012]FIG. 2 is a schematic showing the expanded form of the embodiment of the present invention;  
         [0013]    [0013]FIG. 3 is a schematic showing the contracted form of the embodiment of the present invention;  
         [0014]    [0014]FIG. 4 is a schematic showing the “syringe type” controls for FMSDS; and  
         [0015]    [0015]FIG. 5 is a schematic showing the “vertical type” controls for FMSDS. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    This instrument is primarily designed to deliver stents during stenting operation for coronary artery disease obstruction and to be used for angioplasty purposes. First, thin metal plates, or flexible transparent (bioluminescent or x-ray luminescent) plastic plates  7  are placed adjacent to each other and joined with small hinges  14  between them; see FIG. 1. The plates  7  have elliptical cuts at their center; see FIG. 1. These elliptical cuts form a grove on the embodiment where the stent  63  sits and do not allow the stent  63  to slip away from the stent delivery system during stent placement procedure inside the coronary artery. At the juncture between the plates there are small hidden springs  21  that articulate between adjacent plates  7 , see FIG. 1. The springs  21  are structured such that they provides adequate force to cause adjacent plates  7  to come apart and the angle between them to approach approximately 180 degrees.  
         [0017]    The springs  21  are configured to maintain a specific configuration of the apparatus (a cylindrical one as presented in this embodiment) by guiding the motion of the plates  7 . (Note that instead of the springs and hinges in between the plates one could make this junctional area out of a contiguous “springing” material that will function just as well as the springs and hinges.) At the middle of the plates  7 , holes  35  are provided which act as bearings. In one end, the string/wire  28  permanently attaches onto the last plate  7 , called the anchor point for the string/wire,  77 , see FIG. 1. The string/wire  28  then goes through the bearing holes  35  of all the plates  7 , and exits on the first plate and then it goes through the very small hard protruding tube  42 , see FIG. 2 and FIG. 1, respectively.  
         [0018]    The bearing holes  35  prevent the string/wire  28  from cutting the plates  7  when the tension is very high on the string/wire  28 . Note that the above created and constructed embodiment is called FMSDS I and can be made to sit inside another bigger diameter plastic tube called the introducing catheter  56  from which it can be ejected, FIG. 2 and FIG. 3. After exiting the tube  42 , the string/wire  28 , will travel inside the introducing catheter  56 , going through the string/wire restricted holes  98 , and exit from a small hole of the introducing catheter and permanently attach itself to the screw knob  49 . The screw knob  49  acts as controls for FMSDS  1  and for stent deployment through its action on the string/wire  28 .  
         [0019]    The screw knob  49  has threads to create enough friction, which will not allow the string/wire  28  to unravel or lose its tensile strength unless someone operates the screw knob  49 . The tenacious string/wire  28  has two functions, first, it is used to push (and subsequently pull) the contracted FMSDS  1  apparatus (see FIG. 3 and FIG. 2) over the guide wire  84  to be placed at the coronary artery&#39;s plaque stenosed area and, second, the string/wire  28  is used to inflate FMSDS  1  for stent deployment. (Note that the introducing catheter  56  may have plastic mounds  70  which may or may not be necessary to make the FMSDS  1  be stationed in a stable manner inside the introducing catheter, as shown in FIG. 3.)  
         [0020]    Now, in the following there are two designs mentioned that act as controls for the FMSDS  1 :  
         [0021]    1. One way for the controls of the FMSDS  1  is as shown in FIG. 4. In this configuration, the screw knob holder  91 A has in it screw knob holder holes  105 , see FIG. 4. The screw knob  49 A shaft extends out from one side of the screw knob holder holes  105  and exits out by traversing another set of screw knob holder holes  105  on the other side of  91 A, see FIG. 4. On the distal end of the screw knob  49 A shaft outside the screw knob holder  91 A there is a permanently attached large diameter knob that prevents the screw knob  49 A from disassembly and sliding off the screw knob holder holes  105  and the screw knob holder  91 A itself, see FIG. 4. In the middle of the screw knob  49 A shaft there are screw knob threads  49 B, which wrap the string/wire  28  onto itself, see FIG. 4. The screw knob holder holes  105  are corrugated such that they allows the screw knob  49 A shaft to vertically slide in between the holes  105  passing by the constricted areas present between the screw knob holes as shown in FIG. 4. As the screw knob  49 A shaft goes from one screw knob hole  105  to the next in a downward vertical direction, it causes the string/wire  28  to move in an axial direction hence pushing the FMSDS  1  out of the introducing catheter  56  to be placed inside the coronary artery lumen where the plaque deposit obstruction is located. To inflate the FMSDS  1  the screw knob  49 A must be rotated to unwind the string/wire  28 , from the screw knob threads  49 B, thereby releasing the string/wire  28  tension on the FMSDS  1 ; and automatically the springs  21  exert its centrifugal force to expand the FMSDS  1 , see FIG. 2. With the expanding FMSDS  1 , the stent expands and achieves a uniform and an individually better custom fit onto the arterial wall. At this point note that the FMSDS  1  delivery system need not be removed immediately, because the downstream antegrade blood flow inside the coronary artery is maximally maintained, which in contrast to conventional balloon stent delivery systems. After a stent or angioplasty procedure, the screw knob  49 A is rotated such that the string/wire  28  is wound up onto the screw knob threads  49 B creating back the original tension on the string/wire  28  which overcomes the centrifugal forces exerted by the springs  21  eventually to contract and deflate the FMSDS  1 . Then the screw knob  49 A shaft can be moved upward direction from one screw knob hole  105  to the next causing the reverse axial motion of the string/wire  28 , see FIG. 4. This eventually leads to the drawing in of the contracted FMSDS  1  apparatus into the introducing catheter  56 , see FIG. 3. To control the vertical motion of the screw knob  49 A shaft, a screw knob lock  112  which is a hard cylindrical cover casing structure resides over the screw knob  49 A shaft outside of the screw knob holder  91 A as shown in FIG. 4. At the distal end of the screw knob lock  112  there are few threads on its outside surface that will articulate with the few threads on the screw knob holes  105  inside surface, see FIG. 4. When the screw knob lock  112  is rotated and screwed into the screw knob holder holes  105 , prohibition of rotational and vertical motion of the screw knob  49 A shaft is achieved. So, the screw knob lock  112  allows for the arrest of the axial motion of the string/wire  28  and fixes the FMSDS  1  at any given position along the axial length of the embodiment. One must release the screw knob lock  112  and pull it back in order for the screw knob  49 A shaft to move up and down the screw knob holes  105 . Note the presence of the string/wire restricted holes  98 , which guide the string/wire  28  along its axial motion line inside the embodiment.  
         [0022]    2. Alternatively, as shown in FIG. 5, a syringe type screw knob  49 C can be constructed, which resides inside a screw knob holder  91 B that may be filled with contrast material or saline or the same fluid which is in the introducing catheter  56  or it could remain empty, see FIG. 5. The screw knob syringe plunger  49 C will be slowly pushed through the screw knob syringe holder  91 B pushing (the fluids, if it is present) and causing the axial motion of the string/wire  28  and subsequently the FMSDS  1 . (Note that the hard plastic screw knob syringe plunger stopper mound  119  will not let the screw knob syringe plunger  49 C go beyond a certain point.) By doing so the FMSDS  1  will be placed under the artherosclerosed obstructing plaque of the coronary artery. Then a twisting and unscrewing rotational motion of the screw knob syringe plunger  49 C will cause its miniature threads  49 E to unwind the string/wire  28  reducing its tension and automatically triggering the springs  21  to exert its centrifugal force whereby the FMSDS  1  apparatus completely opens and inflates, see FIG. 2. An expanding FMSDS  1  apparatus will expand the stent onto the obstructive plaque with a uniform and individually better custom fit onto the coronary artery. As mentioned before, at this point note that the FMSDS  1  delivery system need not be removed immediately within seconds because downstream antegrade blood flow inside the coronary artery is maximally maintained, and again, this unfortunately does not happen with the balloon stent delivery systems. Once the stent is in place, the screw knob syringe plunger  49 C will be twisted and rotated in such a way that it winds up the string/wire  28 , increasing its tension to overcome the centrifugal forces exerted by the springs  21  causing the FMSDS  1  to contract and deflate into a smaller diameter configuration from a larger diameter configuration, see FIG. 3. A contracted FMSDS  1  can be pulled into the introducing catheter  56  by slowly pulling the screw knob syringe plunger  49 C upward, see FIG. 3 and FIG. 5. Note the presence of the string/wire restricted holes  98 , helps guide the motion of string/wire  28  along its axial line inside this embodiment.  
         [0023]    Since flow Q is proportional to R 4  (where R is the radius of the artery), any incremental change in the radial length of a given artery will make tremendous difference in flow. Flow is critical to the stenting operation as any obstruction or decrease in radial length will lead to fatal cardiac problems such as ventricular fibrillation, ventricular arrhythmia or ventricular tachycardia etc. Hence, the advantage of FMSDS  1  delivery system unlike the balloon systems is that this delivery system allows the maintenance of maximum possible downstream antegrade blood flow by least possible non-obstruction in the radial length of the coronary artery throughout the stenting or angioplasty process. More over the FMSDS  1  system provides a uniform as well as individualized better custom fit of the stent inside coronary artery walls, just as good as the balloon devices do, but this may not happen with the self-deploying stent delivery systems. Also this delivery system can be cleaned and sterilized and can be used again if it is made from smooth flexible metallic plates. However, if FMSDS  1  is made from non-allergic plastic then it can be disposed.  
         [0024]    The FMSDS  1  must be heparinized, made with complete smooth edges that have great flexibility so as to not cause any coagulations, lacerations and injury inside the coronary arteries. Appropriate markers and bioluminescent dye and materials can be applied to the FMSDS  1  for aiding in positioning the FMSDS  1  inside the heart or other part of the body when doing stenting and angioplasty procedures. Finally, note that many different shapes and sizes and lengths can be designed on this particular theme of the stent delivery system.