Abstract:
Endovascular stent insertion methods are provided. In one embodiment for end-to-side anastomosis the method includes disposing an endovascular stent in a transparent sheath; inserting a guide wire through a guide needle into first and second blood vessels; sliding the endovascular stent into both the first and second blood vessels along the guide wire and the guide needle to dispose in a position between spaced first and second blood vessels; and pulling the sheath when an intermediate annular marker band of the endovascular stent seen through the transparent sheath is substantially disposed between the first blood vessel and the second blood vessel to release the endovascular stent so that the endovascular stent is adapted to expand to securely hold the facing ends of the first and second blood vessel together.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to endovascular stents and more particularly to an improved endovascular stent insertion method to perform sutureless vessel anastomosis. 
     2. Description of Related Art 
     With respect to prior vascular anastomosis techniques, end-to-side anastomosis and end-to-end anastomosis are most used techniques. Suture may be either continuous suture or interrupted suture. However, either suture may lead to the problem of anastomosis stricture. There are two causes for this problem. One is technical error. The other is abnormal vascular intimal hyperplasia caused by iatrogenic endovascular injury after suture injuries. Even an experienced surgeon can not avoid a hundred percent the possible adverse results of vascular anastomosis by sutures which may cause further anastomosis strictures. 
     Improvement of vascular anastomosis techniques had been an issue for vascular surgeons. Surgeons tried whatever they can to decrease the possibility of anastomosis stricture. Some anastmosis methods had been proposed such as applying laser or heat in small blood vessels for a single anastomosis suture and various anastomosis sutures, newly developed variable devices for vascular anastomosis, and applying adhesive materials for blood vessel anastomosis so as to achieve better long term results. 
     However, no perfect anastmosis technique had been developed yet. There are many problems to be overcome. There is a need for a simple, safe, quick, reliable, and cost effective technique as a replacement of the conventional vascular anastomosis techniques using sutures. This anastomosis method using stent grafts to connect vessels are designed to be applied in peripheral vascular anatomosis. 
     As shown in  FIG. 9 , a typical endovascular stent  140  is shown. It is cylindrical (i.e., the same diameter). Hence, it is limited to apply blood vessels with the same diameters. 
     As shown in  FIG. 10 , a typical artificial blood vessel  150  is shown. It is elongated and has one end connected to an artery  160  and the other end connected to a vein  170 . However, in practice the typical artificial blood vessel  150  may in the long run cause stricture at its junction with a human blood vessel after conventional suture anastomosis. As a result, thromboses may form at the junction stenosis. This may be caused due to the following reasons. First reason is that abnormal growth of epithelial tissues, too much platelets coagulation and subsequent thrombi formation are caused by iatrogenic endovascular injury after surgery. Second reason is that thrombi formation is caused by turbulence formed at the junction of an artificial blood vessel and a human blood vessel due to blood vibration. Third reason is the different degrees of compliance at the junction of the inserted artificial blood vessel  150  and a human blood vessel. As a result, thrombosis is formed due to stricture at anastomosis. 
     Hence, the typical vascular anastomosis techniques using conventional sutures are disadvantageous. Both typical endovascular stent  140  and artificial blood vessel  150  have a number of problems. Thus, the need for improvement still exists. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a method of implanting an endovascular stent into a human body vessel for end-to-end anastomosis, comprising the steps of locating first and second blood vessels to be connected together as target vessels; performing a blood control on each end of the first and second blood vessels by clamping; inserting a guide needle into each of the first and second blood vessels; injecting a diluted medicine of heparin into each of the first and second blood vessels for expansion of the lumen and for accurate sizing; using a C-shaped vessel sizer to measure the diameter of each of the first and second blood vessels; taking the measurement result as a basis for selecting an endovascular stent having a waterproof inner membrane, a front section, a rear section, and an intermediate annular marker band between the front section and the rear section; disposing the endovascular stent in a transparent sheath; inserting a guide wire through a guiding needle into the first and second blood vessels; sliding the endovascular stent into the first and second blood vessels along the guide wire and the guide needle to dispose between the spaced first and second blood vessels; and pulling the sheath when the marker band of the endovascular stent seen through the transparent sheath is substantially between the first blood vessel and the second blood vessel to release the endovascular stent, and the endovascular stent expands to fasten the facing ends of the first and second blood vessel together. 
     It is another object of the invention to provide a method of implanting an endovascular stent into a human body for end-to-side anastomosis, comprising the steps of locating first and second blood vessels to be connected together as target vessels; 
     performing a blood control on each of the first and second blood vessels by clamping; inserting a guide needle into each of the first and second blood vessels; injecting a diluted medicine of heparin into each of the first and second blood vessels for expansion of the lumen and for accurate sizing; using a C-shaped vessel sizer to measure the diameter of each of the first and second blood vessels; taking the measurement result as a basis for selecting first and second endovascular stents having a waterproof inner membrane, a front section, a rear section, and an intermediate annular marker band between the front section and the rear section; disposing the first endovascular stent in a transparent first sheath and disposing the second endovascular stent in a transparent second sheath respectively; inserting a first guide wire through a first guide needle into the first blood vessel with an artificial blood vessel put on the first guide wire, the artificial blood vessel including a section to be connected to vein, the section to be connected to vein having a first end and a second end, and the section to be connected to vein being rely on the first blood vessel; putting the first endovascular stent on the first guide wire to slide it through the first guide wire and the first guide needle into the first blood vessel; pulling the first sheath when the marker band of the first endovascular stent seen through the transparent sheath is substantially between the first blood vessel and the first end of the section to be connected to vein to release the first endovascular stent, the first endovascular stent expands to fasten the first end of the section to be connected to vein and the facing end of the first blood vessel together; inserting a second guide wire through a second guide needle into the second blood vessel with the artificial blood vessel put on the second guide wire; putting the second endovascular stent on the second guide wire to slide it through the second guide wire and the second guide needle into the second blood vessel; and pulling the second sheath when the marker band of the second endovascular stent is substantially between the second blood vessel and the second end of the section to be connected to vein to release the second endovascular stent, and the second endovascular stent expands to fasten the second end of the section to be connected to vein and the facing end of the second blood vessel together. 
     It is a further object of the invention to provide an endovascular stent for implanting into a human body for end-to-end anastomosis, the endovascular stent being self-expandable and comprising a waterproof membrane formed on an inner surface thereof; and a forward section having a rear end integrally formed with an artificial blood vessel of the same diameter, a guide needle in front of the forward section, and a guide wire adapted to insert through the guide needle into a blood vessel for securing the endovascular stent to the blood vessel. 
     The advantage of the above endovascular stent is the elimination of the marker band since the artificial blood vessel and the endovascular stent are already formed integrally. This is a great improvement over the prior art which involves an inconvenient registration of the marker band for connecting the separate artificial blood vessel and the endovascular stent together. 
     By utilizing the invention, the following advantages are obtained. Technical error is substantially eliminated during surgery. Abnormal growth of endothelial tissues caused by iatrogenic surgical injury of sutures and needles after surgery is also eliminated. The invention is particularly useful to patients suffered chronic kidney disease or patients needing dialysis treatments because it can greatly reduce surgery time and eliminate anastomosis stricture. The invention can facilitate surgery and greatly increase the surgery success probability. No needle stitching for sewing two separate sections of blood vessel is needed. Surgery time is greatly reduced since no needle stitching being involved. The invention is applicable to anastomosis of artificial blood vessel or autogenous vessels. The diameter of a tubelike endovascular stent can be uniform or the diameter of front section thereof is not equal to that of rear section thereof. This makes the invention to be more adaptable. The T-shaped artificial blood vessel can effectively prevent thromboses from forming. 
     The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1   a  is a perspective view of a first preferred embodiment of endovascular stent according to the invention; 
         FIG. 1   b  is a perspective view of a second preferred embodiment of endovascular stent according to the invention; 
         FIG. 2  is a schematic perspective view of a C-shaped vessel sizer according to the invention; 
         FIG. 3  is a schematic perspective view of end-to-end anastomosis performed in a surgery according to the invention; 
         FIG. 4  is a schematic perspective view of end-to-side anastomosis performed in a surgery according to the invention; 
         FIG. 5  is another schematic perspective view of end-to-side anastomosis performed in a surgery according to the invention as a subsequent step of  FIG. 4 ; 
         FIG. 6  is a schematic perspective view of end-to-side anastomosis performed in a surgery according to the invention where the insertion has been completed; 
         FIG. 7  is a perspective view of a third preferred embodiment of endovascular stent according to the invention; 
         FIG. 8  is a perspective view of a fourth preferred embodiment of endovascular stent according to the invention; 
         FIG. 9  is a perspective view of a typical endovascular stent; and 
         FIG. 10  is a perspective view of a typical artificial blood vessel. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1   a  and  1   b , an endovascular stent  10  according to the invention is shown. The endovascular stent  10  is self-expandable. A medical employee may pull a sheath and the endovascular stent  10  may slide to separate from the sheath subsequently. The separated endovascular stent  10  may expand immediately to have both ends securely fastened at one end of a first blood vessel and a facing end of a second blood vessel respectively. As a result, the two blood vessels are connected together. 
     Referring to  FIGS. 1   a ,  1   b ,  2  and  3 , an endovascular stent insertion method with respect to end-to-end anastomosis in accordance with the invention is illustrated. The method comprises the following steps: 
     A1) locating two blood vessels to be anastomosed (i.e., connected together as target vessels); 
     B1) performing a blood control of a first blood vessel  70  and a blood control of a second blood vessel  80  respectively; 
     C1) Inserting a guide needle into each of the first and second blood vessels  70 ,  80  and injecting a diluted medicine of heparin into each of the first and second blood vessels  70 ,  80  for expanding both the first and second blood vessels  70 ,  80 ; 
     D1) Using a C-shaped vessel sizer  20  to measure diameter of a blood vessel (see  FIG. 2 ) and taking the measurement result as a basis for selecting an appropriate endovascular stent in which the endovascular stent labeled by numeral  60  has a membrane (not shown) on its inner surface, the membrane is waterproof, the endovascular stent  60  has a front half section and a rear half section having a diameter smaller, larger, or the same as that of the front half section so as to accommodate many blood vessels of different diameters for vascular anastomosis, an annular marker band is formed about the central portion of the endovascular stent  60 , the endovascular stent  60  is disposed in a sheath prior to separation, the sheath is transparent, and the marker band of the endovascular stent  60  can be clearly seen prior to the separation; 
     E1) inserting a guide wire  30  through a guide needle  50  into the first blood vessel  70  in which the first blood vessel  70  is either an artificial blood vessel or an autogenous transplant, and the guide wire  30  is further inserted into the second blood vessel  80 , and the endovascular stent  60  is adapted to slide into the first blood vessel  70  and the second blood vessel  80  along the guide wire  30  and the guide needle  50  to dispose in a position between the spaced first and second blood vessels  70 ,  80 ; and 
     F1) clearly viewing the marker band of the endovascular stent  60  through the transparent sheath between the first blood vessel  70  and the second blood vessel  80  so that a medical employee may then pull the sheath to release the endovascular stent  60 , and the endovascular stent  60  expands automatically to securely fasten the facing ends of the first blood vessel  70  and the second blood vessel  80  together. This finishes the anastomosis. 
     Referring to  FIGS. 1   a ,  1   b ,  2 ,  4 ,  5  and  6 , an endovascular stent insertion method with respect to end-to-side anastomosis in accordance with the invention is illustrated. The method comprises the following steps: 
     A2) locating two blood vessels to be anastomosed (i.e., connected together as target vessels); 
     B2) performing a blood control of a first blood vessel  100  and a blood control of a second blood vessel  110  respectively; 
     C2) inserting a guide needle into each of the first and second blood vessels  100 ,  110  and injecting a diluted medicine of heparin into each of the first and second blood vessels  100 ,  110  for expanding the first and second blood vessels  100 ,  110  respectively; 
     D2) using a C-shaped vessel sizer  20  to measure diameter of each of two blood vessels and taking the measurement result as a basis for selecting two appropriate endovascular stents in which each endovascular stent has a membrane (not shown) on its inner surface, the membrane is waterproof, the endovascular stent has a front half section and a rear half section having a diameter smaller, larger, or the same as the diameter of the front half section so as to accommodate many blood vessels of different diameters for vascular anastomosis, an annular marker band  11  (see  FIGS. 1   a  and  1   b ) is formed about the central portion of the endovascular stent, the endovascular stent is disposed in a sheath prior to separation, the sheath is transparent, and the marker band of the endovascular stent can be clearly seen prior to the separation; 
     E2) inserting a first guide wire (not numbered) through a first guide needle (not shown) into the first blood vessel  100 , an artificial blood vessel  40  is already put on the first guide wire, the artificial blood vessel  40  has a section to be connected to vein  42  having a first end  421  and a second end  422 , and the section to be connected to vein  42  is rely on the first blood vessel  100 ; 
     F2) putting a first endovascular stent  90  on the first guide wire to cause it to slide through the first guide wire and the first guide needle into the first blood vessel  100 ; 
     G2) clearly viewing the marker band of the first endovascular stent  90  through the transparent sheath between the first blood vessel  100  and the first end  421  of the section to be connected to vein  42  of the artificial blood vessel  40  so that a medical employee may pull the sheath to release the first endovascular stent  90 , and the first endovascular stent  90  expands automatically to securely fasten the first end  421  of the section to be connected to vein  42  and the facing end of the first blood vessel  100  together; 
     H2) similarly inserting a second guide wire (not numbered) through a second guide needle (not shown) into the second blood vessel  110 , an artificial blood vessel  40  is already put on the second guide wire, and the section to be connected to vein  42  is rely on the first blood vessel  100 ; 
     I2) putting a second endovascular stent  120  on the second guide wire to cause it to slide through the second guide wire and the second guide needle into the second blood vessel  110 ; and 
     J2) clearly viewing the marker band of the second endovascular stent  120  through the transparent sheath between the second blood vessel  110  and the second end  422  of the section to be connected to vein  42  of the artificial blood vessel  40  so that a medical employee may pull the sheath to release the second endovascular stent  120 , and the second endovascular stent  120  expands automatically to securely fasten the second end  422  of the section to be connected to vein  42  and the facing end of the second blood vessel  110  together. This finishes anastomosis. 
     The artificial blood vessel  40  further comprises a section to be connected to artery  41  having one end connected to an artery and the other end to be connected to the section connected to vein  42  in which an enlargement  43  is formed at the joining portion of the section connected to vein  42  and the section to be connected to artery  41 . The enlargement  43  may prevent thrombosis from forming. The section to be connected to artery  41  and the section to be connected to vein  42  are integrally formed together. The artificial blood vessel  40  is T-shaped. 
     Referring to  FIG. 7 , a third preferred embodiment of endovascular stent  131  according to the invention is shown. The characteristics of the third preferred embodiment of endovascular stent  131  are detailed below. The endovascular stent  131  is self-expandable. A membrane (not shown) is formed on an inner surface of the endovascular stent  131 . The membrane is waterproof. The endovascular stent  131  has a forward section  1311  and a guide needle  1312  in front of the forward section  1311 . The forward section  1311  has its rear end integrally formed with an artificial blood vessel  1313  of the same diameter. A guide wire  1314  is inserted through the guide needle  1312  into a desired blood vessel for securing the endovascular stent  131  to the blood vessel. This embodiment is applicable to one end of the endovascular stent. Also, the marker band is eliminated since the artificial blood vessel and the endovascular stent are already formed integrally. This is a great improvement over the prior art which involves registering the marker band for connecting the separate artificial blood vessel and the endovascular stent together. However, this prior art technique is very inconvenient during surgery. 
     Referring to  FIG. 8 , a fourth preferred embodiment of endovascular stent  132  according to the invention is shown. The characteristics of the fourth preferred embodiment of endovascular stent  132  are detailed below. The endovascular stent  132  is self-expandable. A membrane (not shown) is formed on an inner surface of the endovascular stent  132 . The membrane is waterproof. At a front portion, the endovascular stent  132  has a forward section  1321  and a guide needle  1322  in front of the forward section  1321 . The forward section  1321  has its rear end integrally formed with an artificial blood vessel  1323  of the same diameter. At a rear portion, the endovascular stent  132  has a rear section (not numbered) and a guide needle (not numbered) in rear of the rear section. The rear section has its rear end integrally formed with the artificial blood vessel  1323  of the same diameter. Likewise, a guide wire (not numbered) is inserted through the guide needle (not numbered) into a desired blood vessel for securing the endovascular stent  132  to the blood vessel. This embodiment is applicable to both ends of the endovascular stent. Also, the marker band is eliminated since the artificial blood vessel and the endovascular stent are already formed integrally. This is a great improvement over the prior art which involves registering the marker band for connecting the separate artificial blood vessel and the endovascular stent together. This prior art technique is very inconvenient during surgery. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.