Patent Publication Number: US-2010114305-A1

Title: Implantable Valvular Prosthesis

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a prosthesis, more particularly to an implantable valvular prosthesis. 
     2. Description of the Related Art 
     Various artificial heart valves for replacing anatomic valves are available in the market and are capable of curing valvular heart diseases that arise from valvular insufficiency or stenosis. Referring to  FIG. 1 , US2006/0167543 discloses a valvular prosthesis  20  for replacing an anatomic valve such as an aortic valve  101  that has three cusp portions. The valvular prosthesis  20  surrounds a longitudinal axis and includes a stent body member, a graft, and valve flaps. The stent body member includes a distal anchor section  201 , an intermediate annular section  203 , a transitional section  202  that interconnects the distal anchor section  201  and the intermediate annular section  203 , and that extends downward from the distal anchor section  201  to the intermediate annular section  203  and inwardly toward the longitudinal axis, and a proximal anchor flange that projects radially and away from the longitudinal axis. The valvular prosthesis  20  is percutaneously delivered to a position of the aortic valve  101  that controls passage of blood flowing from a left ventricle  103  to an aorta  100  by virtue of cardiac catheterization. Subsequently, the valvular prosthesis  20  is deployed at the position of the aortic valve  101  in order to press each of the cusp portions of the aortic valve  101  against the aorta  100  and thereby replace the aortic valve  101 . 
     The artery (the aorta  100  in this prior art) has a luminal wall that has a tubular juncture region to which a base portion of the anatomic valve (the aortic valve  101  in this prior art) is connected, a tubular proximal region adjacent to the tubular juncture region, and a tubular distal region adjacent to the tubular proximal region and opposite to the tubular juncture region. The tubular juncture region, the tubular proximal region, and the tubular distal region cooperatively define an inner convex surface of a sinus of Valsalva  102 . The ventricle (the left ventricle  103  in this prior art) has a tubular bordering region that confronts a chamber of the ventricle, that is adjacent to the tubular juncture region, and that is upstream of the tubular proximal region and the tubular distal region in terms of an ejected flow of blood under systole pressure. 
     When the valvular prosthesis  20  is deployed at the position of the aortic valve  101 , the distal anchor section  201 , the transitional section  202 , and the intermediate annular section  203  cooperatively press only some parts of each of the cusp portions against the tubular proximal region. Since the shape of the transitional section  202  is not conformable to the shape of the tubular proximal region, the transitional section  202  is incapable of abutting against the tubular proximal region and pressing each of the cusp portions entirely against the inner convex surface of the sinus of Valsalva  102 . Consequently, a space  104  between each of the cusp portions and the inner convex surface of the sinus of Valsava  102  is formed. Blood may flow into the space  104  and be trapped therein, thereby resulting in thrombus. 
     Since the shape of the distal anchor section  201  is not conformable to the shape of the tubular distal region, the distal anchor section  201  is unable to abut against the tubular distal region therealong. Hence immobility of the distal anchor section  201  in the aorta  100  cannot be insured. Particularly, when the blood flows from the left ventricle  103  to the aorta  100 , the valvular prosthesis  20  may further be shaken to shift from the position of the aortic valve  101  as a result of impact by a surge of the blood under the systole pressure. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an implantable valvular prosthesis that can overcome the aforesaid drawbacks of the prior art. 
     According to this invention, an implantable valvular prosthesis is adapted for implantation in a position of an anatomic valve that controls passage of blood flowing from a ventricle to an artery in a patient&#39;s heart. The artery has a luminal wall that has a tubular juncture region to which a base portion of the anatomic valve is connected, a tubular proximal region adjacent to the tubular juncture region, and a tubular distal region adjacent to the tubular proximal region and opposite to the tubular juncture region. The ventricle has a tubular bordering region that confronts a chamber of the ventricle, that is adjacent to the tubular juncture region, and that is upstream of the tubular proximal region and the tubular distal region in terms of an ejected flow of the blood under systole pressure. The implantable valvular prosthesis includes a tubular stent body and at least one valve flap member. 
     The tubular stent body is made from a material expandable at a site of implantation, and has luminal and abluminal surfaces, and a central tubular opening along a central longitudinal axis of the tubular stent body. The tubular stent body includes a valve exclusion region and a tubular flare region. 
     The valve exclusion region is configured to be of a dimension when the tubular stent body is expanded, such that during systole, the valve exclusion region is kept in intimate contact with the tubular juncture region while pressing the base portion of the anatomic valve to deflect a cusp portion of the anatomic valve to orient along the central longitudinal axis. 
     The tubular flare region is divergent from the valve exclusion region towards the artery, terminates at a cusp-concealing waistline that is brought in intimate contact with the luminal wall of the artery so as to ensure concealing of the cusp portion from exposure to a lumen of the artery, and is configured such that the tubular flare region is brought to abut against the tubular proximal region along the central longitudinal axis so as to ensure the concealing of the cusp portion of the anatomic valve when the tubular juncture region is distended as a result of the systole pressure, and such that the tubular flare region counteracts a biasing force of the cusp portion of the anatomic valve. A profile of the tubular flare region is able to ensure immobility of the tubular stent body relative to the tubular juncture region. 
     The valve flap member is disposed to associate with the tubular flare region, extends from the luminal surface of the tubular flare region of the tubular stent body towards the central longitudinal axis, and is biased to a closed position under zero pressure differential across the implantable valvular prosthesis. The closed position acts to interrupt a passage of the blood that flows through the central tubular opening. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiments of this invention, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view illustrating the situation where a valvular prosthesis disclosed in US2006/0167543 is implanted in a sinus of Valsalva; 
         FIG. 2  is a schematic view of the first preferred embodiment of an implantable valvular prosthesis according to this invention; 
         FIG. 3  is a schematic view illustrating a tubular stent body according to the first preferred embodiment; 
         FIG. 4  is a schematic view illustrating how the implantable valvular prosthesis shown in  FIG. 2  is delivered to the sinus of Valsalva by virtue of a catheter according to the first preferred embodiment; 
         FIG. 5  is a schematic view illustrating how the implantable valvular prosthesis shown in  FIG. 2  is implanted in the sinus of Valsalva according to the first preferred embodiment; and 
         FIG. 6  is a schematic view illustrating a tubular stent body of the second preferred embodiment of an implantable valvular prosthesis according to this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before the present invention is described in greater detail, it should be noted that same reference numerals have been used to denote like elements throughout the specification. 
     Referring to  FIGS. 2 ,  3 , and  5 , the first preferred embodiment of an implantable valvular prosthesis according to the present invention is adapted for implantation in a position of an anatomic valve which controls passage of blood flowing from a ventricle to an artery in a patient&#39;s heart. In this embodiment, the implantable valvular prosthesis for the sake of illustration is shown to be implanted in a position of an aortic valve  800  that controls passage of blood flowing from a left ventricle  803  to an aorta  801 . The implantable valvular prosthesis can also be implanted in a position of a pulmonary valve that controls passage of blood flowing from a right ventricle to pulmonary arteries (not shown). The implantable valvular prosthesis includes a tubular stent body  5  and three valve flap members  900 . 
     The tubular stent body  5  is made from a material expandable at a site of implantation, and has luminal and abluminal surfaces, and a central tubular opening along a central longitudinal axis (X) of the tubular stent body  5 . In this embodiment, the tubular stent body  5  is made from a plurality of metal struts  51  that are made from a shape memory material, that intersect with each other, and that cooperatively define a plurality of through-holes  50  each in a shape of a rhombus. It is noted that the shape of the through-holes  50  is not limited to the rhombus in other embodiments of the invention. 
     The tubular stent body  5  includes a valve exclusion region  53  and a tubular flare region  522 . The valve exclusion region  53  has a plurality of apexes  511  that are formed by the intersections of the metal struts  51  and a plurality of the through-holes  50 . The valve exclusion region  53  is configured to be of a dimension when the tubular stent body  5  is expanded, such that during systole, the valve exclusion region  53  is kept in intimate contact with a tubular juncture region of a luminal wall of the aorta  801  while pressing a base portion of the aortic valve  800  to deflect a cusp portion of the aortic valve  800  to orient along the central longitudinal axis (X). 
     The tubular flare region  522  is divergent from the valve exclusion region  53  towards the aorta  801 , and terminates at a cusp-concealing waistline  523  that is brought in intimate contact with the luminal wall of the aorta  801  so as to ensure concealing of the cusp portion from exposure to a lumen of the aorta  801 . The tubular flare region  522  is capable of abutting against a tubular proximal region of the luminal wall of the aorta  801  and of pressing the aortic valve  800  entirely against the inner convex surface of the sinus of Valsalva  802  because the shape of the tubular flare region  522  is conformable to the shape of the tubular proximal region. Furthermore, the tubular flare region  522  is configured such that the tubular flare region  522  is brought to abut against the tubular proximal region along the central longitudinal axis (X) so as to ensure the concealing of the cusp portion of the aortic valve  800  when the tubular juncture region is distended as a result of the systole pressure, and such that the tubular flare region  522  counteracts a biasing force of the cusp portion of the aortic valve  800 . Thus, during the systole or the diastole, there is little or no space formed between each of the cusp portions and the inner convex surface of the sinus of Valsalva  802 , thereby alleviating the possibility of thrombosis. 
     The tubular stent body  5  further includes a tubular tapering region  521  that is convergent from the cusp-concealing waistline  523  towards the aorta  801 . The tubular tapering region  521  is capable of abutting against a tubular distal region of the luminal wall of the aorta  801  because the shape of the tubular tapering region  521  is conformable to the shape of the tubular distal region. Furthermore, the tubular tapering region  521  is configured such that the tubular tapering region  521  is brought to abut against the tubular distal region along the central longitudinal axis (X) when the tubular juncture region is distended as a result of the systole pressure. When the blood flowing from the left ventricle  803  to the aorta  801  impacts against the tubular tapering region  521 , the implantable valvular prosthesis could stand unmoved at the position of the aortic valve  800 . 
     The tubular stent body  5  further includes an artery anchor region  54  that extends from the tubular tapering region  521 , that has a plurality of apexes  511  formed by the intersections of the metal struts  51  and a plurality of the through-holes  50 , and that is configured to be of a dimension when the tubular stent body  5  is expanded, such that during the systole, the artery anchor region  54  is kept in intimate contact with the luminal wall of the aorta  801 . 
     In this embodiment, the valve exclusion region  53 , the tubular flare region  522 , the tubular tapering region  521 , and the artery anchor region  54  are formed integrally. 
     Preferably, the ratio of the external diameter pertaining to the cusp-concealing waistline  523  to the external diameter pertaining to the artery anchor region  54  is 1.3 to 1. The ratio of the external diameter pertaining to the cusp-concealing waistline  523  to the external diameter pertaining to the valve exclusion region  53  is 1.3 to 1 as well. These two ratios correspond to the ratio of the maximum internal diameter pertaining to the sinus of Valsalva  802  to the internal diameter pertaining to the aorta  801 . Consequently, the tubular stent body  5  can be securely installed in the patient&#39;s heart. It is noted that the external diameters of the cusp-concealing waistline  523 , the valve exclusion region  53 , and the artery anchor region  54  can be modified in order to correspond to different ratios of the maximum internal diameter pertaining to the sinus of Valsalva  802  to the internal diameter pertaining to the aorta  801 . 
     The valve flap members  900  which are able to replace the aortic valve  800 , and which are disposed to associate with the tubular flare region  522 , extend from the luminal surface of the tubular flare region  522  of the tubular stent body  5  towards the central longitudinal axis (X) The valve flap members  900  are biased to a closed position under zero pressure differential across the implantable valvular prosthesis. The closed position acts to interrupt a passage of the blood that flows through the central tubular opening. The valve flap members  900  are able to replace the pulmonary valve (not shown) when the implantable valvular prosthesis is implanted in the position of the pulmonary valve. 
     In this embodiment, the valve flap members  900  are sewn to the tubular flare region  522 . The tubular flare region  522  has a plurality of first positioning members  525  that are spaced apart, and a plurality of second positioning members  526  that are spaced apart and that are circular. The first and second positioning members  525 ,  526  are suitable for orienting the implantable valvular prosthesis to a correct position relative to the aortic valve  800 . Preferably, the first and second positioning members  525 ,  526  are made from a radiopaque material. It is noted that the first and second positioning members  525 ,  526  can be omitted in other embodiments. 
     The implantable valvular prosthesis further includes a graft member  7  which covers the abluminal surface of the valve exclusion region  53  of the tubular stent body  5  so as to ensure that the central tubular opening is a sole available route for the ejected flow of the blood under the systole pressure during the systole. In this embodiment, the graft member  7  covers a portion of the abluminal surface of the tubular flare region  522  of the tubular stent body  5  as well. It is noted that the graft member  7  can be applied to other regions of the tubular stent body  5  when needed. 
     The implantable valvular prosthesis further includes a plurality of anchoring needles  6  which are configured when the tubular stent body  5  is expanded, such that the anchoring needles  6  are brought to engage the luminal wall of the aorta  801  and to anchor thereat. In this embodiment, the anchoring needles  6  extend upwardly and obliquely from the apexes  511  of the valve exclusion region  53  and the artery anchor region  54 . 
     Referring to  FIGS. 2 ,  4 , and  5 , a pulling string  903  extends through the through-holes  50  of the artery anchor region  54 . A guide wire  902  extends longitudinally through the tubular stent body  5 . By virtue of the pulling string  903  and the guide wire  902 , the tubular stent body  5  can be stretched in a direction along the central longitudinal axis (X) and contracted inwardly toward the central longitudinal axis (X). Thus, the tubular stent body  5  can be placed into a catheter  901 . Since the feature of the invention does not reside in a method of placing the tubular stent body  5  into the catheter  901 , further details of the same are omitted herein for the sake of brevity. 
     During cardiac catheterization, after one end of the catheter  901  is delivered to the sinus of Valsalva  802  and passed through the aortic valve  800 , the valve exclusion region  53 , the tubular flare region  522 , the tubular tapering region  521 , and the artery anchor region  54  are withdrawn from the catheter  901  in sequence. The valve exclusion region  53  withdrawn from the catheter  901  is expanded to intimately contact the tubular juncture region. The anchoring needles  6  on the apexes  511  of the valve exclusion region  53  are brought to pierce upwardly and obliquely into the luminal wall of the aorta  801 . Afterward, the tubular flare region  522  withdrawn from the catheter  901  is expanded to abut against the tubular proximal region of the luminal wall of the aorta  801 . Subsequently, the tubular tapering region  521  withdrawn from the catheter  901  is expanded to abut against the tubular distal region of the luminal wall of the aorta  801 . Two of the through-holes  50  of the tubular tapering region  521  are oriented to a position such that each of the two through-holes  50  is in spatial communication with a respective one of coronary arteries  804 . Finally, the artery anchor region  54  withdrawn from the catheter  901  is expanded to intimately contact the luminal wall of the aorta  801 . 
     Since the tubular stent body  5  abuts against the luminal wall of the aorta  801  along its length, the implantable valvular prosthesis is securely immobilized at the position of the aortic valve  800  even though the blood flowing from the left ventricle  803  to the aorta  801  impacts against the implantable valvular prosthesis. 
     When the tubular stent body  5  is not positioned at a desired place, the tubular stent body  5  can be pulled back into the catheter  901  via the pulling string  903  that can drag the apexes  511  of the artery anchor region  54  before the artery anchor region  54  is entirely withdrawn from the catheter  901 . Therefore, the position of the tubular stent body  5  can be adjusted when needed. 
     A chest X-ray is suitable for determination of the position of the implantable valvular prosthesis. After the cardiac catheterization, the relative position between the first positioning members  525 , the second positioning members  526 , and the heart can be revealed by way of a chest radiograph. 
     Referring to  FIG. 6 , the second preferred embodiment of the implantable valvular prosthesis according to this invention is illustrated. The structure of this preferred embodiment is similar to the structure of the first preferred embodiment. The difference between this preferred embodiment and the first preferred embodiment resides in that the artery anchor region  54  in the second preferred embodiment is longer than that of the first preferred embodiment, thereby resulting in enhanced secure installation of the implantable valvular prosthesis at the implantation site. 
     While the present invention has been described in connection with what are considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements.