Abstract:
Apparatus for measuring length in a blood vessel includes an inner barrel slideably fitting within an outer barrel. The apparatus also preferably includes a zero ring for initializing a position of the inner barrel relative to the outer barrel, wherein the zero ring is rotatably positioned on the outer barrel. The apparatus further includes a small-diameter clamp extending outwardly from the inner barrel for holding a catherization mechanism for visualizing a blood vessel, wherein the catherization mechanism includes a marker and a scale is positioned on the inner barrel for indicating a displacement of the inner barrel relative to the outer barrel in response to the catherization mechanism marker.

Description:
REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. provisional application Serial Nos. 60/188,313, filed Mar. 10, 2000, and 60/241,118, filed Oct. 17, 2000, the entire contents of both being incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to medical diagnostics and, in particular, to apparatus for measuring length and other physical characteristics of arteries, veins, and other lumens of the body. 
     BACKGROUND OF THE INVENTION 
     In the field of medical diagnostics and treatment, cardiologists often treat patients with conditions affecting blood flow in vessels near the heart. In these treatment procedures, various measurements of affected blood vessels need to be accurately determined. In an effort to restore blood flow through cardiac arteries narrowed by plaque deposits or other obstructions, interventional procedures such as balloon catherization, are often used. In this particular procedure, an inflatable balloon is fed into the cardiac artery and inflated to dilate the artery in the affected length of the vessel. After dilation, a stent, which is a thin scaffold or support typically made of plastic or metal and formed in the shape of a perforated tube, is delivered and installed within the blood vessel to maintain an increased blood flow through the cross-sectional flow path. 
     One of the difficulties cardiologists encounter in this procedure is the measurement of the distance and diameter of the affected length. These measurements are critical, because they are used to determine the stent size appropriate for the length. Accurate sizing of the stent is important to ensure its proper functioning. Consequently, selecting the appropriate stent is critical to the success of the procedure. The prior art contains several methods and apparatuses for making this measurement. 
     In one prior art approach, a cardiologist reviews x-ray images of the heart after contrast material is introduced into the bloodstream of the patient. The cardiologist must rely on experience and training to make a judgment regarding the size of the affected length. As such, this method may not always provide repeatability and precision in the measurement of the length. 
     In another prior art approach, x-ray images are processed by computer image analysis systems, which estimates the dimensions of the affected length. These measurements are based on various assumptions about the position of the artery, the axis of the x-ray image, etc. Also, the additional equipment required for this procedure may make it economically unfavorable or even cost-prohibitive. A further prior art approach uses ultrasonic transducers that are fed into the patient&#39;s arteries via a catheter which “images” the vessel walls to estimate the length. This device is also very expensive and cumbersome to use. 
     In view of the foregoing, there is a need in the art to provide a new, simple device capable of accurately measuring the dimensions of a length, within a blood vessel, such as a cardiac artery. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to devices for measuring length and/or diameter in arteries, veins, and other lumens of the body. In a length-measuring embodiment, the apparatus includes a hand-held unit which remains outside the body, but which couples to, and cooperates with, one or more invasive catheters and/or guidewires to measure a length within a vessel. The hand-held unit further includes an inner barrel and outer barrel that slide relative to one another to position a scale with markings indicative of the length. The preferred embodiment also includes a zero ring for initializing the relative position of the barrels and scale in conjunction with the onset of the length measurement to ensure the accuracy of a measurement. The apparatus optionally includes a feature to hold a guidewire in a stationary position. 
     As is typical in the surgical profession, a radio opaque marker or similar device is placed on the catheter tip or other distal point. The marker point is then positioned at one end of the lesion, and subsequently displaced to the opposite end of the lesion using the inventive device. The measurement of a lesion, plaque region, obstruction, or other length of interest may be made by using the device according to the present invention. 
     One advantage of the invention is that the device may be used to measure the distance between any two points in the blood vessel. Another advantage is that the device may be used for measurement in any vessel that it or an attached catheter and/or guidewire can be inserted into and that fluoroscopy can view. A further advantage of the present invention is that the apparatus is used in a variety of manners to determine the dimensions of a length of the blood vessel. 
     A device for measuring the inside diameter of a vessel according to the invention includes a tube, measuring wires, and a knob. The tube is as long as necessary to reach the desired location, yet flexible enough to maneuver through vasculature. Holes run the length of the tube to accommodate multiple lumens including a central lumen that runs the entire length of the tube and a plurality of other lumens which are uniformly spaced around the central lumen but stop a short distance from the tip of the tube. These other lumens also have a slot cut into them that exposes a portion of the lumen. Wires are inserted in all the lumens except the central lumen. When the wires are pushed on their proximal ends, they expand by bulging out of the slots into the respective lumens. When the wires make contact with the inside of the vessel, they indicate the inside diameter of that vessel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of preferred apparatus in the zero position according to the invention for measuring length in a blood vessel; 
     FIG. 2 is a perspective view of the apparatus of FIG. 1 showing the inner barrel displaced along the length of the outer barrel; 
     FIG. 3 is a perspective view of a zero ring according to the invention; 
     FIG. 4 is a perspective view of an inner barrel associated to the apparatus of FIG. 1; 
     FIG. 5 is a perspective view of the preferred apparatus of FIG. 1 coupled to a catherization assembly; 
     FIG. 6 is a perspective view showing an alternative coupling to a catherization assembly; 
     FIG. 7 is a plan view of an alternative embodiment of the invention having a dual marker; 
     FIG. 8 is a sectional view taken along line  7 — 7  of FIG. 7 with the markers together; 
     FIG. 9 is a sectional view taken along line  7 — 7  of FIG. 7 with the markers separated; 
     FIG. 10 is a perspective view of still another embodiment of the invention having a rotating as opposed to translational indicator; 
     FIG. 11 is an enlarged perspective view of the tip end of the apparatus of FIG. 10; and 
     FIG. 12 is an enlarged perspective view of the knob end of the apparatus of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 through 6 depict a preferred embodiment according to the invention for measuring length in a blood vessel. The apparatus  10  includes two main components, an inner barrel  12  and an outer barrel  14 . The inner barrel  12  is an elongate member having a cross-sectional diameter of sufficient size to allow the inner barrel  12  to slide within the inner diameter  20  of the outer barrel  14 . Hence, the length measuring apparatus  10  of the present invention can be referred to as a telescoping device. All components of the length measuring device  10  can be made from a variety of materials though preferably medical-grade plastic is used, where possible. 
     The inner barrel  12  extends to a small-diameter clamp  22  comprising a pad of resilient material  22   a  having a slit  22   b.  This configuration allows the slit  22   b  to receive and retain smaller-diameter elements such as catheters or guidewires of various diameters through a simple insertion into the slit  22   b  of the pad  22   a.  In one mode of operation, the shaft of a balloon catheter is pushed into the slit  22   b,  as shown in FIG.  5 . Alternatively, a guidewire may be received by the slit, as shown in FIG.  6 . The pad  22   a  may be composed of any resilient material capable of reliably retaining these smaller-diameter elements, preferably without slippage. For example, dense foams and rubber-like materials may advantageously be used for such purpose. 
     Referring to FIGS. 2 and 4, the apparatus  10  includes a scale  24  marked on the inner barrel  12 . The scale  24  serves as a visual reference representing the displacement that occurs during a measurement. The scale  24  contains graduations  26  marked off in units of distance or size. The scale  24  preferably further includes a zero mark  28  that corresponds to zero displacement of the inner barrel  12 . When the small-diameter clamp  22  of the inner barrel  12  is seated in the terminus  30  of the main slot  32  of the outer barrel  14 , the scale  24  is in the zero position. That is, the zero mark  28  of the scale  24  is in line with the edge  34  of the main opening  21  of the outer barrel  14 . In this position, no displacement of the inner barrel  12  has occurred. 
     When the inner barrel  12  is displaced within the outer barrel  14 , the scale  24  is exposed as the inner barrel  12  leaves the main opening  21  of the outer barrel  14 . The distance of the displacement of the inner barrel  12  is indicated on the scale  24 . A reading of the distance is taken by determining the point at which the edge  34  of the main opening  21  of the outer barrel  14  aligns with the scale  24 . Alternatively, a pointer or other indicator may be attached to or defined by the outer barrel  14  and used to indicate the displacement distance on the scale  24 . 
     The outer barrel  14  is an elongate member that defines a main slot  32  for accommodating the small-diameter clamp extension of the inner barrel  12 , while preventing rotational movement of the inner barrel  12  within the outer barrel  14 . The main slot  32  preferably extends from the main opening  21  of the outer barrel  14  to a terminus  30  at the opposite end of the outer barrel  14 , but does not extend completely to the opposite end of the outer barrel  14 . 
     The outer barrel  14  further defines a guidewire hook  35 , shown in FIGS. 5 and 6. The guidewire hook  35  is an outwardly extending projection, or projections, that extend away from the body of the outer barrel  14 . Preferably, the guidewire hook  35  clips to the outer barrel  14 , enabling the guidewire hook  35  to be located at any position along the length of the outer barrel. Alternatively, the guidewire hook  35  can be integrally formed in or attached to the outer barrel  14 . In any case, the guidewire hook  35  is fashioned in a manner so as to allow it to receive a guidewire during a measurement procedure and retain the guidewire in a stationary position until measurement is complete. This allows a user to perform a measurement without moving the guidewire, which can be critical when using the length measuring apparatus  10  in conjunction with certain catheter systems, such as those using a rail system design, as is known in the art. 
     Referring to FIG. 3, the apparatus  10  includes a zero ring  16 , such as a ring- or band-like member, that sits in a recess  17  in the outer surface  18  of the outer barrel  14 . Preferably, the zero ring  16  fits over the outer barrel  14  in a snap fashion. That is, the outer barrel  14  is pressed through the slot  36  of the zero ring  16  until the zero ring  16  snaps around the outer surface  18  of the outer barrel  14 . A portion of the zero ring  16  is cut away, creating a slot  36 , to give the zero ring  16  a “C”-shaped configuration. 
     The width of the slot  36  on the zero ring  16  is sufficient to allow the extension of the inner barrel  12  including the small-diameter clamp to pass through the slot  36  without excessive resistance. The inner diameter of the zero ring  16  is large enough to allow the zero ring  16  to rotate about the outer surface  18  of the outer barrel  14  with only slight friction. This allows the zero ring  16  to remain in a selected position relative to the outer barrel  14  following rotation. Also, the inner diameter of the zero ring  16  is small enough to prevent the zero ring  16  from being easily removed from the outer barrel  14 . 
     The zero ring  16  operatively retains the inner barrel  12  in the zero position. Accordingly, the zero ring  16  can take on any form appropriate for this retention function. For example, the zero ring  16  may include a pin that passes through holes of the inner  12  and outer  14  barrels when aligned properly, a latch that retains the inner barrel within the outer barrel, a clamp that compresses the inner  12  and outer  14  barrels together, or any other form and/or structure capable of achieving the retention function. 
     As shown in FIGS. 5 and 6, the apparatus of the invention may be used with any commercially available catheterization assembly  80 , such as a guide catheter, balloon catheter, and so forth. For example, during a typical angioplasty procedure, a guide catheter  82  is inserted into the ostium (not shown) of either the left or right main coronary artery (not shown). A balloon catheter  84  is then inserted through the guide catheter and advanced to the location of the lesion (not shown). The balloon is inflated to dilate the vessel. It is at this time that a medical professional determines length of the lesion. The length measurement apparatus  10  is clamped onto the side of the guide catheter and balloon catheter. The small-diameter clamp  22  can receive and retain the balloon catheter, as shown in FIG. 5, or a guidewire itself  88 , as shown in FIG.  6 . Preferably, the guidewire hook  35  is utilized with rail-type system catheters. In this type of catheter assembly, the balloon catheter and guidewire are positioned side-by-side. Thus, the balloon catheter may be received within the slit of the small-diameter clamp  22 , with the guidewire being placed within the guidewire hook  35 . 
     The zero ring  16  controls the displacement of the inner barrel  12  of the length measuring device  10 . When displacement of the inner barrel  12  is not desired, such as during attachment of the length measuring apparatus  10  to a catheterization assembly, the zero ring  16  is rotated about the outer surface  18  of the outer barrel  14  to a closed position, i.e., a point where the slot  36  of the zero ring  16  is not aligned with the main slot  32  of the outer barrel  14 . In this configuration, the small-diameter clamp  22  of the inner barrel  12  remains seated in the terminus  30  of the main slot  32  and is physically prevented from moving out of that position. In this configuration, the scale  24  remains in the zero position, indicating that no displacement has occurred. When displacement is desirable, such as during a measurement procedure, the zero ring  16  is rotated about the outer surface  18  of the outer barrel  14  to an open position, i.e., a point at which the slot  36  of the zero ring  16  is aligned with the main slot  32  of the outer barrel  14 . In this position, an open passageway  38  is defined by the slot  36  of the zero ring  16  and the main slot  32  of the outer barrel  14 . The small-diameter clamp  22  of the inner barrel  12  can travel through this open passageway  38 , thereby allowing the inner barrel  12  to be displaced along the length of the outer barrel  14 . 
     The length measuring apparatus  10  may be utilized in conjunction with a catheterization assembly having two catheters, or one catheter and one guidewire. The catheters and/or guidewires contain a radio-opaque marker that marks the ends of the length of interest in the blood vessel. In operation, the length measuring apparatus  10  is attached either to the two catheters, or to the one catheter and one guidewire. Note that the large-diameter hub clamp  11  may be clamped onto either the hub of a guide catheter, a y-connector, a hub of a balloon catheter, or another type of hub, as is known in the art. This is accomplished by forcing the hub into the hub clamp  11 . The hub clamp  11  is an upstanding projection or projections on the outer barrel  14 . The hub clamp  11  has various structural features that allow it to receive and retain hubs and other bodies of various sizes and configurations. 
     Next, the shaft of the balloon catheter or guidewire is pressed into the slit  22   b  of small-diameter clamp  22 . If a rail system catheter is used, the guidewire is secured to the outer barrel  14  by pressing the guidewire into the guidewire hook  35 . During this attachment process, any displacement of the inner barrel  12  may expose a portion of the scale  24  and, consequently, could affect a subsequent measurement. To prevent this, the zero ring  16  is rotated to the closed position, which prevents such displacement by retaining the small-diameter clamp  22  of the inner barrel  12  in the terminus  30  of the main slot  32  of the outer barrel  14 . In this configuration, the length measuring device  10  is attached to the catheter(s) and/or guidewires without disturbing the position of the inner barrel  12 . Furthermore, the zero ring  16  prevents displacement during any positioning of the markers conducted subsequent to the attachment process. 
     Once the length measuring device  10  is attached to the catheter(s) and/or guidewires, the operator performs the measurement. The zero ring  16  is rotated to the open position, i.e., aligning the slot  36  of the zero ring  16  with the main slot  32  of the outer barrel  14 . An open passageway  38  is formed that allows inner barrel  12  to move out of the terminus  30  of the main slot  32  of the outer barrel  14 . Next, the inner barrel  12  and the attached catheter or guidewire are slideably displaced along the length of the outer barrel  14 . During this step, the small-diameter clamp extension  22  travels along the open passageway  38  and the scale  24  is gradually exposed. The inner barrel  12  is displaced until the end of the length of the blood vessel being measured is reached. Once the desired position is reached, the operator obtains the length measurement by reading the last exposed graduation  26  on the scale  24 , i.e., the graduation  26  aligned or nearly aligned with the main edge  34  of the main opening  21 , or an attached or integral pointer or other indicator, if present, of the outer barrel  14 . 
     The length measurement apparatus  10  functions with a catheterization mechanism  80  such as an over-the-wire catheter system or a rail system, as is known in the art. Also, the length measuring apparatus  10  may include a component that allows it to serve as the sole apparatus used in the measurement of a length of the blood vessel. For example, the inner and outer barrels may comprise elongate catheters having a marker such as a radio-opaque marker, fixed on a terminal end. In this example, no catheter or guidewire separate from the length measuring apparatus need be utilized to obtain a measurement of the length. A measurement with this embodiment would be determined in the same manner detailed above, i.e., the displacement distance would be determined by reading the scale. 
     As can be readily understood by persons of ordinary skill in the art, the length measurement apparatus  10  may include other suitable devices, components, accessories and combinations. 
     Referring to FIG. 7, another embodiment of an apparatus  100  for measuring length in a blood vessel is illustrated. The apparatus  100  utilizes a caliper with two main components, an inner barrel  110  and an outer barrel  112 . The inner barrel  110  and outer barrel  112  are in a closed position. The inner barrel  110  is small enough to slide along the inside of the outer barrel  112 . As seen in FIG. 8, a marker such as a radio-opaque marker  114 ,  116  is embedded in the tip of each barrel  110 ,  112 . On the other end of the barrels are hubs  110 ,  112 . The outer barrel hub  112  has a scale  118  on it and the inner barrel hub  10  has an indicator  120 . The hubs  110 ,  112  are designed so that the indicator  120  and scale  118  work together. 
     When the caliper is in a “closed” position, the radio-opaque markers  114 ,  116  of both barrels  110 ,  112  are flush to each other and the hubs  110 ,  112  are flush to each other. Also, the indicator  120  is pointing to the zero mark on the scale  118  in this position. As the barrels  110 ,  112  are pulled apart, the markers  114 ,  116  and the hubs  110 ,  112  separate. The indicator  120  and scale  118  show how far apart the barrels  110 ,  112  have been pulled. The barrels  110 ,  112  are pulled apart to the desired position in order to make the measurement. The radio-opaque markers  114 ,  116  are visible by fluoroscopy, thus allowing the physician to pull the barrels  110 ,  112  apart to the correct distance. For example, one marker  116  would be positioned at the proximal (near) end of the lesion and the other marker  114  would be at the distal (far) end. The barrels  110 ,  112  are flexible so that they can be inserted into the vascular system to the desired location. The inner barrel  110  may also be cannulated so that it can placed over a guidewire to facilitate insertion. Preferably, the diameter of the barrels  110 ,  112  are small enough to be inserted into the lumen of the artery or lesion. 
     FIG. 8 is a sectional view of FIG. 7 illustrating the fit of the barrels  110 ,  112 , the flushness of the radio-opaque markers  114 ,  116 , and the indicator  120  pointing to zero on the scale  118 . FIG. 9 is another sectional view of FIG. 7 illustrating the barrels  110  and  112  pulled apart. The indicator  120  and scale  118  show how far the markers  114  and  116  have been pulled apart. In this example, the barrels  110 ,  112  are relatively short. One skilled in the art will be appreciated that the barrels  110 ,  112  are long enough to reach the desired locations. 
     In this example, the method of showing the measurement is through the use of an indicator  120  and scale  118 , however other methods are possible. As the barrels  110 ,  112  are pulled apart, a hub drives a mechanical means for showing the measurement on a counter or a needle deflected scale. Alternatively, an electronic means is utilized to measure the distance between the markers  114 ,  116 . 
     Referring to FIG. 10, a device for measuring the inside diameter of a vessel illustrated. The device has a tube  132 , measuring wires  130 , and a knob  136 . The tube  132  is long and flexible. Its length is as long as necessary to reach the desired location, for example long enough to reach the coronary arteries from a transfemoral approach. The tube  132  is also flexible enough to maneuver through vasculature. Holes run the length of the tube  132  so that it has multiple lumens. 
     Referring to FIG. 11, a central lumen  138  running the entire length of the tube  132  is illustrated. The other lumens are uniformly spaced around the central lumen  138  and do not run the length of the entire tube  132 . They stop a short distance from the tip of the tube  132 . These lumens also have a slot cut into them that exposes a portion of the lumen. Wires  130  are inserted in all the lumens of the tube  132  except the central lumen  138 . These are measuring wires  130  that will expand to indicate the inside diameter of the vessel. When these wires  130  are pushed on one end, they will expand by bulging out of the tube  132  through the slots  140  cut into the lumen. When the wires  130  make contact with the inside of the vessel, they indicate the inside diameter of that vessel. 
     The proximal end of handle  134  is illustrated in FIG.  12 . The handle  134  can be pushed, pulled, twisted, or turned in order to get the tip of the tube  132  to the correct location. The handle  134  also has a knob  136  built into it. The knob  136  is used to push on the wires  130  as described above. When the knob  136  is turned, it pushes on the end of the wires  130  and they bulge out. The handle  134  also has a scale  144  and pointer  142 . The scale  144  is on one part of the handle  134  and the pointer  142  is on the knob  136 , or vice versa. When the knob  136  is turned so that the pointer  142  indicates zero on the scale  144 , the measuring wires  130  do not bulge out of the tube  132 . As the knob  136  is turned, the wires  130  bulge. The knob  136  will be turned until the wires  130  touch the vessel. At this time, the pointer  142  will indicate the size of the diameter on the scale  144 . 
     This device can be used to measure the inside diameter of a vessel or even the inside diameter of a stent after it has been expanded. It has the advantage of being a convenient, fast, simple, easy, and accurate way to measure diameter. Its probable use is for the inside of vessels, arteries, veins, or other lumens of the body.