Patent Description:
Due to age, high cholesterol and other contributing factors, a large percentage of the population has arterial atherosclerosis that totally occludes portions of the patient's vasculature and presents significant risks to patient health. For example, in the case of a total occlusion of a coronary artery, the result may be painful angina, loss of cardiac tissue or patient death. In another example, complete occlusion of the femoral and/or popliteal arteries in the leg may result in limb threatening ischemia and limb amputation.

Commonly known endovascular devices and techniques are either inefficient (time consuming procedure), have a high risk of perforating a vessel (poor safety) or fail to cross the occlusion (poor efficacy). Physicians currently have difficulty visualizing the native vessel lumen, can not accurately direct endovascular devices toward the visualized lumen, or fail to advance devices through the lesion. Bypass surgery is often the preferred treatment for patients with chronic total occlusions, but less invasive techniques would be preferred.

Described herein are devices and methods employed to exploit the vascular wall of a vascular lumen for the purpose of bypassing a total occlusion of an artery. Exploitation of a vascular wall may involve the passage of an endovascular device into and out of said wall which is commonly and interchangeably described as false lumen access, intramural access, submedial access or in the case of this disclosure, subintimal access.

<CIT> discloses a rotational handle device which rotates a medical instrument for vascular treatment in a tubular form including a tube for insertion by guiding of a medical guide wire inside. The tube includes a helical coil of metal, a tubular tip of metal secured to an end of the helical coil, and a cutting head of a blade shape, formed on the tubular tip, for cutting a lesion upon being rotated. A first rotatable tube rotates with the tube, and has a wire lumen. An externally operable second rotatable tube is secured to the first rotatable tube in an axial direction. An over torque preventing mechanism is disposed between the first and second rotatable tubes and causes the second rotatable tube to rotate free from the first rotatable tube upon application of torque higher than the predetermined level to the second rotatable tube.

The present disclosure is directed to a device for facilitating treatment of a blood vessel. The device includes a shaft having a distal end and a proximal end. The device further includes a handle assembly fixed about the proximal end of the shaft, the handle assembly including a first portion. Further rotation of the first portion in a first direction about a longitudinal axis of the shaft causes rotation of the shaft in the first direction when a torque applied by the first portion to the shaft is below a first maximum torque. Still further, rotation of the first portion in the first direction about the longitudinal axis of the shaft does not cause rotation of the shaft in the first direction when the torque applied by the first portion to the shaft is above the first maximum torque.

The present disclosure is directed to a method (not claimed) of facilitating treatment of a blood vessel. The method may include providing a medical device shaft having a distal end and a proximal end and providing a handle assembly fixed to the proximal end of the shaft. The handle assembly may include a first portion. Further rotation of the first portion in a first direction about a longitudinal axis of the shaft causes rotation of the shaft in the first direction when a torque applied by the first portion to the shaft is below a first maximum torque. Still further rotation of the first portion in the first direction about the longitudinal axis of the shaft does not cause rotation of the shaft in the first direction when the torque applied by the first portion to the shaft is above the first maximum torque. The method may further include rotating the first portion of the handle assembly in a first direction about the longitudinal axis, wherein the rotating applies a torque to the shaft below the first maximum torque, and wherein the rotating causes the shaft to rotate.

Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

It is to be understood that the following detailed description is exemplary and explanatory only and is not restrictive of the invention, as claimed. The invention is defined by the features of the independent claim while preferred embodiments are set forth in the dependent claims.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrates embodiments of the invention and together with the description, serve to explain the principles of the invention.

Reference will now be made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings.

<FIG> is a schematic representation of a human heart <NUM>. Heart <NUM> includes a plurality of coronary arteries <NUM>, all of which are susceptible to occlusion. Under certain physiological circumstances and given sufficient time, some occlusions may become total or complete, such as total occlusion <NUM>. As used herein, the terms total occlusion and complete occlusion are intended to refer to the same or similar degree of occlusion with some possible variation in the age of the occlusion. Generally, a total occlusion refers to a vascular lumen that is ninety percent or more functionally occluded in cross-sectional area, rendering it with little to no blood flow therethrough and making it difficult or impossible to pass a conventional guide wire therethrough. Also generally, the older the total occlusion the more organized the occlusive material will be and the more fibrous and calcified it will become. According to one accepted clinical definition, a total occlusion is considered chronic if it is greater than two weeks old from symptom onset.

<FIG> is an enlarged view further illustrating a portion of heart <NUM> shown in the previous figure. In <FIG>, a total occlusion <NUM> is shown within a coronary artery <NUM>. Generally, a proximal segment <NUM> of artery <NUM> (i.e., the portion of artery <NUM> proximal of total occlusion <NUM>) may be easily accessed using endovascular devices and has adequate blood flow to supply the surrounding cardiac muscle. A distal segment <NUM> of artery <NUM> (i.e., the portion of artery <NUM> distal of total occlusion <NUM>) is not easily accessed with interventional devices and has significantly reduced blood flow as compared to proximal segment <NUM>.

<FIG> is a cross-sectional view of a blood vessel <NUM> having a wall <NUM>. In <FIG>, wall <NUM> of blood vessel <NUM> is shown having three layers. The outermost layer of wall <NUM> is an adventitia <NUM> and the innermost layer of wall <NUM> is an intima <NUM>. The tissues extending between intima <NUM> and adventitia <NUM> may be collectively referred to as a media <NUM>. For purposes of illustration, intima <NUM>, media <NUM> and adventitia <NUM> are each shown as a single homogenous layer in <FIG>. In the human body, however, the intima and the media each comprise a number of sub-layers. The transition between the external-most portion of the intima and the internal-most portion of the media is sometimes referred to as the subintimal space. Intima <NUM> defines a true lumen <NUM> of blood vessel <NUM>. In <FIG>, occlusion <NUM> is shown blocking true lumen <NUM>. Occlusion <NUM> divides true lumen <NUM> into proximal segment <NUM> and distal segment <NUM>. In <FIG>, a distal portion of a crossing device <NUM> is shown extending into proximal segment <NUM> of true lumen <NUM>.

As shown in <FIG>, methods described in this document may include the step of advancing a crossing device to a location proximate an occlusion in a blood vessel. The exemplary methods described in this document may also include the step of advancing crossing device <NUM> between occlusion <NUM> and adventitia <NUM>. In some useful methods, crossing device <NUM> may be rotated as the distal end of crossing device <NUM> is advanced between occlusion <NUM> and adventitia <NUM>. Rotating crossing device <NUM> assures that the coefficient of friction at the interface between the crossing device and the surrounding tissue will be a kinetic coefficient of friction rather than a static coefficient of friction.

<FIG> is a plan view showing an assembly including crossing device <NUM> shown in the previous figure. In the embodiment of <FIG>, a handle assembly <NUM> is coupled to crossing device <NUM>. In <FIG>, handle assembly <NUM> is shown disposed about a proximal portion of a shaft <NUM> of crossing device <NUM>. In <FIG>, a portion of handle assembly <NUM> is positioned between the thumb and forefinger of a left hand LH. A second portion of handle assembly <NUM> is disposed between the thumb and forefinger of a right hand RH. The fingers of left hand LH and right hand RH are shown wrapping in a clockwise direction loosely around shaft <NUM> in <FIG>. The thumb of left hand LH is shown pointing in a generally proximal direction in <FIG>. The thumb of right hand RH is shown pointing in a generally distal direction in <FIG>. For the purposes of this disclosure, clockwise and counter clockwise are viewed from the perspective of a viewer positioned near the proximal end of shaft <NUM> viewing an imaginary clock located near distal tip <NUM>. With reference to <FIG>, it will be appreciated that handle assembly <NUM> is long enough to receive the thumb and forefingers of a physician's right and left hands. When this is the case, a physician can use two hands to rotate handle assembly <NUM>.

Rotation of crossing device <NUM> can be achieved by rolling handle assembly <NUM> between the thumb and forefinger of one hand. Two hands may also be used to rotate handle assembly <NUM> as shown in <FIG>. In some useful methods, crossing device <NUM> can be rotated and axially advanced simultaneously. Rotating crossing device <NUM> assures that the coefficient of friction at the interface between the crossing device and the surrounding tissue will be a kinetic coefficient of friction and not a static coefficient of friction.

In some useful methods in accordance with the present disclosure, crossing device <NUM> is rotated at a rotational speed of between about <NUM> revolutions per minute and about <NUM> revolutions per minute. In some particularly useful methods in accordance with the present disclosure, crossing device <NUM> is rotated at a rotational speed of between about <NUM> revolutions per minute and about <NUM> revolutions per minute. Crossing device <NUM> may be rotated by hand as depicted in <FIG>. It is also contemplated that a mechanical device (e.g., an electric motor) may be used to rotate crossing device <NUM>.

<FIG> is an enlarged plan view showing handle assembly <NUM> shown in the previous figure. Handle assembly <NUM> comprises a handle housing <NUM>. A distal cap <NUM> is fixed (e.g., with a threaded connection) to the distal end of handle housing <NUM>. A handle axle <NUM> is partially disposed in handle housing <NUM>. In the embodiment of <FIG>, handle axle <NUM> is selectively fixed to shaft <NUM> of crossing device <NUM>. A proximal cap <NUM> is fixed (e.g., with a threaded connection) to the proximal end of handle axle <NUM>.

<FIG> is a partial cross-sectional view of handle assembly <NUM> shown in the previous figure. With reference to <FIG> it will be appreciated that shaft <NUM> of crossing device <NUM> extends through handle assembly <NUM>. Handle assembly <NUM> includes handle housing <NUM>, handle axle <NUM>, proximal cap <NUM>, and a collet <NUM>. In the embodiment of <FIG>, proximal cap <NUM>, collet <NUM>, and handle axle <NUM> cooperate to pinch shaft <NUM> between the jaws of collet <NUM>. Under normal operation, handle axle <NUM> will be selectively fixed to shaft <NUM> when shaft <NUM> is pinched between the jaws of collet <NUM>.

As shown in <FIG>, collet <NUM> of handle assembly <NUM> is disposed in a cavity <NUM> defined by handle axle <NUM>. Handle axle <NUM> includes female threads <NUM> that are dimensioned to receive male threads <NUM> of proximal cap <NUM>. In <FIG>, proximal cap <NUM> is shown threadingly engaging a proximal portion of handle axle <NUM>. When handle axle <NUM> and proximal cap <NUM> comprise right handed threads, a distally directed force F can be applied to collet <NUM> by rotating proximal cap <NUM> in a clockwise direction. Applying a distally directed force to collet <NUM> causes the jaws of collet <NUM> to pinch shaft <NUM>. Collet <NUM> and handle axle <NUM> both include tapered surfaces that cause collet <NUM> to pinch shaft <NUM> when collet <NUM> is urged in a distal direction relative to handle axle <NUM>.

Handle assembly <NUM> of <FIG> comprises a torque control mechanism <NUM>. Torque control mechanism <NUM> includes a first camming element <NUM> that is coupled to a distal portion of handle axle <NUM>. In some useful embodiments, the distal portion of handle axle <NUM> includes a plurality of splines <NUM> (see <FIG> and <FIG>) and first camming element <NUM> includes grooves that are dimensioned to receive the splines of the handle axle <NUM>. A distal surface <NUM> of first camming element <NUM> contacts a proximal end <NUM> of a second camming element <NUM>. In the embodiment of <FIG>, a spring <NUM> urges first camming element <NUM> against second camming element <NUM>. Spring <NUM> also urges second camming element <NUM> against distal cap <NUM>.

<FIG> is an enlarged partial cross-sectional view showing a portion of the assembly shown in the previous figure. First camming element <NUM> and second camming element <NUM> are visible in <FIG>. Second camming element <NUM> defines a plurality of recesses 164A. Each recess 164A is dimensioned to receive a ramped surface 166A of first camming element <NUM>. Each recess 164A is partially defined by a wall 122A. Each wall 122A includes a ramp engaging surface 170A. In the embodiment of <FIG>, each ramp engaging surface 170A has a radius.

The distal surface <NUM> of second camming element <NUM> contacts a proximal end <NUM> of distal cap <NUM>. Distal cap <NUM> defines a plurality of recesses 164B. Each recess 164B is dimensioned to receive a ramped surface 166B of second camming element <NUM>. Each recess 164B is partially defined by a wall 122B. Each wall 122B includes a ramp engaging surface 170B. In the embodiment of <FIG>, each ramp engaging surface 170B has a radius.

In the embodiment of <FIG>, first camming element <NUM> and second camming element <NUM> form part of a torque control mechanism <NUM>. If a predetermined maximum torque is applied to shaft <NUM> in a clockwise direction CW, then the ramp engaging surface 170A of second camming element <NUM> will ride up ramped surfaces 166A of first camming element <NUM>. If a predetermined maximum torque is applied to shaft <NUM> in a counter-clockwise direction CCW, then the ramp engaging surface 170B of distal cap <NUM> will ride up ramped surfaces 166B of second camming element <NUM>.

In some useful embodiments, first camming element <NUM> and second camming element <NUM> are dimensioned so that torque control mechanism <NUM> will provide a first maximum torque when shaft <NUM> is being rotated in a clockwise direction and a second maximum torque when shaft <NUM> is being rotated in a counter-clockwise direction. In some useful embodiments, the second maximum torque is different from the first maximum torque. Also in some useful embodiments, the difference between the second maximum torque and the first maximum torque corresponds to a difference in strength of shaft <NUM> when subjected to a counterclockwise torque versus a clockwise torque.

<FIG> is an exploded plan view showing several components of handle assembly <NUM>. Handle assembly <NUM> comprises handle housing <NUM> and handle axle <NUM>. Handle axle <NUM> may be inserted into handle housing <NUM> so that handle housing <NUM> is disposed about a portion of handle axle <NUM>. Collet <NUM> may be inserted into cavity <NUM> defined by handle axle <NUM>. Handle axle <NUM> includes female threads <NUM> that are dimensioned to receive male threads <NUM> of proximal cap <NUM>. Proximal cap <NUM> may be advanced into cavity <NUM> defined by handle axle <NUM>.

A first camming element <NUM> defines a socket <NUM> that is dimensioned to receive the distal portion of handle axle <NUM>. In some useful embodiments, the distal portion of handle axle <NUM> includes a plurality of splines <NUM> and first camming element <NUM> includes grooves that are dimensioned to receive splines <NUM> of the handle axle <NUM>. Handle assembly <NUM> also includes a second camming element <NUM> and distal cap <NUM>.

<FIG> includes a table describing relative freedom of movement between various elements shown in <FIG>. The left-most column of this table lists each of the elements shown in the previous figure. The top row in this table lists two statements. First, the element is free to rotate relative to the shaft. Second, the element is free to rotate relative to the handle housing. The table also includes boolean logic values of O and <NUM>. A boolean logic value of <NUM> indicates that the statement is true for a given element. A boolean logic value of O indicates that the statement is false for a given element.

As described above, proximal cap <NUM>, collet <NUM>, and handle axle <NUM> cooperate to pinch the shaft between the jaws of collet <NUM>. Accordingly, proximal cap <NUM>, collet <NUM>, and handle axle <NUM> are not free to rotate relative to the shaft under normal operating conditions. In the embodiment of <FIG>, first camming element <NUM> and handle axle <NUM> engage one another at a splined connection. Accordingly, first camming element <NUM> and handle axle <NUM> are not free to rotate relative to one another. In the embodiment of <FIG>, distal cap <NUM> and handle housing <NUM> engage one another at a threaded connection. Once this thread is tightened, distal cap <NUM> is not free to rotate relative to handle housing under normal operation.

<FIG> is a partial cross-sectional view of an exemplary crossing device <NUM>. Crossing device <NUM> of <FIG> comprises a tip <NUM> that is fixed to a distal end of a shaft <NUM>. In the exemplary embodiment of <FIG>, shaft <NUM> comprises a coil <NUM>, a sleeve <NUM>, a tubular body <NUM>, and a sheath <NUM>.

Tip <NUM> is fixed to a distal portion of coil <NUM>. Coil <NUM> comprises a plurality of filars that are each wound in a generally helical shape. In the embodiment of <FIG>, coil <NUM> comprises a left-hand wound coil. Embodiments are also possible in which coil <NUM> comprises a right-hand wound coil. In some useful embodiments of crossing device <NUM>, coil <NUM> comprises eight, nine or ten filars wound into the shape illustrated in <FIG>. Crossing device <NUM> includes sleeve <NUM> that is disposed about a portion of coil <NUM>. Sleeve <NUM> may comprise, for example, PET shrink tubing, i.e. polyethylene terephthalate.

Sleeve <NUM> and coil <NUM> both extend into a lumen defined by a tubular body <NUM>. Tubular body <NUM> may comprise, for example hypodermic tubing formed of Nitinol (i.e. nickel titanium alloy). With reference to <FIG>, it will be appreciated that a proximal portion of sleeve <NUM> is disposed between tubular body <NUM> and coil <NUM>. In some embodiments of crossing device <NUM>, a distal portion of tubular body <NUM> defines a helical cut. This helical cut may be formed, for example, using a laser cutting process. The helical cut may be shaped and dimensioned to provide an advantageous transition in lateral stiffness proximate the distal end of tubular body <NUM>.

A proximal portion of coil <NUM> extends proximally beyond the distal end of tubular body <NUM>. A hub is fixed to a proximal portion of coil <NUM> and a proximal portion of tubular body <NUM>. The hub may comprise, for example, a luer fitting. A sheath <NUM> is disposed about a portion of tubular body <NUM> and a portion of sleeve <NUM>. In some embodiments of crossing device <NUM>, sheath <NUM> comprises HYTREL, a thermoplastic elastomer.

With reference to <FIG>, it will be appreciated that tubular body <NUM>, coil <NUM>, sleeve <NUM>, and sheath <NUM> each have a proximal end and a distal end. The proximal end of sheath <NUM> is disposed between the proximal end of tubular body <NUM> and the proximal end of sleeve <NUM>. The distal end of sleeve <NUM> is positioned proximate tip <NUM> that is fixed to the distal end of coil <NUM>. The distal end of sheath <NUM> is located between the distal end of tubular body <NUM> and the distal end of sleeve <NUM>. With reference to <FIG>, it will be appreciated that sheath <NUM> overlays the distal end of tubular body <NUM>.

With reference to <FIG>, it will be appreciated that tip <NUM> has a generally rounded shape. The generally rounded shape of tip <NUM> may reduce the likelihood that crossing device <NUM> will penetrate the adventitia of an artery. Tip <NUM> may be formed from a suitable metallic material including but not limited to stainless steel, silver solder, and braze. Tip <NUM> may also be formed from suitable polymeric materials or adhesives including but not limited to polycarbonate, polyethylene and epoxy. In some embodiments of crossing device <NUM>, the outer surface of tip <NUM> comprises a generally non-abrasive surface. For example, the outer surface of tip <NUM> may have a surface roughness of about <NUM> micrometers or less. A tip member having a relatively smooth outer surface may reduce the likelihood that the tip member will abrade the adventitia of an artery.

<FIG> is an exploded isometric view showing several components of handle assembly <NUM> that is disposed about shaft <NUM> shown in the previous figure. Handle assembly <NUM> of <FIG> comprises torque control mechanism <NUM>. Torque control mechanism <NUM> includes first camming element <NUM> and second camming element <NUM>. First camming element <NUM> and second camming element <NUM> are dimensioned so that torque control mechanism <NUM> will provide a first maximum torque when shaft <NUM> is being rotated in a clockwise direction and a second maximum torque when shaft <NUM> is being rotated in a counter-clockwise direction. In some useful embodiments, the second maximum torque is different from the first maximum torque. Also in some useful embodiments, the difference between the second maximum torque and the first maximum torque corresponds to a difference in strength of shaft <NUM> when subjected to a counterclockwise torque versus a clockwise torque.

Handle assembly <NUM> comprises handle housing <NUM> and handle axle <NUM>. Handle axle <NUM> may be inserted into handle housing <NUM> so that handle housing <NUM> is disposed about a portion of handle axle <NUM>. Collet <NUM> may be inserted into a cavity defined by handle axle <NUM>. Handle axle <NUM> includes female threads that are dimensioned to receive male threads <NUM> of proximal cap <NUM>. Proximal cap <NUM> may be advanced into cavity <NUM> defined by handle axle <NUM>.

First camming element <NUM> defines socket <NUM> that is dimensioned to receive a distal portion of handle axle <NUM>. In some useful embodiments, the distal portion of handle axle <NUM> includes a plurality of splines <NUM> and first camming element <NUM> includes grooves that are dimensioned to receive the splines of the handle axle <NUM>. Handle assembly <NUM> also includes second camming element <NUM> and distal cap <NUM>.

<FIG> is an enlarged isometric view showing distal cap <NUM>, first camming element <NUM>, and second camming element <NUM> shown in the previous figure. With reference to <FIG>, it will be appreciated that second camming element <NUM> comprises a plurality of ramped surfaces 166B and a plurality of faces 190B. Each ramped surface 166B is adjacent to a corresponding face 190B. In the embodiment of <FIG>, each face 190B is generally perpendicular to a distal surface <NUM> of second camming element <NUM>. In the embodiment of <FIG>, distal cap <NUM> comprises a plurality of recesses that are dimensioned to receive ramped surfaces 166B. With reference to <FIG>, it will be appreciated that first camming element <NUM> comprises a plurality of ramped surfaces 166A and a plurality of faces 190A. Each ramped surface 166A is adjacent to a corresponding face 190A. In the embodiment of <FIG>, each face 190A is generally perpendicular to a distal surface <NUM> of first camming element <NUM>. Second camming element <NUM> comprises a plurality of recesses that are dimensioned to receive ramped surfaces 166A in the embodiment of <FIG>.

<FIG> is an isometric view of handle axle <NUM>. With reference to <FIG>, it will be appreciated that a distal portion of handle axle <NUM> includes the plurality of splines <NUM>.

<FIG> is a plan view showing a proximal surface of first camming element <NUM>. With reference to <FIG>, it will be appreciated that first camming element <NUM> defines socket <NUM>. In the embodiment of <FIG>, socket <NUM> is dimensioned to received the distal portion of handle axle <NUM>. With reference to <FIG>, it will be appreciated that socket <NUM> includes grooves <NUM> that are dimensioned to receive the splines of handle axle <NUM> shown in the previous figure.

<FIG> is an enlarged isometric view showing second camming element <NUM>. Second camming element <NUM> defines a plurality of recesses 164A. Each recess 164A is dimensioned to receive a ramped surface of first camming element <NUM> shown in the previous figure. Each recess 164A is partially defined by wall 122A. Each wall 122A includes a ramp engaging surface 170A. In the embodiment of <FIG>, each ramp engaging surface 170A has a radius.

<FIG> is an enlarged isometric view showing distal cap <NUM>. Distal cap <NUM> defines a plurality of recesses 164B. Each recess 164B is dimensioned to receive a ramped surface 166B of second camming element <NUM> shown in the previous figure. Each recess 164B is partially defined by a wall 122B. Each wall 122B includes a ramp engaging surface 170B. In the embodiment of <FIG>, each ramp engaging surface 170B has a radius.

The operation of handle assembly <NUM> will now be described. A physician may fix handle assembly <NUM> about the proximal portion of shaft <NUM> of crossing device <NUM>. Alternatively, crossing device <NUM> may be delivered to the physician with handle assembly <NUM> positioned on shaft <NUM>.

During a therapy procedure, the physician may periodically adjust the position of handle assembly <NUM> along the length of shaft <NUM>. To move the position of handle assembly <NUM> along shaft <NUM>, the physician may loosen proximal cap <NUM> from handle axle <NUM> such that the tapered surfaces of the jaws of collet <NUM> are not in contact with the tapered surface of cavity <NUM> of handle axle <NUM>. The physician may slide handle assembly <NUM> in a lengthwise direction along shaft <NUM> to a desired location. The physician may then tighten proximal cap <NUM> within handle axle <NUM>. In this manner, the tapered surfaces of the jaws of collet <NUM> may contact the tapered surface of cavity <NUM> and cause the jaws of collet <NUM> to pinch shaft <NUM> and fix the position of shaft <NUM> relative to handle assembly <NUM>.

During a therapy procedure, the physician may position the distal portion of shaft <NUM> of crossing device <NUM> within artery <NUM>. Handle assembly <NUM> may be used to advance the distal portion of crossing device <NUM> to a location proximal of occlusion <NUM>. Alternatively, or additionally, handle assembly <NUM> may be used to advance the distal portion of crossing device <NUM> between occlusion <NUM> and adventitia <NUM> to a location distal occlusion <NUM>. In this manner, a physician may grip handle assembly <NUM> via handle housing <NUM> with the thumb and forefinger of one hand, or alternatively, with two hands. As shaft <NUM> is advanced into the vasculature of the patient, the physician may periodically adjust the position of handle assembly <NUM> along the length of shaft <NUM> as described above.

At various times during a therapy procedure, the physician may rotate handle housing <NUM> to rotate crossing device <NUM>, including shaft <NUM> and tip <NUM>. Rotating crossing device <NUM> assures that the coefficient of friction at the interface between the crossing device and the surrounding tissue will be a kinetic coefficient of friction and not a static coefficient of friction. In this manner, crossing device <NUM> may more easily pass through artery <NUM>, occlusion <NUM>, and/or various layers of the wall of artery <NUM>. The physician may rotate handle housing <NUM> in a clockwise (CW) or in a counter-clockwise (CCW) direction.

For purposes of this disclosure, the clockwise and counter-clockwise are oriented from the perspective of a physician having the left hand (LH) and right hand (RH) shown in <FIG>. This physician holding handle assembly <NUM> in his left hand (LH) and right hand (RH) is contemplating the rotation of the tip <NUM>. In <FIG>, the fingers of each hand are shown wrapping in a clockwise direction around shaft <NUM>. In other words, clockwise and counter clockwise are viewed from the perspective of a viewer positioned near the proximal end of the device viewing an imaginary clock near the distal end of the device.

The physician causes shaft <NUM> and tip <NUM> to rotate by rotating handle housing <NUM>. During this rotation, shaft <NUM> and tip <NUM> may experience resistance to rotation. This resistance may, for example, be caused by frictional contact between crossing device <NUM> and features of the patient's anatomy (e.g., the walls of a blood vessel and occlusions located inside the blood vessel). When resistance is encountered, the physician may apply greater torque to shaft <NUM>, up to a predetermined maximum torque. In the exemplary embodiment of <FIG>, this predetermined maximum torque is controlled by a torque control mechanism <NUM>.

The operation of torque control mechanism <NUM> may be described with reference to the exemplary embodiment shown in <FIG>. In this exemplary embodiment, distal cap <NUM> is fixed to handle housing <NUM> by a threaded connection. Accordingly, rotation of handle housing <NUM> in a CCW direction causes distal cap <NUM> to also rotate in a CCW direction. Wall 122B of distal cap <NUM> may then contact face 190B of ramp 166B, causing second camming element <NUM> to rotate in a CCW direction. The rotation of second camming element <NUM> may rotate ramp engaging surface 170A of second camming element <NUM> into contact with ramp 166A of first camming element <NUM>. Specifically, ramp engaging surface 170A may contact, or "ride," a lower portion of the length of ramp 166A. The contact between ramp engaging surface 170A and ramp 166A causes first camming element <NUM> to rotate in the CCW direction. Because handle axle <NUM> is fixed to first camming element <NUM> by the plurality of splines <NUM>, rotation of first camming element <NUM> causes handle axle <NUM> to rotate in the CCW direction. As described above, shaft <NUM> is fixed to handle axle <NUM> by collet <NUM>. Accordingly, rotation of handle axle <NUM> in the CCW direction causes shaft <NUM> to rotate in the CCW direction.

As handle housing <NUM> continues to rotate in the CCW direction, the resistance to rotation that shaft <NUM> and tip <NUM> experience may increase. As this resistance increases, the torque required to rotate shaft <NUM> may increase. As the torque applied to handle housing <NUM> increases, ramp engaging surface 170A may ride further up the length of ramp 166A (i.e. from a lower portion to a higher portion). When this is the case, ramp engaging surface 170A of second camming element <NUM> and ramp 166A of first camming element <NUM> will cooperate to compress spring <NUM>.

In the exemplary embodiment shown in <FIG>, torque control mechanism <NUM> limits the magnitude of torques that may be applied to shaft <NUM> by rotating handle housing <NUM>. Torque control mechanism <NUM> limits the torque in a first direction to a magnitude equal to or less than a first maximum torque and limits the torque in a second direction to a magnitude equal to or less than a second maximum torque. In some useful embodiments, the second maximum torque is different from the first maximum torque. In these embodiments, the shape (e.g., the height) of each ramp 166B of second camming element <NUM> may be different from the shape of each ramp 166A of first camming element <NUM>.

When the first maximum torque is applied to shaft <NUM>, sufficient force is exerted against spring <NUM> to allow ramp engaging surface 170A to ride up the entire length of ramp 166A and over the highest point of ramp 166A. When ramp engaging surface 170A rides over the highest point of ramp 166A, spring <NUM> causes proximal end <NUM> of second camming element <NUM> to rapidly contact distal end <NUM> of first camming element <NUM>. This rapid contact may generate an audible "clicking" sound. This rapid contact may also cause a tactile response (e.g., vibrations in housing handle <NUM>) that can be felt in the finger tips of left hand (LH) and right hand (RH). This audible and/or tactile response may serve to notify the physician that the first maximum torque has been exceeded.

When the first maximum torque has been reached, continued rotation of handle housing <NUM> in the CCW direction will cause no further substantial rotation of shaft <NUM>. Instead, continued rotation of handle housing <NUM> will only produce more "clicking" by torque control mechanism <NUM>. Between a minimum amount of torque necessary to rotate shaft <NUM> and the first maximum torque may represent a range of torque that may be applied to shaft <NUM> to cause rotation of shaft <NUM> in the CCW direction.

When the first maxium torque has been reached, the physician may choose to discontinue rotating handle housing <NUM> in the CCW direction. At this point, the physician may choose to begin rotating handle housing <NUM> in the CW direction. In some applications, reversing the direction of rotation is a useful strategy for crossing restrictions.

As mentioned above, torque control mechanism <NUM> also limits the magnitude of torque that may be applied to shaft <NUM> when handle housing <NUM> is rotated in a clockwise (CW) direction. The operation of torque control mechanism <NUM> when handle housing <NUM> is rotated in the CW direction may be described with continuing reference to the exemplary embodiment shown in <FIG>. In this exemplary embodiment, distal cap <NUM> is fixed to handle housing <NUM> by a threaded connection. Accordingly, rotation of handle housing <NUM> in the CW direction causes distal cap <NUM> to also rotate in the CW direction. Rotation of distal cap <NUM> in the CW direction will rotate ramp engaging surface <NUM> of distal cap <NUM> into contact with ramp 166B of second camming element <NUM>. Specifically, the radius of ramp engaging surface <NUM> may contact, or "ride," a lower portion of the length of ramp 166B. This contact causes second camming element <NUM> to rotate in the CW direction. Rotating second camming element <NUM> in the CW direction causes a wall 122A of second camming element <NUM> to contact a face 190A of first camming element <NUM>, causing first camming element <NUM> to rotate in the CW direction. Because handle axle <NUM> is fixed to first camming element <NUM> by the plurality of splines <NUM>, rotation of first camming element <NUM> causes handle axle <NUM> to rotate. As describe above, shaft <NUM> is fixed to handle axle <NUM> by collet <NUM>. Therefore, shaft <NUM> rotates in the CW direction when handle axle <NUM> is rotated in the CW direction.

As handle housing <NUM> continues to rotate in the CW direction, the resistance to rotation that shaft <NUM> experiences may increase. As this resistance increases, the torque required to overcome the resistance may increase and may result in a higher torque being applied to shaft <NUM>. As the torque increases, ramp engaging surface 170B will ride further up the length of ramp 166B (i.e. from a lower portion to a higher portion). When this is the case, ramp engaging surface 170B and ramp 166B of second camming element <NUM> will cooperate to compress spring <NUM>.

When the second maximum torque is applied to shaft <NUM>, sufficient force is exerted against spring <NUM> to allow ramp engaging surface 170B to ride up the entire length of ramp 166B and over the highest point of ramp 166B. At this point, continued rotation of handle housing <NUM> in the CW direction will result in substantially no further rotation of shaft <NUM>. Instead, continued rotation of handle housing <NUM> will only produce more "clicking" by torque control mechanism <NUM>.

The "clicking" by torque control mechanism <NUM> is produced, for example, as second camming element <NUM> rapidly contacts distal cap <NUM>. When ramp engaging surface 170B rides over the highest point of ramp 166B, spring <NUM> causes distal end <NUM> of second camming element <NUM> to rapidly contact proximal end <NUM> of distal cap <NUM>. In some exemplary embodiments, this rapid contact generates an audible "clicking" sound. This rapid contact may also cause a tactile response (e.g., vibrations in housing handle <NUM>) that can be felt in the finger tips of left hand (LH) and right hand (RH). This audible and/or tactile response may serve to notify the physician that the second maximum torque has been exceeded. Between a minimum amount of torque necessary to rotate shaft <NUM> and the second maximum torque may represent a range of torque that may be applied to shaft <NUM> to cause rotation of shaft <NUM> in the CW direction.

The first maximum torque and the second maximum torque may be varied by varying a number of attributes of torque control mechanism <NUM>. Examples of attributes include the spring constant of spring <NUM>, a magnitude of pre-loading placed on spring <NUM>, the maximum height of each ramp (166A, 166B), and the slope/pitch/angle of each ramp (166A, 166B). The first and second maximum torques may be simultaneously increased or decreased by replacing spring <NUM> with a spring producing greater or lesser spring force. The first and second maximum torques may be independently changed by altering the dimensions of one or more of the components of torque control mechanism <NUM>, such as, for example, the maximum height of each ramp (166A, 166B), the slope/pitch/angle of each ramp (166A, 166B), characteristics of ramp engaging surface 170A and/or ramp engaging surface 170B, or any other modification that would result in a greater or lesser first and/or second maximum torques.

The desired first maximum torque and the desired second maximum torque may be related to the strength of shaft <NUM> relative to the rotational direction. By way of example, when shaft <NUM> is rotated in a CCW direction, coil <NUM> of shaft <NUM> may expand and may be weaker. In this case, the first maximum torque, i.e. the maximum torque applied in the CCW direction should be low enough to not break the expanded coil <NUM>. In a further example, when shaft <NUM> is rotated in a CW direction, coil <NUM> of shaft <NUM> may compress and may be stronger relative to the steady or expanded state of coil <NUM>. In this case, the second maximum torque, i.e. the maximum torque applied in the CW direction should be low enough to not break the compressed coil <NUM>. In this example, the second maximum torque would be higher than the first maximum torque. It is further contemplated that the first and second maximum torques may not be the exact torque necessary to cause coil <NUM> to fail in a respective direction, but that there may be safety factor included in determining the torques.

From the foregoing, it will be apparent to those skilled in the art that the present invention provides devices for the treatment of chronic total occlusions. Further, those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departures in form and detail may be made without departing from the scope of the present invention as described in the appended claims.

Claim 1:
A device for facilitating treatment of a blood vessel, the device comprising:
a shaft (<NUM>) having a distal end and a proximal end;
a handle assembly (<NUM>) disposed about a proximal portion of the shaft, the handle assembly including handle housing (<NUM>), wherein rotation of the handle housing in a first direction about a longitudinal axis of the shaft causes rotation of the shaft in the first direction when a torque applied by the handle housing to the shaft is below a first maximum torque; and
wherein rotation of the handle housing in the first direction about the longitudinal axis of the shaft does not cause rotation of the shaft in the first direction when the torque applied by the handle housing to the shaft is above the first maximum torque;
wherein the handle assembly is slidable in a lengthwise direction along the shaft.