With age a large percentage of the population developing arterial obstructions formed by fats, fibrous material and calcified deposits, resulting in a diminished blood circulation. The disturbance to blood flow which these obstructions cause may induce blood clots which further diminish or block the blood flow. When this process occurs in the coronary arteries it is referred to as a heart attack.
Presently such obstructions are circumvented by surgically grafting a bypass or they are treated by a catheter equipped with a balloon which is inserted through the arterial system, over a flexible guide-wire, into the obstruction and then inflated to expand the obstruction's lumen (angioplasty). Problems with this treatment are that it injures the arterial wall 10 15 20 25 30 creating a rough lumen and in certain cases it is ineffective. Further, angioplasty does not remove the obstruction material out of the arterial system, therefore in a case of a heart attack, immediate angioplasty carries the risk of dislodging the blood clot and allowing it to move down stream creating additional blockages.
An objective of the present invention is to provide an atherectomy catheter rotatable over a flexible guide wire, equipped with a rotary cutting means at its distal end, that would cut and extract the obstruction mate rial, including blood clots if present, create a smooth lumen and not crack the arterial wall. The design of an atherectomy catheter should lend itself to be produceable in diameters down to around 1/mm (millimeter) and a length of up to a meter to be able to reach and enter small and remote arteries. Preferably, the operation of the atherectomy system would resemble the operation of present catheter systems, so that existing skills of the medical staff can be utilized. These and other objectives of the invention will become apparent from the following discussion and the accompanying drawings.
The atherectomy system comprises:
A flexible guide-wire 25 which is insertable into the artery. Optionally, the flexible guide-wire is equipped with a distal barrier means in the form of a flexible collapsible umbrella 26 to counter distal movement of surrounding obstruction material while the blade cuts the obstruction material. The flexible guide-wire may also contain an optical fiber bundle 41 in a plastic jacket 47 and a lens 33 at its distal tip.
An imaging unit and/or laser gun 27 may be optically coupled to the proximal end of the optical fiber bundle for analyzing the inside of the artery and/or opening, respectively, a pilot pas sage for the distal tip of the flexible guide-wire to pass through in a case of complete arterial blockage.
A flexible rotary catheter 13 is rotatably disposed and insertable into the artery, over the flexible guide-wire. A stainless steel hollow blade 16 is attached to the distal end of the flexible rotary catheter. The blade has teeth 18 on its periphery which are rounded and bent toward the center of the blade to ease insertion through the arteries and to reduce the chance of cutting the wall of the artery during the insertion and cutting operation.
A front edge 44 of the teeth is sharpened to cut the obstruction material to pieces 12" which pass into a continuous passage 23 through spaces 39 between the teeth while the blade rotates forward in a direction of arrow 46 (note FIG. 2).
A back side 45 of the teeth is dull to allow a backwards rotation while manipulating and advancing the flexible rotary catheter through the arterial system towards the obstruction with a reduced risk of injuring the arterial wall. The blade has an outer wall 16' which slidingly and rotatably bears against the artery spreading the contact force on a relatively large area and thereby minimizing the damage to the artery.
A rotating inner-wall 42 is formed by the inside surfaces of the blade and of the flexible rotary catheter. The continuous passage 23 is defined between the rotating inner-wall and the flexible guide-wire, and the relative motion between the inner-wall and the flexible guide-wire mechanically acts on the ingested obstruction material in the continuous passage and enables it to move towards the proximal end 15 of the flexible rotary catheter and make room for an additional cut material.
Coupling means affixed to the proximal end of the flexible rotary catheter in the form of a hub 22 is frictionally engaged with a flat belt 21 which couples the flexible rotary catheter to a rotating means in the form of a motor 19 having a pulley 20. The proximal end of the flexible guide-wire slidingly and rotatably extends through the hub. Suction can be applied to the proximal end of the flexible rotary catheter by a suction pump 17 driven by a motor 17", through ports 30 which alternately communicate with a port 31 formed in a sleeve 31', as the hub rotates in the sleeve 31'. Alternatively, a groove 28 (shown in phantom lines) can provide continuous communication between the continuous passage 23 and the port 31. The suction cooperates with the mechanical action taking place in the continuous passage in proximally moving the cut obstruction material 12'. Torque generated by the motor is partially dissipated by frictional losses along the flexible rotary catheter, 4,842,579 3 therefore, the flexible rotary catheter can be manufactured with an increased wall thickness and increased torque carrying capacity at the vicinity of its proximal end compared with the same at its distal end (note FIG. 1), and the wall can be reinforced by a spiral ribbon made from metal 24 (note FIGS. 1 and 3). The atherectomy system can be manufactured in different diameters and lengths depending on the size and site of artery that it is intended for and on whether the system is to be used percutaneously (that is through the skin) or intra-operatively (that is when the artery is surgically exposed for inserting the system into the artery).
Heart attacks constitute one of the major sources of incapacitation or death to human beings. Such failures often result from blockages in coronary arteries that are due to the accumulation of plaque on the arterial walls. Such accumulations of plaque gradually block the flow of blood through the arteries to the heart until there is a complete stoppage or almost a complete stoppage in the flow. In addition to the problems incurred by blockages in coronary arteries, blockages of other arteries can also cause incapacitation or death to human beings. Plaque buildup in the arteries of the arms or legs can result in limb amputations. Plaque buildup in the arteries of the head and neck can result in strokes. Plaque buildup in the arteries of the kidneys can result in hypertension (high blood pressure). Additionally, plaque buildup in other peripheral (non-coronary) arteries can result in degradation of the organs which they supply. Until relatively recently, it has been difficult to diagnose and detect the accumulation of plaque in the arteries of living beings. In recent years, techniques have been devised for detecting and locating accumulations of plaque on the arterial walls of living beings. Indeed, these techniques have become so advanced that it is now not uncommon to advance probes completely through the arteries to locate and estimate the relative amount of arterial blockage at such progressive positions along the artery. Several techniques have also been developed to correct for blockages in the arteries of living beings. One well known technique which is often used is the so called bypass surgery. In bypass surgery, the blocked portion of an artery is shunted using a segment of a vessel from another part of the body of the afflicted human being. Bypass operations, however, can be of considerable danger to the living being undergoing the operation. One reason for this concern is that the living being has to be cut open to expose and treat the diseased site. The patient also has to undergo anesthesia, the effects of which are often unpredictable. Together, the trauma resulting from the anesthesia and the opening of the body of the living being presents a grave danger to the patient. Angioplasty techniques have also been developed in recent years as a means to alleviate blockages in the arteries in living beings.
An atherectomy system includes a guide wire which can be inserted into an artery of a patient to a region of occlusion, a torque tube having a cutter device affixed to its distal end which is insertable into the artery over the guide wire, and a protective support sheath sur rounding the guide wire and the torque tube. A retraction device controllably retracts the support sheath so as to allow the cutter on the distal end of the torque tube to extend progressively greater distances beyond the distal end of the support sheath. The system also in cludes means for rotating the torque tube, thereby si multaneously rotating the cutter, and vacuum means connected to the torque tube for extracting dislodged cuttings from the patient's bloodstream. The guide wire is preferably provided with an abutment on its distal end which both mechanically limits the distance the cutter can advance into the patient's body and assists in re trieving the cutter from the patient's body following the atherectomy operation.
This invention relates to systems and methods for excising obstructive matter from arteries and other lu mens of living beings. More particularly, the invention relates to such systems and methods useful in perform ing atherectomy procedures. This invention relates to systems and methods for excising obstructive matter from arteries and other lu mens of living beings. More particularly, the invention relates to such systems and methods useful in perform ing atherectomy procedures.
Heart attacks constitute one of the major sources of incapacitation or death to human beings. Such failures often result from blockages in coronary arteries that are due to the accumulation of plaque on the arterial walls. Such accumulations of plaque gradually block the flow of blood through the arteries to the heart until there is a complete stoppage or almost a complete stoppage in the flow. In addition to the problems incurred by blockages in coronary arteries, blockages of other arteries can also cause incapacitation or death to human beings. Plaque buildup in the arteries of the arms or legs can result in limb amputations. Plaque buildup in the arteries of the head and neck can result in strokes. Plaque buildup in the arteries of the kidneys can result in hypertension (high blood pressure). Additionally, plaque buildup in other peripheral (non-coronary) arteries can result in degradation of the organs which they supply.
Until relatively recently, it has been difficult to diagnose and detect the accumulation of plaque in the arteries of living beings. In recent years, techniques have been devised for detecting and locating accumulations of plaque on the arterial walls of living beings. Indeed, these techniques have become so advanced that it is now not uncommon to advance probes completely through the arteries to locate and estimate the relative amount of arterial blockage at such progressive positions along the artery. Several techniques have also been developed to correct for blockages in the arteries of living beings. One well known technique which is often used is the so called bypass surgery. In bypass surgery, the blocked portion of an artery is shunted using a segment of a vessel from another part of the body of the afflicted human being. Bypass operations, however, can be of considerable danger to the living being undergoing the operation. One reason for this concern is that the living being has to be cut open to expose and treat the diseased site. The patient also has to undergo anesthesia, the effects of which are often unpredictable. Together, the trauma resulting from the anesthesia and the opening of the body of the living being presents a grave danger to the patient.
Angioplasty techniques have also been developed in recent years as a means to alleviate blockages in the arteries in living beings. As is well known, angioplasty procedures involve the insertion of a deflated balloon into the artery of the living being. The balloon is then moved, as by a conduit, to the blocked position. Thereafter, the balloon is inflated to expand the diameter of the artery and enlarge the passageway through the artery. In this manner, the plaque is at least partially broken up to thereby alleviate the blockage. Angioplasty procedures, however, have certain inherent disadvantages. First, expansion of the arterial wall at the blocked position stretches, and thereby weakens, the arterial wall. This alone may cause ad verse consequences. Further, since plaque blocking the artery is often calcified and quite hard, it can be difficult, and sometimes impossible, for the balloon to overcome the counterforce exerted by the plaque against the balloon.
Still further, and very importantly, angioplasty procedures do not remove plaque from the artery. This is particularly troublesome since the obstructive tissue which remains in the artery creates a condition conducive to the creation of another blockage. Thus, it can be a recurring problem. Importantly, unlike angioplasty, atherectomy procedures cut the plaque, or other obstructive tissue, from the inside of the artery to create a passageway through the plaque. No expansion of the arterial wall is required. As can be easily appreciated, not only must the atherectomy system employed be effective in cutting and removing plaque, it is essential during such a procedure that the cutting device be carefully controlled and not be allowed to cut through the arterial wall. For the present invention, the necessary control is provided by the concerted effort of a control unit which operatively positions the cutting device within a support sheath and a guide wire which establishes the path of the cutting device.
To utilize the atherectomy device, it is contemplated that the atherectomy device will be inserted into a ves sel such as a vascular (blood) vessel, using conventional insertion techniques. The cutter assembly 5 is then ad vanced through the vessel with the cutter recessed until cutting bit 13 is positioned adjacent the stenosis. Guide wire 18 is inserted into the vessel and advanced to the stenosis. The remainder of the atherectomy device 1 is then inserted over guide wire 18 until cutting assembly 5 is positioned adjacent the stenosis (typically within 1-3 cm). An attempt is made to advance guide wire 18 through as much of the stenosis as is safely possible. By advancing the cutting bit 13 over the guide wire 18, the likelihood of the cutting bit deviating from the desired cutting path is greatly decreased. Proper alignment of the cutting bit 13 is further assured by the trailing col lection chamber 17 which stabilizes and centers the cutting bit. When relatively soft stenosis material is encountered, it is desirable to begin the cut with the cutting bit 13 completely recessed within housing
A process for removing an obstruction from a vessel with an atherectomy system, comprises the following steps: Conventionally inserting into a vessel, into an ob struction, a flexible guide-wire. In case of a tight ob struction, an auger shaped flexible guide-wire can be 65 8 rotated backwards so that the auger section will screw and pull itself through the obstruction. Advancing over the flexible guide-wire a rotary cor ing means located at a distal end of an atherectomy catheter. Advancing the rotary coring means to the obstruc tion and coring the obstruction. During the operation the flexible guide-wire and the flexible sleeve (if pres ent) are prevented from being rotationally dragged by the rotary coring means.
Fluid can be delivered to the obstruction site through the flexible sleeve, around the atherectomy catheter. Such fluid can lubricate and cool the coring process and provide a medium for flushing particles of obstruction material into the atherectomy catheter, especially in conjunction with suction applied to the proximal end of the atherectomy catheter. The fluid may be radio-opaque to assist x-raying the process. Prior to coring, fluid can also be delivered through the atherectomy catheter. A mechanical action of the ro tary coring means and the flexible guide-wire on the cored obstruction material due to the relative motion between them enables the cored material into a continu ous passage defined in the atherectomy catheter and around the flexible guide-wire. Removing the catheter containing the obstruction material out of the vessel.
The sequence of insertion of the components into the artery may vary depending on the nature and the loca tion of the obstruction and the preferences of the medi cal staff. Additional steps may be added to assist the process. A standard guiding catheter, which is either straight or pre-formed, may function as a sleeve and be inserted into the vessel to assist in placing the flexible guide-wire and the atherectomy catheter in the obstruc tion site. When an arterial obstruction is further blocked by a fresh blood clot, as is often the case in a heart attack, the flexible guide-wire can usually be inserted through the clot and the atherectomy system can be used to first clear the clot, preferably while employing suction, and then to continue and core the underlying atherosclo rotic obstruction.
Therefore, the atherectomy system can be an effective tool in treating a heart attack, where the treatment will relieve the immediate threat to the patient's life and continue to provide a long term cor rection to the condition that induced the attack. Differing strategies can be employed when dealing with the process of opening an arterial obstruction. A rotary coring means having an opening approximately equal in area to the artery's internal area can be chosen, however this raises the probability of injuring the artery or of leaving a thin layer of obstruction material hang ing on the arterial wall. Such a thin layer which has no structural integrity of its own may separate from the arterial wall and act as a flap of a one way valve which may block the artery. An alternative strategy is to choose a rotary coring means with an area of less than three quarters of the area of the arterial lumen.
Coring the obstruction with such a rotary coring means usually relieves the patient's symptoms and it leaves sufficient material for the obstruction to remain structurally sta ble, reducing the likelihood of creating a flap, and, by using an undersized rotary coring means the probability of injuring the arterial wall is also reduced, even when dealing with an eccentric obstruction. After the ob struction is cored it is also possible to further increase the lumen by angioplasty, however, this will introduce some of the undesirable side effects that are associated 4,883,458 9 with angioplasty, and the choice of strategy will depend on the patient's specific disease characteristics and the judgement of the medical staff.
Coronary artery disease (CAD) remains the leading cause of death in the US. Over the past three decades since the first percutaneous transluminal coronary angioplasty (PTCA) was performed, advances in percutaneous revascularization have revolutionized the management of patients with CAD. Initial experience with PTCA was plagued with serious complications such as abrupt closure due to dissections, elastic recoil of the artery, and restenosis. Indications for PTCA were limited to focal noncalcified lesions in proximal coronary arteries. The development of coronary artery stents addressed the problems of dissection and elastic recoil, but the risk of in-stent restenosis (ISR) remained high in patients with long lesions, small vessel diameters, bifurcation lesions, diabetics, chronic renal failure, chronic total occlusions (CTO), and saphenous vein grafts (SVG). Multiple strategies such as systemic pharmacologic treatments and modified stent designs have failed to show significant improvements in the rates of ISR. Animal and intravascular ultrasound (IVUS) studies in humans have shown that the primary pathological process in ISR is neointimal proliferation [3–5].
In addition to deep artery trauma and exposure to a ‘‘foreign object’’ from the placement of stents, the residual plaque burden left outside the stent is directly proportional to the amount of neointimal proliferation. In theory, the mechanical debulking of atherosclerotic plaques with the use of rotational or direct coronary atherectomy devices prior to stent placement would be beneficial in three ways: (1) the risk of ISR would be lowered by decreasing the underlying plaque burden, (2) the risk of ISR would also be lowered because of an increase in the acute procedural minimal luminal diameter (MLD), and (3) there would be a decrease in the risk of abrupt closure because of the preservation of the original arterial size and decreased barotrauma to the vessel.
Atherosclerosis is a disease of the circulatory system characterized by fatty or calcified deposits or fibrous tissue growth which occlude blood vessels. It is a lead ing cause of death by disease in the United States. The atherosclerotic stenoses or blockages tend to reduce cross sectional area of the blood vessels thereby imped ing blood circulation. In severe cases, the entire vessel may be significantly narrowed or blocked by the depos its, thereby causing or contributing angina pectoris, stroke, myocardial infarction and other conditions. Atherosclerosis may be treated through coronary by-pass surgery wherein an autogenous vein or syn thetic graft is used to by-pass the diseased artery. Of course, this technique involves a major surgical operation at substantial risk and expense to the patient, and a significant recovery period. Balloon angioplasty is another method for treating atherosclerosis. With this technique a balloon catheter is routed through the artery to the site of the blockage.
Once in position, the balloon is inflated to compress or displace the blockage. Balloon angioplasty requires only local anesthesia and avoids many of the risks, expenses and prolonged recovery associated with by-pass surgery. However, if the blockage or stenosis is asymmetrical or fully closed, this technique may be unavailable or ineffective. Similarly, balloon angioplasty may not work with highly calcified or fibrous blockages. Various atherectomy catheters having mechanical cutting edges for cutting blockages have also been pro posed. While these devices have met with varying degrees of success in principle and application, certain disadvantages remain. If a single cutting device is un able to remove a wide range of blockages, then a series of cutting devices of varying size and perhaps shape must be employed. This requires the surgeon to repeat edly locate the blockage, guide a first cutting device to it, perform the cutting operation, withdraw the cutting device from the patient, replace it with the next size cutting device in sequence-and then repeat the operation for as many times as is necessary. Repeatedly inserting and removing the cutting devices from the patient is time consuming and increases risk to the patient. In addition, with all cutting devices there is a need to prevent inadvertent cutting into or through healthy arterial walls. Accordingly, it is an object of the invention to provide an improved atherectomy catheter. It is a further object of the invention to provide an improved stent for use in blood vessels having undergone blockage removal procedures.
An atherectomy catheter includes an expandable cutter and a torque member attached to the cutter. The cutter is reversibly expandable by the surgeon using controls remaining outside of the patient. The cutter is expandable into a generally conical shape. The torque member, or a balloon on the torque member may include a surface provided with a bio-active material to promote healing of the vessel surfaces cut by the cutter.
Also to this end, a method for removing an obstruction in a blood vessel includes the steps of locating the obstruction and guiding an expandable cutter to the obstruction using a guide wire. The cutter is expanded and rotated while it is directed to engage the blockage. The cutter may make repeated passes through the blockage removing additional blockage material with each pass. A dual balloon atherectomy catheter has two spaced apart balloons behind a cutter, for treating cut tissues of a vessel.
A stent is coated with a bio-active agent to promote healing of a vessel. A bio-active surface 53 having biologically active compounds such as epidermal growth factor (EGF); transforming growth factor (TGF), alpha and beta; platelet derived growth factor (PDGF); fibroblast growth factor (FGF); and insulin-like growth factor (IGF), bound to it is provided on the leading cylindrical edge of the torque tube. As the bio-active surface 53 contacts the freshly cut tissues of the blockage, the bio-active compounds on the bio-active surface 53 are brought into contact with the tissues to promote healing or inhibit recurrent growth. The bio-active material may be covalently bonded to the torque tube . After the blockage has been substantially entirely cut away, as shown in FIG. 10, the vacuum pump and torque tube motor 42 are turned off, and the tension cable 56 is released or pushed forward by the expander control 46 causing the cutter head 62 to contract to approximate the original closed configuration shown in FIG. 3. The torque tube 52 is withdraw into the guiding catheter and the guide wire is similarly pulled back into the tension cable 56 with the interior end of the atherectomy catheter in the position as shown in FIG. 3. The guiding catheter containing the cutter head 62 is then withdrawn from the patient.
An application lumen or tube 4.1 may be attached to the guiding catheter 40 to facilitate providing a biologically active compound, such as EGF, TGF, PDGF, FGF or IGF directly to the intervention site. The bio logically active compound in solution, is injected or otherwise pumped into the application lumen which joins to and leads into the guiding catheter. The solution flows through the guiding catheter to the interior end where it is released immediately adjacent to the intervention site or the tissue cut by the atherectomy catheter. Since the biologically active compound is released virtually directly onto the intervention site, therapeutic levels of the compounds can be reached with the administration of an extremely small quantity of the compound.