CUTTING DEVICE WITH EXPANDABLE ANVIL
FIELD OF THE INVENTION
The present invention generally relates to tissue cutting devices, and particularly to a cutting device with an expandable anvil for cutting holes, for example, in an atrium wall to reduce elevated filling pressure incurred by cardiac dysfunction to an acceptable level that provides adequate left ventricle function, while reducing the left atrium and pulmonary venous pressures below the point where pulmonary congestion occurs.
BACKGROUND OF THE INVENTION
Congestive heart failure is a syndrome characterized by left ventricular dysfunction, reduced exercise tolerance, impaired quality of life and dramatically shortened life expectancy. Decreased contractility of the left ventricle leads to reduced cardiac output with consequent systemic arterial and venous vasoconstriction.
CHF develops generally in the course of months or years, and can be the end stage of chronic hypertension, infarction, angina, or diabetes.
Presently available treatments for CHF fall into three generally categories: (1) pharmacological, e.g., diuretics; (2) assist systems, e.g., pumps; and (3) surgical treatments. With respect to pharmacological treatments, diuretics have been used to reduce the workload of the heart by reducing blood volume and preload.
Assist devices used to treat CHF include, for example, mechanical pumps. Mechanical pumps reduce the load on the heart by performing all or part of the pumping function normally done by the heart. Currently, mechanical pumps are used to sustain the patient while a donor heart for transplantation becomes available for the patient. There are also a number of pacing devices used to treat CHF. However, in the chronic ischemic heart, high rate pacing may lead to increased diastolic pressure, indicating calcium overload and damage of the muscle fibers. Finally, there are at least three extremely invasive and complex surgical procedures for treatment of heart failure: 1) heart transplant; 2) dynamic cardiomyoplasty; and 3) the Batista partial left ventriculectomy
Various devices have been developed using stents or conduits to modify blood pressure and flow within a given vessel, or between chambers of the heart. For example, a conduit may be positioned in a hole in the atrial septum of the heart to allow flow from the left atrium into the right atrium. Shunting the blood may reduce left atrial pressures, thereby preventing pulmonary edema and progressive left ventricular dysfunction, and reducing LVEDP.
Methods to puncture and/or create an opening in the atrium septum wall are known in the art and are used in cardiac electro-physiology procedures, percutaneous heart valve insertion and other percutaneous procedures. There are two basic methods to create such a blood bypass flow path:
A) Use the Seldinger technique to puncture the tissue with a needle, and then use several dilators to increase the puncture size. Balloons may also be used to increase the orifice diameter. Since no tissue is removed, the Seldinger method is used to insert catheters for short percutaneous heart treatment like RF ablation, or to open a blood path between the heart atriums when leaving an implant to keep the orifice open, as such unobstructed orifice/hole will close very quickly as the tissue elasticity tends to regain its original shape.
B) Increase the orifice diameter by using abrasive catheters that remove tissue material from the orifice walls by moving a rough abrasive surface against the tissue. However, since the tissue is flexible it is not easy to abrade the tissue. Worse, any small abraded particles may flow directly to the brain and cause stroke and possibly death. RF cutting catheters (usually with a blunt tip) are also used to cut tissue from the atrium wall. Once again, the tissue must be removed afterwards and cannot be left loose in the heart chambers.
SUMMARY
The present invention seeks to provide devices and methods for reducing elevated filling pressure, e.g., incurred by cardiac dysfunction, to acceptable levels, while still providing adequate left ventricle function, and reducing the left atrium and pulmonary venous pressures below the point where pulmonary congestion occurs.
The invention may be applicable to treat several disorders, such as without limitation, increased left atrium pressure (LAP) that occurs as part of Congestive Heart Failure (CHF).
In one aspect of the present invention, a device and method are provided for cutting an orifice in the atrium wall between the right and left atriums, preferably at the fossa-ovalis section of the atrial wall. Such a large orifice reduces elevated left atrium pressure by allowing blood flow directly from the left atrium into the right atrium. In contrast to the prior art, in the present invention, a catheter-based device is used to mechanically cut an orifice in the atrial septum wall and remove the cut tissue in one piece from the septum wall (and afterwards out from the body). The orifice cutting catheter may cut a large orifice from the atrium septum wall in one catheter activation. The cut tissue is locked inside the catheter and removed from the body when removing the catheter.
The orifice cutting catheter of the invention may be adjustable to cut different orifice diameters.
The cutting mechanism may include a specially shaped blade or other hand activated mechanical cutting mechanism. The blade may be round (e.g., circular) and may move relative to an anvil or anvils.
The catheter distal anvil is preferably an expandable anvil. This distal anvil may pass the atrial septum through a small diameter puncture, and then expand to its full size (full diameter) to fit the cutting mechanism diameter. Otherwise, if using standard sheath, balloon or catheter used today to puncture and pass the atrial septum, the diameter of the temporary hole created is unknown at the time the device of the invention is used, usually shortly after the puncture is performed, as the hole created by the sheath or balloon may still be completely or partially open at the time of septum cutting by the catheter of the invention, so it might cut nothing or just small portion of the septum tissue, instead of a full round tissue disk as required.
The orifice is preferably cut in a smooth, round shape, without any jagged edges or bulges that might disturb blood flow.
The round cutting blade may be connected to an RF energy source, using the round blade as an RF electrode, to allow cutting a round large opening in the atrial septum.
The orifice cutting catheter of the invention may be coated with substances, such as but not limited to, Paclitaxel drug used in drug eluting balloons, to prevent cell growth at the edges of the orifice.
The present invention describes, inter alia, methods and apparatus for decreasing pressure in the left side of the cardiac structure of a patient by opening an orifice or a shunt communicating with an area on both left and right sides of the heart atriums, whereby a volume of blood sufficient to reduce pressure in the left atrium is released from one atrium to the other. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic illustration of the heart chambers and the atrial septum. Fig. 2 is a schematic illustration of a cutting device in accordance with a non- limiting embodiment of the present invention, with a distal anvil penetrating the atrial septum.
Fig. 3 is a sectional schematic illustration of heart chambers with a hole in the atrial septum made with the device of the invention.
Fig. 4 is a simplified illustration of the device of the invention with a proximal handle, control knobs and a distal balloon-expandable anvil.
Fig. 5 is a further illustration of the device of the invention with a balloon- expandable anvil.
Fig. 6 is a simplified schematic illustration of the device of the invention after penetrating the atrial septum, before opening the balloon anvil.
Fig. 7 is a simplified schematic illustration of the device of the invention after penetrating the atrial septum, opening the balloon-expandable anvil, and pulling the balloon backwards towards the septum.
Fig. 8 is a simplified schematic illustration of locking the septum tissue between the two anvils.
Fig. 9 is a simplified sectional schematic illustration of the device of the invention after cutting the hole in the atrial septum, keeping the cut tissue within the catheter tip.
Fig. 10 is a simplified sectional schematic illustration of the device of the invention, in accordance with another non-limiting embodiment of the present invention, having a self-expandable distal anvil (e.g., made from a shape memory material) in its contracted, non-expanded position.
Fig. 11 is a simplified sectional schematic illustration of the device of Fig. 10, with the self-expandable distal anvil in its expanded position.
DETAILED DESCRIPTION
Reference is now made to Fig. 1, which illustrates pertinent parts of the cardiovascular anatomy. Shown are a large peripheral vein 9 next to the right atrium 5, and the atrial septum 4 that separates the right atrium 5 from the left atrium 6.
Reference is now made to Fig. 2, which illustrates a cutting device 1 deployed in the cardiovascular anatomy. Cutting device 1, which may be delivered over a guidewire 2, includes a cutting assembly 33, which may be located at a distal portion 31 of a working shaft 34. A distal anvil 32 is located distally of cutting assembly 33 on an anvil shaft 39. A proximal anvil 42 is located near cutting assembly 33. In one embodiment, proximal anvil 42 is arranged to be concentric with, and moved inwards of, cutting assembly 33.
As will be explained more in detail below, the device 1 may be delivered to the right atrium 5 by passing over guidewire 2. The guidewire 2 passes from the right atrium 5 through the atrial septum 4 into the left atrium 6. The distal anvil 32, while in the contracted orientation, passes into the left atrium 6 through the opening formed in the septum 4 by guidewire 2. The distal anvil 32 is then expanded. The proximal anvil 42 and the distal anvil 32 are brought towards each other so as to clamp septum 4. While the septum 4 is clamped, cutting assembly 33 may then be used to cut an aperture 7 (Fig. 3) in septum 4.
Reference is now made to Figs. 4 and 5, which illustrate cutting device 1, in accordance with a non-limiting embodiment of the present invention. Cutting device 1 may include a proximal handle 35 with one or more control knobs 40 and 41. A flexible shaft 34 extends distally from handle 35. The cutting assembly 33 may be located at distal portion 31 of shaft 34. Distal anvil 32 is located distally of cutting assembly 33 on anvil shaft 39. A guidewire lumen 37 may extend distally of distal anvil 32.
Reference is now made to Fig. 6, which illustrates one application of cutting device 1, namely, to cut an aperture in the atrial septum 4 (e.g., at or near the fossa ovalis 8, to allow blood to flow through the aperture between the left and right atriums. This helps reduce elevated filling pressure incurred by cardiac dysfunction, to an acceptable level that provides adequate left ventricle function, while reducing the left atrium and pulmonary venous pressures below the point where pulmonary congestion occurs.
Cutting device 1 may be delivered to the right atrium by passing over guidewire 2. The guidewire 2 passes from the right atrium through the atrial septum 4 into the left atrium. The distal anvil 32, while in the contracted orientation and mounted on anvil shaft 39, passes into the left atrium through the opening formed in the septum 4 by guidewire 2. The proximal anvil 42 is on the proximal side of the septum 4 in the right atrium.
Reference is now made to Fig. 7. The distal anvil 32 is then expanded, such as by expanding a balloon, next to or connected to, distal anvil 32. The portion of anvil 32 which expands is designated in the drawings by numeral 38. The balloon may form part of or all of distal anchor 32. The balloon may be expanded by introducing fluid thereto, as is well known in the art.
Reference is now made to Fig. 8. The proximal anvil 42 and the distal anvil 32 are brought towards each other so as to clamp septum 4.
It is noted that the atrium fossa tissue is very thin and flexible, and moves as the heart beats. Therefore in order to cut the aperture, the atrium fossa must be held tight. On the other hand, it is dangerous to apply uncontrolled pressure on the tissue as it may tear completely or in an uncontrolled shape. The invention solves these problems by the clamping action of the two anvils.
Reference is now made to Fig. 9. While the septum 4 is clamped, cutting assembly 33 may then be used to cut an aperture in septum 4. It is seen that proximal anvil 42 is arranged to be concentric with blade 36 of cutting assembly 33. The cutting assembly may be moved over proximal anvil 42. The rotating round blade 36 may have a uniform, sharp cutting edge, or multiple cutting teeth. Blade 36 may move relative to distal and proximal anvils 32 and 42 to cleanly cut a circular hole in the atrial septum 4. The blade may be moved manually, semi-automatically or automatically by the control button or buttons. In the automatic mode, a motor or other suitable actuator may be used to rotate blade 36.
The cut hole perimeter is free of burrs and ragged edges. The cut material is entrapped between the two anvils and covered by cutting assembly 33, so that no dangerous debris is left to flow in the vasculature. The cut material is removed from the body upon removal of the device from the body.
The cut aperture size may be a few millimeters in diameter, in the range between 2 mm to 10 mm, and more preferably between 5-8 mm in diameter. The aperture is not limited in size or shape (e.g., may be oval or non-round).
In another embodiment of the present invention, blade 36 may be connected to an RF energy source 50 (Fig. 4) so that blade 36 serves as an electrode to cut the tissue by RF ablation. The tissue may vaporize during ablation, minimizing risk of debris entering the vasculature.
The RF ablation/cutting may be combined with mechanical cutting of the blade or other blade. The blade may operate in bipolar, monopolar or combined monopolar and bipolar mode. The distal anchor 32 may include a flexible conductive ring 44 printed at its proximal base, as known in the art for electrodes printing over balloons used in ablation catheters. Flexible ring 44 may be connected to the second pole of the bipolar RF energy source 50, while blade 36 (in the form of a ring) may be connected to the first lead of the bipolar RF energy RF energy source 50. Thus, the distal anchor 32 and the blade 36 may operate as bipolar electrodes.
Reference is now made to Figs. 10 and 11. In another embodiment of the present invention, a distal self-expandable anvil 52 is made from a shape memory material (e.g., nitinol), such as from wires or wire mesh 51. The self-expandable anvil 52 may be initially collapsed inside anvil shaft 39 while penetrating through the atrial septum. After passing from the right atrium into the left atrium, the wires 51 may be deployed and expanded out the shaft 29 to regain the shape of the distal anchor 52 as seen in Fig. 11. The device is then used as described before.
In all embodiments of the invention, the cutting blades 36 and anvils 32 and/or 42 may be coated with drugs (e.g., Paclitaxel) used in drug eluting balloons, to prevent cell growth at the edges of the orifice.
In another embodiment of the invention, the working shaft 34 may have a pre- bended tip or deflected tip mechanism using a pulling wire or other bending mechanism, in order to aim the distal tip 31 of device towards the atrial septum.