Patent Document

PRIORITY CLAIM 
     The present application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/061,170, filed Jun. 13, 2008, which application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a treatment system for percutaneous coronary angioplasty or peripheral angioplasty in which a dilation catheter is used to cross a lesion in order to dilate the lesion and restore normal blood flow in the artery. It is particularly useful when the lesion is a calcified lesion in the wall of the artery. Calcified lesions require high pressures (sometimes as high as 10-15 or even 30 atmospheres) to break the calcified plaque and push it back into the vessel wall. With such pressures comes trauma to the vessel wall which can contribute to vessel rebound, dissection, thrombus formation, and a high level of restenosis. Non-concentric calcified lesions can result in undue stress to the free wall of the vessel when exposed to high pressures. An angioplasty balloon when inflated to high pressures can have a specific maximum diameter to which it will expand but the opening in the vessel under a concentric lesion will typically be much smaller. As the pressure is increased to open the passage way for blood the balloon will be confined to the size of the open in the calcified lesion (before it is broken open). As the pressure builds a tremendous amount of energy is stored in the balloon until the calcified lesion breaks or cracks. That energy is then released and results in the rapid expansion of the balloon to its maximum dimension and may stress and injure the vessel walls. 
     SUMMARY OF THE INVENTION 
     The invention provides a catheter that comprises an elongated carrier, a dilating balloon about the carrier in sealed relation thereto, the balloon being arranged to receive a fluid therein that inflates the balloon, and an arc generator including at least one electrode within the balloon that forms a mechanical shock wave within the balloon. 
     The at least one electrode may include a single metallic electrode of a pair of metallic electrodes. The electrodes may be radially displaced from each other or longitudinally displaced from each other. The at least one electrode may be formed of stainless steel. 
     The balloon may be formed of non-compliant material or of compliant material. The dilating balloon may have at least one stress riser carried on its surface. 
     The catheter may further comprise a sensor that senses reflected energy. The sensor may be distal to the at least one electrode. The sensor may be disposed on the carrier. 
     The catheter may further comprise a reflector within the dilating balloon that focuses the shock waves. The reflector may form one of the at least one electrodes. The catheter has a center line and the reflector may be arranged to focus the shock waves off of the catheter center line. 
     The fluid may be saline. The fluid may include an x-ray contrast. 
     The catheter may further include a lumen for receiving a guide wire. The lumen may be defined by the carrier. 
     The invention further provides a system comprising a catheter including an elongated carrier, a dilating balloon about the carrier in sealed relation thereto, the balloon being arranged to receive a fluid therein that inflates the balloon, and an arc generator including at least one electrode within the balloon that forms a mechanical shock wave within the balloon. The system further comprises a power source that provides electrical energy to the arc generator. 
     The power source is preferably arranged to provide pulsed high voltage. The power source may be arranged to provide high voltage pulses having selectable pulse durations, selectable voltage amplitudes, and/or selectable pulse repetition rates. 
     The system may further comprise an R wave detector that synchronizes the mechanical shock waves with cardiac R waves. 
     The at least one electrode may include a single metallic electrode of a pair of metallic electrodes. The electrodes may be radially displaced from each other or longitudinally displaced from each other. The at least one electrode may be formed of stainless steel. 
     The balloon may be formed of non-compliant material or of compliant material. The dilating balloon may have at least one stress riser carried on its surface. 
     The catheter may further comprise a sensor that senses reflected energy. The sensor may be distal to the at least one electrode. The sensor may be disposed on the carrier. 
     The catheter may further comprise a reflector within the dilating balloon that focuses the shock waves. The reflector may form one of the at least one electrodes. The catheter has a center line and the reflector may be arranged to focus the shock waves off of the catheter center line. 
     The fluid may be saline. The fluid may include an x-ray contrast. 
     The catheter may further include a lumen for receiving a guide wire. The lumen may be defined by the carrier. 
     The invention further provides a method comprising the step of providing a catheter including an elongated carrier, a dilating balloon about the carrier in sealed relation thereto, the balloon being arranged to receive a fluid therein that inflates the balloon, and an arc generator including at least one electrode within the balloon that forms a mechanical shock wave within the balloon. The method further comprises the steps of inserting the catheter into a body lumen of a patient adjacent an obstruction of the body lumen, admitting fluid into the balloon, and applying high voltage pulses to the arc generator to form a series of mechanical shocks within the balloon. 
     The method may include the further step of detecting cardiac R waves of the patient&#39;s heart, and synchronizing the mechanical shocks with the detected R waves. 
     The method may further include the step of varying one of the repetition rate, amplitude and duration of the high voltage pulses to vary the intensity of the mechanical shock waves. 
     The method may include the further step of sensing reflected energy within the catheter. 
     The method may include the further step of placing a guide wire into the body lumen and guiding the catheter into the body lumen along the guide wire. 
     The method may include the further step of focusing the mechanical shockwaves. The mechanical shockwaves may be focused away from the catheter center axis. 
     The method may include the further steps of adding an x-ray contrast to the fluid and visualizing the catheter under fluoroscopy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For illustration and not limitation, some of the features of the present invention are set forth in the appended claims. The various embodiments of the invention, together with representative features and advantages thereof, may best be understood by making reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify identical elements, and wherein: 
         FIG. 1  is a view of the therapeutic end of a typical prior art over-the-wire angioplasty balloon catheter. 
         FIG. 2  is a side view of a dilating angioplasty balloon catheter with two electrodes within the balloon attached to a source of high voltage pulses according to one embodiment of the invention. 
         FIG. 3  is a schematic of a high voltage pulse generator. 
         FIG. 3A  shows voltage pulses that may be obtained with the generator of  FIG. 3 . 
         FIG. 4  is a side view of the catheter of  FIG. 2  showing an arc between the electrodes and simulations of the shock wave flow. 
         FIG. 5  is a side view of a dilating catheter with insulated electrodes within the balloon and displaced along the length of the balloon according to another embodiment of the invention. 
         FIG. 6  is a side view of a dilating catheter with insulated electrodes within the balloon displaced with a single pole in the balloon and a second being the ionic fluid inside the balloon according to a further embodiment of the invention. 
         FIG. 7  is a side view of a dilating catheter with insulated electrodes within the balloon and studs to reach the calcification according to a still further embodiment of the invention. 
         FIG. 8  is a side view of a dilating catheter with insulated electrodes within the balloon with raised ribs on the balloon according to still another embodiment of the invention. 
         FIG. 8A  is a front view of the catheter of  FIG. 8 . 
         FIG. 9  is a side view of a dilating catheter with insulated electrodes within the balloon and a sensor to detect reflected signals according to a further embodiment of the invention. 
         FIG. 10  is a pressure volume curve of a prior art balloon breaking a calcified lesion. 
         FIG. 10A  is a sectional view of a balloon expanding freely within a vessel. 
         FIG. 10B  is a sectional view of a balloon constrained to the point of breaking in a vessel. 
         FIG. 10C  is a sectional view of a balloon after breaking within the vessel. 
         FIG. 11  is a pressure volume curve showing the various stages in the breaking of a calcified lesion with shock waves according to an embodiment of the invention. 
         FIG. 11A  is a sectional view showing a compliant balloon within a vessel. 
         FIG. 11B  is a sectional view showing pulverized calcification on a vessel wall. 
         FIG. 12  illustrates shock waves delivered through the balloon wall and endothelium to a calcified lesion. 
         FIG. 13  shows calcified plaque pulverized and smooth a endothelium restored by the expanded balloon after pulverization. 
         FIG. 14  is a schematic of a circuit that uses a surface EKG to synchronize the shock wave to the “R” wave for treating vessels near the heart. 
         FIG. 15  is a side view, partly cut away, of a dilating catheter with a parabolic reflector acting as one electrode and provides a focused shock wave inside a fluid filled compliant balloon. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a view of the therapeutic end of a typical prior art over-the-wire angioplasty balloon catheter  10 . Such catheters are usually non-complaint with a fixed maximum dimension when expanded with a fluid such as saline. 
       FIG. 2  is a view of a dilating angioplasty balloon catheter  20  according to an embodiment of the invention. The catheter  20  includes an elongated carrier, such as a hollow sheath  21 , and a dilating balloon  26  formed about the sheath  21  in sealed relation thereto at a seal  23 . The balloon  26  forms an annular channel  27  about the sheath  21  through which fluid, such as saline, may be admitted into the balloon to inflate the balloon. The channel  27  further permits the balloon  26  to be provided with two electrodes  22  and  24  within the fluid filled balloon  26 . The electrodes  22  and  24  are attached to a source of high voltage pulses  30 . The electrodes  22  and  24  are formed of metal, such as stainless steel, and are placed a controlled distance apart to allow a reproducible arc for a given voltage and current. The electrical arcs between electrodes  22  and  24  in the fluid are used to generate shock waves in the fluid. The variable high voltage pulse generator  30  is used to deliver a stream of pulses to the electrodes  22  and  24  to create a stream of shock waves within the balloon  26  and within the artery being treated (not shown). The magnitude of the shock waves can be controlled by controlling the magnitude of the pulsed voltage, the current, the duration and repetition rate. The insulating nature of the balloon  26  protects the patient from electrical shocks. 
     The balloon  26  may be filled with water or saline in order to gently fix the balloon in the walls of the artery in the direct proximity with the calcified lesion. The fluid may also contain an x-ray contrast to permit fluoroscopic viewing of the catheter during use. The carrier  21  includes a lumen  29  through which a guidewire (not shown) may be inserted to guide the catheter into position. Once positioned the physician or operator can start with low energy shock waves and increase the energy as needed to crack the calcified plaque. Such shockwaves will be conducted through the fluid, through the balloon, through the blood and vessel wall to the calcified lesion where the energy will break the hardened plaque without the application of excessive pressure by the balloon on the walls of the artery. 
       FIG. 3  is a schematic of the high voltage pulse generator  30 .  FIG. 3A  shows a resulting waveform. The voltage needed will depend on the gap between the electrodes and generally 100 to 3000 volts. The high voltage switch  32  can be set to control the duration of the pulse. The pulse duration will depend on the surface area of the electrodes  22  and  24  and needs to be sufficient to generate a gas bubble at the surface of the electrode causing a plasma arc of electric current to jump the bubble and create a rapidly expanding and collapsing bubble, which creates the mechanical shock wave in the balloon. Such shock waves can be as short as a few microseconds. 
       FIG. 4  is a cross sectional view of the shockwave catheter  20  showing an arc  25  between the electrodes  22  and  24  and simulations of the shock wave flow  28 . The shock wave  28  will radiate out from the electrodes  22  and  24  in all directions and will travel through the balloon  26  to the vessel where it will break the calcified lesion into smaller pieces. 
       FIG. 5  shows another dilating catheter  40 . It has insulated electrodes  42  and  44  within the balloon  46  displaced along the length of the balloon  46 . 
       FIG. 6  shows a dilating catheter  50  with an insulated electrode  52  within the balloon  56 . The electrode is a single electrode pole in the balloon, a second pole being the ionic fluid  54  inside the balloon. This unipolar configuration uses the ionic fluid as the other electrical pole and permits a smaller balloon and catheter design for low profile balloons. The ionic fluid is connected electrically to the HV pulse generator  30 . 
       FIG. 7  is another dilating  60  catheter with electrodes  62  and  64  within the balloon  66  and studs  65  to reach the calcification. The studs  65  form mechanical stress risers on the balloon surface  67  and are designed to mechanically conduct the shock wave through the intimal layer of tissue of the vessel and deliver it directly to the calcified lesion. 
       FIG. 8  is another dilating catheter  70  with electrodes  72  and  74  within the balloon  76  and with raised ribs  75  on the surface  77  of the balloon  76 . The raised ribs  75  (best seen in  FIG. 8A ) form stress risers that will focus the shockwave energy to linear regions of the calcified plaque. 
       FIG. 9  is a further dilating catheter  80  with electrodes  82  and  84  within the balloon  86 . The catheter  80  further includes a sensor  85  to detect reflected signals. Reflected signals from the calcified plaque can be processed by a processor  88  to determine quality of the calcification and quality of pulverization of the lesion. 
       FIG. 10  is a pressure volume curve of a prior art balloon breaking a calcified lesion  FIG. 10B  shows the build up of energy within the balloon (region A to B) and  FIG. 10C  shows the release of the energy (region B to C) when the calcification breaks. At region C the artery is expanded to the maximum dimension of the balloon. Such a dimension can lead to injury to the vessel walls.  FIG. 10A  shows the initial inflation of the balloon. 
       FIG. 11  is a pressure volume curve showing the various stages in the breaking of a calcified lesion with shock waves according to the embodiment. The balloon is expanded with a saline fluid and can be expanded to fit snugly to the vessel wall (Region A)( FIG. 11A ) but this is not a requirement. As the High Voltage pulses generate shock waves (Region B and C) extremely high pressures, extremely short in duration will chip away the calcified lesion slowly and controllably expanding the opening in the vessel to allow blood to flow un-obstructed ( FIG. 11B ). 
       FIG. 12  shows, in a cutaway view, shock waves  98  delivered in all directions through the wall  92  of a saline filled balloon  90  and intima  94  to a calcified lesion  96 . The shock waves  98  pulverize the lesion  96 . The balloon wall  92  may be formed of non-compliant or compliant material to contact the intima  94 . 
       FIG. 13  shows calcified plaque  96  pulverized by the shock waves. The intima  94  is smoothed and restored after the expanded balloon (not shown) has pulverized and reshaped the plaque into the vessel wall. 
       FIG. 14  is a schematic of a circuit  100  that uses the generator circuit  30  of  FIG. 3  and a surface EKG  102  to synchronize the shock wave to the “R” wave for treating vessels near the heart. The circuit  100  includes an R-wave detector  102  and a controller  104  to control the high voltage switch  32 . Mechanical shocks can stimulate heart muscle and could lead to an arrhythmia. While it is unlikely that shockwaves of such short duration as contemplated herein would stimulate the heart by synchronizing the pulses (or bursts of pulses) with the R-wave, an additional degree of safety is provided when used on vessels of the heart or near the heart. While the balloon in the current drawings will provide an electrical isolation of the patient from the current, a device could be made in a non-balloon or non-isolated manner using blood as the fluid. In such a device, synchronization to the R-wave would significantly improve the safety against unwanted arrhythmias. 
       FIG. 15  shows a still further dilation catheter  110  wherein a shock wave is focused with a parabolic reflector  114  acting as one electrode inside a fluid filled compliant balloon  116 . The other electrode  112  is located at the coaxial center of the reflector  114 . By using the reflector as one electrode, the shock wave can be focused and therefore pointed at an angle (45 degrees, for example) off the center line  111  of the catheter artery. In this configuration, the other electrode  112  will be designed to be at the coaxial center of the reflector and designed to arc to the reflector  114  through the fluid. The catheter can be rotated if needed to break hard plaque as it rotates and delivers shockwaves. 
     While particular embodiments of the present invention have been shown and described, modifications may be made. For example, instead of manual actuation and spring loaded return of the valves used herein, constructions are possible which perform in a reversed manner by being spring actuated and manually returned. It is therefore intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention as defined by those claims.

Technology Category: 1