Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Light application
Reexamination Certificate
2000-07-31
2004-11-02
Flanagan, Beverly M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Light application
C128S898000, C606S013000
Reexamination Certificate
active
06811562
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to procedures and to devices for treating cardiac tissue by forming lesions in that tissue using photodynamic therapy techniques. In particular, the procedure is valuable for rectifying various cardiac arrhythymias with those so-formed lesions. Central to this procedure is the delivery of light to the desired lesion site in cooperation with delivery of a photodynamic drug to that site. The invention also relates to devices, particularly catheters, that are suitable for delivering the light for forming those lesions.
BACKGROUND OF THE INVENTION
Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the lining or walls of blood vessels. Treatment of such abnormal wall conditions has included various medical device technologies that deliver various forms of energy to specific regions of vascular wall tissue.
For instance, atherosclerosis, a vascular disease characterized by abnormal deposits upon vessel walls or the thickening of those walls, is an example of an abnormal wall condition. The dangers related to flow blockages or functional occlusions resulting from the disease have made atherosclerosis the focus of many medical devices. Such devices are often categorized by structure and tissue treatment mechanism. The categories include direct contact electrode devices, resistance heating devices, light transmission devices, light-to-heat conversion devices, hot fluid devices, and radio frequency (RF) heated devices.
The first category includes a variety of contact electrode devices. For instance, U.S. Pat. No. 4,998,933, to Eggers et al, describes a catheter for thermal angioplasty using a heated electrode in direct contact with surrounding tissue or plaque deposits. The heated electrode serves to treat the diseased lumen walls. U.S. Pat. No. 4,676,258, to Inokuchi et al, and U.S. Pat. No. 4,807,620, to Strul et al, disclose devices designed to treat surrounding tissues using heat generated by two electrodes within the device and an RF power source.
U.S. Pat. No. 4,672,962, to Hershenson, and U.S. Pat. No. 5,035,694, to Kasprzyk et al, disclose devices which may be categorized as resistance heating probes. In each of these devices, current flowing through a conductive material at the end of the device provides heat that is transmitted to surrounding tissues for treatment of atherosclerosis and other diseases. Current is transmitted in each of these devices by electrically conductive materials. In contrast, U.S. Pat. No. 5,226,430, to Spears et al, discloses a device which uses light transmitting fiber to transmit energy to a heat generating element at the tip of the device. That heat generating element in turn transmits heat energy to a surrounding balloon structure which is in contact with surrounding tissue. Similarly, U.S. Pat. No. 4,790,311, to Ruiz, discloses an angioplasty catheter system having heat generating electrode at the tip of the device that is heated using RF energy. This device may be categorized as an RF heated device.
U.S. Pat. Nos. 5,190,540 and 5,292,321, to Lee, describe hot fluid-containing devices. Lee '540 shows a balloon catheter designed for remodeling a body lumen. This catheter uses a multilumen shaft that delivers a heated fluid to an expandable balloon. The expanded balloon heats the tissue that is in contact with the expanded balloon. Lee '321 shows a somewhat similar device. However, the expandable balloon is instead filled with a selected thermoplastic material that becomes softer and more compliant when heated by a heating element.
Diseased or structurally damaged blood vessels often involve various abnormal wall conditions. The inducement of thrombosis and control of hemorrhaging within such vessels have been the focus of several devices that use catheter-based heat sources for cauterizing damaged tissues. U.S. Pat. No. 4,449,528, to Auth et al, discloses a thermal cautery probe designed for heating specific layers of tissue without producing deep tissue damage. The mechanism of heat generation in this device is a resistive coil within the cautery probe that is electrically connected to a power source. U.S. Pat. No. 4,662,368, to Hussein et al, discloses a device designed for localized heat application within a lumen; In this device, energy in the form of light is delivered to the tip of the device for heat generation, by a flexible fiber. Heat from an element that converts light energy to heat energy passes to the adjacent tissue.
Although there are a variety of devices that deliver energy to vascular lumena, none of them deliver the energy in the form of light which cooperatively forms lesions in cardiac tissue using photodynamic chemicals to treat that cardiac tissue and to prevent various forms of fibrillation.
Atrial Fibrillation
Cardiac arrhythmias, and atrial fibrillation in particular, are common, dangerous medical ailments, particularly in the aging population. In patients with normal sinus rhythm, the heart, which is made up of atrial, ventricular, and excitatory conduction tissue, is electrically excited to beat in a synchronous, patterned fashion. In patients with cardiac arrhythmia, regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction generally occurs at various, specific regions of the heart, for example: in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet re-entrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber. These arrhythmias are often self propagating. Cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. Cardiac arrhythmias, including atrial fibrillation, may be detected using the global technique of an electrocardiogram (EKG). More sensitive procedures of mapping the specific conduction along the cardiac chambers have also been disclosed, such as for example in U.S. Pat. No. 4,641,649 to Walinsky et al and WO 96/32897 to Desai.
A variety of clinical conditions may result from the irregular cardiac function and resulting hemodynamic abnormalities associated with atrial fibrillation, including stroke, heart failure, and other thromboembolic events. Atrial fibrillation is believed to be a significant cause of cerebral stroke; the abnormal hemodynamics in the left atrium caused by the fibrillatory wall motion precipitate the formation of thrombus within the atrial chamber. A thromboembolism is ultimately thrown off into the left ventricle, which then pumps the embolism into the cerebral circulation causing a stroke. For these reasons, there are a number of procedures for treating atrial arrhythmias.
Conventional Atrial Arrhythmia Treatments
There are several pharmacological approaches intended to remedy or otherwise treat atrial arrhythrnias. See. for example, U.S. Pat. No. 4,673,563, to Beme et al; U.S. Pat. No. 4,569,801, to Molloy et al; and Hindricks, et al in “Current Management of Arrhythmias” (1991). However, such pharmacological solutions are not always effective and may in some cases result in proarrhythmia and long term inefficacy.
Several surgical approaches have been developed to treat atrial fibrillation. One example is known as the “maze procedure,” as is disclosed by Cox, J. L. et al in “The surgical treatment of atrial fibrillation. I. Summary”
Thoracic and Cardiovascular Surgery
101(3), pp. 402-405 (1991); and also by Cox, J. L. in “The surgical treatment of atrial fibrillation. IV. Surgical Tech
Epicor, Inc.
Flanagan Beverly M.
Johnson, III Henry M
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