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ACUTE AND CHRONIC ELECTRICAL
SIGNAL THERAPY FOR OBESITY
CROSS-REFERENCE TO RELATED
This application is a continuation of U.S. patent application Ser. No. 10/795,803, filed May 28, 2003, now issued as U.S. Pat. No. 6,993,391, which in turn is a continuation of U.S. patent application Ser. No. 09/734,358, filed Dec. 11, 2000, now issued as U.S. Pat. No. 6,600,953, all of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates generally to treatment of obesity, and specifically to invasive techniques and apparatus for treating obesity.
BACKGROUND OF THE INVENTION
present patent application and in the claims, the use of such a non excitatory signal to modify the response of one or more cells to electrical activation thereof, without inducing action potentials in the cells, is referred to as Excitable Tissue Con
5 trol (ETC). Use of an ETC signal is described with respect to treating obesity, by applying the ETC signal to the stomach so as to delay or prevent emptying of the stomach. In addition, a method is, described for increasing the motility of the gastrointestinal tract, by applying an ETC signal to a portion of
l o the tract in order to increase the contraction force generated in the portion.
PCT Patent Publication WO 97/25098, to Ben Haim et al., entitled "Electrical muscle controller," and the corresponding U.S. patent application Ser. No. 09/101,723, which are 15 assigned to the assignee of the present patent application and are incorporated herein by reference, describe methods for modifying the force of contraction of a heart chamber by applying an ETC signal to the heart.
20 SUMMARY OF THE INVENTION
Invasive treatments for obesity are often recommended for patients with a body mass index (mass/height2 [kg/m2]) which is greater than 35 or 40. For such patients, their weight is commonly associated with increased risk of heart disease, 25 diabetes, and arthritis. Preferably, the invasive treatments are accompanied by changes in lifestyle, such as improved eating habits and an appropriate exercise regimen.
U.S. Pat. No. 6,067,991 to Forsell, U.S. Pat. No. 5,601,604 to Vincent, and U.S. Pat. No. 5,234,454 to Bangs, and U.S. 30 Pat. Nos. 5,449,368, 5,226,429 and 5,074,868 to Kuzmak, which are incorporated herein by reference, describe mechanical instruments for implantation in or around the stomach of an obese patient.
U.S. Pat. No. 5,690,691 to Chen et al., which is incorpo- 35 rated herein by reference, describes a gastric pacemaker for treating obesity and other conditions. The pacemaker includes multiple electrodes which are placed at various positions on the gastrointestinal (GI) tract, and which deliver phased electrical stimulation to pace peristaltic movement of 40 material through the GI tract.
U.S. Pat. No. 5,423,872 to Cigaina, which is incorporated herein by reference, describes apparatus for applying electrical pulses to the distal gastric antrum of a patient, so as to reduce the motility of the stomach and to thereby treat obesity 45 or another condition.
U.S. Pat. Nos. 5,188,104 and 5,263,480 to Wernicke et al, which are incorporated herein by reference, describe a method for stimulating the vagus nerve of a patient so as to alleviate an eating disorder. 50
U.S. Pat. Nos. 6,104,955, 6,091,992, and 5,836,994 to Bourgeois, U.S. Pat. No. 6,026,326 to Bardy, and U.S. Pat. No. 3,411,507 to Wingrove, which are incorporated herein by reference, describe the application of electrical signals to the GI tract to treat various physiological disorders. 55
PCT Patent Publication WO 99/03533 to Ben Haim et al, entitled, "Smooth muscle controller," and U.S. patent application Ser. No. 09/481,253 in the national phase thereof, both of which are assigned to the assignee of the present patent application and are incorporated herein by reference, 60 describe apparatus and methods for applying signals to smooth muscle so as to modify the behavior thereof. In particular, apparatus for controlling the stomach is described in which a controller applies an electrical field to electrodes on the stomach wall so as to modify the reaction of muscle tissue 65 therein to an activation signal, while not generating a propagating action potential in the tissue. In the context of the
It is an object of some aspects of the present invention to provide improved apparatus and methods for treatment of medical conditions which relate to the gastrointestinal tract.
It is a further object of some aspects of the present invention to provide improved apparatus and methods for treating obesity.
In preferred embodiments of the present invention, apparatus for treating a condition such as obesity comprises a set of one or more electrodes which are applied to one or more sites of the gastrointestinal (GI) tract of a patient. A control unit preferably drives the electrode set to apply an Excitable Tissue Control (ETC) signal to the GI tract, so as to modulate contraction of muscles of the gastrointestinal tract and to thereby treat the condition.
In a preferred embodiment, the electrodes are applied to the stomach, and the control unit drives the electrodes to apply an enhancement signal which includes, as appropriate, the ETC signal and/or an excitatory signal. Thus, the enhancement signal may induce contractions and/or increase or otherwise modify the contraction forces generated by muscles of the stomach.
For some applications, the enhancement signal is applied so as to modify a contraction pattern of some of the stomach's muscles, in order to reduce the cross sectional area of a portion of the stomach. The narrow ring thereby generated reduces the volume of a region of the stomach, and increases the sensation of satiety felt by the patient compared to that which would be felt without the application of this embodiment of the invention. For example, the enhancement signal may cause an "indenting" of the stomach wall, whereby food is limited in its ability to vacate the esophageal region of the stomach. Consequently, this portion of the stomach is stretched more than usual for the volume of food ingested, and an earlier sensation of satiety is induced. This embodiment thus employs electrical signals to cause a narrowing of the stomach analogous to that produced mechanically by the gastric bands described in the Background section of the present patent application. Unlike these prior art mechanical bands, however, this application of the present invention allows the extent of the narrowing to be moderated in real time by the control unit without mechanical intermediaries (e.g., modulation of fluid pressure).
Alternatively or additionally, the enhancement signal is applied, prior to and/or during a meal, so as to reduce the overall size of the stomach, thereby increasing the tension in the wall of the stomach when food is in the stomach. This