Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2002-01-30
2004-06-22
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06754536
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to implantable medical devices (IMDs), particularly gastrointestinal stimulator and/or monitor IMDs adapted to be implanted within the interior of the gastrointestinal tract having one or more than one stimulation/sense electrode attached to or pressing against an interior surface site of the gastrointestinal tract wall to conduct electrical stimulation to the site and to conduct electrical signals of the GI tract from the site or other physiologic signals from the interior of the gastrointestinal tract.
BACKGROUND OF THE INVENTION
The GI tract comprises the esophagus, the stomach, the small intestine, the large intestine, the colon, and the anal sphincter and is generally described as having a tract axis. Like other organs of the body, most notably the heart, these organs naturally undergo regular rhythmic contractions. In particular these contractions take the form of peristaltic contractions and are essential for the movement of food through each of the respective organs. Like the heart, these contractions are the result of regular rhythmic electrical depolarizations of the underlying tissue.
In some individuals, however, either the regular rhythmic peristaltic contractions do not occur or the regular rhythmic electrical depolarizations do not occur or both do not occur. In each of these situations the movement of food may be seriously inhibited or even disabled. Such a condition is often called “gastroparesis” when it occurs in the stomach. Gastroparesis is a chronic gastric motility disorder in which there is delayed gastric emptying of solids or liquids or both. Symptoms of gastroparesis may range from early satiety and nausea in mild cases to chronic vomiting, dehydration, and nutritional compromise in severe cases. Similar motility disorders occur in the other organs of the GI tract, although by different names.
Diagnosis of gastroparesis is based on-demonstration of delayed gastric emptying of a radio-labeled solid meal in the absence of mechanical obstruction. Gastroparesis may occur for a number of reasons. Management of gastroparesis involves four areas: (1) prokinetic drugs, (2) antiemetic drugs, (3) nutritional support, and (4) surgical therapy (in a very small subset of patients.) Gastroparesis is often a chronic, relapsing condition; 80% of patients require maintenance antiemetic and prokinetic therapy and 20% require long-term nutritional supplementation. Other maladies such as tachygastria or bradygastria can also hinder coordinated muscular motor activity of the GI tract, possibly resulting in either stasis or nausea or vomiting or a combination thereof.
The undesired effect of these conditions is a reduced ability or complete failure to efficiently propel intestinal contents down the digestive tract. This results in malassimilation of liquid or food by the absorbing mucosa of the intestinal tract. If this condition is not corrected, malnutrition or even starvation may occur. Moreover nausea or vomiting or both may also occur. Whereas some of these disease states can be corrected by medication or by simple surgery, in most cases treatment with drugs is not adequately effective, and surgery often has intolerable physiologic effects on the body.
The concept of electrically stimulating the gastrointestinal tract to restore its proper function originated many years ago, and one early approach is disclosed in commonly assigned U.S. Pat. No. 3,411,507. The '507 patent discloses a system for gastrointestinal stimulation which uses an electrode positioned on a nasogastric catheter and an electrode secured to the skin over the abdomen. In operation, the nasogastric catheter is inserted into the patient's stomach while the patient is lying down such that the electrode is positioned in close proximity to the pylorus of the stomach. Electrical stimulation is delivered for the first five seconds of every minute until peristaltic activity is initiated. The '507 patent also discloses using electrical stimulation of the same order of magnitude as the normal range of periodicity of the inherent peristaltic pacemaker action of the duodenum. The stimulation process is discontinued after the first bowel movement. The '507 patent system is a short-term device that is only useful for patients in a hospital setting, and particularly non-ambulatory patients.
Sensing of the peristaltic electrical wave and gastrointestinal stimulation at various sites on or in the GI tract wall of the digestive system or nerves associated therewith have been conducted to diagnose and treat these various conditions over the years since the publication of the '507 patent. Fully implantable gastrointestinal stimulation systems have been developed and clinically implanted in patient's bodies allowing the patients to be ambulatory. The history and breadth of such sensing and GI tract stimulation is set forth in commonly assigned U.S. Pat. Nos. 5,507,289, 6,026,326, 6,104,965, 6,216,039, and in further U.S. Pat. Nos. 5,690,691 and 6,243,607, for example. The implantable gastrointestinal stimulation systems are referred to as “pacemakers” in certain of these patents and the literature because of their resemblance to implantable cardiac pacemakers in structure and function.
In such fully implantable gastrointestinal stimulation systems, electrical stimuli are applied from an implantable pulse generator (IPG) through elongated leads and lead borne electrodes affixed at sites in the body of the patient or the GI tract wall or the vagus nerve that permit the electrical stimulus to produce a local contraction of a desired portion of the GI tract. The IPG is typically implanted below the skin surface in the abdominal region and leads coupled to the IPG extend to sites of the gastrointestinal tract and/or the vagus nerve where stimulation/sense electrodes are affixed.
The sites of the GI tract wall typically comprise the outermost serosa or sub-serosally in the inner, circumferential and longitudinal (and oblique in the case of the stomach) smooth muscle layers referred to as the “muscularis externa” (although the above referenced '691 patent suggests locating the electrodes within the stomach cavity against the inner stomach surface mucosa). The above-referenced '607 patent discloses one method and system for electrical stimulation of smooth muscle with intact local gastric nerves comprising a portion of the GI tract. The electrical stimulation of the smooth muscle effects local contractions at sites of a portion of the GI tract that are artificially propagated distally therethrough in order to facilitate or aid at least a partial emptying of such portion. This stimulation attempts to create a simulated system that reproduces the spatial and temporal organization of normal gastric electrical activity by creating and controlling local circumferential non-propagated contractions. In this simulated gastric pacing system, each local circumferential contraction is invoked by applying an electrical stimulus to the smooth muscle circumferentially about the portion of the GI tract in a plane substantially perpendicular to the longitudinal axis of the portion. The electrical stimulus is applied at a proximal location and at least one distal location. The distal location is in axially spaced relationship relative to the proximal location. Further, the applied electrical stimulus is selected to be sufficient to stimulate the smooth muscle to produce the local circumferential contractions at the proximal and distal locations.
The Medtronic® Itrel III® Model 7425 IPG and pairs of the unipolar Model 4300 or Model 4301 or Model 4351 “single pass” leads available from MEDTRONIC, INC. have been implanted to provide stimulation to sites in the stomach wall to treat chronic nausea and vomiting associated with gastroparesis. The unipolar electrode of these leads comprises a length of exposed lead conductor and is of the type disclosed in commonly assigned U.S. Pat. Nos. 5,425,751, 5,716,392 and 5,861,014. The above-referenced '039 pat
Starkebaum Warren
Swoyer John M.
Barry Thomas G.
Campbell Keith M.
Layno Carl
Medtronic Inc
Woods Thomas F.
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