In a general sense, the invention is directed to systems and methods for treating interior tissue regions of the body. More specifically, the invention is directed to systems and methods for treating dysfunction in body sphincters and adjoining tissue, e.g., in and around the lower esophageal sphincter and cardia of the stomach.
The gastrointestinal tract, also called the alimentary canal, is a long tube through which food is taken into the body and digested. The alimentary canal begins at the mouth, and includes the pharynx, esophagus, stomach, small and large intestines, and rectum. In human beings, this passage is about 30 feet (9 meters) long.
Small, ring-like muscles, called sphincters, surround portions of the alimentary canal. In a healthy person, these muscles contract or tighten in a coordinated fashion during eating and the ensuing digestive process, to temporarily close off one region of the alimentary canal from an other.
For example, a muscular ring called the lower esophageal sphincter surrounds the opening between the esophagus and the stomach. The lower esophageal sphincter (or LES) is a ring of increased thickness in the circular, smooth-muscle layer of the esophagus. Normally, the lower esophageal sphincter maintains a high-pressure zone between fifteen and thirty mm Hg above intragastric pressures inside the stomach.
When a person swallows food, muscles of the pharynx push the food into the esophagus. The muscles in the esophagus walls respond with a wavelike contraction called peristalsis. The lower esophageal sphincter relaxes before the esophagus contracts, and allows food to pass through to the stomach. After food passes into the stomach, the lower esophageal sphincter constricts to prevent the contents from regurgitating into the esophagus.
The stomach muscles churn the food and digestive juices into a mass called chyme. Then the muscles squeeze the chyme toward the pyloric (intestinal) end of the stomach by peristaltic waves, which start at the top of the stomach and move downward. The pyloric sphincter, another ringlike muscle, surrounds the duodenal opening. The pyloric sphincter keeps food in the stomach until it is a liquid. The pyloric sphincter then relaxes and lets some chyme pass into the duodenum.
Dysfunction of a sphincter in the body can lead to internal damage or disease, discomfort, or otherwise adversely affect the quality of life. For example, if the lower esophageal sphincter fails to function properly, stomach acid may rise back into the esophagus. Unlike the stomach, the esophagus has no natural protection against stomach acids. When the stomach contents make contact with the esophagus, heartburn or other disease symptoms, including damage to the esophagus, can occur.
Gastrointestinal reflux disease (GERD) is a common disorder, characterized by spontaneous relaxation of the lower esophageal sphincter. It has been estimated that approximately two percent of the adult population suffers from GERD. The incidence of GERD increases markedly after the age of 40, and it is not uncommon for patients experiencing symptoms to wait years before seeking medical treatment.
GERD is both a normal physiologic phenomenon that occurs in the general population and a pathophysiologic phenomenon that can result in mild to severe symptoms.
GERD is believed to be caused by a combination of conditions that increase the presence of acid reflux in the esophagus. These conditions include transient LES relaxation, decreased LES resting tone, impaired esophageal clearance, delayed gastric emptying, decreased salivation, and impaired tissue resistance. Since the resting tone of the lower esophageal sphincter is maintained by both myogenic (muscular) and neurogenic (nerve) mechanisms, some believe that aberrant electrical signals in the lower esophageal sphincter or surrounding region of the stomach (called the cardia) can cause the sphincter to spontaneously relax.
Lifestyle factors can also cause increased risk of reflux. Smoking, large meals, fatty foods, caffeine, pregnancy, obesity, body position, drugs, hormones, and paraplegia may all exacerbate GERD. Also, hiatal hernia frequently accompanies severe GERD. The hernia may increase transient LES relaxation and delay acid clearance due to impaired esophageal emptying. Thus, hiatal hernias may contribute to prolonged acid exposure time following reflux, resulting in GERD symptoms and esophageal damage.
The excessive reflux experienced by patients with GERD overwhelms their intrinsic mucosal defense mechanisms, resulting in many symptoms. The most common symptom of GERD is heartburn. Besides the discomfort of heartburn, reflux results in symptoms of esophageal inflammation, such as odynophagia (pain on swallowing) and dysphagia (difficult swallowing). The acid reflux may also cause pulmonary symptoms such as coughing, wheezing, asthma, aspiration pneumonia, and interstitial fibrosis; oral symptoms such as tooth enamel decay, gingivitis, halitosis, and waterbrash; throat symptoms such as a soreness, laryngitis, hoarseness, and a globus sensation; and earache.
Complications of GERD include esophageal erosion, esophageal ulcer, and esophageal stricture; replacement of normal esophageal epithelium with abnormal (Barrett""s) epithelium; and pulmonary aspiration.
Treatment of GERD includes drug therapy to reduce or block stomach acid secretions. Still, daily drug therapy does not eliminate the root cause of the dysfunction.
Invasive abdominal surgical intervention has also been tried with success. One procedure, called Nissen fundoplication, entails invasive, open abdominal surgery. The surgeon wraps the gastric fundis about the lower esophagus, to, in effect, create a new xe2x80x9cvalve.xe2x80x9d Less invasive laparoscopic tehniques have also been tried to emulate Nissen fundoplication, also with success. Still, all surgical intervention entails making an incision into the abdomen and carry with it the usual risks of abdominal surgery.
One aspect of the invention provides a system for treating a tissue region at or near a sphincter comprising first and second electrodes supported to individually apply energy to the tissue region to form a lesion pattern. The system also includes a generator having a power channel and a controller coupling the electrode pair to the generator. The controller operates to short the electrode pair together, so that a single power channel simultaneously powers both electrodes in a monopolar mode to form the lesion pattern.
In one embodiment, each electrode includes a temperature sensor. In one arrangement, the controller is coupled to both temperature sensors. The controller operates to alternatively sample the temperatures sensed by the temperature sensors and select a hottest sensed temperature as an input to control magnitude of power supplied by the single power channel to both electrodes. In another arrangement, the controller is coupled to both temperature sensors in parallel. The controller operates to sample the temperatures sensed by the temperature sensors and receive an approximate average of the temperatures sensed by the temperature sensors as an input to control magnitude of power supplied by the single power channel to both electrodes.
Another aspect of the invention provides a system for treating a tissue region at or near a sphincter. The system comprises a first electrode and a second electrode supported to individually apply energy to the tissue region to form a lesion pattern. The system also includes a generator having a power channel and a controller coupling the first and second electrodes to the generator. The controller includes a switch element operating in alternate first and second modes. In the first mode, the switch element couples the power channel to the first electrode and not the second electrode. In the second mode, the switch element couples the power channel to the second electrode and not the first electrode. In this way, a single power channel powers both electrodes in a monopolar mode to form the lesion pattern.
In one embodiment, each electrode includes a temperature sensor. The controller is coupled to each temperature sensor through the switch element. In first mode, the controller receives temperature sensed only by the sensor of the first electrode as an input to control magnitude of power supplied by the single power channel to the first electrode. In the second mode, the controller receives temperature sensed only by the sensor of the second electrode as an input to control magnitude of power supplied by the single power channel to the second electrode.
In one embodiment, the switch element sequentially switches between the first and second modes to minimize overheating effects.
In one embodiment, the switch element imposes a time delay when switching between the first and second modes to allow tissue moisture to return to dissicated tissue between applications of energy.
Another aspect of the invention provides an assembly for treating a tissue region at or near a sphincter. The assembly comprises a support structure and a bipolar pair of electrodes carried by the support structure for advancement in paths to penetrate the tissue region.
In one embodiment, the assembly comprises a first electrode, a second electrode, a third electrode, and a fourth electrode supported to apply energy to the tissue region to form a lesion pattern. The assembly also includes a generator having a first and second power channel and a power return. A controller couples the first, second, third, and fourth electrodes to the generator. The controller operates to couple the first electrode to the first power channel, to couple the second electrode to the second power channel, and to couple the third and fourth electrodes to the power return, so that two power channels power the first and second electrodes as bipolar pairs with, respectively, the third and fourth electrodes to form a lesion pattern.
In one embodiment, the controller independently couples the third and fourth electrodes to the power return, with no common ground, so that each power channel is an independent bipolar circuit.
In one embodiment, the third and fourth electrodes are shorted to provide a common return.
In one embodiment, each electrode includes a temperature sensor. In one arrangement, the controller samples temperatures sensed by the temperature sensors for each bipolar pair of electrodes and averages the sensed temperatures to provide an input to control magnitude of power supplied to the respective electrode pair. In another arrangement, the controller samples temperatures sensed by the temperature sensors for each bipolar pair of electrodes and selects a maximum temperature to provide an input to control magnitude of power supplied to the respective electrode pair.
Features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended Claims.