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Patent: To Use Your Heart to Treat Medical Problems
Patent: To Use Your Heart to Treat Medical Problems | hou_txbz,Timothy L. Scott, Sugarland, patent, 8239028, cardiac parameter, chronic medical condition, Cyberonics,

Timothy L. Scott of Sugarland, Texas, received earlier this month U.S. Patent 8,239,028 for “Use of Cardiac Parameters in Methods and Systems for Treating a Chronic Medical Condition.”

Texas Business Patent of the Day:  A Texas man has devised a way to monitor one’s heart when treating a lingering medical problem.

Timothy L. Scott of Sugarland, Texas, received earlier this month U.S. Patent 8,239,028 for “Use of Cardiac Parameters in Methods and Systems for Treating a Chronic Medical Condition.”

Scott applied for the patent more than three years ago on April 24, 2009.

The patent assignee is Cyberonics Inc. of Houston.

 Scott’s invention relates generally to medical device systems and, more particularly, to medical device systems capable of determining and/or treating a chronic medical condition, accoding to the patent documents.

Many advancements have been made in treating diseases such as depression and epilepsy. Therapies using electrical signals for treating these diseases have been found to be effective. Implantable medical devices have been effectively used to deliver therapeutic stimulation to various portions of the human body such as the vagus nerve for treating these diseases. The words "stimulation," "neurostimulation," "stimulation signal," or "neurostimulation signal" refers to the application of an electrical, mechanical, magnetic, electromagnetic, photonic, audio, and/or chemical signal to a neural structure in the patient's body.

The stimulation signal (whether electrical, mechanical, magnetic, electromagnetic, photonic, audio or chemical in nature) applied to the nerve in the present invention is a signal applied from an artificial source such as a neurostimulator. 

A "therapeutic signal" refers to a stimulation signal delivered to a patient's body with the intent of treating a medical condition by providing a modulating effect to neural tissue. The effect of a stimulation signal on neuronal activity is termed "modulation"; however, for simplicity, the terms "stimulating" and "modulating", and variants thereof, are sometimes used interchangeably herein.

In general, however, the delivery of an exogenous signal itself refers to "stimulation" of the neural structure, while the effects of that signal, if any, on the electrical activity of the neural structure are properly referred to as "modulation." The modulating effect of the stimulation signal upon the neural tissue may be excitatory or inhibitory, and may potentiate acute and/or long-term changes in neuronal activity.

For example, the "modulating" effect of the stimulation signal to the neural tissue may comprise one more of the following effects: (a) initiation of an action potential (afferent and/or efferent action potentials); (b) inhibition or blocking of the conduction of action potentials, whether endogenous or exogenously induced, including hyperpolarizing and/or collision blocking, (c) affecting changes in neurotransmitter/neuromodulator release or uptake, and (d) changes in neuro-plasticity or neurogenesis of brain tissue. 

In some embodiments, electrical neurostimulation may be provided by implanting an electrical device, i.e., an implantable medical device (IMD), underneath the skin of a patient and delivering an electrical signal to a nerve such as a cranial nerve. Generally, electrical neurostimulation signals that perform neuromodulation are delivered by the IMD via one or more leads, although leadless neurostimulators have also been developed. The leads generally terminate at their distal ends in one or more electrodes, and the electrodes, in turn, are electrically coupled to tissue in the patient's body. For example, a number of electrodes may be attached to various points of a nerve or other tissue inside a human body for delivery of a neurostimulation signal. 

While feedback stimulation such as an electrical signal applied in response to a sensed body parameter such as heart rate, have been proposed, conventional vagus nerve stimulation (VNS) usually involves non-feedback stimulation characterized by a number of parameters. Specifically, conventional vagus nerve stimulation usually involves a series of grouped electrical pulses defined by an "on-time" and an "off-time." Each sequence of pulses during an on-time may be referred to as a "pulse burst." The burst is followed by the off-time period in which no signals are applied to the nerve.

During the on-time, electrical pulses of a defined electrical current (e.g., 0.5-2.0 milliamps) and pulse width (e.g., 0.25-1.0 milliseconds) are delivered at a defined frequency (e.g., 20-30 Hz) for the on-time duration, usually a specific number of seconds, e.g., 10-60 seconds. The pulse bursts are separated from one another by the off-time, (e.g., 30 seconds-5 minutes) in which no electrical signal is applied to the nerve. The on-time and off-time parameters together define a duty cycle, which is the ratio of the on-time to the combination of the on-time and off-time, and which describes the percentage of time that the electrical signal is applied to the nerve. 

In conventional VNS, the on-time and off-time may be programmed to define an intermittent pattern in which a repeating series of electrical pulse bursts are generated and applied to a cranial nerve such as the vagus nerve. The off-time is provided to allow the nerve to recover from the stimulation of the pulse burst, and to conserve power. If the off-time is set at zero, the electrical signal in conventional VNS may provide continuous stimulation to the vagus nerve. Alternatively, the off time may be as long as one day or more, in which case the pulse bursts are provided only once per day or at even longer intervals. Typically, however, the ratio of "off-time" to "on-time" may range from about 0.5 to about 10. 

In addition to the on-time and off-time, the other parameters defining the electrical signal in conventional VNS may be programmed over a range of values. The pulse width for the pulses in a pulse burst of conventional VNS may be set to a value not greater than about 1 msec, such as about 250-500 .mu.sec, and the number of pulses in a pulse burst is typically set by programming a frequency in a range of about 20-150 Hz (i.e., 20 pulses per second to 150 pulses per second). A non-uniform frequency may also be used. Frequency may be altered during a pulse burst by either a frequency sweep from a low frequency to a high frequency, or vice versa. Alternatively, the timing between adjacent individual signals within a burst may be randomly changed such that two adjacent signals may be generated at any frequency within a range of frequencies. 

Although neurostimulation has proven effective in the treatment of a number of medical conditions, it would be desirable to further enhance and optimize neurostimulation for this purpose. For example, it may be desirable to further enhance treatment of chronic medical conditions. Generally, the state of the art implantable medical devices lack efficient treatment based on certain feedback from the patient's body for treating chronic conditions. This may be due to either a belief that no reliable body parameter is a reliable indicator or predictor of the disease state of the chronic medical condition; the difficulty of isolating a particular indicator from many factors that contribute to the disease state; a belief that feedback systems will provide no benefit over non-feedback treatment for chronic medical conditions; or to combinations of the foregoing. In sharp contrast to this general neglect of feedback-based treatments for chronic illnesses, designers have proposed numerous systems to provide treatment of certain episodic or acute medical conditions based upon feedback of certain body parameters. For example, many different feedback schemes for detection and treatment of epileptic seizures have been proposed, including feedback based upon EEG signals, heart rate, and sensing of neural activity. Further, the relative shortage of reliable treatments for many chronic medical conditions may also contribute to the absence of feedback-based treatment options for chronic medical conditions. This lack of sufficient knowledge as to the treatment of chronic or non-episodic type ailments presents difficult challenges in analyzing body parameters to provide feedback-based treatment for such conditions. There is a need for improved treatment options, including feedback-based treatment options, for many chronic medical conditions. 

Scott’s invention provides a method for treating a chronic medical condition. A time of beat sequence of the patient's heart is determined. A regulatory system parameter is determined based on the time of beat sequence. The parameter is indicative of a stress level of the patient's regulatory adaptation systems. The determined regulatory system parameter is compared with a threshold regulatory system parameter value. An electrical signal is applied to a neural structure of the patient to treat the chronic medical condition if the determined regulatory system parameter exceeds the threshold regulatory system parameter value. 

In another aspect of the present invention, another method for treating a chronic medical condition in a patient is provided. A time of beat sequence of the patient's heart is determined. A heart rate variability (HRV) parameter is determined based on the time of beat sequence. The HRV parameter is associated with a parasympathetic function of the patient. The determined HRV parameter is compared with a threshold HRV parameter value. An electrical signal is applied to a neural structure to treat the chronic medical condition if the determined HRV parameter exceeds the threshold HRV value. 

In another aspect of the present invention, an implantable medical device (IMD) for treating a chronic medical condition in a patient is provided. The IMD comprises a sensing module for sensing data relating to a time of beat sequence of the patient's heart and a heart beat data processing module to process the data relating to the time of beat sequence. The IMD also includes a heart parameter module adapted to determine at least one heart parameter selected from a heart rate variability (HRV) parameter associated with a parasympathetic function of the patient and a regulatory system parameter indicative of a stress level of the patient's regulatory adaptation systems. The heart parameter module is also adapted to determine the at least one heart parameter based upon the processed data relating to the time of beat sequence of the patient's heart. The IMD also includes a comparator adapted to compare the heart parameter determined by the heart parameter module with a threshold heart parameter value. The IMD also includes an electrical signal module adapted to generate and apply an electrical signal to a neural structure to treat the chronic medical condition in the patient based upon the comparison of the determined heart parameter value and the threshold heart parameter value. 

In yet another aspect of the present invention, a computer readable program storage device is provided that is encoded with instructions that, when executed by a computer, perform a method for treating a chronic medical condition in a patient is provided. The method includes determining a time of beat sequence of the patient's heart and determining a first index of regulatory activity systems (IARS) value associated with the patient based upon the time of beat sequence. The method also includes comparing the first IARS value to a first threshold IARS value and providing a therapy to the patient in response to a determination that the first IARS value exceeds the first threshold IARS value. 

In yet another aspect of the present invention, a computer readable program storage device is provided that is encoded with instructions that, when executed by a computer, perform a method for treating a chronic medical condition in a patient is provided. The method includes determining a time of beat sequence of the patient's heart and determining an HRV parameter indicative of parasympathetic activity from the time of beat sequence. The method also includes comparing the determined HRV value to a threshold HRV value; and providing a therapy to the patient in response to a determination that the HRV value is below the threshold HRV value. 

In yet another aspect of the present invention, an implantable medical device system is provided for providing an indication of a level of stress upon a regulatory system of a patient having a chronic medical condition. The system includes an implantable medical device (IMD) that comprises a sensing module for sensing data relating to a time of beat sequence of the patient's heart and a heart beat data processing module adapted to process the data relating to the time of beat sequence. The IMD also includes a regulatory activity module adapted to determine an index of regulatory activity systems (IARS) value associated with the patient based upon the data relating to the time of beat sequence of the patient's heart. The IARS value is indicative of level of stress upon the regulatory system of the patient. The IMD also includes a communication module adapted to provide the IARS value to at least one of a patient or a healthcare provider. The medical device is adapted to provide a treatment to the patient in response to a determination that the IRS value indicates a chronic condition in the patient.