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Portable device for monitoring electrocardiographic signals and indices of blood flowRelated Patent Categories: Surgery, Diagnostic Testing, Measuring Electrical Impedance Or Conductance Of Body PortionPortable device for monitoring electrocardiographic signals and indices of blood flow description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070021683, Portable device for monitoring electrocardiographic signals and indices of blood flow. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCES TO RELATED APPLICATIONS [0001] This application is based on and claims the benefit of U.S. Provisional Patent Application No. 60/569,551, filed May 10, 2004, the entire disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] The present invention relates to diagnostic monitoring systems and, more particularly, to a portable diagnostic monitoring system for assessing cardiovascular hemodynamic state during the setting of a normal or abnormal heart rhythm. Advantageously, the monitoring system is capable of detecting abnormalities of blood pressure and/or flow. [0003] Changes in cardiac output or blood pressure may be of value in diagnosis and management chronic and/or recurring disease states (e.g., congestive heart failure, hypertension, syncope). Currently, such measurements require invasive intravascular catheters with attached sensors (e.g., pressure, oxygen saturation) or an intra-arterial cannula. [0004] Devices employing the technique of impedance plethysmography (commonly known as Impedance Cardiographs (ICG) when applied to the thorax) have been developed which are external to the body and can provide a surrogate marker of pulsatile blood volume changes and/or surrogate measure of blood flow by detection of changes in bioelectrical impedance (BEI). Typically, these devices use band or spot electrodes around the ends of the thorax and measure change in chest impedance due to altered vascular volumes corresponding to cardiac activity. Current is transmitted through the chest and seeks the path of least resistance, i.e., the blood filled aorta. With each heartbeat, the blood volume and velocity of the aorta change. Impedance plethysmography measures the corresponding change in impedance and calculates the hemodynamic parameters. BRIEF SUMMARY OF THE INVENTION [0005] The invention addresses the medical problem of evaluating the hemodynamic impact of a cardiac arrhythmia or suspected cardiac arrhythmia in free-living individuals. The objective may be accomplished by correlating electrocardiographic (ECG) recordings with surrogate measurements of blood pressure and/or blood flow obtained from a portable (wearable or insertable) cardiac monitor. In essence, for instances in which there is suspicion that heart rhythm disturbances are causing symptoms (e.g., dizziness, syncope, or weakness), the ability to correlate a documented arrhythmia with its hemodynamic effect will allow the physician to better assess the true impact of the arrhythmia on the patient. Additionally, some patients may exhibit hemodynamic disturbances (e.g., abrupt hypotension) without concomitant arrhythmia. Examples include certain vasodepressor faints in which the main problem is dilation of arterial blood vessels causing a fall in blood pressure, or in some individuals in association with movement from supine or seated to upright posture (e.g., orthostatic hypotension and/or orthostatic faints). In these conditions the heart rhythm may remain normal, or only relatively minor abnormalities are recorded and the heart rate may remain within the normal range; nonetheless, the blood pressure becomes abnormally low. Currently, these latter conditions are difficult to document in free-living individuals as they occur unpredictably over time, and at present there is no available portable monitor systems which can document both ECG and hemodynamic alterations over relatively long periods (e.g., weeks or months). [0006] Embodiments of the present invention are directed to a physiological monitoring device which is configured to record signals that reflect blood flow and/or blood pressure, and which may also record ECG signals. In an exemplary embodiment, a portable diagnostic monitoring device is capable of detecting abnormal cardiac rhythms and assess their impact on blood flow, as well as detect abnormalities of blood flow that may or may not be associated with an abnormal heart rhythm. An example of clinical use is the evaluation of individuals experiencing syncope (faints) of unknown origin. The monitoring device may be worn on the body surface of the patient. A more practical embodiment of the monitoring device is of a sufficiently small size as to be insertable into the body of the patient using techniques essentially identical to placement of a conventional pacemaker generator. In the exemplary embodiment, intra-vascular access is not utilized, so that the system offers diagnostic capabilities without invading blood vessels to insert sensors. In other embodiments, intravascular or extravascular leads may be used to enhance the diagnostic capability. In yet other embodiments, the monitoring device may be incorporated into a conventional pacemaker or implantable defibrillator (ICD) to enhance the diagnostic capability of those instruments. [0007] In accordance with an aspect of the present invention, a portable monitoring device comprises a plurality of impedance electrodes configured to be coupled to a patient's body and to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body. At least a portion of the portable monitoring device is configured to be insertable subcutaneously into the patient's body. [0008] In some embodiments, the impedance electrodes are to be placed in close proximity to (e.g., within less than about 5 cm of) a target region of the patient's body to be monitored. The impedance electrodes are configured to detect local electrical impedance near an artery in the patient's body. The impedance electrodes include two electrodes that are spaced from one another in a direction generally parallel to or transversely across the artery. A temperature sensor may also be used in this device to aid in assessing local blood flow and/or monitoring for recurring disease states that may cause fever. The temperature sensor is configured to measure local tissue temperature of the patient's body near the temperature sensor. A plurality of ECG electrodes are configured to be coupled to the patient's body. A telemetry component is configured to communicate telemetrically with an external device. A warning component, which may be activated or deactivated by an external telemetry link, provides warning based on the detected information. The impedance electrodes are can-mounted surface electrodes. Auxiliary leads are coupled with the impedance electrodes. [0009] In specific embodiments, a memory is configured to store physiological information obtained by detecting the local electrical impedance by the impedance electrodes. The memory is configured to store physiological data based on instructions delineating criteria for data to be stored. The memory has looping memory capability. The memory is configured to store data temporally proximate to an event based on information detected by the impedance electrodes or patient-activated triggering. [0010] In accordance with another aspect of the present invention, a portable monitoring device comprises a plurality of impedance electrodes configured to be coupled to a patient's body and to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field; a plurality of ECG electrodes configured to be coupled to the patient's body; and a memory configured to store physiological information obtained by detecting the local electrical impedance by the impedance electrodes and by the ECG electrodes. [0011] In some embodiments, the impedance electrodes and the ECG electrodes are can-mounted surface electrodes. Auxiliary leads may also be coupled with at least some of the impedance electrodes and the ECG electrodes. [0012] In accordance with another aspect of the invention, a method of monitoring a patient comprises coupling a plurality of impedance electrodes to a patient's body to generate an AC current with an electrical field to detect local electrical impedance of a portion of the patient's body encompassed by the electrical field, the local electrical impedance being a surrogate measure of local blood flow of the portion of the patient's body; and inserting at least a portion of a portable monitoring device including the impedance electrodes subcutaneously into the patient's body. [0013] In some embodiments, the impedance electrodes are placed in the vicinity (e.g., usually within less than about 5 cm) of a target region of the patient's body to be monitored (e.g., an artery such as the subclavian artery). The impedance electrodes may be applied to a muscle of the patient's body to be monitored. Two of the impedance electrodes may be positioned near an artery and spaced in a direction generally parallel to the artery. Local tissue temperature of the patient's body may also be measured. ECG data of the patient may also be measured. The method may further include transferring information obtained by the impedance electrodes and other sensors (e.g., temperature sensors, ECG electrodes) to an external device disposed outside the patient's body. A warning is generated based on the detected information using pre-determined criteria programmed into the device by the user (e.g., physician). The method further comprises storing physiological information obtained by detecting the local electrical impedance by the impedance electrodes. The information is stored based on instructions delineating criteria for data to be stored. The information is stored proximate to an event based on information detected by the impedance electrodes or patient-activated triggering. [0014] In specific embodiments, the method further comprises coupling auxiliary leads to the impedance electrodes and positioning the auxiliary leads in a target location in the patient's body. The method may further comprise providing the impedance electrodes in an implantable diagnostic device. [0015] A further configuration permits automatic telemetry of information to an external receiver/transmitter for automatic transfer to a distant monitoring station such as by radiowaves, wireless telephony, or direct internet connection. BRIEF DESCRIPTION OF THE DRAWINGS [0016] FIG. 1 is a plan view of a portable monitoring device according to an embodiment of the present invention. [0017] FIG. 2 is an elevational view of the portable monitoring device of FIG. 1. [0018] FIGS. 3A-3D are simplified schematic views of the positioning of the impedance electrodes relative to an artery. [0019] FIG. 4 is a simplified schematic view of a monitoring device incorporated in an implantable device such as a pacemaker or ICD. [0020] FIG. 5 is a plan view of a portable monitoring device including leads according to another embodiment of the present invention. Continue reading about Portable device for monitoring electrocardiographic signals and indices of blood flow... Full patent description for Portable device for monitoring electrocardiographic signals and indices of blood flow Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Portable device for monitoring electrocardiographic signals and indices of blood flow patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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