Method and system for continuous monitoring of patients for arrthymias

Abstract

Body-worn systems and methods for continuously monitoring a patient for cardiac electrical signals and identifying rhythm abnormalities including atrial fibrillation.

I claim: 
     
         1 . A body-worn ECG monitor, comprising: 
       at least one ECG lead configured be worn on the body of an individual and to measure electrical signals indicative of electrical activity of the individual's cardiac cycle on a continuous basis and generate therefrom an analog waveform; 
       sensor electronics comprising an analog-to-digital converter operably connected to the at least one ECG lead to receive the analog waveform or a frequency-filtered form thereof and to generate therefrom a digital waveform; 
       a processing component operably connected to the sensor electronics and configured to receive the digital waveform and to continuously monitor the digital waveform for changes in cardiac rhythm indicative of a transient arrhythmic event by
 (i) storing a segment of the digital waveform in a circular data buffer, wherein the stored segment contains digital data for the current cardiac cycle and a plurality of consecutive previous cardiac cycles, and wherein the stored segment is of time length l 1  and is continuously updated for new cardiac cycles, 
 (ii) processing the digital waveform on a beat-by-beat basis to identify an occurrence of a first rhythm transition from a normal cardiac rhythm to an arrhythmia, 
 (iii) upon identifying the first rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the first rhythm transition by a predetermined time length l 2 , and ending the storage of data at a predetermined time length l 3  following the first rhythm transition; 
 (iv) following the first rhythm transition, processing the digital waveform on a beat-by-beat basis to identify an occurrence of a second rhythm transition from the arrhythmia to a normal cardiac rhythm; 
 (v) upon identifying the second rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the second rhythm transition by a predetermined time length l 4  and ending the storage of data at a predetermined time length l 5  following the second rhythm transition; and 
 (vi) repeating steps (ii)-(vi). 
 
     
     
         2 . A body-worn ECG monitor according to  claim 1 , wherein the time lengths l 2  and l 4  are the same, and the time lengths time lengths l 3  and l 5  are the same. 
     
     
         3 . A body-worn ECG monitor according to  claim 1  or  2 , wherein time lengths l 2  and l 3  are selected to provide at least about 10 seconds of recorded data that includes the first rhythm transition. 
     
     
         4 . A body-worn ECG monitor according to  claim 3 , wherein time lengths l 2  and l 3  are selected to provide between about 10 and about 240 seconds of recorded data that includes the first rhythm transition. 
     
     
         5 . A body-worn ECG monitor according to  claim 3 , wherein time lengths l 2  and l 3  are selected to provide between about 60 and about 120 seconds of recorded data that includes the first rhythm transition. 
     
     
         6 . A body-worn ECG monitor according to one of  claims 1 - 5 , wherein time lengths l 4  and l 5  are selected to provide at least about 10 seconds of recorded data that includes the second rhythm transition. 
     
     
         7 . A body-worn ECG monitor according to  claim 6 , wherein time lengths l 4  and l 5  are selected to provide between about 10 and about 240 seconds of recorded data that includes the second rhythm transition. 
     
     
         8 . A body-worn ECG monitor according to  claim 6 , wherein time lengths l 4  and l 5  are selected to provide between about 60 and about 120 seconds of recorded data that includes the second rhythm transition. 
     
     
         9 . A body-worn ECG monitor according to one of  claims 1 - 8 , wherein the circular data buffer holds at least a portion of the digital waveform equal to l 2  or l 4 , whichever is greater. 
     
     
         10 . A body-worn ECG monitor according to one of  claims 1 - 9 , further configured to communicate with an external device to download data stored in the storage memory to a storage medium on the external device. 
     
     
         11 . A body-worn ECG monitor according to one of  claims 1 - 10 , wherein the monitor is a single lead ECG monitor configured to be affixed by means of an adhesive on the chest of the individual at about the level of the heart such that one of the electrodes forming the single lead is positioned superior relative to the other such that the digital waveform approximates a lead II configuration. 
     
     
         12 . A body-worn ECG monitor according to  claim 11 , wherein the processing component determines the polarity of the electrodes forming the single lead from the digital waveform data; or wherein the monitor further comprises an accelerometer that is operably connected to the processing component, wherein the processing component is configured to receive one or more accelerometer waveforms from the accelerometer and determine therefrom which electrode in the electrodes forming the single lead is positioned superior relative to the other. 
     
     
         13 . A body-worn ECG monitor according one of  claims 1 - 12 , wherein the first and second rhythm transitions are identified by calculating a randomness score for a series of R-R intervals from the digital waveform using the processing component. 
     
     
         14 . A body-worn ECG monitor according to  claim 13 , wherein the randomness score is an entropy value. 
     
     
         15 . A body-worn ECG monitor according to  claim 14 , wherein the entropy value is calculated for at least about 128 consecutive QRS complexes in the digital waveform. 
     
     
         16 . A system, comprising,
 the body-worn ECG monitor according to one of  claims 1 - 15 ; and   the external device, wherein the external device comprises a microprocessor and a non-volatile memory operably connected to the microprocessor, wherein the microprocessor is configured to execute code stored on the non-volatile memory, wherein executing the code causes the external device to display the data downloaded to the storage medium as graphical depictions of ECG waveform segments.   
     
     
         17 . A single lead ECG monitor comprising: 
       a pair of electrodes on the underside of a flexible body coupled to a housing as an integral or unitary device; 
       electrode traces in the flexible body operably connected the pair of electrodes and to sensor electronics comprising an analog-to-digital converter to receive an analog waveform from the pair of electrodes, or a frequency-filtered form thereof, and to generate therefrom a digital waveform; and 
       a processing component operably connected to the sensor electronics within the housing and configured to receive the digital waveform and to continuously monitor the digital waveform for changes in cardiac rhythm indicative of a transient arrhythmic event and to store snippets of the digital waveform in a storage memory comprising the changes in cardiac rhythm, 
       wherein the single lead ECG monitor is configured to be affixed to an individual by means of an adhesive on the flexible body on the chest at about the level of the heart such that one of the electrodes is positioned superior relative to the other such that the digital waveform approximates a lead II configuration. 
     
     
         18 . A single lead ECG monitor according to  claim 17 , wherein the processing component determines the polarity of the electrodes forming the single lead from the digital waveform data; or wherein the monitor further comprises an accelerometer that is operably connected to the processing component, wherein the processing component is configured to receive one or more accelerometer waveforms from the accelerometer and determine therefrom which electrode in the electrodes forming the single lead is positioned superior relative to the other. 
     
     
         19 . A single lead ECG monitor according to  claim 17  or  18 , wherein the monitor continuously monitors the digital waveform for changes in cardiac rhythm indicative of a transient arrhythmic event by
 (i) storing a segment of the digital waveform in a circular data buffer, wherein the stored segment contains digital data for the current cardiac cycle and a plurality of consecutive previous cardiac cycles, and wherein the stored segment is of time length l 1  and is continuously updated for new cardiac cycles, 
 (ii) processing the digital waveform using the processing component on a beat-by-beat basis to identify an occurrence of a first rhythm transition from a normal cardiac rhythm to an arrhythmia, 
 (iii) upon identifying the first rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the first rhythm transition by a predetermined time length l 2 , and ending the storage of data at a predetermined time length l 3  following the first rhythm transition; 
 (iv) following the first rhythm transition, processing the digital waveform using the processing component on a beat-by-beat basis to identify an occurrence of a second rhythm transition from the arrhythmia to a normal cardiac rhythm; 
 (v) upon identifying the second rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the second rhythm transition by a predetermined time length l 4  and ending the storage of data at a predetermined time length l 5  following the second rhythm transition; and 
 (vi) repeating steps (ii)-(vi). 
 
     
     
         20 . A method of monitoring a patient, comprising: 
       affixing a body-worn ECG monitor according to one of  claims 1 - 15  to the patient; 
       recording one or more segments of the digital waveform in the storage memory of the ECG monitor for a period of time; 
       operably connecting the ECG monitor to an external device comprising a microprocessor and a storage medium; and 
       downloading the one or more segments of the digital waveform to the storage medium. 
     
     
         21 . A method according to  claim 20 , wherein the external device further comprises a non-volatile memory operably connected to the microprocessor, wherein the microprocessor is configured to execute code stored on the non-volatile memory, wherein executing the code causes the external device to display the data downloaded to the storage medium as graphical depictions of ECG waveform segments; and 
       executing the code on the microprocessor to display the data. 
     
     
         22 . A method of monitoring a patient, comprising: 
       affixing a single lead ECG monitor according to one of  claims 17 - 19  to the patient; and 
       causing the ECG monitor to store snippets of the digital waveform comprising the changes in cardiac rhythm in the storage memory of the ECG monitor for a period of time; 
       operably connecting the ECG monitor to an external device comprising a microprocessor and a storage medium; and 
       downloading the one or more segments of the digital waveform to the storage medium. 
     
     
         23 . A method according to  claim 22 , wherein the external device further comprises a non-volatile memory operably connected to the microprocessor, wherein the microprocessor is configured to execute code stored on the non-volatile memory, wherein executing the code causes the external device to display the data downloaded to the storage medium as graphical depictions of ECG waveform segments; and executing the code on the microprocessor to display the data. 
     
     
         24 . A single lead ECG monitor, comprising
 a pair of electrodes on the underside of a flexible body coupled to a housing as an integral or unitary device;   electrode traces in the flexible body operably connected the pair of electrodes and to sensor electronics comprising an analog-to-digital converter to receive an analog waveform from the pair of electrodes, or a frequency-filtered form thereof, and to generate therefrom a digital ECG waveform; and   a processing component operably connected to the sensor electronics within the housing and configured to receive the digital ECG waveform;   
       wherein the single lead ECG monitor is configured to be affixed to an individual on the chest at about the level of the heart such that one of the electrodes is positioned superior relative to the other on the individual such that the digital ECG waveform approximates a lead II configuration on the individual, 
       wherein the processing component is configured to process the digital ECG waveform and determine therefrom an orientation of the electrodes on the individual such that the single lead ECG monitor is agnostic to the polarity of the digital ECG waveform, and wherein the processing component is further configured to produce ECG data having standard lead II polarity based on the orientation of the electrodes determined by the processing component. 
     
     
         25 . A single lead ECG monitor of  claim 24 , wherein the orientation of the electrodes on the individual is determined by the processor:
 initially assigning an orientation of the electrodes such that a first electrode of the pair of electrodes is considered to be in a superior position to relative to a second electrode of the pair of electrodes for purposes of producing the ECG data,   determining from the digital ECG waveform a polarity metric, and   if the polarity metric indicates that the initial orientation assigned to the electrodes was incorrect, assigning a superior position to the second electrode of the pair of electrodes relative to the first electrode of the pair of electrodes for purposes of producing the ECG data.   
     
     
         26 . A single lead ECG monitor of  claim 25 , wherein the polarity metric is determined from one or more of (a) a slope of the leading edge of the QRS complex, (b) an amplitude of the largest positive wave, (c) an amplitude of the deepest negative wave, (d) a polarity of the R wave, (e) a polarity of the T-wave, and (f) a polarity of the P-wave. 
     
     
         27 . A single lead ECG monitor of one of  claim 25  or  26 , wherein the polarity metric is determined from data in the digital ECG waveform representing a plurality of consecutive cardiac cycles. 
     
     
         28 . A single lead ECG monitor of  claim 27 , wherein the polarity metric is determined from data in the digital ECG waveform representing at least 10 consecutive cardiac cycles, wherein at least 70% of the at least 10 consecutive cardiac cycles must agree on the orientation of the electrodes before the polarity metric is used to produce the ECG data. 
     
     
         29 . A single lead ECG monitor of one of  claims 24 - 28 , wherein the orientation of the electrodes is redetermined by the processing component when the processing component determines from the digital ECG waveform that at least one of the pair of electrodes has been repositioned on the individual. 
     
     
         30 . A single lead ECG monitor of one of  claims 24 - 28 , wherein the orientation of the electrodes is redetermined at a predetermined interval during continued use of the ECG data system. 
     
     
         31 . A single lead ECG monitor of one of  claims 26 - 30 , wherein the polarity metric comprises one or more of the following determinations:
 if the initial slope of the QRS leading edge is negative and the T-wave is negative, then the polarity metric indicates that the initial orientation assigned to the electrodes was incorrect,   if the initial slope of the QRS leading edge is negative and the P-wave is negative, then the polarity metric indicates that the initial orientation assigned to the electrodes was incorrect,   if the T-wave is negative and the P-wave is negative, then the polarity metric indicates that the initial orientation assigned to the electrodes was incorrect; or   if the amplitude of the largest negative wave is larger than the amplitude of the largest positive wave, then the polarity metric indicates that the initial orientation assigned to the electrodes was incorrect.   
     
     
         32 . A single lead ECG monitor according to one of  claims 24 - 31 , wherein following determination of the orientation of the electrodes by the processing component, the monitor continuously monitors the digital ECG waveform for changes in cardiac rhythm indicative of a transient arrhythmic event by
 (i) storing a segment of the digital ECG waveform in a circular data buffer, wherein the stored segment contains digital data for the current cardiac cycle and a plurality of consecutive previous cardiac cycles, and wherein the stored segment is of time length l 1  and is continuously updated for new cardiac cycles,   (ii) processing the digital ECG waveform using the processing component on a beat-by-beat basis to identify an occurrence of a first rhythm transition from a normal cardiac rhythm to an arrhythmia,   (iii) upon identifying the first rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the first rhythm transition by a predetermined time length l 2 , and ending the storage of data at a predetermined time length l 3  following the first rhythm transition;   (iv) following the first rhythm transition, processing the digital ECG waveform using the processing component on a beat-by-beat basis to identify an occurrence of a second rhythm transition from the arrhythmia to a normal cardiac rhythm;   (v) upon identifying the second rhythm transition, initiating storage of data from the data buffer into a storage memory beginning from a point in the data preceding the second rhythm transition by a predetermined time length l 4  and ending the storage of data at a predetermined time length l 5  following the second rhythm transition; and   (vi) repeating steps (ii)-(vi).   
     
     
         33 . A single lead ECG monitor according to one of  claims 24 - 32 , wherein the monitor is configured to attach to the individual by means of an adhesive on the flexible body. 
     
     
         34 . A method of monitoring a patient, comprising: 
       affixing a single lead ECG monitor according to one of  claims 24 - 33  to the patient; 
       receiving a digital ECG waveform at the processing component; 
       executing code on the processing component to determine an orientation of the electrodes on the individual; and 
       recording ECG data having standard lead II polarity based on the orientation of the electrodes determined by the processing component from the digital waveform in a storage memory of the ECG monitor for a period of time. 
     
     
         35 . A method according to  claim 34 , further comprising 
       operably connecting the ECG monitor to an external device comprising a microprocessor and a storage medium; and 
       downloading the recorded ECG data to the storage medium. 
     
     
         36 . A method according to  claim 35 , wherein the external device further comprises a non-volatile memory operably connected to the microprocessor, wherein the microprocessor is configured to execute code stored on the non-volatile memory, wherein executing the code causes the external device to display the data downloaded to the storage medium as graphical depictions of ECG data; and 
       executing the code on the microprocessor to display the ECG data. 
     
     
         37 . A method for collecting and processing ECG data from an individual, comprising: 
       providing, by an analysis entity, an ECG collection and recording device to a medical professional, wherein the ECG collection and recording device comprises a unique identifying code stored on a first computer-readable storage medium within the ECG collection and recording device, wherein the unique identifying code is write-protected to prevent unauthorized modification thereto, and wherein the ECG collection and recording device is provided in sealed packaging; 
       associating, by the medical professional, the ECG collection and recording device to the individual by storing the unique identifying code in a record corresponding to the individual in a database file system without removal of the ECG collection and recording device from the sealed packaging, wherein identifying information corresponding to the individual is not provided to the analysis entity; 
       providing, by the medical professional, the ECG collection and recording device to the individual in the sealed packaging together with return packaging for return of the ECG collection and recording device to the analysis entity following use of the ECG collection and recording device by the individual, wherein the return packaging provides no identifying information corresponding to the individual to the analysis entity; 
       recording, by the individual, of ECG data on a computer-readable ECG storage medium within the ECG collection and recording device by removal of the ECG collection and recording device from the sealed packaging and operably connecting the ECG collection and recording device to the individual's body for a period of time, wherein the computer-readable ECG storage medium may be the first computer-readable storage medium or a second computer-readable storage medium; 
       providing, by the individual, the ECG collection and recording device to the analysis entity by placing the ECG collection and recording device in the return packaging and transferring the return packaging to the analysis entity; 
       reading, by the analysis entity, the ECG data recorded on the computer-readable ECG storage medium, wherein the ECG data, or a processed form thereof, is stored by the analysis entity on data server in a record corresponding to the unique identifying code that is accessible for reading by the medical professional, wherein no identifying information corresponding to the individual is stored on the data server; and 
       electronically transmitting, by the analysis entity to the medical professional, an analysis report derived from the ECG data, wherein the analysis entity associates the analysis report with the unique identifying code such that the medical professional can associate the analysis report with the individual. 
     
     
         38 . The method of  claim 37 , wherein the ECG collection and recording device is a body-worn ECG monitor according to one of  claims 1 - 15  or a single lead ECG monitor according to one of  claim 17 - 19  or  24 - 33 . 
     
     
         39 . A body-worn ECG monitor according to one of  claims 1 - 15 , wherein the body-worn ECG monitor is a single lead ECG monitor according to one of  claim 17 - 19  or  24 - 33 . 
     
     
         40 . A method according to one of  claim 20  or  21 , wherein the body-worn ECG monitor is a single lead ECG monitor is a single lead ECG monitor according to one of  claim 17 - 19  or  24 - 33 . 
     
     
         41 . A method according to one of  claims 34 - 36 , wherein the single lead ECG monitor is a body-worn ECG monitor according to one of  claims 1 - 15 .