Method of and apparatus for detecting arrhythmia and fibrillation

Abstract

The presence of irregular heartbeat and/or possible atrial fibrillation is determined by analyzing a measured pulse rate pattern or heart rate pattern. The standard deviation and mean of time intervals each corresponding to a respective heartbeat are determined and compared to a threshold value. When quotient formed by dividing the standard deviation by the mean has a value greater than or equal to the threshold value, the shortest one of the time intervals and its succeeding time intervals are determined, and the succeeding time interval is compared to the mean. If the succeeding time interval is less than the mean, then the heartbeat is irregular. Alternatively, if the succeeding time interval is greater than the mean, the shortest time interval and its succeeding time interval are eliminated from the sample values, a new mean and standard deviation are determined, and the quotient of the new standard deviation divided by the new mean are compared to the threshold value. When the quotient is greater than the threshold value, the next shortest interval is determined, and the absolute value of the difference between the next shortest interval and the shortest interval is compared to an empirically determined value. If the difference is greater than the empirically determined value, the heartbeat is irregular. Alternatively, if the difference is greater than the empirically determined value, then the next shortest interval and its succeeding interval are redefined as the new shortest interval and is succeeding interval. The steps are repeated until it is determined that the heartbeat is regular or irregular.

What is claimed is:  
     
         1 . A method of verifying regular cardiac activity, said method comprising the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;    (b) determining a mean and a standard deviation of said plurality of time intervals; and    (c) determining, when a quotient formed by dividing said standard deviation by said mean is less than a threshold value, that the cardiac activity is regular.    
     
     
         2 . A method of detecting irregular cardiac activity, said method comprising the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;    (b) determining a mean and a standard deviation of said plurality of time intervals;    (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one; and    (d) determining, when said succeeding time interval has a value less than or equal to said mean, that said cardiac activity is irregular.    
     
     
         3 . A method of detecting irregular cardiac activity, said method comprising the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;    (b) determining a mean and a standard deviation of said plurality of time intervals;    (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;    (d) deleting, when said succeeding time interval has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals;    (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals;    (f) selecting, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is greater than or equal to said threshold value, an adjusted shortest one of said remaining ones of said plurality of time intervals; and    (g) determining, when an absolute value of the difference between said adjusted shortest one and said shortest one is greater than a value within a preselected range between 0.02-0.8 seconds, that said cardiac activity is irregular.    
     
     
         4 . A method of detecting irregular cardiac activity, said method comprising the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;    (b) determining a mean and a standard deviation of said plurality of time intervals;    (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;    (d) deleting, when said succeeding time interval has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals    (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals;    (f) selecting, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is greater than or equal to said threshold value, an adjusted shortest one of said remaining ones of said plurality of time intervals;    (g) redefining, when an absolute value of the difference between said adjusted shortest one and said shortest one is less than or equal to a value within a preselected range between 0.02-0.08 seconds, the value of said shortest one of said plurality to be that of said adjusted shortest one and the value of said succeeding one to be that of an interval immediately following said adjusted shortest one; and    (h) repeating steps (d) through (h) until either an absolute value of a difference between said adjusted shortest one and said shortest one is greater than said value within said preselected range, in which case said cardiac activity is irregular, or until said plurality of time intervals has less than two values, in which case said cardiac activity is regular.    
     
     
         5 . The method of  claim 1  wherein said sequence of heartbeats is derived from taking a sequence of pulse rates.  
     
     
         6 . The method of  claim 2  wherein said sequence of heartbeats is derived from taking a sequence of pulse rates.  
     
     
         7 . The method of  claim 3  wherein said sequence of heartbeats is derived from taking a sequence of pulse rates.  
     
     
         8 . The method of  claim 4  wherein said sequence of heartbeats is derived from taking a sequence of pulse rates.  
     
     
         9 . The method of  claim 1  further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.  
     
     
         10 . The method of  claim 2  further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.  
     
     
         11 . The method of  claim 3  further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.  
     
     
         12 . The method of  claim 4  further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.  
     
     
         13 . The method of  claim 1  wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.  
     
     
         14 . The method of  claim 2  wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.  
     
     
         15 . The method of  claim 3  wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.  
     
     
         16 . The method of  claim 4  wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.  
     
     
         17 . An apparatus for detecting irregular cardiac activity, said apparatus comprising: 
 a detector for detecting an activity related to heartbeats at measured times;    a processor for determining whether said measured heart activity is regular or irregular as a function of at least one of a standard deviation and mean of a plurality of time intervals of said heart activity, and a shortest one of said plurality of time intervals, a time interval immediately succeeding said shortest one, and next shortest time interval; and    a device for outputting an indication whether the activity is regular or irregular.    
     
     
         18 . The apparatus of  claim 17  wherein said device is an inflatable-cuff device and said activity is a pulse beat.  
     
     
         19 . The apparatus of  claim 17  wherein said device detect changes in light transmitted through an appendage of an individual and the activity is a pulse rate.  
     
     
         20 . The apparatus of  claim 17  wherein said detector is an electrode device and the measured activity is an actual heart rate.  
     
     
         21 . The apparatus of  claim 17  wherein said output device is a printer.  
     
     
         22 . The apparatus of  claim 17  wherein output device is a display.  
     
     
         23 . The apparatus of  claim 17  wherein output device is an auditory signal generator.  
     
     
         24 . The apparatus of  claim 17  wherein output device is a vibration signal generator.  
     
     
         25 . The apparatus of  claim 17  further comprising a memory device.  
     
     
         26 . The apparatus of  claim 17  wherein said processor comprises at least one of a microprocessor, and application specific integrated circuit (ASIC), a programmable logic array (PLA) and a reduced instruction set chip (RISC).  
     
     
         27 . The apparatus of  claim 17  wherein said processor verifies normal cardiac activity by carrying out the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;  
 (b) determining a mean and a standard deviation of said plurality of time intervals; and  
 (c) determining, when a quotient formed by dividing said standard deviation by said mean is less than a threshold value, that the cardiac activity is regular.  
 
     
     
         28 . The apparatus of  claim 17  wherein said processor determines irregular cardiac activity by carrying out the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;  
 (b) determining a mean and a standard deviation of said plurality of time intervals;  
 (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one; and  
 (d) determining, when said succeeding time interval has a value less than or equal to said mean, that said cardiac activity is irregular.  
 
     
     
         29 . The apparatus of  claim 17  wherein said processor detects irregular cardiac activity by carrying out the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;  
 (b) determining a mean and a standard deviation of said plurality of time intervals;  
 (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;  
 (d) deleting, when said succeeding time interval has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals;  
 (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals;  
 (f) selecting, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is greater than or equal to said threshold value, an adjusted shortest one of said remaining ones of said plurality of time intervals; and  
 (g) determining, when an absolute value of the difference between said adjusted shortest one and said shortest one is greater than a value within a preselected range between 0.02-0.008, seconds that said cardiac activity is irregular.  
 
     
     
         30 . The apparatus of  claim 17  wherein said processor determines irregular cardiac activity by carrying out the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period between successive ones of a sequence of heartbeats;  
 (b) determining a mean and a standard deviation of said plurality of time intervals;  
 (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;  
 (d) deleting, when said succeeding time interval has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals  
 (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals;  
 (f) selecting, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is greater than or equal to said threshold value, an adjusted shortest one of said remaining ones of said plurality of time intervals;  
 (g) redefining, when an absolute value of the difference between said adjusted shortest one and said shortest one is less than or equal a value within a preselected range between 0.02-0.08 seconds, the value of said shortest one of said plurality to be that of said adjusted shortest one and the value of said succeeding one to be that of an interval immediately following said adjusted shortest one; and  
 (h) repeating steps (d) through (h) until either an absolute value of a difference between said adjusted shortest one and said shortest one is greater than said value within said preselected range, in which case said cardiac activity is irregular, or until said plurality of time intervals has less than two values, in which case said cardiac activity is regular.  
 
     
     
         31 . The method of claim I wherein said threshold value is within the range of 5% to 10%.  
     
     
         32 . The method of  claim 2  wherein said threshold value is within the range of 5% to 10%.  
     
     
         33 . The method of  claim 3  wherein said threshold value is within the range of 5% to 10%.  
     
     
         34 . The method of  claim 4  wherein said threshold value is within the range of 5% to 10%.  
     
     
         35 . The apparatus of  claim 27  wherein said threshold value is within the range of 5% to 10%.  
     
     
         36 . The apparatus of  claim 28  wherein said threshold value is within the range of 5% to 10%.  
     
     
         37 . The apparatus of  claim 29  wherein said threshold value is within the range of 5% to 10%.  
     
     
         38 . The apparatus of  claim 30  wherein said threshold value is within the range of 5% to 10%.  
     
     
         39 . A method verifying regular cardiac activity, said method comprising the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period successive ones of a sequence of heartbeats;    (b) determining a mean and a standard deviation of said plurality of time intervals;    (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;    (d) deleting, when said succeeding time has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals;    (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals; and    (f) determining, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is less than said threshold value, that said cardiac activity is regular.    
     
     
         40 . The method of  claim 39  wherein said sequence of heartbeats is derived from taking a sequence of pulse rates.  
     
     
         41 . The method of  claim 39  further comprising the step of storing at least one of said plurality of time intervals, said mean, said standard deviation, said quotient and said threshold value.  
     
     
         42 . The method of  claim 39  wherein said sequence of heartbeats is determined by measuring a sequence of heartbeats.  
     
     
         43 . The method of  claim 39  wherein said threshold value is within the range 5% to 10%.  
     
     
         44 . The apparatus of  claim 17  wherein said processor verifies regular cardiac activity by carrying out the steps of: 
 (a) determining a plurality of time intervals each corresponding to a respective time period successive ones of a sequence of heartbeats;  
 (b) determining a mean and a standard deviation of said plurality of time intervals;  
 (c) selecting, when a quotient formed by dividing said standard deviation by said mean has a value greater than or equal to a threshold value, a shortest one of said plurality of time intervals and a succeeding time interval that immediately follows said shortest one;  
 (d) deleting, when said succeeding time has a value greater than said mean, said shortest one of said plurality of time intervals and said succeeding time interval from said plurality of time intervals;  
 (e) determining an adjusted mean and an adjusted standard deviation based on remaining ones of said plurality of time intervals; and  
 (f) determining, when an adjusted quotient formed by dividing said adjusted standard deviation by said adjusted mean is less than said threshold value, that said cardiac activity is regular.