Distinguishing premature contractions in a medical device

Abstract

A method and device of distinguishing premature contractions that includes a sensor sensing cardiac signals, and a processor configured to determine a plurality of intervals in response to the sensed cardiac signal, detect a premature contraction being associated with a first R-wave of the plurality of R-waves, determine whether a metric of the first R-wave is greater than a premature contraction threshold, and identify the detected premature contraction as one of a premature atrial contraction or a premature ventricular contraction in response to determining whether a metric of the first R-wave is greater than a premature contraction threshold.

1 . A method of distinguishing cardiac signals in a medical device, comprising:
 sensing cardiac signals;   determining a plurality of R-waves in response to the sensed cardiac signal;   detecting a premature contraction being associated with a first R-wave of the plurality of R-waves;   determining whether a metric of the first R-wave is greater than a premature contraction threshold; and   identifying the detected premature contraction as one of a premature atrial contraction or a premature ventricular contraction in response to determining whether a metric of the first R-wave is greater than a premature contraction threshold.   
     
     
         2 . The method of  claim 1 , further comprising at least one of generating an alert and storing the identifying of the detected premature contraction. 
     
     
         3 . The method of  claim 1 , further comprising:
 computing a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave;   comparing one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold;   detecting a premature ventricular contraction in response to the comparison meeting the detection threshold requirement;   determining intervals between consecutive R-waves;   detecting a premature coupling interval; and   computing the R-wave morphology metric and the preceding R-wave morphology metric in response to detecting the premature coupling interval.   
     
     
         4 . The method of  claim 1 , further comprising:
 computing a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave;   comparing one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold; and   detecting a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, wherein computing the morphology metric comprises:   identifying a fiducial point along the R-wave;   establishing a first time interval ending at the fiducial point;   establishing a second time interval beginning at the fiducial point; and   computing a first area over the first time interval and a second area over the second time interval.   
     
     
         5 . The method of  claim 1 , wherein determining whether a metric of the R-wave is greater than a premature contraction threshold comprises:
 determining a maximum amplitude of the first R-wave; and   comparing the maximum amplitude to an amplitude threshold, wherein the detected premature contraction is identified as a premature atrial contraction in response to the maximum amplitude not being greater than the amplitude threshold and as a premature ventricular contraction in response to the maximum amplitude being greater than the amplitude threshold.   
     
     
         6 . The method of  claim 5 , further comprising determining a maximum amplitude for a second R-wave of the plurality of R-waves, wherein the amplitude threshold corresponds to a percentage change of the determined maximum amplitude of the first R-wave from the maximum ampliutude of the second R-wave. 
     
     
         7 . The method of  claim 4 , wherein the percentage change is approximately 20 percent. 
     
     
         8 . The method of  claim 5 , further comprising:
 computing a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave;   comparing one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold;   detecting a premature ventricular contraction in response to the comparison meeting the detection threshold requirement;   determining intervals between consecutive R-waves;   detecting a premature coupling interval; and   computing the R-wave morphology metric and the preceding R-wave morphology metric in response to detecting the premature coupling interval.   
     
     
         9 . The method of  claim 5 , further comprising:
 computing a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave;   comparing one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold; and   detecting a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, wherein computing the morphology metric comprises:   identifying a fiducial point along the R-wave;   establishing a first time interval ending at the fiducial point;   establishing a second time interval beginning at the fiducial point; and   computing a first area over the first time interval and a second area over the second time interval.   
     
     
         10 . The method of  claim 1 , further comprising computing a measurement of the sensed ventricular R-waves in response to detecting the premature ventricular contraction, wherein computing a measurement of the sensed ventricular R-waves comprises computing a heart rate turbulence measurement. 
     
     
         11 . A medical device for distinguishing cardiac signals, comprising:
 a sensor sensing cardiac signals; and   a processor configured to determine a plurality of R-waves in response to the sensed cardiac signal, detect a premature contraction being associated with a first R-wave of the plurality of R-waves, determine whether a metric of the first R-wave is greater than a premature contraction threshold, and identify the detected premature contraction as one of a premature atrial contraction or a premature ventricular contraction in response to determining whether a metric of the first R-wave is greater than a premature contraction threshold.   
     
     
         12 . The device of  claim 11 , further comprising:
 an alert module generating an alert in response to the identifying of the detected premature contraction; and   a storage device storing the identifying of the detected premature contraction.   
     
     
         13 . The device of  claim 11 , wherein the processor is further configured to compute a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave, compare one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold, detect a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, determine intervals between consecutive R-waves, detect a premature coupling interval, and compute the R-wave morphology metric and the preceding R-wave morphology metric in response to detecting the premature coupling interval. 
     
     
         14 . The device of  claim 11 , wherein the processor is further configured to compute a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave, compare one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold, and detect a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, wherein computing the morphology metric comprises:
 identifying a fiducial point along the R-wave;   establishing a first time interval ending at the fiducial point;   establishing a second time interval beginning at the fiducial point; and   computing a first area over the first time interval and a second area over the second time interval.   
     
     
         15 . The device of  claim 11 , wherein the processor is further configured to determine a maximum amplitude of the first R-wave, and compare the maximum amplitude to an amplitude threshold, wherein the detected premature contraction is identified as a premature atrial contraction in response to the maximum amplitude not being greater than the amplitude threshold and as a premature ventricular contraction in response to the maximum amplitude being greater than the amplitude threshold. 
     
     
         16 . The device of  claim 15 , wherein the processor is further configured to determine a maximum amplitude for a second R-wave of the plurality of R-waves, wherein the amplitude threshold corresponds to a percentage change of the determined maximum amplitude of the first R-wave from the maximum ampliutude of the second R-wave. 
     
     
         17 . The device of  claim 16 , wherein the percentage change is approximately 20 percent. 
     
     
         18 . The device of  claim 15 , wherein the processor is further configured to compute a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave, compare one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold, detect a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, determine intervals between consecutive R-waves, detect a premature coupling interval, and compute the R-wave morphology metric and the preceding R-wave morphology metric in response to detecting the premature coupling interval. 
     
     
         19 . The device of  claim 15 , wherein the processor is further configured to compute a morphology metric of an R-wave and a corresponding preceding morphology metric of an immediately preceding R-wave, compare one of a difference and a ratio of the R-wave morphology metric and the preceding R-wave morphology metric to the detection threshold, and detect a premature ventricular contraction in response to the comparison meeting the detection threshold requirement, wherein computing the morphology metric comprises:
 identifying a fiducial point along the R-wave;   establishing a first time interval ending at the fiducial point;   establishing a second time interval beginning at the fiducial point; and   computing a first area over the first time interval and a second area over the second time interval.   
     
     
         20 . The device of  claim 11 , wherein the processor is further configured to compute a measurement of the sensed ventricular R-waves in response to detecting the premature ventricular contraction, wherein computing a measurement of the sensed ventricular R-waves comprises computing a heart rate turbulence measurement. 
     
     
         21 . A non-transitory computer readable medium storing instructions which cause a medical device to perform a method, the method comprising:
 sensing cardiac signals;   determining a plurality of R-waves in response to the sensed cardiac signal;   detecting a premature contraction being associated with a first R-wave of the plurality of R-waves;   determining whether a metric of the first R-wave is greater than a premature contraction threshold; and   identifying the detected premature contraction as one of a premature atrial contraction or a premature ventricular contraction in response to determining whether a metric of the first R-wave is greater than a premature contraction threshold.