Method and apparatus for detection of tachyarrhythmia using cycle lengths
A method and apparatus for detecting atrial arrhythmias and discriminating atrial fibrillation (AF) and organized atrial tachycardia (OAT) that includes defining a threshold detection criteria for a cluster signature evidence metric corresponding to a Lorenz distribution of ventricular cycle lengths representative of AF or OAT. Using a signal containing VCL information, a number of consecutive ventricular cycle lengths are determined during a selected time interval for generating a one-dimensional or a two-dimensional histogram as a numerical representation of a Lorenz plot of VCLs. A number of cluster signature metrics are computed using the stored ventricular cycle length information, and a cluster signature evidence metric is computed from the cluster signature metrics. AF or OAT is detected if a comparative analysis of a corresponding cluster signature evidence metric meets a respective threshold detection criteria.
1. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
determining cluster signature metrics in response to the determined differences;
identifying the cardiac event in response to the determined cluster signature metrics;
generating a plot corresponding to the determined differences;
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event; and
determining a number of the determined differences that are located in a first segment of the plurality of segments relative to a number of the determined differences that are located in a second segment of the plurality of segments to generate a first output.
2. The method of claim 1 , further comprising:
determining a number of the determined differences that are located in a third segment of the plurality of segments relative to a number of the determined differences that are located in a fourth segment of the plurality of segments to generate a second output; and
determining a sum of the first output and the second output.
3. The method of claim 1 , wherein the cardiac event corresponds to organized atrial tachyarrhythmia.
4. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
determining cluster signature metrics in response to the determined differences;
identifying the cardiac event in response to the determined cluster signature metrics;
generating a plot corresponding to the determined differences;
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event;
determining a number of the determined differences that are located within each of the plurality of segments;
determining a number of segments of the plurality of segments that have a determined difference located therein;
determining, for each segment of the plurality of segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate density counts; and
determining a sum of the density counts.
5. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
determining cluster signature metrics in response to the determined differences;
identifying the cardiac event in response to the determined cluster signature metrics;
generating a plot corresponding to the determined differences;
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event;
determining a number of the determined differences that are located within each segment of first predetermined segments of the plurality of segments;
determining a number segments of the plurality of segments that have a determined difference located therein;
determining, for each segment of the first predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate first density counts;
summing the first density counts to generate a first density sum;
determining a number of the determined differences that are located within each segment of second predetermined segments of the plurality of segments;
determining, for each segment of the second predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate second density counts;
summing the second density counts to generate a second density sum; and
determining a difference between the first density sum and the second density sum.
6. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
determining cluster signature metrics in response to the determined differences;
identifying the cardiac event in response to the determined cluster signature metrics;
generating a plot corresponding to the determined differences; and
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event, wherein a first segment of the plurality of segments corresponds to a predetermined area about the origin of the plot and further comprising determining a total number of the determined differences that are located within the plurality of segments other than the first segment to generate a first cluster signature metric M 1 .
7. The method of claim 6 , further comprising:
determining a number of the determined differences that are located within the first segment to generate a second cluster signature metric M 2 ;
determining a number of the determined differences that are located within each segment of first predetermined segments of the plurality of segments;
determining a number segments of the plurality of segments that have a determined difference located therein;
determining, for each segment of the first predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate first density counts;
summing the first density counts to generate a first density sum;
determining a number of the determined differences that are located within each segment of second predetermined segments of the plurality of segments;
determining, for each segment of the second predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate second density counts;
summing the second density counts to generate a second density sum;
determining a difference between the first density sum and the second density sum to generate a third cluster signature metric M 3 ; and
identifying the cardiac event as a first event in response to a first equation, wherein the first equation corresponds to M 1 −M 2 −J*M 3 , wherein J is a weighting factor associated with a second event different from the first event.
8. The method of claim 6 , further comprising:
calculating a plurality of medians of determined differences corresponding to a plurality of respective sample windows occurring over a predetermined time period;
comparing the calculated plurality of medians to a predetermined baseline median associated with the cardiac event to generate a second cluster signature metric M 2 ;
determining a number of the determined differences that are located within each of the plurality of segments;
determining a number of segments of the plurality of segments that have a determined difference located therein;
determining, for each segment of the plurality of segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate density counts;
determining a sum of the density counts to generate a third cluster signature metric M 3 ;
determining a number of the determined differences that are located in a first segment of the plurality of segments relative to a number of the determined differences that are located in a second segment of the plurality of segments to generate a first output;
determining a number of the determined differences that are located in a third segment of the plurality of segments relative to a number of the determined differences that are located in a fourth segment of the plurality of segments to generate a second output;
determining a sum of the first output and the second output to generate a fourth cluster signature metric M 4 ;
determining a number of the determined differences that are located within each segment of first predetermined segments of the plurality of segments;
determining a number segments of the plurality of segments that have a determined difference located therein;
determining, for each segment of the first predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate first density counts;
summing the first density counts to generate a first density sum;
determining a number of the determined differences that are located within each segment of second predetermined segments of the plurality of segments;
determining, for each segment of the second predetermined segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate second density counts;
summing the second density counts to generate a second density sum; and
determining a difference between the first density sum and the second density sum to generate a fifth cluster signature metric M 5 .
9. The method of claim 8 , further comprising identifying the cardiac event as a first event in response to a first equation, wherein the first equation corresponds to M 1 +M 2 +M 3 +M 4 −J*M 5 wherein J is a weighting factor associated with a second event different from the first event.
10. The method of claim 9 , further comprising:
determining a number of the determined differences that are located within the first segment to generate a sixth cluster signature metric M 6 ;
identifying the cardiac event as a third event in response to a second equation, wherein the second equation corresponds to M 1 −M 6 −J*M 5 ; and
generating an organization index in response to the first equation and the second equation.
11. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
determining cluster signature metrics in response to the determined differences; and
identifying the cardiac event in response to the determined cluster signature metrics, wherein determining cluster signature metrics comprises;
determining the number of a plurality of the determined differences that are within a predetermined range that corresponds to the cardiac event; and
determining the proportion of the determined number of the plurality of the determined differences and a median of the plurality of the determined differences, and wherein determining the determined number of the plurality of the determined differences comprises:
calculating a plurality of medians of determined differences corresponding to a plurality of respective sample windows occurring over a predetermined time period; and
comparing the calculated plurality of medians to a predetermined baseline median associated with the cardiac event.
12. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
generating a representation of a plot corresponding to a temporal relationship between the determined differences;
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event; and
identifying the cardiac event in response to the number of the determined differences that are located within the plurality of segments;
determining a number of the determined differences that are located within each of the plurality of segments;
determining a number segments of the plurality of segments that have a determined difference located therein;
determining a number of the determined differences that are located within a first segment of the plurality of segments corresponding to a predetermined area about the origin of the plot; and
determining, for predetermined segments of the plurality of segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate density counts.
13. A method of determining a cardiac event, comprising:
determining a plurality of cycle lengths associated with sensed cardiac signals;
determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
generating a representation of a plot corresponding to a temporal relationship between the determined differences;
determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event;
identifying the cardiac event in response to the number of the determined differences that are located within the plurality of segments;
determining a number of the determined differences that are located within each of the plurality of segments;
determining a number segments of the plurality of segments that have a determined difference located therein;
determining a number of the determined differences that are located within a first segment of the plurality of segments corresponding to a predetermined area about the origin of the plot;
determining, for predetermined segments of the plurality of segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate density counts;
calculating a plurality of medians of determined differences corresponding to a plurality of respective sample windows occurring over a predetermined time period; and
comparing the calculated plurality of medians to a predetermined baseline median associated with the cardiac event.
14. A medical device for determining a cardiac event, comprising:
means for determining a plurality of cycle lengths associated with sensed cardiac signals;
means for determining differences between consecutive cycle lengths of the determined plurality of cycle lengths;
means for generating a representation of a plot corresponding to a temporal relationship between the determined differences;
means for determining a number of the determined differences that are located within a plurality of segments of the plot defined by a range of magnitudes and phases relative to an origin of the plot and corresponding to patterns associated with the cardiac event;
means for identifying the cardiac event in response to the number of the determined differences that are located within the plurality of segments;
means for determining a number of the determined differences that are located within each of the plurality of segments;
means for determining a number segments of the plurality of segments that have a determined difference located therein;
means for determining a number of the determined differences that are located within a first segment of the plurality of segments corresponding to a predetermined area about the origin of the plot; and
means for determining, for predetermined segments of the plurality of segments, a difference between the determined number of determined differences located therein and the determined number of segments having a determined difference located therein to generate density counts.