Method and system for detection of cardiac arrhythmia

• US 20050165320A1
• Filed: 09/20/2001
• Published: 07/28/2005
• Est. Priority Date: 09/20/2000
• Status: Active Grant

• Current Assignee: McGill University, Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Katsumi Tateno, Leon Glass
• Inventors: Tateno, Katsumi, Glass, Leon
• Granted Patent: US 7,120,485 B2
• Time in Patent Office: Days
• US Class Current: 600/515
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/361 Detecting fibrillation
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting

Abstract

There are many different serious cardiac arrhythmias. The present invention uses measurements of RR intervals (interbeat intervals) to detect, in particular but not exclusively, atrial fibrillation of a patient. Atrial fibrilation is a serious ailment in which the heartbeat is generally rapid and irregular. Probability density histograms of ΔRRs (difference between two successive RR intervals) collected during atrial fibrillation of a plurality of subjects are used as a template for the detection of atrial fibrillation. In one implementation, there are 16 standard probability density ΔRRs histograms every 50 ms of mean RR interval of a certain number of beats, where the mean RR interval ranges from 350 ms to 1149 ms. Similarity between the standard probability density histograms and a test density probability histogram of ΔRRs of a patient is estimated by the Kolmogorov-Smirnov test. If the test density histogram is not significantly different from the standard density histogram, atrial fibrillation is detected.

Claims

1. A method for detecting cardiac arrhythmia of a patient, comprising:

detecting RR intervals of the patient, wherein each RR interval is an interval between two heart beats;

constructing standard histograms of Δ

RRs collected during cardiac arrhythmia of a plurality of subjects, wherein each Δ

RR is a difference between two successive RR intervals;

constructing test histograms of Δ

RRs of the patient from the detected RR intervals of said patient; and

comparing said standard and test histograms to detect whether said patient suffers from cardiac arrhythmia.

2. A method for detecting cardiac arrhythmia as defined in claim 1, wherein the standard and test histograms are probability density histograms.

3. A method for detecting cardiac arrhythmia as defined in claim 1, further comprising calculating a mean value of a given number of successive RR intervals of the patient, and choosing one of the standard probability density histograms in relation to said mean value.

4. A method for detecting cardiac arrhythmia as defined in claim 3, wherein choosing one of the standard probability density histograms comprises selecting the standard histogram corresponding to the range of RR intervals in which said mean value is located.

5. A method for detecting cardiac arrhythmia as defined in claim 1, wherein said comparing of the standard and test histograms comprises adjusting a specificity-altering and sensitivity-altering parameter.

6. A method for detecting cardiac arrhythmia as defined in claim 1, wherein said comparing of the standard and test histograms comprises calculating a standard cumulative probability distribution from said standard Δ

RR probability density histograms, calculating a test cumulative probability distribution from said test Δ

RR probability density histograms, and computing a deviation between said standard and test distributions.

7. A method for detecting cardiac arrhythmia as defined in claim 5, wherein said comparing of the standard and test histograms comprises:

calculating a standard cumulative probability distribution from said standard Δ

RR probability density histograms;

calculating a test cumulative probability distribution from said test Δ

RR probability density histograms;

computing a deviation between said standard and test distributions; and

detecting cardiac arrhythmia when the computed deviation is higher than said specificity-altering and sensitivity-altering parameter.

8. A system for detecting cardiac arrhythmia of a patient, comprising:

a RR interval detecting monitor detecting RR intervals of the patient, wherein each RR interval is an interval between two heart beats;

a standard Δ

RR histogram storage unit in which are stored standard histograms of Δ

RRs collected during cardiac arrhythmia of a plurality of subjects, wherein each Δ

RR is a difference between two successive RR intervals;

a test Δ

RR histogram calculator supplied with the detected RR intervals from the monitor and constructing test histograms of said Δ

RRs of said patient; and

a standard and test Δ

RR histograms comparator supplied with said standard and test histograms, said comparator comprising a detector of cardiac arrhythmia of the patient responsive to the comparison of said standard and test histograms.

9. A system for detecting cardiac arrhythmia as defined in claim 8, wherein the standard and test histograms are probability density histograms.

10. A system for detecting cardiac arrhythmia as defined in claim 8, further comprising a calculator of a mean value of a given number of successive RR intervals of the patient, and a selector of one of the standard probability density histograms in relation to said mean value.

11. A system for detecting cardiac arrhythmia as defined in claim 10, wherein the selector of one of the standard probability density histograms comprises means for selecting the standard histogram corresponding to the range of RR intervals in which said mean value is located.

12. A system for detecting cardiac arrhythmia as defined in claim 8, wherein said standard and test Δ

RR histograms comparator comprises an adjustable, specificity-altering and sensitivity-altering parameter.

13. A system for detecting cardiac arrhythmia as defined in claim 8, wherein said standard and test Δ

RR histograms comparator comprises a calculator of a standard cumulative probability distribution from said standard Δ

RR probability density histograms, a calculator of a test cumulative probability distribution from said test Δ

RR probability density histograms, and a calculator of a deviation between said standard and test distributions.

14. A method for detecting cardiac arrhythmia as defined in claim 12, wherein the standard and test Δ

RR histograms comparator comprises;

a calculator of a standard cumulative probability distribution from said standard Δ

RR probability density histograms;

a calculator of a test cumulative probability distribution from said test Δ

RR probability density histograms;

a calculator of a deviation between said standard and test distributions; and

a detector of a cardiac arrhythmia when the computed deviation is higher than said specificity-altering and sensitivity-altering parameter.