Methods and devices for accurately classifying cardiac activity
Methods, systems, and devices for signal analysis in an implanted cardiac monitoring and treatment device such as an implantable cardioverter defibrillator. In some examples, captured data including detected events is analyzed to identify likely overdetection of cardiac events. In some illustrative examples, when overdetection is identified, data may be modified to correct for overdetection, to reduce the impact of overdetection, or to ignore overdetected data. Several examples emphasize the use of morphology analysis using correlation to static templates and/or inter-event correlation analysis.
1. A method of operation in an implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the canister having a canister electrode disposed thereon, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry; the method comprising:
detecting electrical events occurring within the patient;
constructing event representations for the detected electrical events;
for a set of events N, N-1, N-2 and N-3, comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis;
determining, using the results of the correlation analysis, whether the set of events indicates one of the following:
overdetection,
benign cardiac rhythm, or
likely cardiac arrhythmia; and
if likely cardiac arrhythmia is identified, determining whether stimulus is needed; and
if stimulus is needed, delivering electrical stimulus to the patient from the ICS system;
wherein overdetection is identified if the correlation analysis indicates a pattern of correlations between the events N, N-1, N-2 and N-3 that corresponds to overdetection.
2. The method of claim 1 wherein the method includes determining that overdetection is occurring if the step of comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis results in a pattern of correlations of the following type: low correlation to N-1 and N-3 events, and high correlation to the N-2 event.
3. The method of claim 1 further comprising:
calculating a cardiac rate using the detected electrical events; and
if the set of events, N, N-1, N-2, N-3 indicates overdetection, correcting data relating to one or more overdetected events and recalculating the calculated cardiac rate.
4. The method of claim 1 wherein the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates highly to at least one of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring.
5. The method of claim 4 wherein the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates closely to each of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring, further wherein “correlates highly” indicates a relatively higher correlation than “correlates closely.”
6. An implantable cardiac stimulus (ICS) system comprising a canister housing operational circuitry for the ICS system, the ICS including a plurality of electrodes including at least a canister electrode disposed on the canister, and a lead having at least a first lead electrode disposed thereon, the canister electrode and the first lead electrode electrically coupled to the operational circuitry; wherein the operational circuitry is configured to perform a method of cardiac signal analysis comprising:
detecting electrical events occurring within the patient using the electrodes of the ICS system;
constructing event representations for the detected electrical events;
for a set of events N, N-1, N-2 and N-3, comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis;
determining, using the results of the correlation analysis, whether the set of events indicates one of the following:
overdetection,
benign cardiac rhythm, or
likely cardiac arrhythmia; and
if likely cardiac arrhythmia is identified, determining whether stimulus is needed; and
if stimulus is needed, delivering electrical stimulus to the patient from using the electrodes of the ICS system;
wherein overdetection is identified if the correlation analysis indicates a pattern of correlations between the events N, N-1, N-2 and N-3 that corresponds to overdetection.
7. The ICS of claim 6 wherein the operational circuitry is further configured such that the method includes determining that overdetection is occurring if the step of comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis results in a pattern of correlations of the following type: low correlation to N-1 and N-3 events, and high correlation to the N-2 event.
8. The ICS of claim 6 wherein the operational circuitry is further configured such that the method further comprises:
calculating a cardiac rate using the detected electrical events; and
if the set of events, N, N-1, N-2, N-3 indicates overdetection, correcting data relating to one or more overdetected events and recalculating the calculated cardiac rate.
9. The ICS of claim 6 wherein the operational circuitry is further configured such that the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates highly to at least one of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring.
10. The ICS of claim 9 wherein the operational circuitry is further configured such that the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates closely to each of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring, further wherein “correlates highly” indicates a relatively higher correlation than “correlates closely.”
11. An implantable cardiac stimulus device (ICSD) comprising a canister housing operational circuitry and having at least one canister electrode disposed thereon and being configured to couple electrically to a lead having at least one lead electrode thereon such that, when so coupled, the operational circuitry is electrically connected to the canister electrode and at least one lead electrode to form an implantable cardiac stimulus system (ICS) having a plurality of electrodes, wherein the operational circuitry is configured to perform a method of cardiac signal analysis comprising:
detecting electrical events occurring within the patient using the electrodes of the ICS system;
constructing event representations for the detected electrical events;
for a set of events N, N-1, N-2 and N-3, comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis;
determining, using the results of the correlation analysis, whether the set of events indicates one of the following:
overdetection,
benign cardiac rhythm, or
likely cardiac arrhythmia; and
if likely cardiac arrhythmia is identified, determining whether stimulus is needed; and
if stimulus is needed, delivering electrical stimulus to the patient from using the electrodes of the ICS system;
wherein overdetection is identified if the correlation analysis indicates a pattern of correlations between the events N, N-1, N-2 and N-3 that corresponds to overdetection.
12. The ICSD of claim 11 wherein the operational circuitry is further configured such that the method includes determining that overdetection is occurring if the step of comparing the Nth event to each of the N-1, N-2 and N-3 events by correlation analysis results in a pattern of correlations of the following type: low correlation to N-1 and N-3 events, and high correlation to the N-2 event.
13. The ICSD of claim 11 wherein the operational circuitry is further configured such that the method further comprises:
calculating a cardiac rate using the detected electrical events; and
if the set of events, N, N-1, N-2, N-3 indicates overdetection, correcting data relating to one or more overdetected events and recalculating the calculated cardiac rate.
14. The ICSD of claim 11 wherein the operational circuitry is further configured such that the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates highly to at least one of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring.
15. The ICS of claim 14 wherein the operational circuitry is further configured such that the step of determining whether the set of events indicates one of the following: overdetection, benign cardiac rhythm, or likely cardiac arrhythmia includes determining whether the Nth event correlates closely to each of the N-1, N-2 or N-3 events and, if so, determining that a benign cardiac rhythm is occurring, further wherein “correlates highly” indicates a relatively higher correlation than “correlates closely.”