Method and apparatus for selection and use of virtual sensing vectors

Patent metadata

Field	Value
Publication number	US-9566012-B2
Application number	US-201414524090-A
Country	US
Kind code	B2
Filing date	Oct 27, 2014
Priority date	Oct 27, 2014
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

A medical device is configured to receive at least two physical cardiac electrical signals from a patient's heart via electrodes defining at least two physical sensing vectors. The medical device determines a signal feature for each of a plurality of virtual sensing vectors extending at a plurality of angles relative to one of the at least two physical sensing vectors during a known cardiac rhythm, compares the determined signal features and establishes criteria for confirming a suspected condition in response to the comparing.

First claim

The invention claimed is:

1. A method performed by a medical device, comprising:
receiving at least two physical cardiac electrical signals from a patient's heart via a plurality of electrodes that define at least two physical sensing vectors;
computing a plurality of virtual cardiac electrical signals using the at least two physical cardiac electrical signals during a first, known cardiac rhythm, each of the plurality of virtual cardiac electrical signals corresponding to one of a plurality of virtual sensing vectors extending at a respective one of a plurality of angles relative to one of the at least two physical sensing vectors, wherein computing the plurality of virtual cardiac electrical signals comprises calculating a projection of the at least two physical cardiac electrical signals along each of the plurality of virtual sensing vectors;
determining, for each of the plurality of virtual cardiac electrical signals, a plurality virtual cardiac electrical signal features;
comparing the determined signal features;
establishing criteria for confirming a suspected condition in response to the comparing;
detecting a suspected condition during a second, unknown cardiac rhythm; and
confirming the suspected condition in response to the established criteria being met during the second, unknown cardiac rhythm.

2. The method of claim 1 , wherein:
establishing the criteria for confirming the suspected condition comprises determining one of the at least two physical sensing vectors and the plurality of virtual sensing vectors as a cardiac electrical axis based on the comparing during the first, known cardiac rhythm;
confirming the suspected condition comprises determining a different one of the at least two physical sensing vectors and the plurality of virtual sensing vectors as the cardiac electrical axis during the second, unknown cardiac rhythm.

3. The method of claim 2 , wherein determining one of the at least two physical sensing vectors and the plurality of virtual sensing vectors as the cardiac electrical axis comprises:
identifying an isoelectric cardiac electrical signal feature from among the at least two physical sensing vectors and the plurality of virtual sensing vectors;
identifying a vector of the isoelectric cardiac electrical signal feature; and
selecting a vector orthogonal to the identified vector of the isoelectric cardiac electrical signal feature as the cardiac electrical axis.

4. The method of claim 2 , wherein determining one of the at least two physical sensing vectors and the plurality of virtual sensing vectors as the cardiac electrical axis comprises:
determining a maximum peak R-wave amplitude for each of the at least two physical sensing vectors and the plurality of virtual sensing vectors;
comparing the determined maximum peak R-wave amplitudes to identify a greatest maximum peak R-wave amplitude; and
identifying the cardiac electrical axis as one of the at least two physical sensing vectors and the plurality of virtual sensing vectors having the greatest maximum peak R-wave amplitude.

5. The method of claim 1 ,
wherein establishing the criteria for confirming the suspected condition comprises determining a first order of at least the plurality of virtual sensing vectors based on the comparing of the signal features determined during the first, known cardiac rhythm; the method further comprising determining a second order of at least the plurality of virtual sensing vectors based on determining and comparing the signal features for the plurality of virtual cardiac electrical signals during the second, unknown cardiac rhythm; and
wherein confirming the suspected condition comprises confirming the suspected condition in response to the first order being different than the second order.

6. The method of claim 5 , wherein determining the first order and the second order comprises ranking the determined signal features from largest to smallest.

7. The method of claim 1 ,
wherein establishing the criteria for confirming the suspected condition comprises identifying one of the at least two physical sensing vectors and the plurality of virtual sensing vectors having a lowest T-wave window signal energy; and
wherein confirming the suspected condition comprises:
redetermining the T-wave window signal energy during the second, unknown rhythm from the identified vector having the lowest T-wave window signal energy during the first, known cardiac rhythm; and
detecting an increase in the T-wave window signal energy of the identified vector.

8. The method of claim 7 , further comprising detecting T-wave oversensing in response to the T-wave window signal energy during the second, unknown rhythm not being greater than the T-wave window signal energy during the first, known cardiac rhythm.

9. The method of claim 1 , wherein establishing the criteria for confirming the suspected cardiac condition comprises:
determining the signal features for each of the at least two physical sensing vectors and the plurality of virtual sensing vectors during a third cardiac rhythm,
identifying one of the at least two physical sensing vectors and the plurality of virtual sensing vectors having a greatest difference between the signal feature determined during the first, known cardiac rhythm and the signal feature determined during the third cardiac rhythm, the first known cardiac rhythm being a non-shockable rhythm and the third cardiac rhythm being a shockable rhythm.

10. The method of claim 1 , further comprising:
selecting a detection vector among the at least two physical sensing vectors and the plurality of virtual sensing vectors based on the comparing;
wherein confirming the suspected condition in response to the established criteria comprises determining a cardiac electrical signal feature of the detection vector during the second, unknown cardiac rhythm.

11. The method of claim 10 , further comprising:
selecting a monitoring vector from among the at least two physical sensing vectors and the plurality of virtual sensing vectors;
wherein detecting the suspected condition comprises detecting the suspected condition in response to a signal feature of the monitoring vector.

12. The method of claim 10 , wherein selecting the detection vector comprises identifying among the at least two physical sensing vectors and the plurality of virtual sensing vectors a vector having at least one of: a lowest T-wave amplitude, a highest R-wave amplitude, a highest R-wave amplitude to T-wave amplitude ratio, a highest R-amplitude and T-wave amplitude difference, a most biphasic T-wave signal, a most monophasic R-wave signal, a lowest baseline noise metric, a highest low slope content, a highest normalized waveform area, and a lowest waveform variability metric.

13. The method of claim 1 , further comprising:
detecting a plurality of different patient body posture signals during the first, known rhythm;
repeating the steps of receiving, computing, determining, comparing and establishing for each of the plurality of the patient body posture signals;
wherein confirming the suspected condition in response to the established criteria being met during the second, unknown cardiac rhythm comprises detecting a body posture signal during the second, unknown cardiac rhythm and using the criteria established during a matching one of the plurality of different patient body posture signals during the first, known cardiac rhythm.

14. The method of claim 1 , wherein confirming the suspected condition comprises detecting a shockable rhythm, the method further comprising delivering a therapy to the patient's heart in response to detecti

Assignees

• Medtronic Inc

Inventors

• Greenhut Saul E
• Zhang Xusheng
• Stadler Robert W

Classifications

• A61B5/0245

  by using sensing means generating electric signals, {i.e. ECG signals} · CPC title

• A61B5/0205

  Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition · CPC title

• A61N1/3956

  Implantable devices for applying electric shocks to the heart, e.g. for cardioversion · CPC title

• A61B5/7275

  Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor · CPC title

• A61N1/3702

  Physiological parameters (A61N1/365 takes precedence; evoked response A61N1/371) · CPC title