ECG system with minute ventilation detector

• US 6,741,886 B2
• Filed: 10/25/2001
• Issued: 05/25/2004
• Est. Priority Date: 10/25/2001
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Yonce, David J.
• Primary Examiner(s): MANUEL, GEORGE C
• Application Number:
  US10/037,773
• Publication Number:
  US 20030083707A1
• Time in Patent Office: 943 Days
• Field of Search: 600/508, 600/509, 600/510, 600/529, 600/534, 600/536, 607/5, 607/9, 607/20, 607/27, 607/28, 607/29
• US Class Current: 600/510
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/276 Protection against electrode failure
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

The ability of an ecg apparatus to detect and display pacing pulses from the surface electrodes on a patient in whom a minute ventilation-based rate adaptive pacemaker is implanted is improved by providing the ecg apparatus with a minute ventilation detection circuit capable of indicating the time of occurrence and repetition rate of bursts of AC carrier signals which the implanted pacemaker generates in deriving a minute ventilation related control signal for the implanted pacemaker. In addition to improving the ability of the ecg system to detect and record paced events, the incorporation of the MV detection into the ecg system accommodates leads-off detection by coordinating the generation of the leads-off drive signal with the MV carrier signal generated by the implanted pacer.

Claims

1. An ecg recorder for detecting and displaying cardiac signals picked up on a plurality of skin contacting surface electrodes disposed on a patient at predetermined body locations in whom a rate-adaptive cardiac rhythm management device is implanted, the cardiac rhythm management device being of the type having minute ventilation as a control parameter for the rate at which the device produces pacing pulses, the device having a means for impressing a carrier signal of a given frequency in timed bursts of a predetermined repetition rate between a first electrode disposed within the patient'"'"'s thoracic cavity and a reference electrode, comprising:

(a) a minute ventilation detection circuit in the ecg recorder connected to receive signals picked up by pairs of said surface electrodes, the signals picked up by the pairs of said surface electrodes including cardiac signal components, pacing pulse components, noise components and components due to said carrier, said minute ventilation detection circuit indicating the time of occurrence of the components due to said carrier signal.

2. The ecg recorder of claim 1 wherein the minute ventilation detection circuit comprises:

(a) a matched filter coupled to receive said signals picked up by the pairs of surface electrodes, along with signals of said given frequency and producing an output; and

(b) a comparator coupled to receive the output of the matched filter, along with a reference signal, the comparator producing an output indicating the time of occurrence of the components due to the carrier signal when the output of the matched filter exceeds the reference signal.

3. The ecg recorder of claim 2 and further including:

(a) a frequency detector coupled to the minute ventilation detection circuit for monitoring the repetition rate of said timed bursts; and

(b) a reference signal adjustment device for varying the reference signal in response to an output from the frequency detector.

4. The ecg recorder of claim 3 wherein the reference signal adjustment device is operative to increase the reference signal when timed bursts occur at a repetition rate greater than the predetermined repetition rate and to decrease the reference signal when the timed bursts occur at a repetition rate less than the predetermined repetition rate.

5. An ecg recorder for detecting and displaying cardiac signals picked up on a plurality of skin contacting surface electrodes disposed on a patient at predetermined body locations in whom a rate-adaptive cardiac rhythm management device is implanted, the cardiac rhythm management device being of the type having minute ventilation as a control parameter for the rate at which the device produces pacing pulses, the device having a means for impressing a carrier signal of a given frequency in timed bursts of a predetermined repetition rate between a first electrode disposed within the patient'"'"'s thoracic cavity and a reference electrode, comprising:

(a) a pacing pulse detection apparatus in the ecg recorder connected to receive signals picked up by pairs of said surface electrodes, the signals picked up by the pairs of said surface electrodes including cardiac signal components, pacing pulse components, noise components and components due to said carrier, the pacing pulse detection apparatus being operative to compare energy present in a predetermined frequency band to a dynamic threshold whose value is based upon an amplitude of a preceding pacing pulse;

(b) a minute ventilation detection apparatus in the ecg recorder connected to receive said signals picked up by said pair of surface electrodes and operative to indicate the time of occurrence of the components due to said carrier signal; and

(c) means responsive to detection of a pacing pulse by the pacing pulse detection apparatus at the time of occurrence of the components due to said carrier signal as detected by the minute ventilation detection apparatus for inhibiting any change in the dynamic threshold.

6. The ecg recorder of claim 5 wherein the minute ventilation detection circuit comprises:

(a) a matched filter coupled to receive said signals picked up by the pairs of surface electrodes, along with signals of said given frequency and producing an output; and

(b) a comparator coupled to receive the output of the matched filter, along with a reference signal, the comparator producing an output indicating the time of occurrence of the components due to the carrier signal when the output of the matched filter exceeds the reference signal.

7. The ecg recorder of claim 6 and further including:

(a) a frequency detector coupled to the minute ventilation detection circuit for monitoring the repetition rate of said timed bursts; and

(b) a reference signal adjustment device for varying the reference signal in response to an output from the frequency detector.

8. The ecg recorder of claim 7 wherein the reference signal adjustment device is operative to increase the reference signal when timed bursts occur at a repetition rate greater than the predetermined repetition rate and to decrease the reference signal when the timed bursts occur at a repetition rate less than the predetermined repetition rate.

9. An ecg recorder for detecting and displaying cardiac signals picked up on a plurality of surface electrodes disposed on a patient at predetermined body locations in whom a rate-adaptive cardiac rhythm management device is implanted, the ecg recorder intermittently applying an AC signal to one of said plurality of surface electrodes to determine the state of conduction between the other of said plurality of surface electrodes and the patient'"'"'s skin, the cardiac rhythm management device being of the type having minute ventilation as a control parameter for the rate at which the device produces pacing pulses, the device having a means impressing a carrier signal of a given frequency close to said AC signal in timed bursts of a predetermined repetition rate between a first electrode in the patient'"'"'s thoracic cavity and a reference electrode, comprising:

(a) a minute ventilation detection apparatus in the ecg recorder connected to receive signals picked up by pairs of said surface electrodes, the signals picked up by the pairs of said surface electrodes, including cardiac signal components, pacing pulse components, noise components, components due to said carrier signal and operative to indicate the time of occurrence of the components due to said carrier signal; and

(b) control means responsive to the minute ventilation detection apparatus for causing the AC signal applied to said one of said plurality of surface electrodes to be interlaced in time with said carrier signal.

10. The ecg recorder of claim 9 wherein the minute ventilation detection circuit comprises:

(a) a matched filter coupled to receive said signals picked up by the pairs of surface electrodes, along with signals of said given frequency and producing an output; and

(b) a comparator coupled to receive the output of the matched filter, along with a reference signal, the comparator producing an output indicating the time of occurrence of the components due to the carrier signal when the output of the matched filter exceeds the reference signal.

11. The ecg recorder of claim 10 and further including:

(a) a frequency detector coupled to the minute ventilation detection circuit for monitoring the repetition rate of said timed bursts; and

(b) a reference signal adjustment device for varying the reference signal in response to an output from the frequency detector.

12. The ecg recorder of claim 11 wherein the reference signal adjustment device is operative to increase the reference signal when timed bursts occur at a repetition rate greater than the predetermined repetition rate and to decrease the reference signal when the timed bursts occur at a repetition rate less than the predetermined repetition rate.

13. An ecg recorder for detecting and displaying cardiac signals picked up on a plurality of skin contacting surface electrodes disposed on a patient at predetermined body locations in whom a rate-adaptive cardiac rhythm management device is implanted, the cardiac rhythm management device being of the type having minute ventilation as a control parameter for the rate at which the device produces pacing pulses, the device having a means for impressing a carrier signal of a given frequency in timed bursts of a predetermined repetition rate between a first electrode disposed within the patient'"'"'s thoracic cavity and a reference electrode, comprising:

(a) a minute ventilation detection circuit in the ecg recorder connected to receive signals picked up by pairs of said surface electrodes, the signals picked up by the pairs of said surface electrodes including cardiac signal components, pacing pulse components, noise components and components due to said carrier, said minute ventilation detection circuit indicating the time of occurrence of the components due to said carrier signal; and

(b) a communication link in the ecg recorder response to the minute ventilation detection circuit for transmitting data to and receiving data from the implanted cardiac rhythm management device only during time intervals between occurrences of components due to said carrier signal.

14. The ecg recorder of claim 13 wherein the minute ventilation detection circuit comprises:

(a) a matched filter coupled to receive said signals picked up by the pairs of surface electrodes, along with signals of said given frequency and producing an output; and

(b) a comparator coupled to receive the output of the matched filter, along with a reference signal, the comparator producing an output indicating the time of occurrence of the components due to the carrier signal when the output of the matched filter exceeds the reference signal.

15. The ecg recorder of claim 14 and further including:

(a) a frequency detector coupled to the minute ventilation detection circuit for monitoring the repetition rate of said timed bursts; and

(b) a reference signal adjustment device for varying the reference signal in response to an output from the frequency detector.

16. The ecg recorder of claim 15 wherein the reference signal adjustment device is operative to increase the reference signal when timed bursts occur at a repetition rate greater than the predetermined repetition rate and to decrease the reference signal when the timed bursts occur at a repetition rate less than the predetermined repetition rate.

17. A method of operating an ECG recorder/programmer on a non-interfering basis with a minute ventilation based rate-adaptive pacemaker implanted in a patient, the pacemaker producing timed bursts of AC carrier signal, comprising the steps of:

(a) providing the ECG recorder/programmer having a plurality of surface electrodes with a minute ventilation detection circuit coupled to said surface electrodes for detecting the time of occurrence of said timed bursts of AC carrier signal;

(b) determining from the time of occurrence of the timed bursts of AC carrier signal a predicted time interval between successive bursts of the timed bursts of AC carrier signal; and

(c) telemetering information between the ECG recorder/programmer and the implanted pacemaker in the predicted time interval.

18. A method of operating an ECG recorder/programmer of a type having a leads-off indicator in which an AC signal of a predetermined frequency is periodically applied to a patient'"'"'s body at a first ECG surface electrode location and picked up by ECG surface electrodes at a second location on a non-interfering basis with a minute ventilation based rate adaptive pacemaker implanted in the patient, the pacemaker producing timed bursts of AC carrier signal, comprising the steps of:

(a) providing the ECG recorder/programmer with a minute ventilation detection circuit that is coupled to said surface electrodes for detecting the time of occurrence of said timed bursts of AC carrier signal;

(b) determining from the time of occurrence of the timed bursts of AC carrier signal a predicted time interval between successive bursts of the timed bursts of AC carrier signal; and

(c) generating the AC signal of a predetermined frequency within the predicted time interval.