Low noise, high bandwidth, augmented lead circuit for acquisition of cardiac pacing artifacts

• US 5,709,213 A
• Filed: 09/17/1996
• Issued: 01/20/1998
• Est. Priority Date: 09/17/1996
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc), Uno A ERRE Italia SPA (Zeta4 Srl)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Jurek, Dave R., Kruse, John M.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/714,910
• Time in Patent Office: 490 Days
• Field of Search: 128/695, 128/696, 128/697, 128/901, 128/902, 607/27
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/327 Generation of artificial ECG signals based on measured signals, e.g. to compensate for missing leads
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

Disclosed are a method of and apparatus for deriving augmented lead electrocardiograph (ECG) signals from electrical signals sensed at three skin surface, limb electrodes attached to a patient'"'"'s limbs without the use of a high impedance resistor network. First, second and third pairs of the three limb electrodes are combined to provide first, second and third positive and negative limb lead signal pairs. The first, second and third positive and negative limb lead signal pairs are combined and amplified to provide first, second, and third limb lead signals (LI, LII and LIII). The first, second and third amplified lead limb signals LI, LII and LIII are combined into augmented lead signals aVR, aVL, aVF through a low impedance resistor network and operational amplifiers, in accordance with the formulas: aVR=-0.5 (LI+LII), aVL=0.5 (LI-LIII), and aVF=0.5 (LII+LIII).

Claims

1. An apparatus for deriving augmented lead electrocardiograph (ECG) signals from electrical signals sensed at three skin surface, limb electrodes attached to a patient'"'"'s limbs without the use of a high impedance resistor network, comprising:

means for combining first, second and third pairs of the three limb electrodes to provide fast, second and third, positive and negative, limb lead signal pairs;

means for combining and amplifying the first positive and negative limb lead signal pair into a first limb lead signal (LI);

means for combining and amplifying the second positive and negative limb lead signal pair into a second limb lead signal (LII);

means for combining and amplifying the third positive and negative limb lead signal pair into a third limb lead signal (LIII); and

low impedance resistor network and amplifier means for combining the first, second and third lead limb signals into augmented lead signals.

2. The apparatus of claim 1, wherein said low impedance resistor network and amplifier means further comprises:

a first operational amplifier configured as a differential amplifier having a gain of 0.5 and positive and negative input terminals and a first output terminal; and

a first low impedance network branch of said low impedance resistor network coupled to said positive input terminal of said first operational amplifier for summing the first and second lead signals, wherein the first augmented lead signal (aVR) is derived at the first output terminal in accordance with the formula;

aVR=-0.5 (LI+LII).

3. The apparatus of claim 2, wherein said low impedance resistor network and amplifier means further comprises:

a second operational amplifier configured as a differential amplifier having a gain of 0.5 and positive and negative input terminals and a second output terminal; and

a second low impedance branch coupled to said positive and negative input terminals of said second operational amplifier for summing the first and second lead signals, wherein the second augmented lead signal (aVL) is derived in accordance with the formula;

aVL=0.5 (LI-LIII).

4. The apparatus of claim 3, wherein said low impedance resistor network and amplifier means further comprises:

a third operational amplifier configured as a differential amplifier having a gain of 0.5 and positive and negative input terminals and a third output terminal; and

a third low impedance branch of coupled to said negative input terminal of said third operational amplifier for summing the second and third lead signals, wherein the third augmented lead signal (aVF) is derived in accordance with the formula;

aVF=0.5 (LII+LIII).

5. An apparatus for deriving augmented lead electrocardiograph (ECG) signals from electrical signals sensed at skin surface, right and left arm electrodes designated RA and LA and a leg electrode designated LL without the use of a high impedance resistor network comprising:

means for sensing a fast limb lead signal pair from the RA and LA limb electrodes;

means for sensing a second limb lead signal pair from the RA and LL limb electrodes;

means for sensing a third limb lead signal pair from the LA and LL limb electrodes;

means for amplifying and subtracting the first limb lead signal pair to derive a first, amplified limb lead signal (LI);

means for amplifying and subtracting the second limb lead signal pair to derive a second, amplified limb lead signal (LII);

means for amplifying and subtracting the third limb lead signal pair to derive a third, amplified limb lead signal (LIII);

first low impedance network and amplifier means for combining the first and second lead signals for deriving a first augmented lead signal (aVR) in accordance with the formula;

aVR=-0.5 (LI+LII);

second low impedance network and amplifier means for combining the first and third lead signals for deriving a second augmented lead signal (aVL) in accordance with the formula;

aVL=0.5 (LI-LIII); and

third low impedance network and amplifier means for combining the second and third lead signals for deriving a third augmented lead signal (aVF) in accordance with the formula;

aVF=0.5 (LII+LIII).

6. A method of deriving augmented lead electrocardiograph (ECG) signals from electrical signals sensed at three skin surface, limb electrodes attached to a patient'"'"'s limbs without the use of a high impedance resistor network, comprising the steps of:

combining first, second and third pairs of the three limb electrodes to provide first, second and third positive and negative limb lead signal pairs;

combining and amplifying the first positive and negative limb lead signal pair into a first limb lead signal (LI);

combining and amplifying the second positive and negative limb lead signal pair into a second limb lead signal (LII);

combining and amplifying the third positive and negative limb lead signal pair into a third limb lead signal (LIII); and

combining the first, second and third lead limb signals LI, LII and LIII into augmented lead signals through a low impedance resistor network and operational amplifier.

7. A method of deriving augmented lead electrocardiograph (ECG) signals from electrical signals sensed at skin surface, right and left arm electrodes designated RA and LA and a leg electrode designated LL without the use of a high impedance resistor network, comprising the steps of:

sensing a first limb lead signal pair from the RA and LA limb electrodes;

sensing a second limb lead signal pair from the RA and LL limb electrodes;

sensing a third limb lead signal pair from the LA and LL limb electrodes;

amplifying and subtracting the first limb lead signal pair to derive a first, amplified limb lead signal (LI);

amplifying and subtracting the second limb lead signal pair to derive a second, amplified limb lead signal (LII);

amplifying and subtracting the third limb lead signal pair to derive a third, amplified limb lead signal (LIII);

deriving a first augmented lead signal (aVR) by combining the first and second limb lead signals in a first low impedance network and amplifier in accordance with the formula;

aVR=-0.5 (LI+LII);

deriving a second augmented lead signal (aVL) by combining the first and third limb lead signals in a second low impedance network and amplifier in accordance with the formula;

aVL=0.5 (LI-LIII); and

deriving a third augmented lead signal (aVF) by combining the second and third limb lead signals in a third low impedance network and amplifier in accordance with the formula;

aVF=0.5 (LII+LIII).