Cardiac pacemaker with auto-capture function

• US 5,324,310 A
• Filed: 07/01/1992
• Issued: 06/28/1994
• Est. Priority Date: 07/01/1992
• Status: Expired due to Term

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Greeninger, Daniel R., Thompson, David L.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): SCHAETZLE, KENNEDY
• Application Number:
  US07/907,369
• Time in Patent Office: 727 Days
• Field of Search: 128/419 PG, 128/419 PT
• US Class Current: 607/28
• CPC Class Codes: A61N 1/365 controlled by a physiological parameter, e.g. heart potential evoked response A61N1/371
• CPC Class Codes: A61N 1/3706 Pacemaker parameters stimulation threshold A61N1/371
• CPC Class Codes: A61N 1/3716 with reduction of residual polarisation effects

Abstract

A pacemaker having two bipolar leads, one atrial, one ventricular, each with TIP and RING electrodes, configured as for conventional bipolar pacing/sensing in both chambers. Switching circuitry in the pacemaker is operable to select from among various possible sensing configurations, including one configuration in which sensing is performed between the ring electrodes of the respective pacing/sensing leads. Pacing is preferably performed in a conventional unipolar configuration in each chamber, from the respective tip electrodes. The "ring-to-ring" EGM signal is applied to filtering and EGM amplifier circuitry, and then provided to a telemetry system for transmission to an external receiver. The ring-to-ring EGM signal possesses the high resolution properties of conventional intracardiac signals, and is relatively unaffected by the after-potentials and tissue polarization effects that arise when the same lead is used for pacing and sensing. Additionally, the ring-to-ring EGM signal is a composite of atrial and ventricular electrical signals, and thus has an appearance similar to that of surface ECGS. In the disclosed embodiment, separate atrial and ventricular EGM amplifiers are provided, with the atrial EGM amplifier receiving a conventional atrial unipolar sensing signal and the ventricular EGM amplifier receiving a conventional ventricular unipolar sensing signal. The outputs from the respective atrial and ventricular EGM amplifiers are algebraically multiplied, and the multiplied signal is applied to a threshold detector. Capture is verified when the multiplied signal experiences a positive voltage spike that exceeds a predetermined threshold in the threshold detector.

Claims

1. An implantable cardiac pacemaker system comprising:

a pulse generator, adapted to produce cardiac stimulating pulses;

an atrial bipolar pacing/sensing lead having atrial tip and ring electrodes, a first atrial conductor therein coupled to said atrial tip electrode and a second atrial conductor therein coupled to said atrial ring electrode, said atrial tip and ring electrodes being disposed in a patient'"'"'s atrium;

a ventricular bipolar pacing/sensing lead having ventricular tip and ring electrodes, a first ventricular conductor therein coupled to said ventricular tip electrode and a second ventricular conductor therein coupled to said ventricular ring electrode, said ventricular tip and ring electrodes being disposed in said patient'"'"'s ventricle;

an indifferent electrode, disposed apart from said atrial and ventricular tip and ring electrodes;

an atrial EGM amplifier having first and second inputs and an output, said first atrial EGM amplifier input coupled to said first atrial conductor and said second atrial EGM amplifier input coupled to said indifferent electrode, said atrial EGM amplifier adapted to generate an atrial EGM output signal corresponding to a difference between respective voltages on said first and second atrial EGM amplifier inputs;

a ventricular EGM amplifier having first and second inputs and an output, said first ventricular EGM amplifier input coupled to said first ventricular conductor and said second ventricular EGM amplifier input coupled to said indifferent electrode, said ventricular EGM amplifier adapted to generate a ventricular EGM output signal corresponding to a difference between respective voltages on said first and second ventricular EGM amplifier inputs;

an analog voltage multiplier having first and second inputs and an output, said multiplier coupled to said atrial EGM output and said ventricular EGM output and adapted to produce a multiplier output signal corresponding to an algebraic multiplication of said atrial EGM amplifier output signal and ventricular EGM amplifier output signal;

a threshold detector circuit, coupled to said multiplier and adapted to produce an output pulse when said multiplier output signal exceeds a predetermined threshold.

2. A pacemaker system in accordance with claim 1, wherein said indifferent electrode comprises a conductive pacemaker canister.

3. A pacemaker system, comprising:

a pulse generator, adapted to produce cardiac stimulating pulses;

an atrial bipolar pacing/sensing lead having atrial tip and ring electrodes, a first atrial conductor therein coupled to said atrial tip electrode and a second atrial conductor therein coupled to said atrial ring electrode, said atrial tip and ring electrodes being disposed in a patient'"'"'s atrium;

a ventricular bipolar pacing/sensing lead having ventricular tip and ring electrodes, a first ventricular conductor therein coupled to said ventricular tip electrode and a second ventricular conductor therein coupled to said ventricular ring electrode, said ventricular tip and ring electrodes being disposed in said patient'"'"'s ventricle;

an indifferent electrode, disposed apart from said atrial and ventricular tip and ring electrodes;

an atrial EGM amplifier having first and second inputs and an output, said first atrial EGM amplifier input coupled to said first atrial conductor and said second atrial EGM amplifier input coupled to said indifferent electrode, said atrial EGM amplifier adapted to generate an atrial EGM output signal corresponding to a difference between respective voltages on said first and second atrial EGM amplifier inputs;

a ventricular EGM amplifier having first and second inputs and an output, said first ventricular EGM amplifier input coupled to said first ventricular conductor and said second ventricular EGM amplifier input coupled to said indifferent electrode, said ventricular EGM amplifier adapted to generate a ventricular EGM output signal corresponding to a difference between respective voltages on said first and second ventricular EGM amplifier inputs;

an analog telemetry system, coupled to said atrial EGM amplifier and said ventricular EGM amplifier and adapted to transmit said atrial EGM signal and said ventricular EGM signal to an external receiving device;

a voltage multiplier, coupled to said external receiving device and adapted to multiply said transmitted atrial and ventricular EGM signals to produce a multiplied signal;

a threshold detector, coupled to said voltage multiplier and adapted to produce an output pulse when said multiplied signal exceeds a predetermined threshold.

4. A pacemaker system in accordance with claim 3, wherein said indifferent electrode comprises a conductive pacemaker canister.

5. A method for verifying that a cardiac stimulating pulse has achieved capture, comprising the steps of:

(a) sensing an atrial signal between a transvenous atrial lead and an indifferent electrode;

(b) sensing a ventricular signal between a transvenous ventricular lead and an indifferent electrode;

(c) multiplying said sensed ventricular and atrial signals to produce a multiplied signal;

(d) producing a signal indicative of capture when said multiplied signal exceeds a predetermined threshold.