Pacemaker monitoring recorder

• US 4,291,703 A
• Filed: 12/26/1979
• Issued: 09/29/1981
• Est. Priority Date: 11/01/1978
• Status: Expired due to Term

• Current Assignee: DEL Mar Medical Systems, LLC (Bio-Techne Corporation)
• Original Assignee: Del Mar Avionics
• Inventors: Kelen, George J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/106,692
• Time in Patent Office: 643 Days
• Field of Search: 128/697, 128/711, 128/419 PT
• US Class Current: 600/524
• CPC Class Codes: A61B 5/337 Playback at speeds other than the recording speed
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents

Abstract

A recorder for monitoring the operation of a cardiac pacemaker and the response of the patient to the pacemaker includes a recorder module which receives a composite signal including an ECG signal, a pacemaker spike having a frequency spectrum that lies substantially at frequencies greater than the frequency band required to pass the ECG signal, and further includes artifact noise within the frequency spectrum of the pacemaker spike. The recorder module distinguishes the pacemaker spike from the artifact noise and upon recognizing the pacemaker spike, the recorder module produces a distinctive synthesized signal whose frequency spectrum lies substantially within the frequency band required to pass the ECG signal so that the synthesized signal will pass through the pre-emphasis filter that is used to reject artifact noise and will then be recorded.

Claims

1. In a magnetic tape recorder for recording signals indicative of the operation of a pacemaker and of the response of a patient to the pacemaker as revealed by the time relationship between a pacemaker spike signal generated by the pacemaker and an ECG generated by the patient equipped with the pacemaker, said magnetic tape recorder having at least two channels for recording separate tracks on a magnetic tape, each channel including a pre-emphasis filter, at least a pair of ECG electrodes to be connected to the patient for receiving said pacemaker spike signal and said ECG signal;

first means for sensing the occurrence of a pacemaker spike signal, said pacemaker spike signal having a frequency spectrum higher than the frequency spectrum required to pass the ECG signal, and for producing in response to the pacemaker spike signal a synthesized signal whose frequency spectrum lies within the frequency spectrum required to pass the ECG signal; and

second means for separating and recording the synthesized signal and the ECG signal through respective ones of said channels on separate tracks on magnetic tape, whereby the synthesized signal is recorded by a recorder normally used for recording ECG signals.

2. The apparatus of claim 1 wherein said first means further comprise:

a differentiator circuit connected to the ECG electrodes to receive as an input signal the signals educed by the ECG electrodes, and responsive to the input signal to produce a differentiator output signal related to the rate of change of the input signal;

a synthesized signal generator connected to said differentiator circuit to receive the differentiator output signal and to generate said synthesized signal when the magnitude of said differentiator output signal exceeds a preset threshold level, said synthesized signal having a predetermined waveform capable of passing through the pre-emphasis filter of the recorder so as to be recorded.

3. The apparatus of claim 2 wherein said synthesized signal is a pulse of duration longer than 10 milliseconds.

4. The apparatus of claim 3 wherein said synthesized signal generator is a one-shot multivibrator.

5. The apparatus of claim 2 wherein said synthesized signal has an amplitude greater than 0.5 millivolt.