Recorder for cardiac signals with manually actuated event marking

• US 4,123,785 A
• Filed: 03/02/1977
• Issued: 10/31/1978
• Est. Priority Date: 08/25/1976
• Status: Expired due to Term

• Current Assignee: Del Mar Avionics
• Original Assignee: Del Mar Avionics
• Inventors: Anderson, Donald L., Cherry, Isaac R.
• Primary Examiner(s): Tupper, Robert S.
• Application Number:
  US05/773,618
• Time in Patent Office: 608 Days
• Field of Search: 360/5, 360/6, 360/73, 360/75, 360/4, 128/2.06 G, 346/20, 346/33 ME
• US Class Current: 360/6
• CPC Class Codes: A61B 5/337 Playback at speeds other than the recording speed
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: A61B 5/358 Detecting ST segments
• CPC Class Codes: G11B 15/026 by using processor, e.g. microcomputer
• CPC Class Codes: G11B 15/29 through pinch-rollers or tape rollsG11B15/295 takes precedence
• CPC Class Codes: G11B 15/54 by stroboscope; by tachometer
• CPC Class Codes: G11B 27/10 Indexing; Addressing; Timing or synchronising; Measuring tape travel

Abstract

A miniature tape recorder intended for ambulatory recording of cardiac signals over a twenty-four-hour interval includes a clock with a visual display and an event marking circuit. Cardiac signals are recorded simultaneously on two tracks on the magnetic tape used by the recorder. The event marking circuit, activated by the patient, interrupts briefly the recording of cardiac signals on one of the tracks to record in its place an event marker signal easily recognizable on playback. The event marking circuit includes a clock circuit, a counter, and logic circuits to generate a burst of exactly eight square pulses of predetermined width, the duration of the burst being one second.

Claims

1. A recorder for use with a dynamic multispeed ECG computer for reproducing ECG information contained on a recording medium recorded at a particular speed and with the computer including first means for moving the recording medium past a plurality of readout positions and with the computer including second means for controlling the first means to move the recording medium at a plurality of speeds including a movement at a speed corresponding to the particular speed of recording, and including a movement of the recording medium at at least one speed greater than the particular speed to provide real time and high speed playbacks of the recorded information and with the computer including third means located at a first one of the readout positions for reproducing the recorded information when the first means moves the recording medium to provide real time playback and with the computer including fourth means located at a second one of the readout positions for reproducing the recorded information when the first means moves the recording medium to provide high speed playback and with the computer including fifth means responsive to an event signal contained within the ECG information played back at high speed to control the second means to move the recording medium for real time playback for a predetermined period of time and then control the second means to return to high speed playback, the recorder including:

a recording medium system including a channel for recording ECG information in response to applied ECG input signals,

an event marker means for producing an event signal consisting of a short burst of a predetermined number of pulses in a predetermined period of time, and

switching means coupled to the event marker means and the recording medium system for selectively interrupting the recording of the ECG information and recording the event signal on said channel of said recording medium in response to manual actuation of the switching means.

2. A portable magnetic tape recorder contained in a case and affixable to a patient for extended ambulatory recording on a magnetic tape of a cardiac signal obtained from an electrode affixed to the patient, said recorder comprising:

a recording head;

an event marker circuit connected to said recording head, connected to the electrode, and including patient-activated means for selectively interrupting the cardiac signal normally being recorded by said recording head on one track of the magnetic tape and for generating and applying to said recording head during the selective interruption in place of the cardiac signal, a burst of pulses of predetermined number, in a predetermined period of time, and of predetermined amplitude and pulsewidth, so that said burst of pulses is reliably identifiable upon subsequent playback of the magnetic tape; and

,

a visual time display included within the case of the recorder to permit the patient to note the time of the interruption.

3. An event marker for interrupting a cardiac signal normally being recorded by a recording head on one track of a magnetic tape and for recording in its place a burst of pulses of predetermined number, amplitude and pulsewidth reliably identifiable upon playback of the magnetic tape, said event marker comprising:

binary counter means for counting applied pulses, having a clock input terminal to which pulses to be counted are applied, a reset terminal for resetting said binary counter means when a predetermined pulse is applied to it, a first output terminal for presenting a signal representing the Pth digit of the count, and a second output terminal for presenting a signal representing the Nth digit of the count, where P is greater than N;

clock means for generating a continuing train of pulses at a predetermined fixed rate;

an enabling circuit having an input terminal connected to said clock means to receive the continuing train of pulses, having an enabling terminal connected to the first output terminal of said binary counter means, having an output terminal connected to the clock input terminal of said binary counter means said enabling circuit responsive to a logic "zero" signal on the first output terminal of said binary counter to enable pulses generated by said clock means to be applied to the clock input terminal of said binary counter means, whereby only 2^P pulses are applied to the clock input terminal of said binary counter in each cycle of operation;

event marker switch means connected to the reset terminal of said binary counter and actuated manually to apply a reset pulse to the reset terminal of said binary counter means; and

,

interruptor switch means having an output terminal connected to the recording head to provide to it signals to be recorded, a first input terminal connected to the second output terminal of said binary counter, a second input terminal to which the cardiac signal is applied, and a switching terminal connected to the first output terminal of said binary counter said interruptor switch normally connecting said second input terminal to said output terminal and selectively operable in response to a logic "zero" signal on the first output terminal of said binary counter to disconnect said output terminal from the second input terminal to said output terminal,

whereby, the first 2^P pulses generated by said clock means after said event marker switch means is actuated are counted by said binary counter, defining a time interval during which exactly 2^P-N-1 pulses from the second output terminal of said binary counter are conducted through said interruptor switch means to its output terminal for recording in place of the cardiac signal.

4. The product comprising the magnetic tape produced by the event marker of claim 3 during an extended time interval in which said event marker switch means was actuated at least once.

5. A process for generating a magnetic tape bearing a recorded track in which a cardiac signal is normally recorded by a recording head, in which track an event marking signal is selectively recorded by the same recording head in place of the cardiac signal, said process comprising the steps of:

normally recording the cardiac signal on a track of the magnetic tape;

generating a continuing train of pulses;

initiating a counting interval by actuation of an event marker switch;

counting the number of pulses that have occurred during the counting interval;

interrupting the normal recording of the cardiac signal during the first 2^P pulses following actuation of the event marker switch;

applying to the recording head, in place of the cardiac signal, a signal representing the Nth binary digit of the number of pulses that have occurred in the counting interval, where N is less than P, for recording on the same track of the magnetic tape as the cardiac signal is normally recorded on.

6. The magnetic tape produced as a product by applying the process of claim 5.