Patent GB-1010486-A (GB)
Title: Electrocardiographic means
IPC: A61B5/336
Filed: 1963-03-27
Abstract: 1,010,486. Displaying cardiograms. HOLTEN RESEARCH FOUNDATION Inc. March 27,1963 [July 6,1962],No. 12145/63. Heading G1U. [Also in Division H4] Aperiodic signals of generally similar waveform, such as electrocardiograms, are displayed in substantially overlapping positions on a cathoderay tube screen by deriving trigger pulses from each aperiodic signal and utilizing such pulses to trigger the tube sweep circuit. Heart conditions of the kind which produce abnormal electrocardiac (EKG) signals at only random intervals are then manifest as a departure of occasional tube display traces e.g. trace 112 (Fig. 3) fromthe average trace 110 produced by normal EKG signals. The randomly occurring abnormal signals, however, also occur infrequently or only when the patient is engaged in certain forms of activity and for economy in the time which the electrocardiologist would have to expend in examination and for the practical convenience of the patient the latter is provided with means whereby during an extended period in which he may be engaged in various activities the EKG signals which he produces and which are sensed by conventional skin electrodes are recorded on a slowly moving (e.g. 7¢ inch per minute) magnetic tape (Fig. 1, not shown) which may form part of miniaturized equipment carried by the patent. Alternatively, the latter may be provided with a radio-transmitter which radiates a signal containing the EKG signal information which is then recorded at a fixed station. In the recording apparatus the EKG signals are recorded on separate tracks by two recording heads spaced apart in the direction of tape movement so that when the tape is subsequently played-back triggers signal may be derived from the "first" head and utilized to initiate the cathode-ray tube sweep for displaying the signals subsequently reproduced by the "second" head. Fig. 2 shows the play-back arrangement in which the recorded tape 16 moves between supply reel 42 and take-up reel 44 at the rate of 7<SP>1</SP>/2 inch. per second (i.e. at sixty times the recording rate) the trigger signals being derived from head 48 in association with the apparatus chain 52 and utilized to trigger the horizontal time base of the display oscilloscope 54 the vertical deflection of which is produced by signals derived from head 50 and supplied to the vertical deflection circuit of 54 via apparatus chain 56 including either a compensating amplifier 62 having an integrating characteristic (to compensate for the fact that, owing to the tape motion with respect to the reproduction head, the signal from the latter is a derivative of the recorded EKG signal) or a non-compensating amplifier 68. The occurrence of abnormal E.K.G. signals may also be indicated audibly by the change in the note produced by a loudspeaker 72 connected to either amplifier 62 or 68. The triggering of the horizontal time-base may be controlled either by the commencement of the termination of the R wave (Fig. 3) by operation of the receiving switch 80 and the instant of triggering determined by a control 92 which adjusts the duration of the output square wave 6 of multivibrator 90. By supplying the trigger signals for oscilloscope 54 as vertical deflection signals for a second oscilloscope 108 having a free-running horizontal time-base abnormal EKG signals may be indicated by departure of the vertical line traces from average length.