Abstract: Apparatus for printing alpha-numeric characters for plotting an incoming signal at rates on the order of one page every seven seconds for rapidly verifying that the system producing the incoming signal is operating properly. Both printing and plotting are done by styli mounted on a moving carriage and individually electrified to produce marks on a specially prepared paper. The styli are moved back and forth across the paper, marking in both directions. The carriage is not stepped across the page, but instead is moved smoothly from one side to the other side under control of a velocity servo. A controller generates and applies velocity command inputs to the servo, based on the position of the carriage as sensed by an optical encoder, and based on certain characteristics of the incoming signal. A first buffer memory accumulates the incoming signal until a line has been stored for plotting, while a second buffer memory is applying its accumulated contents to the printhead.

Abstract: Method and apparatus for arrhythmia analysis of Holter-type ECG recordings including a tape playback unit having an analog signal output of successive ECG complexes or heart beats, a converter for generating data composites representing each complex, a computer for making and storing data templates in bins corresponding to operator classification of complexes as normal, supraventricular ectopic (SVE), ventricular ectopic (VE), or unknown, for comparing successive composites with stored templates and conditions to determine a match condition, and for signaling a corresponding event to an event counter and display. In learn mode the computer signals the tape playback to stop and to display an unmatched complex for operator classification and possible subsequent generation of a new template, after which scanning is resumed.

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.

Abstract: An intelligent printer-plotter for use with a source of time-correlated digital systolic and diastolic blood pressure data and heart rate data receives, stores, analyzes, and edits the data, producing tables of data and graphs having a particular format. The charter smooths the data by a moving average technique and includes modes which permit the operator to edit the data manually or to command the charter to perform the editing automatically. In the automatic editing mode, the data are tested against pre-established criteria. Data not meeting the criteria is flagged so that it can be passed over in subsequent calculation and printing operations; however, the flagged data is not destroyed, but is retained in a memory to permit subsequent re-examination and to permit verification of the editing process.

Abstract: Apparatus is disclosed for long-term ambulatory monitoring of blood pressure by an auscultation method, employing a pressurizable cuff and requiring no intervention by the patient. Heartbeats are sensed by ECG electrodes, and a microphone is used to sense the Korotkow sounds as the pressure in the cuff is varied. The presence or absence of a Korotkow sound within a preset interval following each heartbeat is used in determining when the cuff pressure equals the systolic and diastolic pressures. Those pressures are determined in each cycle of operation and are recorded on a continuously-running portable tape recorder, along with the ECG signals. In each cycle of operation, the initial pressure to which the cuff is inflated is based on the systolic pressure measured in the immediately preceding cycle. The pressure in the inflated cuff is thereafter stepped downward in small discrete decrements triggered by successive heartbeats during the measurement phase of each cycle.

Abstract: A system for encoding, recording, playing back, decoding, validating, and displaying cardiac signals obtained from a patient during ambulatory monitoring. The system permits the recording on a single track in a magnetic tape of a channel of ECG signals interrupted intermittently by blood pressure signals, time of day signals, and event marker signals. The ECG signal is recorded in analog form, but the other signals are recorded as pulse coded signals each having its own format. In the playback apparatus, decoders identify and verify each of the signals when they occur, and the played back information is plotted on a chart. If the time of day signal was not recorded on the tape, timing information can be produced by the playback apparatus from the cumulative tape travel. Fiducial signals introduced in the recording, playback, and charting operations are used in a method for identification and measurement of recording tape speed error, playback tape error, and plotter speed error.

Abstract: Apparatus under control of an operator for selectively displaying signals stored on a magnetic tape. The tape is normally first played back at a high speed, with the reproduced signal displayed at high speed to permit the operator to determine which parts of the tape to view at real-time speed. In the real-time viewing mode, a segment of the tape is played again at high speed to provide a better quality signal; the signal from the segment is converted to digital form and stored in a memory for use in creating a real-time display. The operator then can view the display of the stored signal in a variety of ways: stationary, advancing at real-time speed, or in reverse at real-time speed. The length of the segment stored is relatively short to minimize the size of the memory. After a segment is played back, the tape is brought to a stop and then moved in the opposite direction to position it for playing back the next segment.

Abstract: ECG signals from two approximately orthogonal leads are combined in a rectangular-to-polar coordinate converter to obtain signals representing the magnitude and angle of the vector. The vector angle existing at the instant the magnitude of the QRS vector reaches its peak is first identified, and a voltage corresponding to the vector angle is sampled and stored for later use. Secondly, the vector angle existing at the instant the magnitude of the T-wave vector reaches its peak later in the cardiac cycle, is identified, and a voltage corresponding to this second vector angle is sampled and stored. The voltages representing the QRS and the T-wave vector angles are then applied to a differential amplifier to obtain a difference voltage representing the angular difference existing between the two maximal vectors. This angular difference possesses certain characteristics which are diagnostically significant. A classifying circuit determines which one of a number of angular ranges the angular difference falls into.

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.

Abstract: A pulse echo ultrasonic system is provided for medical diagnosis, and the like, which has particular application to echocardiography, and which includes a digital memory for presenting a rolling dynamic display in shades of gray on the screen of a cathode-ray tube scanned in accordance with present-day television standards, and which may be interfaced with present-day video tape recorders. The system of the invention involves a time extrapolating function which serves to expand the effective memory capacity when used in a selective mode applicable to echocardiography, and certain other bio-medical areas, such as scintillation camera displays, and other radiographic displays used in the area of medicine.

Abstract: A method of obtaining a continuous sequence of horizontal vectorcardiograms from an ambulatory patient throughout a 24-hour period. A simplified five-electrode ECG lead system is affixed to the patient and the ECG signals are recorded on a portable magnetic tape recorder attached to the patient. Thereafter, the tape is removed from the recorder and taken to a processing station for playback, display, and analysis. The tape is played back at high speed to permit rapid scanning of the tape for anomalies in the vectorcardiograph. Anomalies can then be studied in detail by playing back the tape at a reduced speed. The vectorcardiographs exhibit high correlation with those obtained by use of the more common, but more complex, Frank lead system.

Abstract: A multi-speed ECG magnetic tape scanning device for processing and observing in a relatively short interval of time large quantities of ECG signals from two pairs of ECG leads. The ECG information is recorded on a miniature recorder which the patient carries to record the information for a long period of time, such as 24 hours. The recorder includes a built-in clock with a visible display. The recorder also includes an event marker, which is activated by the patient when the patient experiences an event. The play-back of the ECG information is in real time or at multiple high speed play-back speeds of 30, 60 and 120 times real time. During play-back at high speed, a multi-speed multi-channel paper writer reproduces analog trend data, digital printed data and event marking. The trend information is usually heart rate and ST segment level, so as to produce a scanning of an entire 24 hour information tape in as short a period as 12 minutes.

Abstract: A multi-speed ECG magnetic tape scanning device for processing and observing in a relatively short interval of time large quantities of ECG signals from two pairs of ECG leads. The ECG information is recorded on a miniature recorder which the patient carries to record the information for a long period of time, such as 24 hours. The recorder includes a built-in clock with a visible display. The recorder also includes an event marker, which is activated by the patient when the patient experiences an event. The play-back of the ECG information is in real time or at multiple high speed play-back speeds of 30, 60 and 120 times real time. During play-back at high speed, a multi-speed multi-channel paper writer reproduces analog trend data, digital printed data and event marking. The trend information is usually heart rate and ST segment level, so as to produce a scanning of an entire 24 hour information tape in as short a period as 12 minutes.