A method and apparatus for digitally storing episodic signals, such as, electrocardiogram signals is disclosed. In a preferred embodiment, the apparatus includes, for each signal channel, an input amplifier, an analog-to-digital converter, and a double data buffer. The incoming signal on each channel is converted to a multibit digital number a fixed sampling rate. Each multibit digital number is stored in a location in the double data buffer. When a fixed amount of data is stored in the buffer, a processor examines the data to determine the periods during which the signal is undergoing the most rapid rate of change. For these periods, both an indicator of the period, and a first number of data samples per unit time is stored in a bulk solid state memory. Preferably, the data stored is a number relating to the difference between the value of the sample and a number related to the value of the last sample. For other periods, having rates of data change high, but not as high as those of the first period, a smaller number of samples per unit time is stored. These samples are chosen to faithfully reproduce the minima and maxima of the waveform. For all other waveform periods, every Rth sample is stored. The storage media is preferrably dynamic random access memory, the refresh rate of which is determined by the temperature of the circuitry.

An electrocardiograph which includes a detecting circuit for detecting a cardiographic signal from a living body; a storage circuit for storing the cardiographic signal from the detecting circuit; a storage control circuit capable of performing a storage control operation in such a way as to sequentially and continuously store a new cardiographic signal in the storage circuit for the formation of cardiographic data and as to successively erase old cardiographic data which are stored in the storage circuit; and a cardiographic data hold commanding circuit operable in response to a cardiographic data hold commanding signal to command the retaining of cardiographic data in the storage circuit.

Ambulatory ECG data monitoring and recording method and apparatus that selectively captures recorded data based upon the occurrence of a defibrillation pulse from an implantable cardioverter/defibrillator monitor (ICDM) device is described. The apparatus uses a single pair of skin electrodes to sample the ECG signal waveform and to monitor the voltage therebetween for the detection of a ICDM-produced pulse of characteristic amplitude and duration. ECG data are continuously stored in a scrolling buffer of limited depth. Detection of a defibrillation pulse is treated as a trigger event, prompting the continuation of ECG data storage only for a limited further period of time after which the present ECG data record is captured. The buffered data are marked by the occurrence of the defibrillation pulse that prompted their capture, so that the information stored for subsequent playback indicates the timing relationship therebetween. A new buffer is initialized and ECG data recording and defibrillation pulse detection continues. Selectively capture-stored and marked ECG data can be played back to a remote site for diagnosis of a relatively longterm, ambulatory cardiac patient monitoring and recording session. Optionally, the cardiac patient may manually trigger the capture-store of ECG data.

Portable, two-way ECG data-storage apparatus for the selective window-capturing of successive plural-lead ECG data records. The apparatus receives its information from the analogue output terminals in a conventional ECG machine, and operates a store multiple-lead data in flagged time-windowed fashion in order to assure stable signal information and efficient meory use. Playback can occur either directly in an analogue manner back to any selected ECG machine, and/or audibly for listening to by a user or for transtelephonic transmission.

An electronic health care diary is provided for a patient logging data concerning predetermined health conditions, such as for monitoring angina attacks. Upon the onset of e.g. the angina attack the patient presses a start button whereupon a real time clock generates a data and time signal which is stored in a memory along with the fact that the episode started. When the episode is over the patient presses a "stop" switch which generates another date and time signal from the real time clock and stores it in memory along with the fact that the episode terminated. A multi-position switch is actuated by the patient to indicate the extent of the condition, such as the severity of the attack. Optionally, a switch can be provided for correcting a previous erroneous entry, and another switch indicating the time and dosage of any medication. Data logged in the memory can be downloaded through a communications port and programming instructions can be uploaded into the device. An appropriate display provides various messages for the user.