Electrocardiographic monitoring and recording device

An electrocardiographic monitoring and recording device that includes continuous long-term recording with real time evaluation of the incoming data in an evaluation buffer for the occurrence of a clinically significant event. The occurrence of an event meeting programmable parameters causes the data stored in the evaluation buffer (which covers the period of time both before and after the event) to be transferred to a holding buffer and also triggers a patient alert. The patient, thus alerted, can then download the holding buffer via telephone to a central monitoring station. The patient can also manually trigger the transfer of data to the holding buffer. The monitor includes a separate long-term memory for storing up to 12-24 hours of data, which can also be down loaded.

This invention relates to portable, wearable devices for recording and 
transmitting electrocardiographic data. More specifically, this invention 
relates to a wearable device for the selective and continuous recording of 
electrocardiographic data. The selective recording of data can be timed or 
centered around the occurrence of a clinically significant event, as 
detected by the device or triggered by the wearer. The data may thereafter 
be transferred to a holding buffer and subsequently transmitted digitally 
or via telephone to a remote station for evaluation. Simultaneously with 
the selective recording, continuous extended recording occurs, allowing 
for 24 hours or more of ECG data to be captured for evaluation or all or 
any portion. 
BACKGROUND OF THE INVENTION 
For a number of years, cardiac patients have been evaluated with a device 
known as "Holter" monitor. The patient wears a small sensor which will 
pick up his or hers heart signal. The signals are recorded on recording 
tape by the holter monitor for a 24 hour period (or other extended time). 
The tape is sent to a central station for evaluation by an external 
computer, which searches for irregularities which may have occurred during 
the monitored period. However, these devices have been found to be less 
than completely satisfactory in that the patient may not have been 
symptomatic during the monitored period, and therefore any recorded 
arrhythmias may have no clinical significance. Furthermore the recording, 
transmittal and subsequent evaluation of the data may cause unacceptable 
delays. More modem variants of Holter recorders have substituted flash 
memory for recording tape or provide limited onboard analysis; however, 
the above described problems remain. 
More recently, devices known as event recorders have been employed for 
cardiac monitoring. These devices, which are also worn by the patient, 
record ECG data when triggered by the patient or by the occurrence of a 
clinically significant event. The recordings usually last for about 1-5 
minutes and can be transmitted over ordinary telephone lines. The 
advantage of event recorders are extended monitoring periods (because the 
device is not operating continuously) and relatively quick access to the 
data. A disadvantage is the limited amount of electrocardiographic data 
available to the physicians, who are accustomed to and comfortable with 
the extended monitoring and extensive data provided by the Holter type 
devices. 
Another type of device is illustrated in U.S. Pat. No. 4,622,979 (to 
Katehis, et al.), which is directed to an electrocardiographic monitoring 
device which continually monitors, and digitally stores in memory, the 
electrocardiograph signals of the patient. When the memory is full the new 
electrocardiograph data overwrites the older data. Upon the occurrence of 
symptoms the patient may activate a switch to halt overwriting of the 
data, which may then be downloaded by telephone to a central location. The 
device can be programmed to retain a defined time before and after 
activation, e.g., 40 seconds before and 20 seconds after, or 15 seconds 
before and 70 seconds after, etc. This device, like the event recorders 
described above, has the disadvantage of not providing the extensive data 
or extended monitoring period of Holter type devices. 
Another significant disadvantage of some of these devices is that they rely 
on the patient to trigger the recording (or halt the overwriting of data). 
A clinically significant cardiac event may occur without the patient being 
symptomatic (e.g. the patient feels no pain) and thus no recording of the 
event occurs. Another common occurrence is that the event may disable the 
patient, e.g., the patient suffers syncope (fainting), and thus is unable 
to trigger a recording of the event. 
The present invention is directed to overcoming the shortcomings of both 
Holter type and event type cardiac monitors. 
SUMMARY OF THE INVENTION 
The present invention is directed to an electrocardiographic monitoring and 
recording device that includes the continuous long-term recording of a 
Holier device and the selective recording of event type recorders. The 
selective recording permits real time evaluation of the incoming data in 
an evaluation buffer for the occurrence of a clinically significant event. 
The parameters of what constitutes a clinically significant event are 
adjustable and may be remotely programmable in accordance with the 
physicians' orders based upon the patients medical history. Upon the 
occurrence of an event meeting the programmed parameters, the data stored 
in the evaluation buffer (which can cover a period of time both before and 
after the event) is transferred to a holding buffer and a patient alert 
can be triggered. The patient can also manually trigger the transfer of 
data to the holding buffer. Several events could be held in this buffer. 
The patient can then download the holding buffer digitally or via 
telephone to the doctor or a central monitoring station. The monitor 
device of the present invention also includes a separate long-term memory 
for storing more data, hours before and/or after the trigger event, e.g., 
12-24 hours or more of additional data, which can also be downloaded. The 
extended, usually continuous, recording can be terminated by the patient 
or by medical personnel via telephone, thus allowing any time period to be 
observed and evaluated in relation to documented events isolated by the 
selective data recording system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates the portable, wearable electrocardiographic recording 
and monitoring device 10 of the present invention. Device 10 includes an 
electrode 12 (or electrodes) for attachment to the skin of the person 
whose heart rhythms are to be monitored. Connecting electrode 12 to an 
amplifying/signal processing circuit 16 are wires 14. 
Circuit 16 amplifies the weak signals from electrode 12 and removes the 
noise so as to provide an electrocardiograph signal 18 (e.g., a standard 
"QRS" waveform) for evaluation and recording by the other components of 
device 10. Electrode 12 and circuit 16 are standard components used in a 
variety of cardiac monitors. If the subsequent storage media is digital, 
rather than analog, circuit 16 will include suitable analog to digital 
circuitry. Circuit 16 also preferably includes diagnostic routines to 
determine that electrode 12 is in proper electrical contact with the skin 
of the patient so that the signals are not interrupted or attenuated. Such 
diagnostic circuitry may include a continuity cheek of electrode 12. 
Electrocardiograph signal 18 is applied to two memories, a first buffer 
means (also referred to as an evaluation buffer) and a long-term storage 
means (also referred to as long-term memory or extended memory). In the 
drawing the memories are represented by evaluation buffer 20 and long-term 
memory 22, respectively. Evaluation buffer 20 may be in the form of a 
"flashcard", or other solid state memory, and typically will store about 1 
to 10 minutes of the electrocardiograph signal 18. 
The evaluation buffer is configured to overwrite the first stored data with 
new data from the incoming electrocardiographic signals 18. The 
overwriting of the electrocardiograph signals will continue until the 
buffer receives an activation signal to either stop overwriting or to 
transfer the stored data to a second buffer means (also referred to as a 
holding buffer) before continuing overwriting. 
The long-term memory may be either solid state memory or a magnetic tape or 
disk, etc. recorder. Preferably, the long-term memory is solid state 
memory sufficient to hold at least 12 hours of EGG data, more preferably 
at least 24 hours of data. Moreover, the long-term memory may continuously 
overwrite the earliest stored data with new data, thereby being capable of 
operating for days. In preferred embodiments, recording by the long-term 
memory may be terminated by the device, by the patient via a switch on the 
device or by medical personnel via telephonic communication, as described 
in further detail below. 
In one embodiment of the invention, the activation signal is manually sent 
to the evaluation buffer by the patient via a switch, typically when the 
patient feels the occurrence of a cardiac event. In the simplest form of 
the device, evaluation buffer then stops its overwriting and the patient 
must bring the evaluation buffer and the long-term memory to a remote 
station for further evaluation. The remote station may comprise medical 
personnel or an external computer which provides further analysis of the 
EGG data. 
In more preferred embodiments of the device, the evaluation buffer upon 
receipt of the activation signal transfers its data to a holding buffer 
and then continues the overwriting until the next activation signal. In 
this manner selective recordings of several cardiac events may occur 
before transferring the data to a remote station from the holding buffer. 
In other even more preferred embodiments of the invention, the activation 
signal may also or instead be automatic upon the occurrence of a cardiac 
event, thereby eliminating the need to rely on patient activation. In such 
embodiments, evaluation buffer 20 may incorporate a microprocessor or 
digital signal processor to evaluate the electrocardiograph signal in real 
time. The electrocardiograph signal is evaluated in relation to certain 
stored parameters that are used to determine if a clinically significant 
event has occurred. If a clinically significant event has not occurred, 
e.g., the preprogrammed criteria have not been met, evaluation buffer 20 
overwrites the first stored data and continues to evaluate the incoming 
electrocardiographic signals 18. The overwriting and evaluation of the 
electrocardiograph signals will continue until the preprogrammed 
parameters are met. 
If the preprogrammed parameters are met, the electrocardiographic data 
stored in evaluation buffer 20 will be transferred to a holding buffer 24 
and a patient alert 26 will preferably be activated. Patient alert 26 may 
be in the form of a light or sound generator to alert the patient that an 
event has occurred and that holding buffer has data to be transferred to 
remote station 32 for further evaluation. 
In addition to automatic actuation of the transfer of data to holding 
buffer 24, a patient operated switch 27 may also be included and used to 
manually transfer the data to holding buffer 24. Of course, the device may 
also be designed so that the automatic activation signal does not transfer 
the stored data but only signals the patient to manually transfer the data 
to the holding buffer. This would be a less desirable embodiment of the 
invention. 
Typically, the evaluation buffer will contain about 1-10 minutes of data 
which will contain electrocardiograph data both before and after the 
triggering event. This aspect of the invention is similar to the unit 
shown in U.S. Pat. No. 4,622,979, whose disclosure is hereby incorporated 
by reference into the present disclosure. The amount of data held by the 
evaluation buffer after overwriting ceased or transferred to holding 
buffer 24 (i.e., how much pre and post event data) may be pre-programmed. 
As discussed above, after transfer of the data to holding buffer 24, 
evaluation buffer 20 may resume normal operation. The holding buffer 24 
may be of such size as to permit the holding of data from several events 
prior to transmission for further evaluation. 
Either the evaluation buffer (in embodiments where there is no holding 
buffer) or the holding buffer may be connected to a transtelephonic unit 
28 which is used to transfer the data stored by the buffer by digital 
communications or telephone lines 30 to an external location or remote 
station 32 for further display and evaluation by an external computer or 
medical personnel. It is contemplated that the transmission of the data in 
the evaluation buffer or the holding buffer can be performed manually by 
the patient or automatically without reliance on the patient. 
Transtelephonic unit 28 may be similar to a computer modem (and the unit 
shown in U.S. Pat. No. 4,622,979) in that it encodes and decodes data for 
transmission over telephone lines to permit two way data flow, e.g., 
electrocardiographic data out, and receipt of program and operational 
data. It is contemplated that data transmission can be in analog or 
digital form, and that various transmission devices may be utilized as 
they become available, e.g., cellular devices, satellite or cable 
transmission, etc. 
In addition to transmitting the data in the evaluation or holding buffer, 
unit 28 (or a separate unit) may also permit downloading of some or all 
data from the 12-24 hour long-term memory 22 and can receive programming 
commands, e.g., for re-programming the parameters of evaluation buffer 20 
or terminating the recording of the long-term memory. 
Remote station 32 may include a computer and storage for the data 
downloaded from device 10 and can output commands to device 10. For 
example, station 32 may be programmed to request that, in addition to the 
data contained in holding buffer 24, a preprogrammed amount of data from 
long-term memory 22 be also sent by unit 28 (or another unit) to remote 
site 32. The request for additional data can be based on the identity of 
the patient, the particular cardiologist involved or further analysis by 
remote site 32 of the data received from buffer 24. 
In addition to the downloading of data to remote site 32, transtelephonic 
unit 28 may also be used to reprogram the parameters used in the 
evaluation buffer 20. Evaluation buffer 20 can be programmed to trigger 
upon the occurrence of a number of clinically significant events. Among 
the significant events are tachycardia (rapid heartbeat), bradycardia 
(slow heartbeat), a pause in heartbeat, and any other form of arrhythmia. 
A number of algorithms for evaluating electrocardiograph signals are 
commercially available and these or new algorithms may be used in the 
signal processing of evaluation buffer 20 to trigger the transfer of the 
contents to holding buffer 24. 
Additional elements for the manufacture or use of devices in accordance 
with the present invention are known in the industry, e.g., power supply, 
apparatus to permit the carrying of the device, etc. The present 
disclosure is not intended as a treatise on cardiac monitors and readers 
are referred to appropriate, available texts in the field for additional 
information. 
The invention has been described with respect to preferred embodiments. 
However, as those skilled in the art will recognize, modifications and 
variations in the specific details which have been described and 
illustrated may be resorted to without departing from the spirit and scope 
of the invention as defined in the appended claims.