Condensing relevant data from a magentic tape

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Sale of leaflets to ('IMPRIMERIE NATIONALE 27 denies He la Convention _ 7E772 PARIE! CFnFY 1F

- The present invention relates to a method and a device for processing and displaying a signal for reading an EKG recording read at a speed greater than the recording speed.

We know that an electrocardiogram is a periodic curve in which each cycle or pattern normally presents three waves referenced by the letters P, QRS and T (Figure 1).

The so-called HOLTER investigation method consists in carrying out a continuous recording of an electrocardiogram o n a patient over a long period of time, for example over 24 hours. This recording is made on the magnetic tape of a cassette.

The object of the invention is in particular to propose a method and a device allowing a rapid and effective exploitation of this recording of electrocardiogram, with a view to establishing a precise and sure diagnosis.

To this end, the process for processing an electrocardiogram signal recorded over a long period and read at a speed at least ten times greater than the recording speed, is characterized according to the invention, by the selective and simultaneous detection of several different types of pathological complexes on the signal read, and the visualization on each of several distinct visualization locations, of each signal sequence presenting the complex of a type corresponding to said viewing location.

Advantageously, a determined type of pathological complex is selectively detected by measuring each cycle period or duration of the electrocardiogram signal and / or by measuring the average value of n consecutive periods, n being an integer greater than 1, and / or by comparing this period or this average value with a reference value, and detecting each period or average value lower or higher than this reference value, and / or by detecting each series of £ consecutive cycles whose periods are less - or greater - than this reference value, and / or by comparing the period or the average value with two reference values ​​and by detecting each period whose value is included - or not included - between these two reference values, and / or by calculating each difference between a period and the immediately preceding period and by comparing this difference with a reference value.

A pathological complex can also be detected by comparing the shape of each cycle with a reference shape by a shape recognition method.

This process is advantageously implemented in a device comprising:

- a magnetic stripe reader;

- a device introducing a delay in the signal supplied by the reader;

- several random access memories each receiving the signal from the delay device;

- discriminators each associated with a random access memory and each receiving the signal, not delayed, from the reader;

a display device comprising several distinct display locations, each of which is associated with a random access memory to display the content of this memory;

each discriminator being arranged to recognize a pathological complex of corresponding type and to send to the memory with which it is associated, an order to record a sequence of the signal of the delay device, whereby, to each display location is associated a type of a particular pathological complex and each pathological complex of a type detected by a discriminator is displayed on the corresponding viewing location.

Thus, the selective visualization of certain types, suitably chosen, of pathological complexes allows a rapid investigation of the recording of the electrocardiogram.

In addition, this process allows the establishment of exact statistics, allowing the visual examination, by the operator, of each cycle detected as pathological by the device.

Other characteristics and advantages of the invention will be better understood on reading the following description of an exemplary embodiment and with reference to the appended drawings in which:

- Figure 1 is an electrocardiogram plot; and

- Figure 2 is a diagram of a processing and display device according to an embodiment of the invention.

The device shown is designed to selectively and simultaneously detect several, for example three different types of pathological complexes appearing in an electrocardiogram recorded over a long period, for example 24 hours, on a patient; this device allows viewing

- 3 2425231 simultaneously and on different screen parts, the sequences comprising these complexes, each screen part being associated with a particular type of complex.

For this purpose, a cassette comprising an electrocardiogram recording on magnetic tape carried out over a long period of time is read at high speed in a cassette player 1 whose motor drives the tape at a speed of approximately 100 times the speed of recording of this tape.

The output signal 1b from reader 1 is applied, after being delayed in a delay device 2, to three random access memories 3, 4, 5 simultaneously; this signal is also applied, but without being delayed, to three discriminators 6, 7, 8 simultaneously. Each discriminator 6, 7, 8 is associated with a random access memory 3, 4, 5 respectively, the content of which is observed on a channel 9, 10, 11 respectively of a display device 12; each discriminator 6, 7, 8 has the function of recognizing a particular type of pathological complex.

When a discriminator 6, 7, 8 detects the type of pathological complex with which it is associated, it gives the memory 3, 4, 5 with which it is associated, an order 13 to record a sequence of the signal coming from the device to delay 2. Three sequences of the cassette playback signal are thus obtained simultaneously on the screen of the display device 12, each sequence appearing on a particular part of the screen, part corresponding to the associated channel 9, 10, 11, each sequence - or signal sample - comprising a pathological complex of the particular type associated with said screen portion.

The display device 12 allows the display of length sequences corresponding to a reading time t of the reader 1; the capacity of each memory 3, 4, 5 is equal to the information content of such a length of sequence and the delay device 2 introduced into the signal from the reader 1, a delay of t / 2; it follows that the pathological complex detected by a discriminator 6, 7, 8 and displayed on the screen of the device 12, is located in the middle of the sequence displayed on this screen.

According to a preferred embodiment of the invention, a first display channel 9 is reserved for samples in which a large difference between two consecutive periods of the electrocardiogram signal 1b is detected; a second channel 10 is reserved for samples in which either a period corresponding to an actual electrocardiogram period greater than two seconds or a pause, that is to say an absence of signal, of actual duration greater than 2, is detected seconds; a third channel 11 is reserved for samples in which a rhythm corresponding to a real rhythm greater than 150 patterns per minute or less than 45 patterns per minute is detected; and a fourth channel 14 displays the curve of the value of the periods £ ^ as a function of time.

For these effects, the discriminator 6 measures each period £ ^ of the signal using the consecutive QRS signals, calculates A p = / p ^ ~ Pi-i / r compares Δρ with a reference threshold value and transmits an order 13 to the memory 3 as soon as Δρ exceeds this threshold; the discriminator 7 also measures each period £ ^ and applies an order 13 to memory 4 as soon as £ ^ 2 sec. ; the discriminator 8 measures each period £ ^, calculates the average value of n £ ^ consecutive ^ being an integer greater than 1, and applies to memory 5 an order 13 to as soon as this average value corresponds to a real value less than 60 / 150 seconds or more than 60/45 seconds; the discriminator 6 also permanently applies to the channel 14 a signal representing the value of each period £ ^ which it measures.

Alternatively, or simultaneously, a discriminator 6, 7 or 8 can be designed to detect on the read signal 1b supplied by the reader 1 a peak corresponding to 1¹ emission of an electrical pulse from a pacemaker worn by the patient; the discriminator 6, 7 or 8 is then arranged to give the memory 3, 4 or 5 with which it is associated, in response to the detection of said peak, an order 13 ·

Alternatively or simultaneously, a discriminator 6, or 8 can be designed to compare the shape of the patterns of signal 1b with a shape of reference, corresponding to a normal electrocardiogram. This discriminator is arranged to apply to the associated memory 3, 4 or 5 a signal 13 when the difference between the shape of a pattern of the signal lb and the reference shape exceeds a predetermined importance. This difference can for example be quantitatively evaluated by measuring the area delimited between the plots of the measured and reference patterns. This shape recognition and this difference measurement can be limited by the discriminator to the QRS wave and / or to the P wave and / or to the T wave of the pattern.

Of course, each discriminator 6, 7 or 8 can be provided with both form recognition means and means for measuring the periods and for comparing these periods in real or average value, with a reference value: it is thus possible to select a pathological complex characterized both by an abnormal value of the period and by an abnormal form of the cycle, for example an enlargement of the QRS signal.

The display device 12 is arranged so that the recording of each sequence remains stable on the screen and does not disappear until the appearance on signal 1b of a new pathological event or complex of the same type, to be replaced by the corresponding new sequence. Centering means are provided so that the wave qrs of the pattern presenting an anomaly is located in the same place on the screen.

The operator can of course stop at any time the scrolling of the magnetic tape in the reader 1, in order to examine a sequence for a longer time and / or to save it on paper.

According to an embodiment of the invention, a diseriminator, for example the diseriminator 6, is designed to supply a stop order 14 to the engine 1a when it detects a highly pathological complex such as a very abnormal widening of the signal QRS or a very abnormally short period or a succession of very short periods (burst of extrasystoles). The operator can at this moment give-or not give to a computer 16 exploiting the signal lb, a validation order 17 allowing the computer 16 to take into account or not to take into account this pathological event for statistical processing such than a histogram.

Instead of a multi-channel display device, a single-channel device provided with a suitable device can be used to allow viewing of the contents of memories 3, 4, 5 in different screen locations, for example, successively receiving the different contents on the display device and adding to the signal from each memory 3, 4, 5, a continuous signal of different level.

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