Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-08-07
2002-09-03
Schaetzle, Kennedy (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
C607S027000
Reexamination Certificate
active
06445946
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of German patent application number 199 38 376.6, filed Aug. 6, 1999.
BACKGROUND OF THE INVENTION
The invention concerns a cardiological apparatus having a sensor for picking up electrical signals from the heart and signal processing means which are connected to the sensor and which are adapted to process signals received from the sensor and include pre-processing means.
The state of the art discloses apparatuses which are used either for detecting spontaneous excitations of the heart or for detecting stimulated excitations of the heart, which are triggered by an electrical stimulus.
Those known apparatuses are based on the aspect that the variation in respect of time of that electrical signal of the heart, which accompanies the progress of the excitation, contains typical features which make it possible to arrive at a distinction between spontaneous excitations and stimulated excitations.
Electrical cardiac pacemakers of different embodiments serve for stimulation of the heart in situations in which either there is a disturbance to the physiological occurrence and/or propagation of the excitation or therapeutic considerations indicate the stimulation of excitations. The operational control for providing for control in respect of time of the electrical cardiac pacemaker must be capable of recognizing whether and when a spontaneous excitation occurs. In particular the situation is not to entail any adverse effect on the pump action of the heart, which is produced by the excitation, due to a stimulation which occurs at the wrong time.
In the heart the location of spontaneous excitation formation and the location where spontaneous excitation formation is detected by measurement procedures are separated in respect of space. Usually ventricular pacemaker electrodes are implanted in the tip of the ventricle. Ventricular contractions which are triggered by a pacemaker due to electrical stimulation in the tip of the ventricle are propagated in an excitation front which moves from the tip of the ventricle over the entire periphery of the ventricle in the direction of the AV-node of a heart. Ventricular contractions of the ventricle, which are triggered by the heart itself, in contrast originate from the sinus node in the atrium of the heart and are transmitted into the ventricle by way of the AV-node. That means that, in the event of a contraction caused by the heart itself, the ventricular excitation front is triggered by the AV-node and moves in the direction of the tip of the ventricle. Accordingly, at the pacemaker electrode which is placed there, it can also be detected only relatively late after the commencement of its occurrence, namely after the expiry of the so-called latency time. As an excitation is propagated in the heart at relatively low speed, it can happen that electrical stimulation occurs although spontaneous excitation has already taken place, as the spontaneous excitation had not yet occurred at that time at which electrical stimulation was triggered. In that case, two excitation fronts move towards each other, one starting from the location of spontaneous excitation and the other from the location of electrical stimulation. Excitation of a part of the cardiac tissue is effected by spontaneous excitation, while excitation of the other part of the cardiac tissue is effected by electrical stimulation. Such events are referred to as fusion events. Fusion events can influence the electrophysiological co-ordination which forms the basis for the pump action of the heart, and therewith the mechanical processes involved and therewith the pump output and efficiency.
SUMMARY OF THE INVENTION
The object of the present invention is to detect fusion events of that kind.
In accordance with the invention that object is attained by an apparatus of the kind set forth in the opening part of this specification, the signal processing means of which include:
a reference time generator (
8
) which is adapted to output a time signal upon the occurrence of a periodically recurring signal feature,
averaging means (
11
,
12
,
21
,
22
,
6
) which are adapted to form a signal portion which is averaged over a plurality of signal portions between each two time signals, and are connected to the pre-processing means (
2
,
3
,
4
) and the reference time generator (
8
),
an average store (
7
) which is adapted to store the average values and which is connected to the averaging means, and
parameter determining means (
9
) which are connected to the pre-processing means (
2
,
3
,
4
) and the average store and which are adapted to ascertain a parameter characterizing a signal portion.
Advantageous alternative configurations are optionally distinguished by the following features:
the parameter determining means are adapted to derive the parameter from the respective signal portion last detected by the sensor;
the parameter determining means are adapted to derive the parameter from the averaged signal portion;
the signal processing means include comparison means which are connected to the parameter determining means and a limit value store for comparing the derived parameter and a limit value stored in the limit value store and are adapted to output a fusion signal;
the signal processing means include scatter value determining means which are adapted to output a scatter value for time-successive signals and which are connected to the pre-processing means;
the scatter value determining means are connected to the average value store;
the signal processing means additionally include limit value determining means which are adapted to determine the limit value from the scatter values and are connected to the scatter value determining means and to a limit value store. In that respect the limit value store can be an integral component of the limit value determining means;
the pre-processing means include an instantaneous signal store for the respective signal portion last detected by the sensor. In that case the units connected downstream of the signal pre-processing operation access the instantaneous signal store of the pre-processing means for the parameter-determining operation and for the averaging operation and also for the scatter value-determining operation;
the signal processing means include inhibitor means which are adapted to suppress such signal portions for further signal processing, for which comparison means output a fusion signal. Signals as a result of fusion events are therefore not taken into consideration for the averaging operation and for the scatter value-determining operation; and
the inhibitor means are such that they erase the instantaneous signal store when a fusion signal occurs.
The invention embraces the technical teaching that, upon the detection of a fusion event, such relationships must also be taken into account, which go beyond direct association with the mechanical efficiency and output of the heart. In particular the invention takes into consideration the secure knowledge that individual particularities such as the shape and size of the heart, the measurement location for any spontaneous depolarization which may possibly occur and pathophysiological disturbances can have an effect on loss of the measurements signal.
The invention is also based on the realization that signals which occur in succession in a biological system never have precisely the same fine signal structure but may involve certain deviations, the cause of which does not exclusively have to be the occurrence of a fusion event.
The signals which are used to detect fusion events are electrical signals which are obtained in known manner with a sensor which is conductively connected to an apparatus suitable for pre-processing and further processing of those signals. The pre-processing operation, for example amplification and frequency-determining filtering to remove signal components which are not information-relevant in the sense of detecting a fusion event can be effected in a manner in accordance with the state of the art. Some of
Biotronik Mess-und Therapiegerate GmbH & Co. Ingenieurburo Berli
Christie Parker & Hale LLP
Droesch Kristen
Schaetzle Kennedy
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