Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-06-01
2003-04-22
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06553261
ABSTRACT:
The invention concerns a method of signaling an internal status of an implantable cardiac stimulation device, which status is defined by a value of a status parameter, as set forth in the classifying portion of claim
1
. The invention further concerns a cardiac stimulation device as set forth in the classifying portion of claim
10
.
BACKGROUND OF THE ART
Methods and apparatuses for external recognition of the technical status of an implantable cardiac stimulation device are known, which make it possible to take the desired information about the technical status from the stimulation pulses which are delivered by the device. In particular, U.S. Pat. No. 5,899,928 discloses a signaling method in which the item of information to be communicated is encoded as a defined period of time between two successive stimulation pulses. After a measurement value representing a status parameter has been recorded, it is associated by comparison with one of three comparative value intervals. Associated with each of those comparative intervals is a defined pulse spacing in respect of time, of 500, 600 or 700 ms. Delivery of signal pulses of that kind is effected after detection of an external magnetic field. In order to clearly identify a subsequent pulse or a subsequent pulse sequence as signaling pulses, a “synchronization pulse” which is not described in greater detail is previously produced. A disadvantage with that method is that it can only be used when the natural cardiac rhythm is totally nullified by the use of pacemaker therapy. A method of that kind cannot therefore be used in relation to a “demand” pacemaker or cardioverter/defibrillator because in that case stimulation pulses are delivered only in situations in which the status of the heart, which is monitored by a measurement procedure, requires that.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method and a cardiac stimulation device of the kind set forth in the opening part of this specification, which do not suffer from the stated disadvantages.
In terms of a method of the kind set forth in the opening part of this specification, that object is attained by a method of signaling an internal status of an implantable cardiac stimulation device, which status is defined by a value of a status parameter, including the following steps:
a) recording a measurement value representing the status parameter,
b) ascertaining the existence of the status by comparison of the measurement value with a comparative value,
c) measuring the time difference of equal, predetermined phases of two successive, periodically recurring sequences of events, and
d) delivering at least one signal pulse with a predetermined, measurable pulse parameter, if the measurement value corresponds to the comparative value within predetermined limits, wherein the pulse parameter is uniquely associated with the status by the delivery of the signal pulse being effected prior to the next expiry of the measured time difference by a predeterminable period of time uniquely associated with the status.
The method according to the invention provides that the moment in time of delivery of the signal pulse is coupled to a predetermined phase of a periodically recurring sequence of events. The term sequence of events is used to denote a number of events which occur in succession in respect of time. A phase of that sequence of events is defined by a given one of those events. The moment in time at which the phase occurs is the moment in time at which that given event occurs. The spacing in respect of time between the individual events of the sequence of events can vary from one period to another so that the duration of the sequence of events, that is to say of a period, can also be variable each and every time. This is an essential advantage of the method according to the invention: there is no need for coupling of the moment in time of delivery of the signal pulse, to a predetermined period duration. Implementation of the method according to the invention is not bound to predetermined boundary conditions in regard to period duration and can thus be used in a more variable fashion.
The current period duration is measured in the course of implementation of the method with step c) only shortly before delivery of the signal pulse. For that purpose, the time difference of two predetermined, identical phases of successive periods is determined. The later one of those two phases is within the last, completely passed period, prior to delivery of the signal pulse. Determining the moment in time of delivery of the signal pulse relative to the periodic sequence of events is based on the measured moment in time of the last occurrence of the predetermined phase, the measured period duration and the predetermined time displacement.
The predetermined, measurable pulse parameter which serves for signaling purposes is a time displacement in respect of delivery of the signal pulse with respect to the occurrence of the given phase of the periodic sequence of events.
The method is preferably used in relation to an implantable cardiac stimulation device. However, implantation of the device in the human body is neither a partial step in nor a necessary prerequisite for executing the method according to the invention. The method can equally be used in relation to a non-implanted cardiac stimulation device, for example for test purposes in the context of quality control immediately after manufacture or immediately prior to an implantation procedure.
The periodically recurring sequence of events can be internal or external in relation to the implantable cardiac stimulation device. Delivery of the signal pulse can for example be coupled to a periodic clock signal which is an internal signal, that is to say which is produced in the cardiac stimulation device, and the frequency of which is pre-settable, that is to say independent of the duration of a cardiac period. That frequency can also be variable.
In preferred embodiments of the invention the signal pulse is delivered in time relationship with a periodically recurring sequence of events which is external, that is to say which is produced outside the cardiac stimulation device. This involves for example an external ultrasonic pulse which is detected by means of an ultrasonic sensor integrated in the cardiac stimulation device. The ultrasonic sensor produces a pulsed electrical signal corresponding to the ultrasonic pulse. The time difference of equal, predetermined phases of two successive pulses of that electrical signal is measured and used for control in respect of time of the subsequent delivery of the signal pulse.
In a particularly preferred embodiment of the invention the periodically recurring sequence of events is coupled to cardiac activity. The sequence of events can be for example the occurrence of a defined phase of a measurement signal which reflects the time pattern or variation in cardiac activity. In this respect, it is already sufficient if that measurement signal only reflects the onset of a given phase of cardiac activity. In this connection, c) of the method of the invention involves measurement of the time difference of equal, predetermined phases of two successive cardiac periods prior to delivery of the signal pulse. In terms of the implementability of the method according to the invention, it is immaterial whether the cardiac activity is stimulated or natural.
Measurement of the time difference of equal, predetermined phases of two successive cardiac periods is effected here solely to determine the moment in time of the subsequent delivery of the signal pulse, in accordance with step d) of the method. The measurement data obtained are not used to produce a medical diagnosis in respect of cardiac activity, but serve solely for technical purposes.
It will be appreciated however that the measurement data obtained with step c) of the method can be used for diagnostic measures. Such diagnostic measures however are not related to the claimed method which is concerned solely with signaling an internal tech
Biotronik Mess -und Therapiegeraete GmbH & Co. Ingenieurbuero Be
Getzow Scott M.
Grant Stephen L.
Hahn Loeser + Parks LLP
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