Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Patent
1992-05-29
1994-09-27
Cohen, Lee S.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
A61N 100
Patent
active
053504089
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a rate controlled cardiac pacemaker including a component group to adapt a stimulation rate to a patient's momentary physical stress.
2. Background Information
The publication "Biomedizinische Technik (Biomedical Technology), 34 (1989), pages 191-196" discloses a cardiac pacemaker developed for rate-adaptive single and dual chamber stimulation whose rate control is effected on the basis of measuring the low frequency oscillation spectrum as signals characterizing the patient's activity. For this purpose, the signals are limited in level, are amplified in a frequency selective manner and their spectral component is evaluated for the physical stress.
With the aid of a piezoelectric transducer integrated in the pacemaker housing and with a subsequently connected signal processing circuit, the motion values generated by physical stress can be detected and the pacemaker can be optimally physiologically adapted to the patient's given stress state.
However, the signal processing unit connected to the output of the piezoelectric transducer that is integrated in the pacemaker housing requires additional current beyond that required by the other circuit components of the pacemaker.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a cardiac pacemaker which reduces the energy requirement for the pacemaker when the physical activity of the patient is reduced.
This is accomplished in a cardiac pacemaker as defined in the preamble of claim 1 by the features defined in its characterizing portion.
The invention is based on the realization that with reduced activity the components for detecting and adapting the heart rate to this activity can also be operated with reduced energy since the initiation of changes in the heart rate is not required or only very rarely.
The detection of the patient's activity can here be effected either by a sensor that is separate from the sensor for determining physical stress for controlling the heart rate as, for example, by a position sensor for determining the patient's position in space (recumbent or standing) or by the sensor for physical stress itself. In that case, the average frequency of the determination of the momentary stress is preferably raised with the stress so that the adaptation is slower during rest phases.
The component for changing the heart rate may possibly be switched off completely during a rest phase. If the heart rate is determined by way of a sensor for determining the performance capability of the patient, which sensor is separated from the activity sensor, this sensor may also be switched off during a rest phase. In the other case, regular temporary switching in at relatively great time intervals is sufficient.
To determine the rest phase of a patient, a circuit may also be utilized which determines the periodicity of the regular rest phases of the patient and derives a control signal therefrom that causes the energy consumption of the component influencing the pacemaker stimulation rate to be reduced. If necessary, the repetition rate of the temporary switching in of the means for detecting activity may then also be reduced during the regular rest phases.
Other modifications and advantageous features of the invention are defined in the claims, the description below and in the drawings.
In order to prevent the relatively current intensive evaluation program of the subsequently connected signal processing circuit of an activity sensor system from being activated without interruption, a circuit is preferably employed which detects the periodic rhythm of the patient's activity and rest phases and switches the energy supply of the circuit for the activity dependent control of the heart rate to its highest value only during the activity phases. Preferably, this results in an adaptation to a day
ight rhythm (activity and rest phases) for the patient with respect to the connection of the activity sensor system during the patient's day phase and its disconnection durin
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patent: 4856522 (1989-08-01), Hansen
patent: 4860751 (1989-08-01), Callaghan
patent: 4865036 (1989-09-01), Chirife
patent: 4869251 (1989-09-01), Lekholm et al.
patent: 5010893 (1991-04-01), Sholder
patent: 5040536 (1991-08-01), Riff
Biomed. Technik 34(1989), 191-196, "Motion Energy as a Control Variable for ensor-Driven Rate Adaptation," M. Hubmann et al.
Biotronik Mess- und Therapiegerate GmbH & Co. Ingenieurburo Berl
Cohen Lee S.
Parker Marianne
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