Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-11-13
2004-06-01
Sykes, Angela D. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06745074
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The invention relates to an implantable heart stimulator set forth in the preamble of the independent claim.
BACKGROUND OF THE INVENTION
The sensitivity is a pacemaker parameter, which determines the lowest amplitude of a heart signal to which the device's sense amplifier will respond. Sensitivity is stated in millivolts. Note that the higher millivolt value, the lower the sensitivity. If, for example, the sensitivity is 6 mV, a signal has to be 6 mV or larger before the signal is recognized; on the other hand, if the sensitivity is 2 mV, a signal only has to be 2 mV or larger before it is recognized. Thus, the lower the mV value, the more sensitive the device.
A ventricular event occurring early in the heart cycle (prior a normally timed QRS-complex) and arising from a focus in the ventricles is often referred to as a premature ventricular contraction (PVC).
If a PVC not is detected due to undersensing it can result in that inappropriately timed, asynchronous or competitive stimulation pulses are delivered. Undersensing is defined as a failure of the pacemaker to sense an electrical signal related to a heart event, e.g. a PVC, due to that the sensitivity of the sensing circuit of the pacemaker is too low. This can often be corrected by programming the pacemaker to a more sensitive setting, i.e. decreasing the value of the sensitivity level.
U.S. Pat. No. 4,513,743 discloses a device , e.g. a cardiac pacemaker, adapted for implantation in a human patient. The implanted device comprises circuitry for registering the occurrence of sensed or evoked events and means for classifying registered events into respective classes of one or more parameters associated with the events. The device is arranged, on demand, to communicate these data to an external device that is arranged to present it in a histogram convenient for further analysis. The purpose of these analyses could be e.g. for making diagnosis, to have a more complete history of the device operation and the patient response thereto and to be able to make a judgement concerning the programming of the device. For a cardiac pacemaker sensed events include e.g. QRS-waves, P-waves and PVCs and examples of parameters include peak QRS-amplitude, peak P-amplitude and A-V interval.
U.S. Pat. No. 5,292,341 discloses a method and a system for determining and automatically adjusting the sensor parameters of a rate responsive pacemaker. A sensor indicated rate (SIR) histogram is established and processed by an external programmer. Instructions are given to a physician to collect diagnostic data from the pacemaker and the patient and the system then calculates a new set of operating parameters that, according to one embodiment, automatically is programmed into the pacemaker. The operating parameters or sensor control parameters are e.g. a threshold parameter, a reaction time parameter and a slope parameter. They all control, in different ways, how the raw sensor signal should be processed.
EP-A-0 321 764 discloses an event detector in which an optimal setting of the detector sensitivity is achieved by passing the input signal through a circuit which measures the signal's maximal values, then establishes the difference between the maximal values and the established threshold, and, in a preferred embodiment, controls the threshold in accordance with the difference and a given desired threshold value.
Many factors influence the characteristics, e.g. the amplitude and the morphology, of the heart signals. These factors could be the use of drugs and the activity and respiration of the patient. The sensitivity settings of the heart signal detectors in an implantable pacemaker is normally done based on the amplitude of the heart signal observed at the time when the programming of the pacemaker is performed at the implantation and at follow-ups. Many of the above-mentioned factors change over time which might result in an inappropriate setting of the sensitivity level of the heart signal detectors.
Another aspect is that it is a lengthy and complicated procedure during follow-up examinations to review and analyze all parameter settings of the pacemaker in order to make appropriate changes.
The main object of the invention is to take changes of amplitude values of the heart signal during a predetermined period of time into account for setting a sensitivity level of a heart signal sensing means of an implantable heart stimulator. In particular to be able to identify PVCs with a peak amplitude below the sensitivity level.
An additional object of the invention is to shorten the time of programming the heart stimulator at follow-up examinations.
SHORT DESCRIPTION OF THE INVENTIVE CONCEPT
These objects are achieved according to a heart stimulator having the characterizing features of the independent claim. Preferred embodiments are set forth in the dependent claims. According to an alternative embodiment is the analysis and determination performed in an extracorporeale programming device.
REFERENCES:
patent: 4513743 (1985-04-01), van Arragon et al.
patent: 5292341 (1994-03-01), Snell
patent: 6539259 (2003-03-01), Weinberg et al.
patent: 0 321 764 (1989-06-01), None
“Elektrokardiografisk mätteknik,” Jacobsson, Medicin och Tecknik, 4thEdition (1995) p. 206.
“Elektriskt test,” Lindgren et al., Pacemakern och hjärtat (1992) pp. 174-175.
Bradford Roderick
Schiff & Hardin LLP
St. Jude Medical AB
Sykes Angela D.
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