Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1999-06-23
2001-06-12
Getzow, Scott M. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06246910
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to “active implantable medical devices” as defined, for example, by the Jun. 20, 1990 Directive 90/385/CEE of the Council of the European Communities, including but not limited to pacemaker devices, defibrillators and/or cardiovertors which are able to deliver to the heart electric pulses of low energy for the treatment of heart rate disorders. It more particularly relates to devices having an operation controlled by a sensed parameter using an appropriate sensor, such as rate responsive devices.
BACKGROUND OF THE INVENTION
There are active implantable medical devices which are known to adapt their actions, for example, the stimulation frequency, to a measured or calculated value of a parameter that is representative of the metabolic needs of the person in which the device is implanted. One sensor which is generally used to measure such a parameter is the so-called minute volume or minute ventilation sensor (often called “sensor MV” or “sensor VE”).
EP-A-0 804 939 describes a pacemaker in which the signals delivered by a minute ventilation sensor are used in addition to a control function, to diagnose the decompensation (i.e., the deterioration or worsening) of the cardiac insufficiency and to cause a modification of the programming of the pacemaker.
One problem with this device is that it presents the disadvantage of not taking into account the real level of activity of the patient. Indeed, it is known that persons with cardiac insufficiency have a deteriorated ventilatory function because of their pathology. As a result, these patients will present, during an effort level of activity (i.e., a level of activity above rest), an oxygen consumption (VO
2
) which is lower than that of healthy patients; on the other hand, the heart rate and minute ventilation of these patients will increase significantly more than is the case for healthy patients, for the same level of activity.
Thus, a relative or absolute variation in time of the signals detected by the minute ventilation sensor, or in a more general way, by a different physiological sensor which is provided to give an adequate representation of the metabolic needs of the patient, can be due to cardiac insufficiency or to a simple change of the activity level of the patient.
It also has been proposed, for example, in EP-A-0 750 920 and its corresponding U.S. Pat. No. 5,722,996 (commonly assigned to the assignee of this application, ELA Méedical, Montrouge, France) to combine the information delivered by two sensors, one physiological (typically a minute ventilation sensor), the other of physical activity (typically an accelerometer, often called “sensor G”). The two sensors operate a so-called “cross monitoring” of their respective indications, and the pacemaker combines the information from the two sensors as described therein to control the heart rate. However, this device also does not take into account the evolution over the long term of the pathology of the patient, who can present greater or lesser cardiac decompensation over time.
This pathology can indeed evolve according to various factors such as the effectiveness of cardiac stimulation, the effectiveness of the drugs delivered, or the food, or the presence of atrial and/or ventricular arrhythmias.
OBJECTS AND SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to propose a pacemaker which is able to follow the evolution of the patient over the course of time so as to give an adequate representation of the patient's real metabolic needs. In the event of an aggravation of or an improvement in the patient's condition, the pacemaker will then be able advantageously to modify its operation, for example, by reprogramming one or more of its functions. This reprogramming can be automatic or physician initiated.
One aspect of the invention is directed to a device of the type with two parameter sensors, e.g., comprising at least one sensor of effort, measuring a parameter which is predominantly physiological and delivering an output signal which is a function of the effort developed by a patient wearing the device, and at least one sensor of activity, measuring a parameter which is predominantly physical, and having an output signal which is a function of the patient's activity level. Such a device is described in the aforementioned EP-A-0 750 920 (U.S. Pat. No. 5,722,996), the disclosure of which is hereby incorporated hereinby by reference in its entirety.
In accordance with this aspect of the invention, this device also includes a processing means for analyzing the acquired effort and activity related data to evaluate the evolution over time of the patient's effort and activity levels. In one embodiment, the analysis means operates: (a) to measure periodically using the two sensors “couples of values” corresponding to a level of effort/activity developed by the patient, (b) to establish a characteristic function of the couples of values thus measured, and (c) to evaluate the evolution over the course of time of this established characteristic. Preferably, the evolution is evaluated by seeking a possible increase in the signals delivered by the effort sensor as compared to the signals delivered by the activity sensor.
Very advantageously, the analysis means also operates: (d) to modify the programming of the device when the results of the subpart (c) evaluation indicate an increase in the signals delivered by the effort sensor beyond a given threshold compared to the signals delivered by the activity sensor.
The present invention is particularly applicable to a device including the functionality of a pacemaker of the “multisite” type, i.e., in which electrodes are placed in a plurality of distinct myocardial stimulation sites, and the control of the stimulation and/or the configuration of the stimulation sites are modified when the results of the evaluation indicate an increase beyond a given threshold in the output signals delivered by the effort sensor as compared to the output signals of the activity sensor.
In one embodiment, the analysis means can evaluate the shift of the established characteristic in the direction of increasing effort, or evaluate the increase in an effort/activity slope of the established characteristic. Optionally, this evaluation can be operated regularly, i.e., at periodic intervals (typically, daily or every selected number of cardiac cycles).
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patent: 5003975 (1991-04-01), Hafelfinger et al.
patent: 5154170 (1992-10-01), Bennett et al.
patent: 5330505 (1994-07-01), Cohen
patent: 5423869 (1995-06-01), Poore et al.
patent: 5476485 (1995-12-01), Weinberg et al.
patent: 5562711 (1996-10-01), Yerich et al.
patent: 0 654 285 (1985-05-01), None
patent: 0 804 939 (1997-11-01), None
Bonnet Jean-Luc
Limousin Marcel
ELA Medical S.A.
Getzow Scott M.
Orrick Herrington & Sutcliffe LLP
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