Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
1998-03-03
2001-03-27
Evanisko, George R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S018000
Reexamination Certificate
active
06208901
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus for monitoring heart performance and a pacemaker equipped with such an apparatus.
BACKGROUND OF THE INVENTION
Setting the time span between a natural or stimulated atrial action and the stimulation pulse for stimulating a ventricular action, the so-called AV delay, is of considerable significance for the hemodynamic optimization of pacemaker function and in connection with preventing pacemaker-induced tachycardia; see M. Schaldach, Electrotherapy of the Heart—Technical Aspects in Cardiac Pacing, Springer Verlag, Berlin, Heidelberg, 1992, pp. 58-60.
Hence, in recent years, pacemakers have been developed in which the AV delay, which was formerly fixed as a function of parameters that reflect the present state of a particular patient in a particular manner, can be changed. The reference basis is the current heart or stimulation rate, with the AV delay decreasing as the stimulation rate increases—see
FIG. 30
on page 60 of the above-cited document.
EP 0 450 387 A2 describes an arrangement for automatic setting of the AV delay in a dual-chamber pacemaker, taking into consideration (patient-specific) intra-atrial delay times.
EP 0 494 487 A2 describes an AV-sequential, dual-chamber pacemaker having automatic AV delay programming, in which an objective is to consider pacemaker-stipulated, interatrial and interventricular transmission times. In a test phase prior to the actual pacing, the natural heart rate and a natural AV delay—as a temporal difference between either the natural P wave or an atrial pacemaker “spike” and the natural R wave or a ventricular pacemaker “spike” (with all signals being detected via the pacemaker electrodes)—are determined.
Because this arrangement cannot provide normal stimulation during the test phase, a value of the AV delay obtained from several (for example, four) natural cardiac actions constitutes the basis of a subsequent, long-term stimulation phase (for example, 100 pulses). A truly near-time determination and use of a current AV delay for controlling the pacemaker is therefore not possible, so the pacemaker cannot operate hemodynamically optimally with respect to sudden changes in state, such as the onset or cessation of stresses in the patient.
This disadvantage, of course, also affects the known methods of determining the AV transmission time from a surface EKG, echo-cardiographic methods and the like, because these tests cannot be performed on the patient on a daily, permanent basis.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide an apparatus for monitoring heart performance, specifically AV transmission time, and which—particularly in connection with a cardiac pacemaker—is suited for permanent use in the patient. It is an additional object of the invention to provide a pacemaker equipped with such an apparatus.
The invention includes the concept of performing a near-time or real-time determination of the natural AV transmission time on a mechanical basis, utilizing the correlation between characteristic stimulation states of the conductive heart tissue and the respective mechanical state of the heart. The invention utilizes the knowledge that characteristic signals in the surface EKG or corresponding changes in the bundle of His potential that are detected in the recording of an intracardial EKG, and which can be used to determine the AV transmission time, have a mechanical equivalent in the valve movements of the tricuspid valve, in particular, or intracardial pressure fluctuations. It could be determined, in particular, that pressure spikes occur synchronously with the R wave and at the beginning of the P wave.
To suppress interference, an embodiment can advantageously encompass a pressure- or movement-sensor arrangement comprising a plurality of pressure or movement sensors that are disposed in different positions relative to the tricuspid valve, with each sensor having a signal output; and a processing unit having a number of individual signal inputs corresponding to the number of pressure or movement sensors, as well as means for common evaluation of the signals received by the sensors, taking into consideration the respective signal time delay.
With this type of arrangement, a plurality of essentially identical pressure or movement signals can be obtained, the signals being offset in time with respect to one another due to the limited speed of the intracardial pressure propagation. The signals can be used to increase the signal
oise ratio by means of, for example, signal accumulation (following elimination of the time offset) or correlation analysis.
In a useful embodiment, at least one pressure or movement sensor is disposed in the atrium, and at least one is disposed in the ventricle.
An embodiment that serves as an alternative, or supplement, to the aforementioned variation, and has increased suppression of interference, is characterized in that sensor means, which are provided with a signal output for detecting a spontaneous or induced atrial signal, are associated with the processing unit, the signal output being connected to a corresponding signal input of the processing unit. Furthermore, the processing unit includes timing means and switching means for blocking the signal input connected to the pressure- or movement-sensor arrangement in order to preset a time window for detecting the input signals of the pressure- or movement-sensor arrangement. This time window is opened upon the perception of an atrial signal or stimulation, and only remains open for the time span during which the systolic pressure increase is a factor, that is, about 250-300 ms. Pressure fluctuations occurring outside of this time frame, which can only represent interference signals for the provided measurement anyway, are excluded at the outset from any processing.
In an embodiment that is particularly flexible with respect to evaluation options, the processing unit includes means for discriminating movement and pressure components in a signal of a pressure or movement sensor, for example, at least one low-frequency bandpass filter. The design and/or programming of the actual evaluation stages is or are tailored to the respective, specific information content of the course of valve movement or the intracardial changes in pressure that are resolved by movement influences.
The sensor arrangement is advantageously disposed on a cardiac catheter. One of skill in the art can embody the arrangement corresponding to known sensors for intraarterial or intracardial blood-pressure measurement. In an advantageous embodiment, the arrangement has, for example, a sensor, particularly a piezoelectric pressure sensor, that detects the movement or deformation of a pressure-sensor surface on the electrical path, or a sensor that detects this movement or deformation on the optical path, particularly through the diversion or changing of the transmission of a light bundle that is directed at the surface and transmitted via fiber optics to the measurement site. In an arrangement having a plurality of pressure sensors, a plurality of pressure-sensing surfaces that are formed or connected by jacket-surface segments of the cardiac catheter that are separated by one another are disposed on the cardiac catheter.
To ensure a detection of pressure or movement without the influence of wall contacts, the cardiac catheter is constructed with a bending resistance and, possibly, is provided with a preset curvature over its length such that it can be positioned, exposed, in the atrium and/or the ventricle essentially without contact between the pressure-sensor surfaces and the inside walls of the heart.
To determine the AV delay with respect to a detected, natural atrial signal, at least one electrode should be provided in the atrium for receiving a cardiac-action potential. The electrode is connected to a corresponding signal input of the processing unit, and the processing unit includes means for determining the time interval between a signal that has been derived from the cardiac-action pote
Biotronik Mess-und Therapiegeraete GmbH & Co. Ingenieurbuero Ber
Evanisko George R.
Kinberg Robert
Spencer George H.
Venable
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