Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1999-06-08
2001-04-24
Jastrzab, Jeffrey R. (Department: 3737)
Surgery
Diagnostic testing
Cardiovascular
C607S025000
Reexamination Certificate
active
06223072
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of methods and medical devices for cardiac pacing and for modulating cardiac muscle activity and contractility and more specifically to the field of methods for determining timing of delivery of excitable tissue controller (ETC) signals under a variety of conditions including varying heart rates, paced or sensed triggering and the absence and presence of ETC signals.
BACKGROUND OF THE INVENTION
Excitable tissue controllers (ETCs) are devices which modulate the activity of excitable tissues by application of non-excitatory electrical stimulation to the excitable tissue through suitable electrodes in contact with the tissue. For example, ETC devices may be used, inter alia, to increase or decrease the contractility of cardiac muscle in vitro, in vivo and in situ., as disclosed in detail in PCT application, International Publication Number WO 97/25098 to Ben-Haim et al., titled “ELECTRICAL MUSCLE CONTROLLER”, incorporated herein by reference. Other methods and applications of ETC devices are disclosed in PCT applications commonly-assigned to the assignee of the present application, International Publication Number WO 98/10828, titled “APPARATUS AND METHOD FOR CONTROLLING THE CONTRACTILITY OF MUSCLES” to Ben Haim et al., incorporated herein by reference, International Publication Number WO 98/10829, titled “DRUG-DEVICE COMBINATION FOR CONTROLLING THE CONTRACTILITY OF MUSCLES” to Ben Haim et al., incorporated herein by reference and International Publication Number WO 98/10830, titled “FENCING OF CARDIAC MUSCLES” to Ben Haim et al., incorporated herein by reference, International Publications Number WO 98/10831 to Ben Haim et al., titled “CARDIAC OUTPUT CONTROLLER”, incorporated herein by reference.
Further applications of the ETC including devices combining cardiac pacing and cardiac contractility modulation are disclosed in PCT Application, International Publication No. WO 98/10832, titled “CARDIAC OUTPUT ENHANCED PACEMAKER” to Ben Haim et al., co-assigned to the assignee of the present application. Such ETC devices function by applying non-excitatory electrical field signals of suitable amplitude and waveform, appropriately timed with respect to the heart's intrinsic electrical activity to selected cardiac segments. The contraction of the selected segments can be modulated to increase or decrease the stroke volume of the heart. The timing of the ETC signals must be carefully controlled since application of the ETC signal to the myocardium at inappropriate times may be arrhythmogenic. The ETC signals must therefore be applied to the selected cardiac segment within a defined time interval during which the selected cardiac segment will not be stimulated by the ETC signals.
As disclosed in International Publication No. WO 98/10832, the ETC signals may be timed relative to a trigger signal which is also used as a pacing trigger, or may be timed relative to locally sensed electrogram signals.
U.S. Patent application to Mika et al., Ser. No. 09/276,460, Titled “APPARATUS AND METHOD FOR TIMING THE DELIVERY OF NON-EXCITATORY ETC SIGNALS TO A HEART”, filed Mar. 25, 1999 and assigned to the common assignee of the present application, the entire specification of which is incorporated herein by reference, discloses a method for timing the delivery of non-excitatory ETC signals to a heart using, inter alia, an alert window period for reducing the probability of delivering an improperly timed ETC signal to the heart due to spurious detection of noise or ectopic beats.
The methods of timing of the delivery of ETC signals disclosed hereinabove do not take into account the fact that naturally occurring and pacemaker induced changes in heart rate (HR) may cause changes in the velocity of propagation of the depolarization wave in the myocardium. Additionally, the delivery of the ETC signals to the myocardium may also cause changes in the velocity of propagation of the depolarization wave in the myocardium. Other factors such as, inter alia, various cardio-active drug treatments and myocardial pathological conditions such as ischemia may also cause changes in the velocity of propagation of the depolarization wave in the myocardium. It is therefore desirable to have a method for determining proper timing of the delivery of ETC signals which takes into account variations in velocity of propagation of the depolarization wave in the myocardium under different cardiac conditions.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide apparatus and methods for obtaining data from a heart of a patient. The obtained data is useful for on-line determining of the parameters of a detection time window. The detection time window is used in an ETC device to detect depolarization events for triggering the application of non-excitatory ETC signals to the heart of the patient. The detection time window is also referred to as the “alert time window” or “alert window” hereinafter.
A feature of the present invention is the applying of electrodes to a first cardiac site and a second cardiac site of the patient. The electrodes are operatively connected to a data collection device. In accordance with one preferred embodiment of the present invention the first cardiac site is in or about the right ventricle of the heart and the second cardiac site is in or about the left ventricle of the heart. In accordance with another preferred embodiment of the present invention the first cardiac site is in or about the right atrium of the heart and the second cardiac site is in or about the left ventricle of the heart.
In accordance with a preferred embodiment of the present invention, the device has circuitry adapted for sensing and detecting cardiac depolarization events using one or more of the applied electrodes and for delivering non-excitatory ETC signals to the heart. In accordance with another preferred embodiment of the present invention, the device may also include circuitry for delivering pacing pulses to one or more sites of the patients heart.
Another feature of the present invention is the triggering of a data collection time interval for detecting depolarization events at the second cardiac site. In accordance with one preferred embodiment of the present invention, the data collection time interval is triggered by the detection of a depolarization event at the first cardiac site. In accordance with another preferred embodiment of the present invention, in a device capable of delivering pacing pulses to the heart, the data collection time interval is triggered by the detection of a depolarization event at the first cardiac site or by the delivery of a pacing pulse to the first cardiac site.
The data collection time interval is virtually divided into a plurality of contiguous time bins. All of the time bins have an identical duration which is smaller than the duration of the data collection time interval.
The data collection device includes a memory for storing a plurality of histogram data sets. Each of the histogram data sets is stored in the memory of the device as a separate data structure including a plurality of data elements. Each of the data elements of a histogram data set is associated with a single time bin of the data collection interval. The number of time bins is identical to the number of data elements included in any of the data histogram sets. The value stored in each of the data elements is an integer number representing the cumulative number of depolarization events detected within the time bin associated with the data element at said second cardiac site in a plurality of cardiac beats.
Each of the plurality of the histogram data sets represents a cumulative time distribution histogram of cardiac depolarization events detected at said second cardiac site in a plurality of cardiac beats.
Each histogram data set is associated with a plurality of histogram parameters. The histogram parameters have values indicative of the cardiac conditions common to the plurality of cardiac beats used to o
Belsky Ziv
Mika Yuval
Prutchi David
Routh Andre G.
Cowen, Liebowitz & Latman, P.C.
Dippert William H.
Impulse Dynamics N.V.
Jastrzab Jeffrey R.
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