News Column

Patent Issued for Methods for Promoting Intrinsic Activation in Single Chamber Implantable Cardiac Pacing Systems

June 30, 2014

By a News Reporter-Staff News Editor at Cardiovascular Week -- A patent by the inventors Demmer, Wade M (Coon Rapids, MN); Kleckner, Karen J (New Brighton, MN); Belk, Paul A (Maple Grove, MN), filed on July 1, 2013, was published online on June 17, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also Medtronic, Inc.).

Patent number 8755884 is assigned to Medtronic, Inc. (Minneapolis, MN).

The following quote was obtained by the news editors from the background information supplied by the inventors: "The traditional implantable cardiac pacemaker includes a pulse generator device to which one or more flexible elongate lead wires are coupled. The device is typically implanted in a subcutaneous pocket, remote from the heart, and each of the one or more lead wires extends therefrom to a corresponding electrode, coupled thereto and positioned at a pacing site, either endocardial or epicardial. Mechanical complications and/or MRI compatibility issues, which are sometimes associated with elongate lead wires and well known to those skilled in the art, have motivated the development of cardiac pacing systems that are wholly contained within a relatively compact package for implant in close proximity to the pacing site, for example, within the right ventricle (RV) of the heart. With reference to FIGS. 1A-B, such a system 100 is illustrated, wherein pace/sense electrodes 111, 112 are formed on an exterior surface of a capsule 101 that hermetically contains a pulse generator 103 (shown in FIG. 1B via a block diagram). FIG. 1A further illustrates tine members 115 mounted to an end of capsule 101, in proximity to electrode 111, in order to secure electrode 111 against the endocardial surface of RV, and electrode 112 offset distally from electrode 111. Capsule 101 is preferably formed from a biocompatible and biostable metal such as titanium overlaid with an insulative layer, for example, medical grade polyurethane or silicone, except where electrode 112 is formed as an exposed portion of capsule 101. An hermetic feedthrough assembly (not shown), such as any known to those skilled in the art, couples electrode 111 to pulse generator 103 contained within capsule 103.

"With further reference to FIGS. 1A-B, those skilled in the art will appreciate that system 100, via electrodes 111, 112, has the capability to sense intrinsic ventricular depolarization (i.e. R-waves) and, in the absence of the intrinsic depolarization, to apply stimulation pulses to the RV in order to create paced ventricular depolarization. Pulse generator 103 of system 100 further includes rate response sensor 135 that monitors a patient's general level of physical activity to determine an appropriate pacing rate for the patient. Examples of suitable rate response sensors include, without limitation, a force transducing sensor, such as a piezoelectric crystal like that described in commonly assigned U.S. Pat. No. 4,428,378 Anderson et al.; an AC or DC accelerometer like those described in commonly assigned U.S. Pat. No. 5,957,957 to Sheldon; and any type of physiological sensor known in the art, such as those that measure minute ventilation, QT intervals, blood pressure, blood pH, blood temperature, blood oxygen saturation etc. Numerous cardiac pacing methods that employ such RV pacing and sensing and physical activity monitoring are known in the art, for example, as disclosed in commonly assigned U.S. Pat. No. 4,428,378 (to Anderson et al.), U.S. Pat. No. 6,772,005 (to Casavant et al.), and U.S. Pat. No. 5,522,859 (to Stroebel et al.), as well as U.S. Pat. No. 5,374,281 (to Kristall et al.) and U.S. Pat. No. 6,122,546 (to Sholder et al.). Many of the aforementioned disclosures address the desire to limit the amount of pacing stimulation delivered from implantable pacemakers, particularly right ventricular stimulation in patients that have intact AV conduction (through the AV node, from the sinus node in the right atrial wall to the right and left bundle branches in the ventricular septum), in order to preserve the patient's natural conduction and increase pacemaker efficiency. However, the relatively more sophisticated pacing methods that are geared toward preserving the patient's natural conduction rely upon dual chamber sensing as these methods were developed in concert with the evolution of pacemaker systems from single chamber to dual chamber. Thus, there is a need for new cardiac pacing methods that preserve natural conduction and increase system efficiency for single chamber implantable pacing systems, of either the traditional type or the relatively compact type, like that shown in FIGS. 1A-B."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventors' summary information for this patent: "Embodiments of the present invention include single chamber pacing systems that employ the methods disclosed. According to some methods of the present invention, an offset rate for pacing is established according to a predetermined decrement of either a baseline rate or a greater of the baseline rate and an intrinsic rate, wherein the baseline rate is established according to input from one or more rate response sensors. Pacing stimulation is applied when necessary to maintain the offset rate (for example, as determined via sensing for intrinsic ventricular depolarization), until x of y successive events (x>1 and y.gtoreq.x) are paced events, at which time the offset rate is switched to the baseline rate and pacing stimulation at the baseline rate is applied over a predetermined period of time. According to some methods, the predetermined period of time may be shortened in response to the detection of intrinsic events occurring at a rate greater than the baseline rate. At the end of the predetermined period of time, sensing for intrinsic events resumes, and, according to some preferred methods, if an intrinsic event is not immediately detected, within the time interval necessary to at least maintain the offset rate, the rate is switched back to the baseline rate for pacing over an increased period of time.

"According to some preferred methods, the predetermined decrement may be increased to establish an even lower offset rate, when a preference rate is established in between the baseline and offset rates. The establishment of the preference rate is associated with inclusion of another switching criterion in addition to the aforementioned x of y criterion. When the preference rate is employed, a switch from the offset rate to the baseline rate occurs, even if the aforementioned x of y criterion is not met, when successive intrinsic events meet another predetermined criterion with respect to the preference rate, for example, when a detected measure of central tendency for successive intrinsic events, over a predetermined interval, falls below the preference rate."

URL and more information on this patent, see: Demmer, Wade M; Kleckner, Karen J; Belk, Paul A. Methods for Promoting Intrinsic Activation in Single Chamber Implantable Cardiac Pacing Systems. U.S. Patent Number 8755884, filed July 1, 2013, and published online on June 17, 2014. Patent URL:

Keywords for this news article include: Cardiology, Pacemakers, Pacing System, Medtronic Inc., Medical Devices.

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Source: Cardiovascular Week

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