Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2000-12-27
2003-06-24
Wolfe, Willis R. (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S032000, C607S060000
Reexamination Certificate
active
06584352
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sensing of cardiac activity via electrocardiographic (ECG) data. In particular, this invention relates to a new and improved method of gathering ECG data and to the transmission of the collected data to a remote location for analysis. Alternatively, such ECG data may also be transmitted to a co-implanted device to provide data for the delivery of various therapies including pacing, cardioversion and defibrillation therapies, drug delivery, to effect capture detection and automatic stimulation threshold adaptation, to record PMT (pacemaker mediated tachycardia) episodes, to measure refractory periods, to set timing windows for anti-tachycardia pacing therapies, and to adjust the pacing rate to physiologic demand.
BACKGROUND OF THE INVENTION
The electrocardiogram (ECG) is commonly used in medicine to determine the status of the electrical conduction system of the human heart. As currently practiced, the ECG recording device is commonly attached to the patient via ECG leads connected to pads arrayed on the patient's body so as to achieve a recording that displays the cardiac waveforms in any one of 12 possible vectors.
The detection and discrimination between various arrhythmic episodes in order to trigger the delivery of an appropriate therapy is of considerable interest. Prescription for implantation and programming of the implanted device are based on the analysis of the PQRST electrocardiogram (ECG) that currently requires externally attached electrodes and the electrogram (EGM) that requires implanted pacing leads. The EGM waveforms are usually separated for such analysis into the P-wave and R-wave in systems that are designed to detect the depolarization of the atrium and ventricle respectively. Such systems employ detection of the occurrence of the P-wave and R-wave, analysis of the rate, regularity, and onset of variations in the rate of recurrence of the P-wave and R-wave, the morphology of the P-wave and R-wave and the direction of propagation of the depolarization represented by the P-wave and R-wave in the heart. The detection, analysis and storage of such EGM data within implanted medical devices are well known in the art. Acquisition and use of ECG tracing(s), on the other hand, has generally been limited to the use of an external ECG recording machine attached to the patient via surface electrodes of one sort or another.
Recently, however, an alternative method of collecting ECG tracings from a set of subcutaneous electrodes, or a subcutaneous electrode array (SEA), has been described in the following patents or patent applications. U.S. Pat. No. 5,331,966 to Bennett, incorporated herein by reference, discloses a method and apparatus for providing an enhanced capability of detecting and gathering electrical cardiac signals via an array of relatively closely spaced subcutaneous electrodes (located on the body of an implanted device).
More recently, a patent application entitled “
Surround Shroud Connector and Electrode Housings for a Subcutaneous Electrode Array and Leadless ECGs
”, by Ceballos, et al., filed on Oct. 26, 2000, Ser. No. 09/697,438, incorporated herein by reference in its totality, discloses an alternate method and apparatus for detecting electrical cardiac signals via an array of subcutaneous electrodes located on a shroud circumferentially placed on the perimeter of an implanted pacemaker. Similarly, a patent application entitled “
Subcutaneous Electrode for Sensing Electrical Signals of the Heart
”, by Brabec et al, filed Oct. 31, 2000, Ser. No. 09/703,152, incorporated herein by reference in its totality, discloses the use of a spiral electrode using in conjunction with the shroud described in the Ceballos et al disclosure. In addition, two applications, entitled “
Multilayer Ceramic Electrodes for Sensing Cardiac Depolarization Signals
”, by Guck et al, filed Oct. 25, 2000, Ser. No. 09/696,365 and P-8787
“Thin Film electrodes for Sensing Cardiac Depolarization Signals
” by Guck and Donders, filed Dec. 13, 2000, Ser. No. as yet unknown, both incorporated herein by reference in their totality, disclosed the use of sensing electrodes placed into recesses incorporated along and into the peripheral edge of the implantable pacemaker. Finally, the submission entitled, “
Subcutaneous Electrode Array Virtual ECG Lead
” by Panken and Reinke, filed Nov. 22, 2000, Ser. No. 09/721,275, also incorporated by reference to its entirety, describes the algorithm used by the implanted device that compiles the ECG from any two subcutaneous electrodes found in the SEA.
As the functional sophistication and complexity of implantable medical device systems increased over the years, it became increasingly more important for such systems to include a system for facilitating communication between one implanted device and another implanted device and/or an external device, for example, a programming console, monitoring system, or the like. For diagnostic purposes, it is desirable that the implanted device be able to communicate information regarding the device's operational status and the patient's condition to the physician or clinician. State of the art implantable devices are available which can even transmit a digitized electrical signal to display electrical cardiac activity (e.g., an ECG, EGM, or the like), programmed pacing parameters, therapy status, etc. for storage and/or analysis by an external device.
To diagnose and measure cardiac events, the cardiologist has several tools from which to choose. Such tools include twelve-lead electrocardiograms, exercise stress electrocardiograms, Holter monitoring, radioisotope imaging, coronary angiography, myocardial biopsy, and blood serum enzyme tests. In addition, a record of the programmed parameters, the status of atrial and ventricular auto-capture, the atrial and ventricular sensing threshold, and other such pacing system parameters are required for an adequate diagnosis. Such ECG tracings and printed reports are placed into the patient's records and used for comparison to more recent tracings and reports. It must be noted, however, that whenever an ECG recording is required (whether through a direct connection to an ECG recording device or to a pacemaker programmer), external electrodes and leads must be used. Moreover, the acquisition of programmed data and pacing therapy status requires the use of a programming system that is in immediate proximity to the patient.
Unfortunately, surface ECG electrodes have some serious drawbacks. For example, electrocardiogram analysis performed using existing external or body surface ECG systems is likely to be limited by mechanical problems and poor signal quality. Electrodes attached externally to the body are a major source of signal quality problems and analysis errors because of susceptibility to interference such as muscle noise, power line interference, high frequency communication equipment interference, and baseline shift from respiration or motion. Signal degradation also occurs due to contact problems, ECG waveform artifacts, and patient discomfort. Externally attached electrodes are subject to motion artifacts from positional changes and the relative displacement between the skin and the electrodes. Furthermore, external electrodes require special skin preparation to ensure adequate electrical contact. Such preparation, along with positioning the electrode and attachment of the ECG lead to the electrode needlessly prolongs the pacemaker follow-up session. One possible approach is to equip the implanted pacemaker with the ability to detect cardiac signals, transform them into a tracing, and transmit them to a remote receiving device such as a programmer, transtelephonic pacemaker monitoring system, or a central database system. Once captured, these ECG tracing could be available for use by medical personnel for analysis and diagnosis.
Similarly, it is often difficult if not impossible to have a programming unit nearby to gain a visual or printed report or all the various programmed parameters and the
Berg Gary
Combs William J.
Medtronic Inc.
Wolde-Michael Girma
Wolfe Willis R.
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