Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-05-07
2003-09-16
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
C607S037000
Reexamination Certificate
active
06622046
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to implantable pacemakers and more particularly to subcutaneous electrodes implemented to sense, acquire, and store electrocardiographic data and waveform tracings from an implanted pacemaker. More particularly, the present invention relates to various embodiments including the manufacture and assembly of such electrodes with feedthroughs that facilitate their electrical connection to a pacemaker's circuitry.
BACKGROUND OF THE INVENTION
Electrocardiogram (ECG) signals are commonly used in medicine to determine the status of the electrical conduction system of the human heart. As practiced, an ECG recording device is commonly attached to the patient via ECG leads connected to skin electrodes arrayed on the patient's body so as to achieve a recording that displays the cardiac waveforms in any one of 12 possible vectors.
Since the implantation of the first cardiac pacemaker, implantable IMD technology has advanced with the development of sophisticated, programmable cardiac pacemakers and pacemaker-cardioverter-defibrillator (PCD) arrhythmia control devices designed to detect arrhythmias and dispense appropriate therapies. 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) and the electrogram (EGM). The 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.
The aforementioned ECG systems that use detection and analysis of the PQRST complex are all dependent upon the spatial orientation and number of externally applied electrodes available near or around the heart to detect or sense the cardiac depolarization wave front.
As the functional sophistication and complexity of implantable medical device systems increased over the years, it has become necessary for such systems to include communication means between implanted devices and/or an external device, for example, a programming console, monitoring system, and similar systems. 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 transmit or telemeter a digitized electrical signal to display electrical cardiac activity (e.g., an ECG, EGM, or the like) 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 spite of these advances in the medical device art, the surface ECG has remained a standard diagnostic tool since the very beginning of pacing and remains so today. The twelve-lead electrocardiogram (ECG) is generally the first procedure used to determine cardiac status prior to implanting a pacing system. Thereafter, the physician will typically use an ECG available through the programmer or extra corporeal telemetry transmission to check the pacemaker's efficacy after implantation. Previous ECG tracings are placed into the patient's records for later use in comparing against more recent tracings. It must be noted, however, that current art practice in ECG recording (whether through a direct connection to an ECG recording device or to a pacemaker programmer), involves the use of external ECG electrodes and leads.
Unfortunately, surface ECG electrodes have technical drawbacks. For example, electrocardiogram analysis performed using existing external or body surface ECG systems can be limited by mechanical problems and poor signal quality. Electrodes attached externally to the body are a major source of signal quality problems and errors because of susceptibility to interference such as muscle noise, electromagnetic interference, high frequency communication equipment interference, and baseline shift from respiration, for example. Signal degradation also occurs due to contact problems, ECG waveform artifacts, and patient discomfort. Externally attached electrodes are also subject to motion artifacts from positional changes and the relative displacement between the skin and the electrodes. Furthermore, external electrodes require special skin preparation, for example, application of electrolyte ointment or cream, 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 features for detecting cardiac signals and transforming them into a tracing that is the same as or comparable to tracings obtainable via ECG leads attached to surface (skin) electrodes.
Monitoring electrical activity of the human heart for diagnostic and related medical purposes is well known in the art. For example, U.S. Pat. No. 4,023,565 issued to Ohlsson describes circuitry for recording ECG signals from multiple lead inputs. Similarly, U.S. Pat. No. 4,263,919 issued to Levin, U.S. Pat. No. 4,170,227 issued to Feldman, et al, and U.S. Pat. No. 4,593,702 issued to Kepski, et al, describe multiple electrode systems that combine surface EKG signals for artifact rejection.
The primary application of multiple electrode systems in the prior art appears to be vector cardiography from ECG signals taken from multiple chest and limb electrodes. This is a technique for monitoring the direction of depolarization of the heart including the amplitude of the cardiac depolarization waves. U.S. Pat. No. 4,121,576 issued to Greensite discloses such a system.
Numerous body surface ECG monitoring electrode systems have been implemented in the past to detect the ECG and conduct vector cardiographic studies. For example, U.S. Pat. No. 4,082,086 issued to Page, et al., discloses a four electrode orthogonal array that may be applied to the patient's skin both for convenience and to ensure precise orientation of one electrode with respect to the other. U.S. Pat. No. 3,983,867 issued to Case describes a vector cardiography system employing ECG electrodes disposed on the patient in commonly used locations and a hex axial reference system orthogonal display for displaying ECG signals of voltage versus time generated across sampled bipolar electrode pairs.
U.S. Pat. No. 4,310,000 to Lindemans and U.S. Pat. Nos. 4,729,376 and 4,674,508 to DeCote, incorporated herein by reference, disclose the use of a separate passive sensing reference electrode mounted on the pacemaker connector block or otherwise insulated from the pacemaker case. The passive electrode is implemented to provide a sensing reference electrode that is not part of the stimulation reference electrode and thus does not carry residual after-potentials at its surface following delivery of a stimulation pulse.
Moreover, in regard to subcutaneously implanted EGM electrodes, the aforementioned Lindemans U.S. Pat. No. 4,310,000 discloses one or more reference
Fraley Mary A.
Hoch Ronald F.
Johnstone George
Lessar Joseph F.
Seifried Lynn M.
Layno Carl
Medtronic Inc.
Wolde-Michael Girma
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