Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-10-31
2004-04-27
Layno, Carl (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06728576
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to implantable medical devices such as pacemakers and more particularly to a method and apparatus to acquire electrocardiographic data, waveform tracings, and other physiologic data displayable by a programmer from an implantable medical device patient without the need for, or use of, surface (skin) contacting electrodes.
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 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 generate a recording that displays the cardiac waveforms in any one of 12 possible vectors.
The history of the ECG dates back to 1842 when the Italian physicist, Carlo Matteucci discovered that each heartbeat was accompanied by a detectable electric signal. In 1878, two British physiologists, John Burden Sanderson and Frederick Page, determined that the heart signal consisted of, at least, two phases, the QRS (ventricular depolarization) and the repolarization or T-wave. It was not until 1893, however, that Willem Einthoven introduced the term ‘electrocardiogram’ at a meeting of the Dutch Medical Association, although he later disavowed he was the originator of the term.
Einthoven may, however, be called the father of electrocardiography, since he won the Nobel Prize for his achievements in 1924. It was he who finally dissected a heart and named all of the cardiac waveforms (P, Q, R, S, T) that commonly appear on an ECG tracing from a ‘normal’ person.
Einthoven and other medical practitioners of that time were aware of only three vectors (I, II, and III) that are achieved by placement of the ECG electrodes on specific body sites. The remaining nine sites were discovered later in the twentieth century. In 1938, American Heart Association and the Cardiac Society of Great Britain defined the standard positions (I-III) and wiring of the chest leads V1-V6. The ‘V’ stands for voltage. Finally, in 1942, Emanuel Goldberger added the augmented limb leads aVR, aVL and aVF to Einthoven's three limb leads and the six chest leads thereby creating the 12-lead electrocardiogram that is routinely used today for cardiac diagnostic purposes.
Since the implantation of the first cardiac pacemaker, implantable medical device technology has advanced with the development of sophisticated, programmable cardiac pacemakers, pacemaker-cardioverter-defibrillator arrhythmia control devices and drug administration devices designed to detect arrhythmias and apply 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) that currently requires externally attached electrodes and the electrogram (EGM) that requires implanted pacing leads. 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 utilize detection and analysis of the PQRST complex are all dependent upon the spatial orientation and number of electrodes available in or around the heart to pick up the depolarization wave front.
As the functional sophistication and complexity of implantable medical device systems increased over the years, it has become 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 that transmit 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. The surface ECG, in fact, has remained the standard diagnostic tool since the very beginning of pacing and remains so today.
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. Of these, 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 normally use an ECG available through the programmer to check the pacemaker's efficacy after implantation. Such ECG tracings are placed into the patient's records and used for comparison to more recent tracings. 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.
Another possible approach is described in pending applications Ser. No. 09/749,169, Leadless Fully Automatic Pacemaker Follow-Up filed Dec. 27, 2000; Ser. No. 09/696,365, Multilayer Ceramic Electrodes For Sensing Cardiac Depolarization Signals, filed Oct. 25, 2000; Ser. No. 09/697,438, Surround Shroud Connector and Electrode Housings For A Subcutaneous Electrode Array and Leadless ECGs, filed Oct. 26, 2000; Ser. No. 09/703,152, Subcutaneous Spiral Electrode For Sensing Electrical Signals of the Heart, filed Oct. 31, 2000; Ser. No. 09/736,640, Atrial Aware VVI—A Method For Atrial Synchronous Ventricular (VDD/R) Pacing Using the Subcutaneous Electrode Array and a Standard Pacing Lead, filed Dec. 14, 2000; Ser. No. 09/850,331, Subcutaneous Sensing Feedthrough/ Electrode Assembly, filed May 7, 2000; and Ser. No. 09/721,275, System And Method For Deriving a Virtual ECG IR EGM Signal, filed Nov. 22, 2000; whereby a subcutaneous leadless pseudo EKG is sensed from the can of the IMD and transmitted to an external programmer via telemetry. The '169, '365, '438, '152, '640, '331, and '275 applications are incorporated herein by reference in their entireties.
In the art known to the inventors and current practice there are noticeable limitations. 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 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. Su
Thompson David L.
Wilson Suzanne L.
Layno Carl
Medtronic Inc.
Wolde-Michael Girma
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