Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2001-03-14
2003-09-02
Wolfe, Willis R. (Department: 3747)
Surgery
Diagnostic testing
Cardiovascular
C600S517000
Reexamination Certificate
active
06615075
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electrocardiographic localization and classification of cardiac arrhythmias. More particularly, the present invention relates to noninvasive analysis of TU wave obscured atrial activity.
BACKGROUND ART
An arrhythmia is any deviation from or disturbance of the normal heart rhythm. This is when the heart's natural pacemaker develops an abnormal rate or rhythm (e.g. a tachycardia where the heart rate is faster than normal), the normal conduction pathway is interrupted, an abnormal or accessory conduction pathway controls the rhythm, or when another part of the heart takes over as an ectopic pacemaker. Arrhythmias may be benign, life threatening or even fatal depending on the type of arrhythmia. Several different types of arrhythmias can be distinguished, for example atrial tachycardia, atrioventricular (AV) node reentrant tachycardia, atrial fibrillation, atrial flutter, and ventricular tachycardia.
Although electrocardiographic arrhythmia evaluation is currently feasible by capturing spontaneous tachycardia episodes via ambulatory or emergency electrocardiogram (ECG) recording, analysis of the timing and presumed origin of atrial activation on the body surface is frequently hampered by the simultaneous occurrence of the higher voltage ventricular activation or recovery potentials. During both focal and incisional reentrant atrial tachycardia, the low-amplitude P wave (atrial activity) may be obscured by the preceding high-amplitude QRST segment (ventricular activity). Difficulties are encountered when visually assessing the P wave morphology of TU wave superimposed ectopic atrial beats that are critically related to atrial fibrillation triggered by a focal source, typically situated in one of the pulmonary veins. Similarly, localization of the atrial insertion site using the retrograde P wave morphology obtained during orthodromic AV reentrant tachycardia may be difficult due to partial or complete concealment by the TU wave.
The ability to completely isolate the P wave from a preceding cardiac cycle is particularly relevant with regard to recent reports describing the role of focal triggers in the initiation of atrial fibrillation (e.g. Haissaguerre, M. et al. (1998)
Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins, N. Engl. J. Med.
339:659-666). Localized adequately, these focal triggers are amenable to treatment and cure using radiofrequency catheter ablation. However, mapping of the premature beats that cause the initiation of atrial fibrillation using standard catheter techniques is cumbersome, lengthy, and unpredictable. Therefore, noninvasive electrocardiographic localization of these atrial premature beats before or during the invasive mapping procedure is highly preferable. However, since the P wave of these atrial premature beats is usually obscured by the preceding TU wave, application of a QRST subtraction algorithm to isolate and preserve the detailed P wave morphology is of critical importance to enable ECG-based trigger localization. However, to date no such algorithms exist that are capable of isolating and preserving the detailed P wave morphology.
So far, most people use QRST subtraction algorithms to detect P waves, fibrillation waves, or flutter waves by either a frequency analysis (e.g. U.S. Pat. No. 6,064,906), morphological filters (e.g. Sedaaghi, M. H. (1998),
ECG wave detection using morphological filters, Appl. Sign. Process.
5:182-194), suppression and cross correlation techniques (e.g. U.S. Pat. No. 5,840,038), or an impulse correlated adaptive filter (e.g. Zhu Y. S. and Thakor N. V. P (1987),
P-wave detection by an adaptive QRST cancellation technique, In: Computers in Cardiology
; Eds. Ripley K. L.,
IEEE Comput. Soc. Press,
Washington, D.C., pp. 249:252). A previously reported method on QRST algorithms employs additional measures to correct for rate-related differences in QRST duration (e.g. Slocum J. et al. (1992),
Diagnosis of atrial fibrillation from surface electrocardiograms based on computer-detected atrial activity, J. Electrocardiol.
25:1-8). In addition, in previous reports and methods, the design of the QRST templates was done on the same data set that was subsequently subjected to QRST removal. In that case, the presence of AV dissociation was considered imperative to ensure that atrial activity would be preserved in the remaining signal after QRST subtraction.
Although, most of the before mentioned methods work well for P wave or fibrillation wave detection, they do not provide the ability to retain important spatial and temporal details regarding the specific morphology of the atrial activity. There is therefore a strong need for an improved clinical tool to achieve adequate isolation of TU wave superimposed atrial activity so that noninvasive electrocardiographic screening, localization and analysis of atrial arrhythmias can be carried out more effectively before or during an invasive electrophysiologic intervention.
OBJECTIVES AND ADVANTAGES
In light of the above, it is the primary objective of the present invention to provide an apparatus and method for electrocardiographically localizing and classifying atrial arrhythmias. More specifically, it is the objective of the present invention to provide a noninvasive apparatus and method for analysis of TU wave obscured atrial activity.
It is another objective of the present invention to provide an automatic QRST subtraction algorithm based on using an adaptive QRST template constructed from averaged QRST complexes combined with ECG recordings to enable discrete isolation of TU wave obscured ectopic atrial activity on the surface ECG while retaining the intricate spatial and temporal details in P wave morphology.
It is yet another objective of the present invention to obtain an optimal morphology subtraction performance in the TU wave range by correcting specifically for differences in both the QRST duration and voltage of the T wave.
It is still another objective of the present invention to provide a QRST template design based on a separate data set obtained during sinus rhythm and/or atrial pacing to ensure that atrial and ventricular activity are clearly separated.
It is still another objective of the present invention to provide for an optimal visualization of the P wave morphology in both supraventricular arrhythmias (i.e. atrial tachycardia and orthodromic AV reentrant tachycardia) and focal atrial ectopy where atrial activity coincides with ventricular recovery of the preceding cardiac cycle.
It is another objective of the present invention to isolate P waves from the superimposed TU wave during AV associated rhythms other than atrial ectopy (e.g. flutter waves in atrial flutter).
It is another objective of the present invention to isolate fibrillation waves during atrial fibrillation and to provide a clinical tool to achieve noninvasive localization of the triggers that initiate atrial fibrillation.
It is another objective of the present invention to enable the application of analyzing atrial arrhythmias, when atrial depolarization is obscured by the preceding ventricular repolarization.
It is another objective of the present invention to provide a tool that is used to develop and apply a database for classification of atrial arrhythmias.
The advantage of the present invention over the prior art is that it provides for a QRST subtraction algorithm based on using an adaptive QRST template while retaining the intricate spatial and temporal detail in atrial activity morphology, including P waves, fibrillation waves and flutter waves.
SUMMARY
The present invention provides an apparatus and method for localizing and classifying atrial arrhythmias. More specifically, the present invention provides a noninvasive apparatus and method for analysis of TU wave obscured atrial activity. The present invention includes an apparatus and method to isolate atrial activity wherein atrial activity is commonly known as, but not limited to: (1) a P wave in case of focal atrial fibr
Groenewegen Arne Sippens
Lesh Michael D.
Mlynash Michael D.
Lumen Intellectual Property Services Inc.
The Regents of the University of California
Wolfe Willis R.
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