Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
2000-05-25
2004-03-02
Jastrzab, Jeffrey R. (Department: 3762)
Surgery
Diagnostic testing
Cardiovascular
Reexamination Certificate
active
06701182
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an apparatus for analyzing a physiological waveform, and particularly to a medical device for acquiring, analyzing and selecting a multi-lead electrocardiogram.
Electronic medical devices are used to acquire, record and manipulate a variety of different data with the purpose of analyzing a patient's health. An electrocardiogram (ECG) is one example of data that is acquired, recorded and manipulated using an electronic medical device. The ECG is a valuable record of the electrical impulses stimulating a patient's heart and is used to analyze the patient's health. An example where an ECG is important is when a patient performs an exercise test. The ECG can be used to, among other things, calculate a patient's heart rate or determine if the patient has an arrhythmia.
SUMMARY OF THE INVENTION
During an exercise test, one or more patient monitors are connected to a patient to record physiological information generated by the patient. One particularly important measurement obtained is an ECG, i.e., a representation of the electrical impulses generated by the patient's heart. A plurality of electrodes (e.g., 10 electrodes) are placed on the patient (e.g., in a standard 12-lead electrode placement) to acquire a multi-lead ECG signal from the patient. However, because the patient is exercising (i.e., moving), the patient's muscles constrict and contract and create noise potential (commonly called muscle artifact) which is acquired by the electrodes. Additionally, because the patient moves, the electrodes also move resulting in an impedance change in the patient-electrode connection. The impedance change of the electrodes results in an additional artifact signal in the ECG. Because the movement is typically a repetitive movement (e.g., running at a constant speed on a treadmill), the artifact generated thereby is typically a cyclic artifact over the short-term.
The resulting cyclic artifact is similar to the frequency content associated with the cardiac cycle. This results in the cyclic artifact being difficult to detect and difficult to remove from the ECG. Moreover, the artifacts are dangerous to cardiac cycle analysis because the artifact disturb the detection of QRS complexes. Disturbing detection of QRS complexes may lead to improper heart rate detection, erroneous arrhythmia analysis results, and a poor assessment of cardiovascular health.
Because the electrodes for acquiring the ECG signals are placed in different locations on the patient, different ECG leads will register different levels of the cyclic artifact. However, for QRS complex detection, heart rate calculation and arrhythmia analysis, it is not necessary to use all leads. A monitor can take advantage of the redundancy of the multi-lead systems and select only leads with good ECG quality. By selecting only good leads during exercise testing, the QRS complex detection quality can be improved.
Accordingly, the invention provides a medical device for acquiring and analyzing a physiological waveform. The medical device includes an input terminal for connection of a plurality of electrodes to a patient to acquire the physiological waveform from the patient, an instrumentation amplifier connected to the input terminal to filter the physiological waveform, and an analysis module including a processor and software for operating the processor to detect artifact in the physiological waveform.
The invention further provides a medical device for acquiring and analyzing a physiological signal. The medical device includes an input terminal for connection to a patient to acquire a physiological signal from the patient, an instrumentation amplifier connected to the input terminal to filter and amplify the physiological signal, and means for detecting cyclic artifacts in the physiological signal.
The invention further provides a medical device for acquiring and analyzing a multi-lead electrocardiogram. The medical device includes an input terminal for connection to a patient to acquire multi-lead ECG signals from the patient, an instrumentation amplifier connected to the input terminal to filter the ECG signals and combine the signals to generate a multi-lead ECG, and an analysis module including a processor and software for operating the processor to detect cyclic artifact in the multi-lead ECG and select a lead for analysis based on a lack of cyclic artifact in that lead.
The invention further provides a method of analyzing a lead of a multi-lead electrocardiogram (ECG), where each lead has one or more independent complex rhythms. The method includes the acts of obtaining the ECG and determining whether there is more than one independent complex rhythm within the lead. The method further includes selecting the first lead for analysis if there is only one independent complex rhythm within the first lead. The method further includes the acts of determining whether there is more than one independent complex rhythm within the second lead and selecting the lead for analysis if there is only one independent complex rhythm within the second lead.
The invention further provides a software program for detecting cyclic artifact in a multi-lead electrocardiogram (ECG), where each lead has one or more independent complex rhythms. The software program detects the artifact by sampling the ECG and processing a lead to determine whether there is more than one independent complex rhythm within the lead. In addition, the software program selects the lead for analysis if there is not more than one independent complex rhythm within the lead.
REFERENCES:
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patent: 5687735 (1997-11-01), Forbes et al.
patent: 5967994 (1999-10-01), Wang
patent: 6263235 (2001-07-01), Kaiser et al.
patent: 6266554 (2001-07-01), Hsu et al.
Kaiser, Willi et al., “Artifact Processing During Exercise Testing”, Journal of Electrocardiology, vol. 32 Supplement 1999, pp. 212-219.*
Journal of Electrocardiology, 1999, vol. 32(5).
Van Alste, et al., Removal of Base-Line Wander and Power-Line Interference from the ECG by an Efficient FIR Filter with Reduced Number of Taps, IEEE Transactions on Biomedical Engineering, vol. BME-32, No. 12, Dec. 1985.
Findeis Martin
Kaiser Willi
GE Medical Systems Information Technologies GmbH
Jastrzab Jeffrey R.
Michael & Best & Friedrich LLP
Oropeza Frances P.
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