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Using motion sensors to reduce motion artifact in the ECG
Poster Session I
43
Poyee P. Tung, and Barbara J. Drew, University of California, San Francisco, CA
before and after applying the adaptive filter. A percent improvement was calculated for each data set. These results are shown in the table.
A wide variety of electrocardiographic (ECG) abnormalities have been reported in patients with subarachnoid hemorrhage (SAH). The purpose of this study was to compare the ECG in patients with SAH to those in normal persons in order to identify differences in ECG characteristics between the two groups, and to determine which waveform and interval abnormalities occur more frequently in SAH. Method: A standard ECG was recorded as soon as possible after admission. Computer-assisted measurements of ST segment deviation and QTc intervals were made with the Mortara ST Review Station (Milwaukee, WI). Results: ECGs of 200 patients with SAH and 30 patients in a normal control group were analyzed. Of 237 quantitative ECG measurements, 91 were significantly different between the two groups. Mean PR interval duration was shorter in the SAH group (p⫽.000). Mean R wave amplitude was higher in lead I (p⫽.001) and lead V2 (p⫽.016) in the normal group, and higher in V6 (p⫽.003) in the SAH group. S wave amplitudes were greater in SAH patients across all six precordial leads (p⫽.003–.027). T wave axis differed significantly between the two groups (p⫽.001), and. T wave inversion was found to occur in 44 (22%) of SAH patients but only 1 (3%) of the normal control group (p⫽.013). In addition, 48 (24%) patients in the SAH group met ECG criteria for left ventricular hypertrophy, while none did so in the control group (p⫽.011). Conclusions: There are significant ECG differences between normal patients and those with SAH. It is further concluded that T wave inversion and ECG evidence of left ventricular hypertrophy occur significantly more frequently in patients with SAH than in normal patients.
Percent Improvement After Filtering
Using Motion Sensors to Reduce Motion Artifact in the ECG David A. Tong, Keith A. Bartels, and Kevin S. Honeyager, Southwest Research Institute, San Antonio, TX, USA Motion artifact is an unsolved problem in electrocardiography. Motion artifact may produce large amplitude signals in the ECG that may be misinterpreted by clinicians and automated systems resulting in misdiagnosis, prolonged procedure duration, and delayed or inappropriate treatment decisions. The hypothesis being investigated in this project is that motion artifact can be reduced by using electrode motion as a noise reference in an adaptive filter. The initial results of a novel approach to reducing motion artifact in the ECG using motion sensors attached to the ECG electrodes and adaptive filtering are presented. To measure electrode motion, two custom-designed motion sensors were developed and attached to the ECG electrode. One sensor utilized a two axis anisotrophic magnetoresistive (AMR) sensor and the other sensor utilized a three axis accelerometer (ACC). In an iterative fashion, both sensors were attached to the right arm electrode where motion was induced by (1) pushing directly on the ECG electrode, (2) pushing on the skin around the electrode, and (3) pulling on the ECG lead wire. The motion sensor signals and ECG leads I and II were recorded from eight subjects at 500 Hz. An LMS adaptive filter was implemented in Matlab and was used to post-process the electrode motion and ECG data. System performance was assessed by calculating two measures of the noise in the ECG (the L2 Norm and the MaxMin statistic)
AMR Sensor Noise Type All Data Sets Push Electrode Pull Lead Push Skin
ACC Sensor
L2 Norm
Max Min
L2 Norm
Max Min
67.6% 70.6% 45.2% 77.3%
37.7% 48.7% 24.5% 51.0%
83.6% 78.6% 91.3% 89.6%
58.5% 50.7% 49.2% 67.5%
As shown in the table, the data support the hypothesis that electrode motion can be used in an adaptive filter to reduce motion artifact in the ECG. The ACC sensor out performed the AMR sensor because the ACC sensor provided an additional axis of measurement and the relationship between the ACC signal and the motion artifact noise is better modeled by a linear time-varying system.
What Are the Implications for Using Modified (Mason-Likar) Exercise Lead System in Research? Shu-Fen Wung, PhD, RN, Amelia Sieger, BS, Monique Leon, BS, Jessica Redondo, BS, Vincent Sorrell, MD, and Steven Goldman, MD, University of Arizona, Southern Arizona VA Health Care System Tucson, Arizona, USA Researchers often use the Mason-Likar exercise lead system to maintain stability of the waveforms for continuous ECG monitoring research. The purpose of this large prospective study was conducted to determine the agreement in axes and the diagnosis of myocardial infarction (MI) between the 12-lead ECGs recorded via standard and Mason-Likar systems in 133 patients who presented to Emergency Departments for evaluation of an acute MI. Method: 12-lead ECGs were first recorded by the standard immediately followed by the Mason-Likar method. Computerized measurements of waveforms and intervals were obtained. Percent of agreement was used to determine the similarities and differences in the interpretations. Results: By moving the limb electrode closer to the torso, there was a mean 27° right-ward shift in the QRS axis. A high agreement (94%) was found in the QRS axis interpretation between the 2 lead systems. Agreements in the presence or absence of abnormal Q wave duration between the 2 lead systems were higher in leads I (99%), II (96%), V4 (98%), V5 (99%), and V6 (96%) and were lower in leads aVL (90%) and aVF (86%). All subjects had 100% agreement in the presence and absence of anterior MI. The majority (87%) of the subjects also had high agreement in the presence or absence of inferior wall MI. The agreements in the presence and absence of posterior MI by widen R waves in leads V1 and V2 were also high, 99% and 95%, respectively. Conclusions: The Mason-Likar electrode sites produce a 27° rightward frontal plane QRS axis shift; however, in the majority of subjects, the QRS axis interpretation remained the same. This MasonLikar system also had a high agreement in the presence or absence of anterior, posterior, and inferior MI in this population. Moving electrodes to the body torso can produce false-positive and false-negative abnormal Q waves in lead I in 10% of subject and lead aVF in 14% of subjects. Funding source: NlH/NINR: RO1 NR008092
43
Poyee P. Tung, and Barbara J. Drew, University of California, San Francisco, CA
before and after applying the adaptive filter. A percent improvement was calculated for each data set. These results are shown in the table.
A wide variety of electrocardiographic (ECG) abnormalities have been reported in patients with subarachnoid hemorrhage (SAH). The purpose of this study was to compare the ECG in patients with SAH to those in normal persons in order to identify differences in ECG characteristics between the two groups, and to determine which waveform and interval abnormalities occur more frequently in SAH. Method: A standard ECG was recorded as soon as possible after admission. Computer-assisted measurements of ST segment deviation and QTc intervals were made with the Mortara ST Review Station (Milwaukee, WI). Results: ECGs of 200 patients with SAH and 30 patients in a normal control group were analyzed. Of 237 quantitative ECG measurements, 91 were significantly different between the two groups. Mean PR interval duration was shorter in the SAH group (p⫽.000). Mean R wave amplitude was higher in lead I (p⫽.001) and lead V2 (p⫽.016) in the normal group, and higher in V6 (p⫽.003) in the SAH group. S wave amplitudes were greater in SAH patients across all six precordial leads (p⫽.003–.027). T wave axis differed significantly between the two groups (p⫽.001), and. T wave inversion was found to occur in 44 (22%) of SAH patients but only 1 (3%) of the normal control group (p⫽.013). In addition, 48 (24%) patients in the SAH group met ECG criteria for left ventricular hypertrophy, while none did so in the control group (p⫽.011). Conclusions: There are significant ECG differences between normal patients and those with SAH. It is further concluded that T wave inversion and ECG evidence of left ventricular hypertrophy occur significantly more frequently in patients with SAH than in normal patients.
Percent Improvement After Filtering
Using Motion Sensors to Reduce Motion Artifact in the ECG David A. Tong, Keith A. Bartels, and Kevin S. Honeyager, Southwest Research Institute, San Antonio, TX, USA Motion artifact is an unsolved problem in electrocardiography. Motion artifact may produce large amplitude signals in the ECG that may be misinterpreted by clinicians and automated systems resulting in misdiagnosis, prolonged procedure duration, and delayed or inappropriate treatment decisions. The hypothesis being investigated in this project is that motion artifact can be reduced by using electrode motion as a noise reference in an adaptive filter. The initial results of a novel approach to reducing motion artifact in the ECG using motion sensors attached to the ECG electrodes and adaptive filtering are presented. To measure electrode motion, two custom-designed motion sensors were developed and attached to the ECG electrode. One sensor utilized a two axis anisotrophic magnetoresistive (AMR) sensor and the other sensor utilized a three axis accelerometer (ACC). In an iterative fashion, both sensors were attached to the right arm electrode where motion was induced by (1) pushing directly on the ECG electrode, (2) pushing on the skin around the electrode, and (3) pulling on the ECG lead wire. The motion sensor signals and ECG leads I and II were recorded from eight subjects at 500 Hz. An LMS adaptive filter was implemented in Matlab and was used to post-process the electrode motion and ECG data. System performance was assessed by calculating two measures of the noise in the ECG (the L2 Norm and the MaxMin statistic)
AMR Sensor Noise Type All Data Sets Push Electrode Pull Lead Push Skin
ACC Sensor
L2 Norm
Max Min
L2 Norm
Max Min
67.6% 70.6% 45.2% 77.3%
37.7% 48.7% 24.5% 51.0%
83.6% 78.6% 91.3% 89.6%
58.5% 50.7% 49.2% 67.5%
As shown in the table, the data support the hypothesis that electrode motion can be used in an adaptive filter to reduce motion artifact in the ECG. The ACC sensor out performed the AMR sensor because the ACC sensor provided an additional axis of measurement and the relationship between the ACC signal and the motion artifact noise is better modeled by a linear time-varying system.
What Are the Implications for Using Modified (Mason-Likar) Exercise Lead System in Research? Shu-Fen Wung, PhD, RN, Amelia Sieger, BS, Monique Leon, BS, Jessica Redondo, BS, Vincent Sorrell, MD, and Steven Goldman, MD, University of Arizona, Southern Arizona VA Health Care System Tucson, Arizona, USA Researchers often use the Mason-Likar exercise lead system to maintain stability of the waveforms for continuous ECG monitoring research. The purpose of this large prospective study was conducted to determine the agreement in axes and the diagnosis of myocardial infarction (MI) between the 12-lead ECGs recorded via standard and Mason-Likar systems in 133 patients who presented to Emergency Departments for evaluation of an acute MI. Method: 12-lead ECGs were first recorded by the standard immediately followed by the Mason-Likar method. Computerized measurements of waveforms and intervals were obtained. Percent of agreement was used to determine the similarities and differences in the interpretations. Results: By moving the limb electrode closer to the torso, there was a mean 27° right-ward shift in the QRS axis. A high agreement (94%) was found in the QRS axis interpretation between the 2 lead systems. Agreements in the presence or absence of abnormal Q wave duration between the 2 lead systems were higher in leads I (99%), II (96%), V4 (98%), V5 (99%), and V6 (96%) and were lower in leads aVL (90%) and aVF (86%). All subjects had 100% agreement in the presence and absence of anterior MI. The majority (87%) of the subjects also had high agreement in the presence or absence of inferior wall MI. The agreements in the presence and absence of posterior MI by widen R waves in leads V1 and V2 were also high, 99% and 95%, respectively. Conclusions: The Mason-Likar electrode sites produce a 27° rightward frontal plane QRS axis shift; however, in the majority of subjects, the QRS axis interpretation remained the same. This MasonLikar system also had a high agreement in the presence or absence of anterior, posterior, and inferior MI in this population. Moving electrodes to the body torso can produce false-positive and false-negative abnormal Q waves in lead I in 10% of subject and lead aVF in 14% of subjects. Funding source: NlH/NINR: RO1 NR008092