Browsing by Author "Wong, Johnson"

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Method for detection and quantification of non-invasive skin sympathetic nerve activity
(2018-01-01)
Liu, Chun
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Wong, Johnson
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Doytchinova, Anisiia
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Chen, Peng-Sheng
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Lin, Shien-Fong
Sympathetic nerve activity is an important trigger of cardiac arrhythmia. Our laboratory recently developed a new method for non-invasive recording of the skin sympathetic nerve activity (SKNA) using conventional electrocardiography (ECG) patch electrodes. Recent studies showed that SKNA can adequately estimate sympathetic tone in humans. In order to improve the analysis of SKNA, we developed automatic standard assessment system based on the concept of microneurography and applied to non-invasive SKNA recording via 4 steps of signal processing. Every parameters in procedures can be manually selected by users in order to meet requirements. After using these signal processing, the results obtained by this system show improved nerve burst morphology and trend. Intuitive nerve discharge pattern and occurrence frequency can be automatically generated. Verification of the method with the cold water pressor test data further established the reliability and usefulness of the system. This new method offered a convenient tool to evaluate SKNA for comprehensive and detailed application in neurocardiology. The analysis system may facilitate the study between SKNA and cardiac arrhythmia, thus advance the field of neurocardiology research.
Simultaneous noninvasive recording of electrocardiogram and skin sympathetic nerve activity (neuECG)
(2020-05-01)
Kusayama, Takashi
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Wong, Johnson
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Liu, Xiao
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He, Wenbo
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Doytchinova, Anisiia
neuECG is the simultaneous noninvasive recording of ECG and skin sympathetic nerve activity and thus can directly record sympathetic nerve activity over a long period of time without the need for invasive procedures. neuECG, the simultaneous noninvasive recording of ECG and skin sympathetic nerve activity (SKNA), directly records sympathetic nerve activity over a long period of time. It can be used to measure sympathetic tone in healthy subjects and in subjects with non-cardiovascular diseases. The electrical activity that can be measured on the surface of the skin originates from the heart, the muscle or nerve structures. Because the frequency content of nerve activity falls in a higher frequency range than that of the ECG and myopotential, it is possible to use high-pass or band-pass filtering to specifically isolate the SKNA. neuECG is voltage calibrated and does not require invasive procedures to impale electrodes in nerves and thus has advantages over microneurography. Here, we present a protocol that takes <10 min to set up. The neuECG can be continuously recorded over a 24-h period or longer. We also describe methods to efficiently analyze neuECG from humans using commercially available hardware and software to facilitate adoption of this technology in clinical research.
Skin sympathetic nerve activity as a biomarker for syncopal episodes during a tilt table test
(2020-05-01)
Kumar, Awaneesh
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Wright, Keith
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Uceda, Domingo E.
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Vasallo, Peter A., III
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Rabin, Perry L.
BACKGROUND Autonomic imbalance is the proposed mechanism of syncope during a tilt table test (TTT). We have recently demonstrated that skin sympathetic nerve activity (SKNA) can be noninvasively recorded using electrocardiographic electrodes. OBJECTIVE The purpose of this study was to test the hypothesis that increased SKNA activation precedes tilt-induced syncope. METHODS We studied 50 patients with a history of neurocardiogenic syncope undergoing a TTT. The recorded signals were band-pass filtered at 500-1000 Hz to analyze nerve activity. RESULTS The average SKNA (aSKNA) value at baseline was 1.38 +/- 0.38 mu V in patients without syncope and 1.42 +/- 0.52 mu V in patients with syncope (P = .77). On upright tilt, aSKNA was 1.34 +/- 0.40 mu V in patients who did not have syncope and 1.39 +/- 0.43 mu V in patients who had syncope (P = .65). In all 14 patients with syncope, there was a surge of SKNA before an initial increase in heart rate followed by bradycardia, hypotension, and syncope. The peak aSKNA immediately (<1 minute) before syncope was significantly higher than baseline aSKNA (2.63 +/- 1.22 vs 1.39 +/- 0.43 mu V; P = .0005). After syncope, patients were immediately placed in the supine position and aSKNA dropped significantly to 1.26 +/- 0.43 mu V; (P = .0004). The heart rate variability during the TTT shows a significant increase in parasympathetic tone during syncope (low-frequency/high-frequency ratio: 7.15 vs 2.21; P = .04). CONCLUSION Patients with syncope do not have elevated sympathetic tone at baseline or during the TTT except immediately before syncope when there is a transient surge of SKNA followed by sympathetic withdrawal along with parasympathetic surge.