Browsing by Author "Wright, Keith"

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    Simultaneous noninvasive recording of skin sympathetic nerve activity and electrocardiogram
    (Elsevier, 2017-01) Doytchinova, Anisiia; Hassel, Jonathan L.; Yuan, Yuan; Lin, Hongbo; Yin, Dechun; Adams, David; Straka, Susan; Wright, Keith; Smith, Kimberly; Wagner, David; Shen, Changyu; Salanova, Vicenta; Meshberger, Chad; Chen, Lan S.; Kincaid, John C.; Coffey, Arthur; Wu, Gang; Li, Yan; Kovacs, Richard J.; Everett, Thomas H., IV; Victor, Ronald; Cha, Yong-Mei; Lin, Shien-Fong; Chen, Peng-Sheng; Medicine, School of Medicine
    BACKGROUND: Sympathetic nerve activity is important to cardiac arrhythmogenesis. OBJECTIVE: The purpose of this study was to develop a method for simultaneous noninvasive recording of skin sympathetic nerve activity (SKNA) and electrocardiogram (ECG) using conventional ECG electrodes. This method (neuECG) can be used to adequately estimate sympathetic tone. METHODS: We recorded neuECG signals from the skin of 56 human subjects. The signals were low-pass filtered to show the ECG and high-pass filtered to show nerve activity. Protocol 1 included 12 healthy volunteers who underwent cold water pressor test and Valsalva maneuver. Protocol 2 included 19 inpatients with epilepsy but without known heart diseases monitored for 24 hours. Protocol 3 included 22 patients admitted with electrical storm and monitored for 39.0 ± 28.2 hours. Protocol 4 included 3 patients who underwent bilateral stellate ganglion blockade with lidocaine injection. RESULTS: In patients without heart diseases, spontaneous nerve discharges were frequently observed at baseline and were associated with heart rate acceleration. SKNA recorded from chest leads (V1-V6) during cold water pressor test and Valsalva maneuver (protocol 1) was invariably higher than during baseline and recovery periods (P < .001). In protocol 2, the average SKNA correlated with heart rate acceleration (r = 0.73 ± 0.14, P < .05) and shortening of QT interval (P < .001). Among 146 spontaneous ventricular tachycardia episodes recorded in 9 patients of protocol 3, 106 episodes (73%) were preceded by SKNA within 30 seconds of onset. Protocol 4 showed that bilateral stellate ganglia blockade by lidocaine inhibited SKNA. CONCLUSION: SKNA is detectable using conventional ECG electrodes in humans and may be useful in estimating sympathetic tone.
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    Skin Sympathetic Nerve Activity as a Biomarker for Syncopal Episodes during a Tilt Table Test
    (Elsevier, 2020-05) Kumar, Awaneesh; Wright, Keith; Uceda, Domingo E.; Vasallo, Peter A., III.; Rabin, Perry L.; Adams, David; Wong, Johnson; Das, Mithilesh; Lin, Shien-Fong; Chen, Peng-Sheng; Everett, Thomas H., IV.; Medicine, School of Medicine
    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 μV in patients without syncope and 1.42 ± 0.52 μV in patients with syncope (P = .77). On upright tilt, aSKNA was 1.34 ± 0.40 μV in patients who did not have syncope and 1.39 ± 0.43 μV 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 μV; P = .0005). After syncope, patients were immediately placed in the supine position and aSKNA dropped significantly to 1.26 ± 0.43 μV; (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.