Browsing by Author "Wright, Keith"

Now showing 1 - 2 of 2

Simultaneous noninvasive recording of skin sympathetic nerve activity and electrocardiogram
(2017-01)
Doytchinova, Anisiia
;
Hassel, Jonathan L.
;
Yuan, Yuan
;
Lin, Hongbo
;
Yin, Dechun
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 (V1V6) 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.
Skin sympathetic nerve activity as a biomarker for syncopal episodes during a tilt table test
(2020-05-01)
Kumar, Awaneesh
;
Wright, Keith
;
Uceda, Domingo E.
;
Vasallo, Peter A., III
;
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.