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Type: Journal article
Title: QT interval variability and cardiac norepinephrine spillover in patients with depression and panic disorder
Author: Baumert, M.
Lambert, G.
Dawood, T.
Lambert, E.
Esler, M.
McGrane, M.
Barton, D.
Nalivaiko, E.
Citation: American Journal of Physiology-Heart and Circulatory Physiology, 2008; 295(3):H962-H968
Publisher: Amer Physiological Soc
Issue Date: 2008
ISSN: 0363-6135
Statement of
Mathias Baumert, Gavin W. Lambert, Tye Dawood, Elisabeth A. Lambert, Murray D. Esler, Mariee McGrane, David Barton and Eugene Nalivaiko
Abstract: Suggestions were made that increased myocardial sympathetic activity is reflected by elevated QT variability (dynamic changes in QT interval duration). However, the relationship between QT variability and the amount of norepinephrine released from the cardiac sympathetic terminals is unknown. We thus attempted to assess this relationship. The study was performed in 17 subjects (12 with major depressive disorder and 5 with panic disorder). Cardiac norepinephrine spillover (measured by direct catheter technique coupled with norepinephrine isotope dilution methodology) was assessed before and 4 mo after treatment with selective serotonin reuptake inhibitor (SSRI) antidepressants. The distribution of the cardiac norepinephrine spillover was bimodal, with the majority of patients having values of 10 ng/min. There was a positive correlation between cardiac norepinephrine spillover and corrected QT interval (r = 0.7, P = 0.03) but not with any of the QT variability measures. However, in a subgroup of five patients who had high levels of cardiac norepinephrine spillover (>20 ng/min) a tendency for a strong positive correlation with variance of QT intervals (r = 0.9, P = 0.08) was observed. There were significant correlations between the severity of depression and QT variability indexes normalized to the heart rate [QTVi and QT interval/R-R interval (QT/RR) coherence] and between the severity of anxiety and the QT/RR residual and regression coefficient, respectively. Treatment with SSRI antidepressants substantially reduced depression score but did not affect any of the QT variability indexes. We conclude that in depression/panic disorder patients with near-normal cardiac norepinephrine levels QT variability is not correlated with cardiac norepinephrine spillover and is not affected by treatment with SSRI.
Keywords: sympathetic activity; antidepressants
Description: Copyright © 2008 by the American Physiological Society.
RMID: 0020082548
DOI: 10.1152/ajpheart.00301.2008
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Appears in Collections:Electrical and Electronic Engineering publications

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