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Neuropsychobiology. 2007;55(3-4):213-8. Epub 2007 Sep 17.

Exaggerated beat-to-beat R amplitude variability in patients with panic disorder after intravenous isoproterenol.

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Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA.



Anxiety symptoms are associated with a marked increase in sudden cardiac death, suggesting an abnormality in cardiac autonomic function. Our previous studies show a relationship between R amplitude variability and sympathetic function.


We examined the effects of beta-adrenergic stimulation on R and T amplitude variability in panic disorder patients by infusing the beta-adrenergic agonist isoproterenol in 6 panic disorder patients and 11 normal subjects. The ECG signal was analyzed before the infusion and 5 min after the infusion was started. The outcome measures were the R and T detrended variance normalized for mean amplitudes (R(vm) and T(vm)) and the R(vi) and T(vi), measures which are normalized for the inter-beat interval variability in addition.


Patients with panic disorder had significantly more variability in R and T amplitude than normal controls and the R amplitude variability was increased further by beta-adrenergic stimulation with isoproterenol, which was more pronounced in the patients.


The isoproterenol-associated increase in R amplitude variability occurred in controls in the absence of significant anxiety. However, the increase in R amplitude variability was greater in patients with panic disorder, suggesting a greater sensitivity to beta-adrenergic effects of isoproterenol or to isoproterenol-induced anxiety.

[Indexed for MEDLINE]

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