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


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Yeragani
Vikram K
VK
Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, Michigan, USA. vikramyershr@yahoo.com
Pohl
Robert
R
Bär
Karl-Jürgen
KJ
Chokka
Pratap
P
Tancer
Manuel
M
D000318:Adrenergic beta-Agonists / Q000627:therapeutic use*; D000328:Adult; D000704:Analysis of Variance; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007275:Injections, Intravenous / Q000379:methods; D007545:Isoproterenol / Q000627:therapeutic use*; D008297:Male; D016584:Panic Disorder / Q000188:drug therapy* / Q000503:physiopathology*
D000318:Adrenergic beta-Agonists; D007545:Isoproterenol