Heart rate and QT interval variability: abnormal alpha-2 adrenergic function in patients with panic disorder

Area of Science:

• Cardiology
• Psychiatry
• Pharmacology

Background:

• Anxiety disorders are linked to increased cardiovascular mortality.
• Abnormal sympathovagal balance, indicated by heart rate (HR) and QT interval variability, is associated with arrhythmias.
• Panic disorder patients show altered responses to alpha-2 adrenergic agents.

Purpose of the Study:

• To investigate changes in QT variability index (QTvi) in response to clonidine and yohimbine in panic disorder patients.
• To assess the role of alpha-2 adrenergic receptors in panic disorder and its cardiovascular implications.

Main Methods:

• A double-blind study involving 12 healthy controls and 19 panic disorder patients.
• Administration of placebo, oral clonidine (150 mg), and oral yohimbine (20 mg).
• Measurement of HR and QT variability, particularly QTvi, in supine and standing postures before and after drug administration.

Main Results:

• Panic disorder patients experienced increased anxiety with yohimbine and decreased anxiety with placebo.
• Patients showed a significant increase in QTvi after yohimbine and a decrease after clonidine, unlike controls.
• Decreased anxiety post-placebo correlated with decreased QTvi in patients.

Conclusions:

• Panic disorder patients exhibit abnormal alpha-2 adrenergic receptor sensitivity.
• Altered QTvi responses to clonidine and yohimbine in panic disorder patients suggest impaired cardiac sympathetic function.
• QTvi is a valuable non-invasive tool for studying cardiac sympathetic function and its relation to anxiety disorders.