Cardiovascular variability in major depressive disorder and effects of imipramine or mirtazapine (Org 3770).
Spectral analysis of fluctuations in heart rate (HR) and blood pressure (BP) was applied to assess sympathetic and parasympathetic cardiovascular control mechanisms in patients with unipolar affective disorder before and after treatment with imipramine (IMI) or mirtazapine (MIR). In a double-blind randomized study, 10 patients received treatment with IMI and 10 patients received treatment with MIR. Cardiovascular parameters were studied before and after 4 weeks of treatment: HR and BP (Finapres) were recorded continuously during supine rest (SR) and orthostatic challenge (OC; 60-degrees head-up tilting). During SR and OC, power spectra were calculated for HR and systolic BP. Spectral density was assessed for three frequency bands: low (0.02-0.06 Hz), mid (0.07-0.14 Hz), and high (0.15-0.50 Hz). Before treatment, the depressed patients (N = 20) differed from age-matched controls (N = 20) only in their response to OC: the depressed patients showed more suppression of HR variability (both mid- and high-frequency band fluctuations), indicating stronger vagal inhibition, and a reduced increase of BP variability (mid-frequency band fluctuations), indicating reduced sympathetic activation. After 4 weeks of treatment, patients treated with either antidepressant drug showed significant changes of HR (increase) and HR variability (decrease) during SR and OC; the suppression of mid- and high-frequency fluctuations of HR was larger for IMI than for MIR. The increase in HR and decrease in HR variability may be attributed to the anticholinergic properties of IMI (strong) and MIR (weak), resulting in cardiac vagal inhibition. Whereas MIR had no effect on BP or BP variability, IMI specifically reduced mid-frequency band fluctuations of BP as the result of a suppression of central sympathetic activity. Our data confirm and extend previous observations on the presence of autonomic dysfunctions in unmedicated depressed patients: spectral analysis of HR and BP fluctuations suggested that both parasympathetic and sympathetic mechanisms are involved, specifically during OC. The preexisting autonomic cardiovascular dysfunctions were not normalized by antidepressant drugs. In fact, some of the components of the cardiovascular autonomic dysfunction were further aggravated, depending on the pharmacologic profile of the drug under investigation.
Tulen
J H
JH
Department of Psychiatry, University Hospital Rotterdam Dijkzigt, The Netherlands.
Bruijn
J A
JA
de Man
K J
KJ
Pepplinkhuizen
L
L
van den Meiracker
A H
AH
Man in 't Veld
A J
AJ
D000328:Adult; D000368:Aged; D000929:Antidepressive Agents, Tricyclic / Q000009:adverse effects / Q000627:therapeutic use*; D001143:Arousal / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D003866:Depressive Disorder / Q000188:drug therapy* / Q000503:physiopathology; D004311:Double-Blind Method; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D007099:Imipramine / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D008803:Mianserin / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D008875:Middle Aged; D000078785:Mirtazapine; D010275:Parasympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D014630:Vagus Nerve / Q000187:drug effects / Q000503:physiopathology
D000929:Antidepressive Agents, Tricyclic; D008803:Mianserin; D000078785:Mirtazapine; D007099:Imipramine