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.

Spectral analysis of fluctuations in heart rate and blood pressure was employed to explore sympathetic and parasympathetic cardiovascular control mechanisms in relation to trait anxiety in major depressive disorder. Sixteen drug-free female depressed patients were divided into two groups: those who were high on trait anxiety (HTA, n = 9) and those who were normal or low on trait anxiety (LTA, n = 7). In patients and age-matched female controls (n = lo), heart rate (HR), blood pressure (BP; Finapres device) and respiration were recorded during a period of supine rest (10 min), orthostatic challenge (60" head-up tilting, 8 min), and post-orthostatic supine rest (8 min). Power spectra were calculated over the last 4 min of these three situations for HR, systolic BP, as well as for respiration. 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). Patients did not differ from controls during supine rest. During orthostatic challenge, HTA patients showed significantly more HR increase and suppression of high-frequency fluctuations of HR (suggesting stronger vagal inhibition) in comparison with the controls; this effect was accompanied by a significant increase in respiratory frequency. Both patients groups did not show the normal increase in mid-frequency band fluctuations of BP during orthostatic challenge, indicating reduced sympathetic activation. Low-frequency fluctuations of HR, as well as respiratory frequency during post-orthostatic supine rest of the HTA patients were significantly increased versus controls. This exploratory study indicates that trait anxiety may be a relevant factor when evaluating parasympathetic and sympathetic dysbalances in the state of a major depressive disorder.

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The physiological response of the cardiac autonomic nervous system during shock wave lithotripsy (SWL) remains unclear. Heart rate variability (HRV) is an index of cardiac autonomic balance. This study aimed to analyze HRV during SWL in patients with urolithiasis. Electrocardiograms of patients who underwent SWL were obtained. Recordings were obtained before and after SWL. For each time point, the recordings were obtained continuously for 6 min, after which R wave-to-R wave (RR) intervals were extracted. The time digital sequence derived from RR intervals was the HRV signal. Time-domain analysis revealed that the mean of RR intervals (MRR) and standard deviation of normal beat-to-normal beat (NN) intervals (SDNN), but not the square root of the mean squared difference of successive NNs (RMSSD) or triangular interpolation of NN intervals (TINN), significantly increased during SWL. The increase in SDNN persisted after SWL but MRR returned to the initial level. Frequency-domain analysis revealed that very low frequency (VLF), low frequency (LF), and LF/high frequency (HF) ratio significantly increased after SWL, while there was no statistically significant difference in HF. Thus, the patients had significantly high MRR and SDNN during SWL and significantly high SDNN, VLF, LF, and LF/HF ratio after SWL. SWL could alter the functioning of the cardiac autonomic nervous system, resulting in reduction in sympathetic activity and increase in parasympathetic activity. Further studies with larger samples are required to confirm these findings and understand the underlying mechanisms.