Effects of imipramine, fluvoxamine and depressive mood on autonomic cardiac functioning in major depressive disorder.

Objective: Diminished HR variability is considered to be associated with depression and the increased risk of cardiovascular disease. The pharmacological effects of antidepressants and depressive mood itself may contribute to alterations in autonomic cardiac functioning, but a limited amount of data is available. We studied the effects of two different types of antidepressant treatments (imipramine and fluvoxamine), in addition to the effect of depressive mood, on the cardiovascular system in depressed patients.

Methods: Depressed inpatients were studied during a drug-free period and after 4 weeks of adequate treatment with imipramine (n = 17) or fluvoxamine (n = 24). Heart rate variability, blood pressure variability, and a baroreflex sensitivity index during supine rest and orthostatic challenge were analyzed by means of spectral techniques to obtain noninvasive parameters of sympathetic and parasympathetic activity.

Results: Both imipramine and fluvoxamine reduced sympathetic and parasympathetic activity, although the effects of imipramine were much more pronounced. Severity of depression was positively related to mean levels of heart rate and blood pressure in the total patient group. There was no convincing evidence that these relationships differed between depressed patients treated with imipramine and those treated with fluvoxamine.

Conclusion: Our findings suggest that alterations in mean heart rate and blood pressure in depressed patients after antidepressant treatment are the result of a combined effect of pharmacological actions of antidepressants and improvement of depressive mood state. The present study did not confirm the relationship between clinical state and cardiovascular variability or baroreflex sensitivity.