TRICYCLIC ANTIDEPRESSANTS AND CARDIAC AUTONOMIC CONTROL IN CHILDREN AND ADOLESCENTS

Objective: To elucidate the effects of tricyclic antidepressants on sy mpathetic and vagal modulation of heart rate variability. Method: Seve nty-five children and adolescents (mean age 10.5 years, SD 2.0) from t herapeutic and regular schools underwent challenges of paced breathing and orthostatic postural change, while heart rate was continuously re corded. Teachers completed dimensional ratings of behavior to quantify anxiety and conduct disorder. Spectral analysis of heart rate variabi lity was utilized to decompose the postural (sympathetic) and respirat ory (vagal) contributions to beat-to-beat variations in heart rate. Re sults: Under conditions in which cardiac vagal effects were expected t o predominate, subjects medicated with tricyclic antidepressants (n = 13) showed significantly reduced vagal modulation of heart rate variab ility (F[5,69] = 5.23, p <.003), higher heart rates (F[5,69] = 5.54, p <.002), and higher relative sympathovagal balance (F[5,69] = 5.51, p <.002) than nonmedicated (n = 42) and medicated comparison groups (n = 20), even after controlling for the effects of age and psychopatholog y. Conclusions: The relative loss of cardiac vagal control in young su bjects medicated with tricyclic antidepressants, considered in the con text of factors known to be associated with the development of tachyar rhythmias, presents as yet another risk, especially when coupled with factors such as maturational effects and psychopathology.