Does parasympathetic modulation prior to ECT treatment influence therapeutic outcome?

Electroconvulsive therapy (ECT) is an established treatment option for major depressive disorder when other treatments have failed. However, the underlying mechanisms responsible for these therapeutical effects are insufficiently understood to date. Furthermore, treatment outcome is difficult to predict. Recent research suggested an important role of autonomic modulation for successful treatment. We aimed to examine putative associations between autonomic modulation and response to ECT treatment and hypothesized a role for vagal modulation prior to therapy. Twenty-four patients with MDD who received ECT were assessed by means of heart rate and blood pressure variability analysis as well as baroreflex sensitivity measurements before, during and after a course of ECT. Autonomic parameters from the complete study population revealed that ECT did not significantly alter basic autonomic modulation after six sessions. Analyses showed a significant association of the reduction of HAMD scores during therapy when compared with baseline autonomic function as reflected in SDNN(RR) (p<0.004), Forbword(RR) (p<0.025) and compression entropy Hc(RR) (p<0.0003). A significant correlation was observed when overall HAMD reduction and changes of LFnu(RR) (p<0.026) or HFnu(RR) (p<0.026) during the course of therapy were analyzed. Our findings suggest that high levels of parasympathetic modulation at baseline might be associated with a beneficial effect upon ECT treatment. Adding to this, levels of parasympathetic activity seemed to increase in patients who respond to ECT treatment. Given these findings can be confirmed in future studies, autonomic modulation might be used as a predictor for therapeutic efficacy of ECT.