Heart Rate Variability Predicts Treatment Outcome in Major Depression

Aims: Autonomic nervous system (ANS) dysregulation is associated with various symptoms of depressive disorder. The beat-to-beat pattern of heart rate (Heart Rate Variability) (HRV) provides a noninvasive portal to ANS function through the quantification of periodic heart rate patterns. In this study we quantified two components of HRV: Respiratory Sinus Arrhythmia (RSA), and Low Frequency HRV (LF-HRV). Both of these components have been extensively reported in studies of depression and have been at least partially associated with reduction in vagal nerve tone. We quantified RSA and LF-HRV in patients with Major Depressive Disorder (MDD) as measures of ANS regulation seeking to establish the utility of components of HRV as potential diagnostic and prognostic biomarkers for treatment outcome. Methods: Sixty-six MDD patients were enrolled. In two separate and consecutively run studies they received either Escitalopram or Quetiapine fumarate ER over 12 weeks. Forty-one patients completed the studies. RSA and LF-HRV were assessed at pretreatment and end of study. Thirty-six healthy subjects served as controls. RSA and LF-HRV were quantified using an algorithm that incorporates time and frequency domains to address the non-stationarity of the beat-to-beat heart rate pattern. Results: No significant differences in baseline RSA or LF-HRV were found between MDD and healthy controls. However, baseline RSA and LF-HRV were significantly higher in treatment responders (lnRSA = 6.20, lnLF-HRV = 5.76) than non-responders (lnRSA = 4.75, lnLF-HRV = 4.53) (p = 0.005, p = 0.006). No significant changes in RSA or LF-HRV were detected over the course of either treatment. Conclusions: Components of HRV may be predictive of antidepressant response in MDD patients.