Cerebral metabolic rate of oxygen is correlated to treatment effect of electroconvulsive therapy in patients with depression.

BACKGROUND

Neurobiological understanding of the antidepressant mechanisms of electroconvulsive therapy (ECT) is important to advance the treatment. ECT may work by improving depression-related alterations in the cerebral oxygen metabolism.

METHODS

21 in-patients with depression treated with an ECT series were examined 1) within two days before, and 2) a few days (median = 4 days) after the last ECT session. Depression severity was assessed by the six-item Hamilton Depression Rating Scale (HDRS-6). Magnetic resonance imaging (MRI) was used to measure 1) global cerebral blood flow (CBF) by phase contrast mapping technique and 2) global cerebral metabolic rate of oxygen (CMRO2) by measuring cerebral extraction of oxygen (A-V.O2) using susceptibility-based oximetry. Statistical analyses were performed using multiple linear regression, adjusting for age and gender.

RESULTS

ECT relieved depressive symptoms from HDRS-6 = 13.9 to 5.2 (p < 0.001), as expected. A larger increase in CMRO2 after ECT was correlated with a better treatment effect (0.5 % reduction in HDRS-6 per 1 % increase in CMRO2, adjusted R2 = 0.24, p = 0.026). The effect was driven by both higher A-V.O2 and increased CBF. Before ECT, an abnormal decoupling between CMRO2 and CBF was observed, which was normalized after the treatment (adjusted R2 = 0.17, p = 0.03).

CONCLUSIONS

The treatment effect of ECT for depression was associated with increased CMRO2. Furthermore, ECT restored the normal coupling between CBF and CMRO2. The results suggest that the cerebral oxygen metabolism may be abnormally altered in patients with depression and ECT restores such dysfunction.