Twenty-Four-Hour Heart Rate Is a Trait but Not State Marker for Depression in a Pilot Randomized Controlled Trial With a Single Infusion of Ketamine
A 4-day electrocardiogram (ECG) was recorded for 16 treatment-resistant patients with major depressive disorder (MDD) and 16 age- and sex-matched controls before, and for the patient group only, after a single treatment with the rapid-acting antidepressant ketamine or placebo (clinical trial registration available on https://www.clinicaltrialsregister.eu/ with EUDRACT number 2016-001715-21). Two features were calculated from the ECG signal: the mean HR and the root mean square of the successive differences (RMSSD) in RR peaks. Both features were calculated in a window of 5min (overlap of 4min). The activity level of the participants was calculated as the standard deviation of the magnitude of acceleration as derived from the accelerometer of the ECG patch. In accordance with the ECG features, activity levels were calculated in windows of 5min with 4-min overlap. A quality indicator based on research published by Orphanidou et al. (2014) was assigned to every 10-s segment of the signal. All 5-min windows with an average QI below 0.8 were excluded. In addition, following Smets et al. (2018) , all segments of high activity (std ACC > 0.04) were excluded as well. Lastly, all retained windows were averaged into either hourly measurements. These hourly measurements are provided in the attached database.