Depression and heart rate variability

Since there is evidence suggesting an increased incidence of cardiovascular morbidity in patients with major depression and phobic anxiety (Dalack et al 1990: Kawachi et al 1994), we have been conducting studies on cardiac autonomic function in these disorders using noninvasive techniques such as spectral analysis of heart rate (HR). Low frequency (LF:0.01-0.05 Hz) power has been related to renin angiotensin and thernmregulatory mechanisms, midfrequency (MF:0.07-0.15 Hz) power to baroreceptor control, and high-frequency (HF:0.16-0.5 Hz) power to respiratory sinus arrhythmia (Malliani et al 1991). Our previous findings suggest that patients with panic disorder have decreased variance of heart rate time series, higher standing re lame midfrequency power, and higher increases in standing midfrequency power when challenged v, ith yohimbine (Yeragani et al 1992, 1993). We have also found that patients with panic disorder have exaggerated vagal withdrawal and higher sympathovagal ratios during sodium lactate and isoproterenol infusions (Yeragani et al 1994, 1995). In a previous report on time domain measures of heart rate variability, we did not find any significant differences in the standard deviation of heart rate between patients with depression and normal controls (Yeragani et al 199l). However, the data acquisition and determination of R-R intervals were done manually, and we did not use spectral analysis of HR in this study. In the present relx)rt, we compare heart rate variability data on 16 patients with major depression with no current or past history of panic attacks, and 29 patients with panic disorder without a current history of major depression. The data on these 16 patients with depression have not been published elsewhere. However.