Power spectrum of the QRS complex: comparison of patients with panic disorder and controls

The QRS complex of the electrocardiogram relates to ventricular depolarization, and previous studies using spectral analysis mainly focused on the inverse power law distribution of the spectral components. Some evidence suggests that there is a decrease in high frequency voltage of QRS in patients with myocardial infarction compared to controls. There are no studies to our knowledge on the effects of posture on frequency domain analysis of the QRS complex, and also on the comparison of QRS power spectra between patients with panic disorder and normal controls. We performed spectral analysis on the QRS complex of the electrocardiogram obtained using standard limb leads, sampled at 500 Hz with 12 bit precision in 20 normal subjects and 15 patients with panic disorder. Using an automated program, we extracted and analyzed 24 QRS complexes before, and 24 after postural challenge to minimize noise level. We used a 256 msec window for the Fourier analysis, which was performed after removing any linear trend. We divided the frequency range of the QRS in to two bands based on spectral patterns before and after the postural challenge; Mid Frequency (MF): 7.8-20 Hz and High Frequency (HF): 21-250 Hz. Postural change from supine to standing produced a significant increase in absolute (p=0.003) and relative HF power (p=0.0001). There was also a significant decrease of the QRS interval in standing posture (p=0.001). Patients with panic disorder had a significantly decreased QRS HF power (p=0.003). The increase in QRS HF power may have been due to the shortening of the QRS interval in standing posture. The decreased QRS HF power in patients with panic disorder should be further investigated due to the recent reports of an association of phobic anxiety and fatal coronary heart disease.