The frequency spectrum of sympathetic nerve activity and arrhythmogenicity in ambulatory dogs

Abstract Background Sympathetic nerve activity (SNA), heart rate (HR) and blood pressure (BP) all have very low frequency (VLF), low frequency (LF) and high frequency (HF) oscillations. Objective To test the hypotheses that the frequency spectra of the subcutaneous nerve activity (ScNA), stellate ganglion nerve activity (SGNA), HR and BP are important to cardiac arrhythmogenesis. Methods We used radiotransmitters to record SGNA, ScNA, HR and BP in 6 ambulatory dogs and determined the dominant frequency and PAT episodes in 3-min windows over a 24-hr period. Results The frequency spectra determined in the ScNA reflected that in the SGNA. HF oscillations were present in both ScNA and SGNA at all time but could be overshadowed by the much larger LF and VLF burst activities. The dominant frequency could occur in any of the 3 frequency bands. There were circadian variations with more frequent occurrences of the HF oscillations at night. The HF oscillations in HR and BP matched the HF oscillations in SGNA and ScNA. PATs occurred only when dominant frequencies of SGNA and ScNA were in the LF and VLF bands. Conclusions The HF oscillations in BP and HR correlate with the HF oscillations in SNA and are present at all time. HF oscillations can be overshadowed by the much larger LF and VLF burst activities. The PATs only occur when LF or VLF but not when HF is the dominant frequency. The frequency spectra determined in the ScNA reflect that in the SGNA.