Vagal nerve electrostimulation significantly altered the heart rate autospectrum, with the LF:HF peak ratio increasing from 0.64 during stimulation to 1.99 when turned off (P<0.001).
Case Report (n=1)
No
Does vagal nerve electrostimulation alter the power spectrum of heart rate variability in a patient with an implanted stimulator?
Vagal nerve electrostimulation directly alters the heart rate autospectrum, demonstrating an unequivocal relationship between vagal tone and heart rate variability components.
Absolute Event Rate: 0.64% vs 1.99%
p-value: p=<0.001
The power spectrum of heart rate variability contains low frequency (LF = 0.08-0.12 Hz) and high frequency (HF = 0.18-0.30 Hz) components said to represent neurocardiac rhythms. To verify whether such a relationship exists we report a unique study where the heart rate autospectrum was determined in a 28-year-old epileptic male patient with an implanted vagal electrical stimulator. The stimulator was activated at 20 Hz, 300 microseconds pulse, and 1.25 V. Continuous ECG and respiratory waveform records were obtained over 45 minutes every 8 hours (7-8 AM; 3-4 PM; 11-12 PM) with the stimulator ON, then 24 hours OFF and then 24 hours ON again. The overall LF:HF peak ratio increased from 0.64 to 1.99 (P less than 0.001) after the stimulator was turned OFF. There was a dramatic increase in the LF peak power (greater than 60%) and a corresponding decrease in the HF peak power (greater than 65%) when the stimulator was turned OFF. These values were reversed when the stimulator was turned ON again. In the early morning and late evening hours, there was a significant rightward shift in the LF peak power frequency (average 0.057 to 0.075 Hz) whenever the stimulator was ON. Otherwise, there were no significant circadian variations in any of the autospectral components. The results demonstrate an unequivocal relationship between selective vagal nerve electrostimulation and alterations in the heart rate autospectrum.
Kamath et al. (Sat,) conducted a case report in Epilepsy (n=1). Vagal nerve electrostimulation vs. Stimulator OFF was evaluated on LF:HF peak ratio (p=<0.001). Vagal nerve electrostimulation significantly altered the heart rate autospectrum, with the LF:HF peak ratio increasing from 0.64 during stimulation to 1.99 when turned off (P<0.001).