Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2007 Jan;4(1):20-6.
doi: 10.1016/j.hrthm.2006.09.017. Epub 2006 Sep 16.

The effects of rate and irregularity on sympathetic nerve activity in human subjects

Nathan M Segerson  1 , Niraj Sharma, Michael L Smith, Stephen L Wasmund, Robert C Kowal, Moeen Abedin, John F Macgregor, Rakesh K Pai, Roger A Freedman, Richard C Klein, T Scott Wall, Gregory Stoddard, Mohamed H Hamdan
Affiliations

The effects of rate and irregularity on sympathetic nerve activity in human subjects

Nathan M Segerson et al. Heart Rhythm. 2007 Jan.

Abstract

Background: We have recently shown that atrial fibrillation is associated with an increase in sympathetic nerve activity (SNA) compared with sinus rhythm. It remains unclear, however, whether these findings are true at various rates and whether the magnitude of sympathoexcitation is related to the degree of irregularity.

Objective: To determine the role of irregularity in mediating the SNA changes at various pacing rates. Univariate analysis showed that as the irregularity increased, SBP increased (r = 0.44, P < .001) but that MAP and DBP did not change significantly.

Methods: Using custom-made software, atrioventricular sequential pacing with predetermined rates (100, 120, and 140 bpm) and irregularities (standard deviation = 0%, 5%, 15%, and 25% of mean cycle length) was performed in 23 patients referred for electrophysiologic evaluation. Pacing at each rate/irregularity was performed for 2 minutes, with 2 minutes of recovery in between. Systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP), central venous pressure (CVP), and SNA were measured at baseline and during pacing.

Results: Univariate analysis showed that as the irregularity increased, SBP increased (r = 0.44, P < .001 but that MAP and DBP did not change significantly. A significant correlation was found between the pacing irregularity and SNA, with greater sympathoexcitation noted at greater degrees of irregularity (r = 0.2, P = .04). A five-variable linear model using DBP, MAP, CVP, and degree of pacing irregularity to predict SNA was highly statistically significant (r = 0.46, P < .001). After controlling for hemodynamic changes, for every 1% increase in irregularity, there was a 6.1% increase in SNA.

Conclusion: We have shown that greater degrees of irregularity cause greater sympathoexcitation and that the effects of irregular pacing on SNA are independent of the hemodynamic changes.

PubMed Disclaimer

Publication types