Clinical Autonomic Research

, Volume 8, Issue 3, pp 165–171 | Cite as

Effect of parasympathetic blockade on the signalaveraged electrocardiogram

Research Paper


Low parasympathetic activity is associated with late potentials detected at a noise level of 0.4 μV in a signal-averaged electrocardiogram (SAECG) following myocardial infarction. In contrast, at a noise level of 0.2 μV, lowering parasympathetic activity influences late potential parameters in the opposite direction in healthy subjects. The aim of this study was to estimate the relationship between parasympathetic activity and the SAECG obtained at noise levels of 0.4 and 0.2 μV in healthy subjects. Two SAECG recordings in 10 healthy subjects were obtained at noise levels of 0.2 and 0.4 μV before and after parasympathetic blockade using atropine (1 mg). Signal-averaged QRS duration (SA-QRS), late potential duration (LPD) defined as duration of terminal signals below 40 μV, and root mean square voltage of the terminal 40 ms of the averaged QRS (RMS40) were measured. At a noise level of 0.2 μV SA-QRS reduced from 124±14 to 114±17 ms (P=0.008), LPD from 37±10 to 28±14 ms (P=0.01), and RMS40 increased from 26±22 to 41±25 μV (P=0.006) during parasympathetic blockade compared to baseline values. At a noise level of 0.4 μV the SA-QRS (115±15 ms) and LPD (29±11 ms) were lower and the RMS40 (37±23 μV) was higher compared to the noise level 0.2 μV, and no systematic alterations of the three variables were found during parasympathetic blockade. The parasympathetic nervous system may induce a very low-amplitude late potential in the SAECG. The data suggest that parasympathetic activity and a low noise level may lead to a false late potential-positive SAECG in low arrhythmia risk subjects. Therefore, we recommend the use of a noise level of 0.4 μV or identification of high arrhythmia risk patients by late potentialand low parasympathetic activity.


signal-averaged electrocardiogram noise level parasympathetic activity late potentials 


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Copyright information

© Lippincott-Raven Publishers 1998

Authors and Affiliations

  1. 1.Department of Cardiology, Skejby SygehusUniversity HospitalAarhusDenmark

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