Autonomic nervous system activity measured directly and QT interval variability in normal and pacing-induced tachycardia heart failure dogs.
OBJECTIVE
This study sought to find out more about the relationship between sympathetic and vagal nerve activity and the cardiac repolarization in a canine model of pacing-induced tachycardia congestive heart failure (CHF).


BACKGROUND
The QT variability index (QTVI), a noninvasive marker of temporal cardiac repolarization dispersion, is among the risk factors for sudden death during CHF. Among factors influencing this variable are the myocardial damage and the autonomic nervous system activity typical of dilated cardiomyopathy.


METHODS
We assessed autonomic nervous system activity recorded from an implanted data transmitter that monitored integrated left stellate-ganglion nervous activity, integrated vagus nerve activity, and electrocardiogram. We collected 36 segments recorded at baseline and 36 after induced CHF. We then arbitrarily identified recording segments as containing low or high sympathetic activity values, and we compared corrected QT intervals and the QTVI under a given sympathetic activity condition at baseline and after inducing CHF.


RESULTS
In the high sympathetic activity subgroup, both QT variables increased from baseline to CHF (corrected QT intervals, p < 0.01; QTVI, p < 0.05) whereas in the low sympathetic activity subgroup they remained unchanged. The baseline QTVI correlated inversely with integrated vagus nerve activity (r(2) = 0.16; beta = -0.47; p < 0.05) whereas, during CHF, the QTVI correlated directly with integrated left stellate-ganglion nervous activity (r(2) = 0.32; beta = 0.27, p < 0.01).


CONCLUSIONS
During CHF, sympathetic activation is associated with an increase in the QT interval and QTVI. Because these changes vary over time, they could result from myocardial structural damage and sympathetic activation combined. Conversely, under normal conditions, no relationship exists between sympathetic activation and the QT variables.
Piccirillo
Gianfranco
G
Dipartimento di Scienze dell'Invecchiamento, Università degli Studi di Roma La Sapienza, Rome, Italy. gianfranco.piccirillo@uniroma1.it
Magrì
Damiano
D
Ogawa
Masahiro
M
Song
Juan
J
Chong
Voon J
VJ
Han
Seongwook
S
Joung
Boyoung
B
Choi
Eue-Keun
EK
Hwang
Samuel
S
Chen
Lan S
LS
Lin
Shien-Fong
SF
Chen
Peng-Sheng
PS
D000704:Analysis of Variance; D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology* / Q000503:physiopathology*; D002304:Cardiac Pacing, Artificial; D004195:Disease Models, Animal; D004285:Dogs; D004562:Electrocardiography; D006333:Heart Failure / Q000209:etiology*; D013564:Sympathetic Nervous System / Q000502:physiology / Q000503:physiopathology; D013610:Tachycardia / Q000150:complications* / Q000175:diagnosis; D014630:Vagus Nerve / Q000502:physiology / Q000503:physiopathology
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