TY - JOUR
T1 - The influence of cardiac autonomic activity on the QT-variability index in able-bodied and incomplete spinal cord injured individuals
AU - Sharif, Hisham
AU - Cotie, Lisa M.
AU - La Fountaine, Michael F.
AU - Ditor, David S.
N1 - Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/7/1
Y1 - 2015/7/1
N2 - Objectives: To investigate, via autonomic blockade, if the QT-variability index (QTVI) is a measure of cardiac autonomic regulation in able-bodied (AB) and incomplete spinal cord injured (SCI) individuals. Methods: Four SCI (41.6. ±. 13.4. years; C4-C7, AIS B-D, 13.4. ±. 13.4. years post injury) and 4 AB (33.0. ±. 7.8. years) individuals were tested. QTVI was determined from electrocardiographic readings obtained during supine rest and cardiovascular (CV) stress, with and without autonomic blockade. CV stress was induced by 40° head-up tilt, the hand submerged in 10. °C water and the jaw clenched. Autonomic blockade was achieved with metoprolol (β-blockade) and atropine (cholinergic blockade). Results: There was no group. ×. condition interaction for QTVI, although there was a significant main effect for condition. After collapsing across groups, QTVI increased with CV stress (p. =. 0.01) and decreased with subsequent β-blockade (p. =. 0.04), suggesting that during CV stress, QTVI is reflective of cardiac sympathetic activity. During supine rest, β-blockade did not change QTVI (p. =. 0.24), however, cholinergic blockade increased QTVI (p. <. 0.001), suggesting that during rest, QTVI is inversely related to cardiac parasympathetic regulation. Conclusion: During times of CV stress, QTVI reflects cardiac sympathetic activity, while during resting conditions, QTVI is inversely related to cardiac parasympathetic activity. These relationships persist after autonomically incomplete SCI.
AB - Objectives: To investigate, via autonomic blockade, if the QT-variability index (QTVI) is a measure of cardiac autonomic regulation in able-bodied (AB) and incomplete spinal cord injured (SCI) individuals. Methods: Four SCI (41.6. ±. 13.4. years; C4-C7, AIS B-D, 13.4. ±. 13.4. years post injury) and 4 AB (33.0. ±. 7.8. years) individuals were tested. QTVI was determined from electrocardiographic readings obtained during supine rest and cardiovascular (CV) stress, with and without autonomic blockade. CV stress was induced by 40° head-up tilt, the hand submerged in 10. °C water and the jaw clenched. Autonomic blockade was achieved with metoprolol (β-blockade) and atropine (cholinergic blockade). Results: There was no group. ×. condition interaction for QTVI, although there was a significant main effect for condition. After collapsing across groups, QTVI increased with CV stress (p. =. 0.01) and decreased with subsequent β-blockade (p. =. 0.04), suggesting that during CV stress, QTVI is reflective of cardiac sympathetic activity. During supine rest, β-blockade did not change QTVI (p. =. 0.24), however, cholinergic blockade increased QTVI (p. <. 0.001), suggesting that during rest, QTVI is inversely related to cardiac parasympathetic regulation. Conclusion: During times of CV stress, QTVI reflects cardiac sympathetic activity, while during resting conditions, QTVI is inversely related to cardiac parasympathetic activity. These relationships persist after autonomically incomplete SCI.
KW - Autonomic blockade
KW - QTVI
KW - Spinal cord injury
UR - http://www.scopus.com/inward/record.url?scp=84930083243&partnerID=8YFLogxK
U2 - 10.1016/j.autneu.2015.04.002
DO - 10.1016/j.autneu.2015.04.002
M3 - Article
C2 - 25935652
AN - SCOPUS:84930083243
SN - 1566-0702
VL - 190
SP - 46
EP - 52
JO - Autonomic Neuroscience: Basic and Clinical
JF - Autonomic Neuroscience: Basic and Clinical
ER -