Document Detail

Autonomic Modulation of Repolarization Instability In Patients With Heart Failure Prone To Ventricular Tachycardia.
MedLine Citation:
PMID:  23934852     Owner:  NLM     Status:  Publisher    
QT variability (QTV) signifies repolarization lability and increased QTV is a risk predictor for sudden cardiac death. The aim of this study was to investigate the role of autonomic nervous system activity on QTV. The study was performed in 29 subjects: 10 heart failure patients with spontaneous ventricular tachycardia [HFVT(+)], 10 heart failure patients without spontaneous VT [HFVT(-)], 9 subjects with structurally normal hearts (HNorm). Beat-to-beat QT interval was measured on 3-minutes records of surface ECG at baseline and during interventions [atrial pacing, esmolol, isoprenaline and atropine infusion]. Variability in QT intervals was expressed as standard deviation of all QT intervals (SDQT). The ratio of SDQT to SDRR was calculated as an index of QTV normalized to heart rate variability. There was a trend towards higher baseline SDQT/SDRR in the HFVT(+) group compared to the HFVT(-) and HNorm groups (p=0.09). SDQT increased significantly in the HFVT(+) and HFVT(-) groups compared to HNorm patients during fixed rate atrial pacing (p=0.008). Compared to baseline, isoprenaline increased SDQT in the HNorm group (p=0.02), but not in HF patients. SDQT remained elevated in the HFVT(+) group relative to the HNorm group despite acute beta-adrenoceptor blockade with esmolol (p= 0.02). In conclusion, patients with HF and spontaneous VT have larger fluctuations in beat-to-beat QT intervals. This appears to be a genuine effect that is not solely a consequence of heart rate variation. The effect of acute autonomic nervous system modulation on QTV appears to be limited in HF patients.
Sachin Nayyar; Kurt Charles Roberts-Thomson; Muhammad A Hasan; Thomas Sullivan; Judith Harrington; Prashanthan Sanders; Mathias Baumert
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2013-8-9
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  -     ISSN:  1522-1539     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2013 Aug 
Date Detail:
Created Date:  2013-8-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
1Centre for Heart Rhythm Disorders, University of Adelaide and Royal Adelaide Hospital.
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