Journal article
Effect of β-adrenergic stimulation on QT interval accommodation
Heart rhythm, Vol.8(2), pp.263-270
02/2011
DOI: 10.1016/j.hrthm.2010.10.012
PMID: 20950708
Abstract
QT interval correction formulas are based on instantaneous heart rate (HR), but QT interval adaptation to sudden HR change occurs gradually. In humans, the QT interval has been reported to reach a new steady-state value in about 2 minutes.
This study sought to assess β-adrenergic stimulation effects on QT interval response to HR change.
Ten subjects (42.1 ± 15.3 years, 3 men) undergoing radiofrequency ablation of supraventricular tachycardia were studied. Atrial pacing for 5 minutes at an HR ranging from 60 to 140 beats/min was performed before and during dobutamine infusion (10 μg/kg/min). The QT response to sudden HR change was evaluated.
The QT response to sudden HR change consists of an immediate response (IR), followed by a gradual monoexponential course to the new steady-state value. Linear function results in inferior fit of QT adaptation course (P < .05 compared with exponential). The time constant of the exponential is approximately 1 minute (50.9 ± 11.4 seconds). The IR magnitude is approximately 3% of the RR interval change (2.97% ± 2.01%). Dobutamine shortens steady-state QT at given HR (from 301.8 ± 11.2 ms to 290.6 ± 13.2 ms at 120 beats/min; P < .001) and increases IR magnitude (to 13.28% ± 8.99% of RR change; P < .01). During sinus rhythm, QT variability and QT variability index were significantly increased by dobutamine.
QT adaptation has 2 distinct phases, which might have different mechanisms. The effect of β-adrenergic stimulation on IR may increase QT variability by increasing the immediate response to HR variability. These results may be important in the assessment of drug effects on repolarization and for understanding of QT variability.
Details
- Title: Subtitle
- Effect of β-adrenergic stimulation on QT interval accommodation
- Creators
- Srikanth Seethala - Department of Medicine, Texas Tech University Health Science Center, El Paso, TexasVladimir Shusterman - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PennsylvaniaSamir Saba - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PennsylvaniaSusan Mularski - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, PennsylvaniaJan Němec - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
- Resource Type
- Journal article
- Publication Details
- Heart rhythm, Vol.8(2), pp.263-270
- Publisher
- Elsevier Inc
- DOI
- 10.1016/j.hrthm.2010.10.012
- PMID
- 20950708
- ISSN
- 1547-5271
- eISSN
- 1556-3871
- Grant note
- Boston Scientific Company
- Language
- English
- Date published
- 02/2011
- Academic Unit
- Cardiovascular Medicine; Internal Medicine
- Record Identifier
- 9984094539602771
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