Circadian rhythmicity of rate-normalized QT interval in hypothyroidism and its significance for development of class III antiarrhythmic agents

Details

Serval ID
serval:BIB_81882256D022
Type
Article: article from journal or magazin.
Collection
Publications
Title
Circadian rhythmicity of rate-normalized QT interval in hypothyroidism and its significance for development of class III antiarrhythmic agents
Journal
American Journal of Cardiology
Author(s)
Sarma  J. S., Venkataraman  K., Nicod  P., Polikar  R., Smith  J., Schoenbaum  M. P., Singh  B. N.
ISSN
0002-9149 (Print)
Publication state
Published
Issued date
10/1990
Volume
66
Number
12
Pages
959-63
Notes
Journal Article --- Old month value: Oct 15
Abstract
Lengthening of repolarization and refractoriness occurs in hypothyroidism; it is associated with a reduced probability of arrhythmias, with the converse occurring in hyperthyroidism. Because the QT interval and its circadian rhythmicity relative to heart rate is poorly defined in man, we used our new computer-assisted technique to measure QT interval in our analysis of 24-hour Holter tapes before and after (8 to 12 weeks) thyroxine (T4) replacement in 10 patients with hypothyroidism; the findings were compared to those in 6 normal control subjects. QTc interval was prolonged (p less than 0.02) and heart rate decreased (p less than 0.005) during the hypothyroid state. Data were analyzed for circadian rhythmicity by repeated-measures analysis. Circadian variation in QTc and heart rate was statistically significant during hypothyroid and euthyroid states (p less than 0.001) as well as in control subjects, but the circadian rhythmicity of QTc interval and heart rate were out of phase; the maximum prolongation of QTc occurred between midnight and 6 A.M., at a time when heart was at its lowest. QTc interval remained significantly prolonged after 8 to 12 weeks of T4 replacement, when biochemical indexes of hypothyroidism had returned to normal values. The computer-assisted QTc interval determination technique that we used, and our data on the circadian rhythmicity of QTc and heart rate, have significant implications for the development of new class III antiarrhythmic agents.
Keywords
Adult Anti-Arrhythmia Agents/*classification Circadian Rhythm/*physiology Data Interpretation, Statistical *Electrocardiography, Ambulatory Female Heart Rate/*physiology Humans Hypothyroidism/*physiopathology Male Middle Aged Thyroid Function Tests
Pubmed
Web of science
Create date
25/01/2008 15:00
Last modification date
03/03/2018 18:48
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