Document Detail

Sex differences in QTc interval and QT dispersion: dynamics during exercise and recovery in healthy subjects.
MedLine Citation:
PMID:  12422156     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Sex differences have been described in resting cardiac repolarization and susceptibility to torsade de pointes in humans. This study compares the QT-interval and QT-dispersion dynamics during exercise and recovery between healthy men and women. METHODS: Twenty healthy subjects (10 males aged 30 +/- 4 years, 10 females aged 31 +/- 11 years) underwent symptom-limited bicycle ergometry followed by a 10-minute recovery period. Digital 12-lead electrocardiograms (ECG) were recorded every 10 seconds during exercise and recovery. For each lead, the QTp interval (Q onset to T peak) was automatically measured by use of QT Guard (GE Marquette, Milwaukee, Wis). QTp dispersion was defined as the difference between the maximum and minimum QTp for each ECG. To quantify QT dynamics, we fit the QTp in lead V(3) (QTpV(3)) versus cycle length (CL) relationship to a quadratic function during exercise and recovery with nonlinear regression analysis. Similar regression analysis was performed for the QTp dispersion versus CL relationship. RESULTS: At baseline, QTpcV(3) was longer in women than in men (338 +/- 25 vs 278 +/- 15 ms, P <.0001), but QTp dispersion was similar (35 +/- 18 vs 41 +/- 19 ms). At peak exercise, QT dispersion decreased compared with baseline in both men and women. During exercise and recovery, women had a steeper QTpV(3)-CL relationship. QTpV(3) hysteresis, a measure of the exercise and recovery QTpV(3)-CL curve separation, was greater in women than in men when measured 1 minute into recovery (33 +/- 20 vs 6 +/- 8 ms, P <.001). No sex difference in QTp-dispersion-rate adaptation was observed during exercise or recovery. CONCLUSIONS: Healthy women exhibit greater QT-interval-rate adaptation during both exercise and recovery than men, resulting in more QT-interval hysteresis. Greater QT prolongation during decelerating heart rates in recovery may play a role in increasing proarrhythmia risk in women.
Vijay S Chauhan; Andrew D Krahn; Bruce D Walker; George J Klein; Allan C Skanes; Raymond Yee
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  American heart journal     Volume:  144     ISSN:  1097-6744     ISO Abbreviation:  Am. Heart J.     Publication Date:  2002 Nov 
Date Detail:
Created Date:  2002-11-07     Completed Date:  2002-12-30     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370465     Medline TA:  Am Heart J     Country:  United States    
Other Details:
Languages:  eng     Pagination:  858-64     Citation Subset:  AIM; IM    
Division of Cardiology, University of Western Ontario, London, Ontario, Canada.
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MeSH Terms
Exercise / physiology*
Exercise Test
Heart Rate / physiology*
Sex Characteristics*
Statistics as Topic

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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