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Heart rate-corrected QT interval in men increases during winter months
Daniel M Beyerbach1, Richard J Kovacs, Alexei A Dmitrienko
1Krannert Institute of Cardiology, Department of Medicine, Indiana University, Indianapolis, Indiana 46202, USA.
Heart Rhythm
|March 8, 2007
Summary
Seasonal variations in the heart rate-corrected QT (QTc) interval were observed in men, with the longest QTc in October. No significant seasonal QTc variation was found in women.
Area of Science:
- Cardiology
- Clinical Electrophysiology
- Public Health
Background:
- Sudden cardiac death incidence rises in winter.
- The heart rate-corrected QT (QTc) interval shows circadian variation.
- Limited data exists on QTc interval variation by month of year.
Purpose of the Study:
- To investigate seasonal variations in the QTc interval.
- To determine if QTc interval differs across months of the year.
Main Methods:
- Retrospective analysis of 24,370 electrocardiograms (ECGs).
- Included 7,976 normal baseline ECGs from adults (>=18 years) north of the equator.
- Used QTc = QT*(HR/60)(0.4) for heart rate correction and ANOVA with Bonferroni correction for monthly comparisons.
Main Results:
- Women consistently had higher mean QTc intervals than men (5.2 +/- 2.3 ms).
- Men showed significant seasonal QTc variation (6.1 +/- 1.5 ms, P <.01), peaking in October.
- Women's QTc interval variation was not significant (3.5 ms).
Conclusions:
- Significant seasonal variation in QTc interval is present in adult men.
- The QTc interval in men is longest in October.
- No significant seasonal QTc interval variation was observed in women.
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