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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
PubMed

Insights

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.
Abstract

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