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(Circulation. 2002;106:1488.)
© 2002 American Heart Association, Inc.

Clinical Investigation and Reports

Sex-Selective QT Prolongation During Rapid Eye Movement Sleep

Paola A. Lanfranchi, MD; Abu S.M. Shamsuzzaman, MBBS, PhD; Michael J. Ackerman, MD, PhD; Tomas Kara, MD; Pavel Jurak, MS, PhD; Robert Wolk, MD, PhD; Virend K. Somers, MD, PhD

From the Department of Internal Medicine, Divisions of Hypertension and Cardiovascular Diseases; Department of Pediatric and Adolescent Medicine, Division of Pediatric Cardiology (A.J.A.); and Department of Molecular Pharmacology and Experimental Therapeutics (A.J.A.), Mayo Clinic, Rochester, Minn; and Institute of Scientific Instruments (P.J.), Czech Academy of Sciences, Brno, Czech Republic.

Correspondence to Virend K. Somers, MD, PhD, Divisions of Hypertension and Cardiovascular Diseases, Mayo Clinic, SMH Do 4-350 2nd Street SW, Rochester, MN 55905. E-mail somers.virend{at}mayo.edu

Background— We examined the effects of the various sleep stages on RR and QT intervals in healthy subjects and tested the hypothesis that there is a differential effect of sleep stage on QT interval in women compared with men.

Methods and Results— Eighteen healthy subjects (9 women, age 22 to 45 years) underwent polysomnography and simultaneous recording of ECG, blood pressure, and respiration. RR interval, RR variability, and QT values were measured in stable conditions (no abrupt changes of heart rate or blood pressure, stable breathing pattern) during inactive wakefulness during stages 2 and 3 to 4 of non-REM sleep and during REM sleep. The absolute QT interval was normalized for variations of RR (QTc). In men, RR interval and RR variability increased through all sleep stages. The QTc remained stable from wakefulness through all sleep stages. In women, however, RR interval increased only during non-REM and was virtually identical in wakefulness and in REM. RR variability remained very stable from wakefulness through all stages of sleep. Also, during REM in women, both absolute QT interval and QTc, regardless of the correction maneuver used, increased compared with wakefulness.

Conclusions— The influence of sleep on RR, RR variability, and QTc is sex-dependent. We speculate that these differential sex effects on cardiac rate and repolarization may have important implications for sleep-selected cardiac arrhythmias in women.

Key Words: sleep • sex • nervous system