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Sex differences in repolarization homogeneity and its circadian pattern
Peter Smetana1, Velislav N Batchvarov, Katerina Hnatkova
1Department of Cardiological Sciences, St. George's Hospital Medical School, London SW17 0RE, United Kingdom.
Insights
Sex differences in heart repolarization patterns exist, with women showing higher localized heterogeneity. Repolarization irregularity peaked in the morning for both sexes, but patterns differed from heart rate and QTc intervals.
Area of Science:
- Cardiology
- Electrophysiology
- Chronobiology
Background:
- Sex differences in cardiac arrhythmia risk are established but poorly understood.
- Ventricular repolarization heterogeneity is a key factor in arrhythmogenesis.
- Investigating sex-specific circadian patterns of repolarization homogeneity is crucial.
Purpose of the Study:
- To investigate sex differences in ventricular repolarization homogeneity.
- To analyze the circadian patterns of repolarization homogeneity in men and women.
- To correlate repolarization homogeneity with cardiac electrical activity.
Main Methods:
- 24-hour Holter recordings in 60 healthy subjects (27 males).
- Calculation of repolarization homogeneity using singular-value decomposition on 12-lead ECG data.
- Analysis of RR intervals, corrected QT (QTc) intervals, and repolarization homogeneity descriptors over 10-min bands.
Main Results:
- Significant sex differences in global and regional repolarization homogeneity were observed.
- Women exhibited higher localized repolarization heterogeneity compared to men.
- Repolarization irregularity was highest in the morning for both sexes, with distinct circadian patterns compared to HR and QTc.
Conclusions:
- Ventricular repolarization exhibits distinct sex-specific circadian patterns.
- Women demonstrate greater localized repolarization heterogeneity, potentially contributing to sex differences in arrhythmia risk.
- Further research is needed to elucidate the clinical implications of these findings.
Abstract:
The reason for sex differences in arrhythmic risk remains unclear. Heterogeneity of ventricular repolarization is directly linked to arrhythmogenesis; thus we investigated repolarization homogeneity and its circadian pattern in men and women. During 24-h Holter recordings in 60 healthy subjects (27 males), a 12-lead electrocardiogram (ECG) was obtained every 30 s. RR and QT intervals, and, after singular-value decomposition, two characteristics of repolarization homogeneity were calculated in each ECG. Corrected QT (QTc) values were obtained using an individually optimized heart rate (HR) correction formula. All values were averaged over 10-min time bands from 0000 to 2400. There were substantial sex differences in both global repolarization homogeneity (measured by the total cosine of the angle between QRS and T wave vectors) and regional homogeneity of repolarization (quantified independently by the relative T wave residuum). Whereas women throughout the 24 h followed more closely the pattern of inverse sequence between depolarization and repolarization, they also showed much higher localized repolarization heterogeneity than men. In both women and men, repolarization irregularity was greatest during morning hours. A sex difference was also observed for HR and QTc interval; however, the circadian patterns of the repolarization homogeneity descriptors were different from those of HR and QTc intervals.