Sleep-disordered breathing destabilizes ventricular repolarization: Cross-sectional, longitudinal, and experimental...

Area of Science:

• Cardiology
• Sleep Medicine
• Physiology

Background:

• Sleep-disordered breathing (SDB) is a known risk factor for cardiac arrhythmias and sudden cardiac death.
• Ventricular repolarization lability, measured by the QT variability index (QTVI), is associated with increased cardiac event risk.

Purpose of the Study:

• To investigate the relationship between SDB, intermittent hypoxemia, and QTVI.
• To determine if SDB and hypoxemia predict adverse cardiac events and mortality.

Main Methods:

• Cross-sectional and longitudinal analyses of SDB cohorts (n=122 and n=52) from the Sleep Heart Health Study.
• Experimental study exposing healthy adults (n=19) to acute intermittent hypoxia.
• Electrocardiographic measures, including QTVI, were analyzed.

Main Results:

• Severe SDB was associated with significantly higher QTVI.
• Reduced oxygen saturation during sleep predicted QTVI, not arousal frequency.
• QTVI during sleep predicted all-cause mortality.
• Incident SDB led to a significant increase in QTVI over 5 years.
• Acute intermittent hypoxia progressively increased QTVI in healthy adults.

Conclusions:

• Both prevalent and incident SDB are associated with ventricular repolarization instability.
• Intermittent hypoxemia is implicated as the mechanism driving QTVI changes in SDB.
• These findings suggest a pathway linking SDB, repolarization instability, and increased mortality.