Changes In QTc Interval And QT Variability During The Rhythmic Masticatory Muscle Activities In Patients With Sleep Bruxism

Background:Sleep bruxism（SB）has been shown to be associated with cardiovascular diseases,but the pathophysiological mechanisms remain unclear.Aims:We sought to characterize QT interval corrected for heart rate（QTc interval）and QT variability during the rhythmic masticatory muscle activities（RMMAs）in patients with SB.Methods:Polysomnographic recordings were performed on 10 SB patients and10 normal controls.The heart rate variability（HRV）,RR interval,QTc interval,and QT variability index（QTVI）during the RMMAs accompanied with or without limb movements（LMs）（RMMAs/LMs）at different arousal levels were analyzed in the SB patients and controls.Results:The low frequency（LFnu）band of normalized spectral HRV started its predominance before the onset of RMMAs/LMs and ended after the offset of events in the SB patients and controls.The RR and QTc intervals,and QTVI were significantly shorter,longer,and higher（P<0.001 for all）during the RMMAs/LMs than those during the 10 s periods(from 10^th to 20^th s)before the onset and after the offset of RMMAs/LMs,respectively,and were significantly shorter,longer and higher（P<0.01-0.001）during the RMMAs/LMs with awakenings（AW）than those during the RMMAs/LMs with microarousals（m AR）and no arousals（NA）in the SB patients and controls,respectively.The QTc interval and QTVI during the 10 s periods(from 10^th to 20^th s)before the onset and after the offset of the RMMAs/LMs were significantly longer and higher（P<0.001 for both）in the SB patients than those in the controls,respectively.In addition,QTc interval and QTVI were both significantly correlated with the duration of events of RMMAs/LMs（P<0.01-0.0001）.Conclusions:The events of RMMAs/LMs are associated with the increases in QTc interval and QT variability,which might increase the risks for ventricular arrhythmia and sudden cardiac death.The increased autonomic nervous activation and arousal levels might associate with the changes occurred during the RMMAs/LMs in the SB patients and controls.