BACKGROUND: Obstructive sleep apnea (OSA) is associated with increases in QT interval corrected for heart rate (QTc interval) and QT variability index (QTVI) and sleep bruxism (SB) is prevalent in OSA patients.
OBJECTIVE: To examine whether QTc interval and QT variability were changed during episodes of rhythmic masticatory muscle activities (RMMAs)/SB in SB patients with and without OSA.
METHODS: The RR and QTc intervals, and QTVI during RMMAs with or without accompanied limb movements (RMMAs/LMs) in 10 normal controls and 10 SB patients without OSA and during apneic and recovery periods of OSA in 10 SB patients with OSA were analysed.
RESULTS: In the SB patients without OSA and controls, QTc intervals and QTVI were significantly increased during RMMAs/LMs compared with those during the 10 s periods (from 10th to 20th s) before the onset and after the offset of RMMAs/LMs, and significantly increased during RMMAs/LMs with awakenings compared with those with microarousals and no arousals. In addition, QTc interval and QTVI were positively correlated with the duration of RMMAs/LMs. Moreover, in the SB patients with OSA, QTc interval and QTVI during the recovery period of OSA events were significantly longer and higher than those during the apneic period regardless of accompanied RMMAs/LMs, and QTc interval and QTVI during the apneic and recovery periods accompanied with RMMAs/LMs were significantly longer and higher than those without accompanied RMMAs/LMs.
CONCLUSIONS: OSA and RMMAs/LMs events were associated with longer QTc intervals and higher QTVI, and RMMAs/LMs might contribute to these changes associated with OSA events accompanied with RMMAs/LMs.

UNASSIGNED: This study investigated the contribution of the regulator of G-protein signaling 5 (Rgs5) knockout to the alteration of the action potential duration (APD) restitution and repolarizing dispersion in ventricle.
UNASSIGNED: The effects of Rgs5-/- were investigated by QT variance (QTv) and heart rate variability analysis of Rgs5-/- mice. Monophasic action potential analysis was investigated in isolated Rgs5-/- heart. Rgs5-/- did not promote ventricular remodeling. The 24-h QTv and QT variability index (QTVI) of the Rgs5-/- mice were higher than those of wild-type (WT) mice (P < 0.01). In WT mice, a positive correlation was found between QTv and the standard deviation of all NN intervals (r = 0.62; P < 0.01), but not in Rgs5-/- mice (R = 0.01; P > 0.05). The absence of Rgs5 resulted in a significant prolongation of effective refractory period and APD in isolated ventricle. In addition, compared with WT mice, the knockout of Rgs5 significantly deepened the slope of the APD recovery curve at all 10 sites of the heart (P < 0.01) and increased the spatial dispersions of Smax (COV-Smax) (WT: 0.28 ± 0.03, Rgs5-/-: 0.53 ± 0.08, P < 0.01). Compared with WT heart, Rgs5-/- increased the induced S1-S2 interval at all sites of heart and widened the window of vulnerability of ventricular tachyarrhythmia (P < 0.05).
UNASSIGNED: Our findings indicate that Rgs5-/- is an important regulator of ventricular tachyarrhythmia in mice by prolonging ventricular repolarization and increasing spatial dispersion in ventricle.