QT Interval Variability Index and QT Interval Duration in Different Sleep Stages: Analysis of Polysomnographic Recordings in Nonapneic Male Patients

Table 3

The values of heart rate, QT interval variability, and duration between sleep stages.

Variables	Awake/NREM	Awake/REM	NREM/REM
	P value
NN	0.03	0.71	0.05
QT mean	0.02	0.23	0.23
Tp-e	0.05	0.28	0.33
QTVI	0.22	0.05	0.45

Significance of differences between sleep stages: ; REM: nonrapid eye movement sleep stage; REM: rapid eye movement sleep stage; NN: Normal-to-Normal interval; QT: QT interval; Tp-e: T-wave peak to T-wave end interval; QTVI: QT variability index.