The absence of difference of the mean QTc interval values between NREM and REM stages seems to confirm our conclusion that sympathetic surges during REM stage do not induce repolarization variability. Therefore, elevated QTVI values found in patients with OSA cannot be interpreted as physiological sympathetic impact during REM sleep and should be considered as a risk factor for potentially life-threatening ventricular arrhythmias. Mean QTVI values were not statistically different between sleep stages. QTVI and QTc values were calculated as means of 2 awake, 3 NREM, and 3 REM sleep episodes the duration of each episode was 300 sec. For QTc interval calculation, in addition to Bazett’s formula, linear and parabolic heart rate correction formulas with two separate α values were used. Beat-to-beat QT interval variability was calculated using QTV index (QTVI) formula. Polysomnographic recordings of 30 patients were analyzed. The aim of the study was to determine whether different sleep stages, especially REM sleep, affect QT interval duration and variability in male patients without obstructive sleep apnea (OSA).
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