Key result
During sleep, the mean QT interval in patients with a VVI pacemaker and constant heart rate was significantly prolonged by 9 msec compared to awake hours.
Why the study?
Does the QT interval prolong during sleep independently of heart rate in patients with VVI pacemakers?
Observational (n=9)
Yes
Does the QT interval prolong during sleep independently of heart rate in patients with VVI pacemakers?
In patients with a fixed heart rate via VVI pacemaker, the QT interval is slightly but significantly prolonged during sleep, suggesting a rate-independent mechanism that may contribute to nocturnal arrhythmias.
In nine patients with chronically implanted ventricular pacemaker (VVI), diurnal variation of the QT interval was studied. The mean age of the patients was 74.2 years and underlying diseases were atrioventricular block (three patients), sick sinus syndrome (four patients) and chronic atrial fibrillation with bradycardia and heart failure (two patients). Eight of the nine patients showed longer QT intervals during sleep than during waking. Only one patient showed no change in QT interval during sleep and during wake time. The mean QT interval of the nine patients at each hour was slightly longer (9 msec) during sleep than that during each awake hour (p less than 0.001). The prolongation of QT interval during sleep may offer a possible mechanism of some nocturnal arrhythmias.
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Oda et al. (1985) conducted an observational in Chronically implanted ventricular pacemaker (VVI) (n=9). Sleep vs. Awake state was evaluated on Mean QT interval (MD 9 msec, p=<0.001). During sleep, the mean QT interval in patients with a VVI pacemaker and constant heart rate was significantly prolonged by 9 msec compared to awake hours.
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