Cardiac arrhythmias during sleep

Abstract

Sleep SummaryDifferent types of cardiac arrhythmias may arise in healthy subjects during sleep. Whereas bradyarrhythmias (severe sinus bradycardia, sinus arrest, first and second degree A-V blocks) predominate in the young, elderly subjects more commonly present supraventricular and ventricular ectopic beats and tachyarrhythmias (supraventricular paroxysmal tachycardia, atrial flutter, etc.). A rare potentially life-threatening syndrome, characterised by sinus arrests accompanied by vagal overactivity, has been described in young healthy adults during REM sleep. A sudden death during sleep in apparent healthy Southeast Asian immigrants in the U.S., has been described, may be related to ventricular fibrillation. The frequency of episodes of paroxysmal supraventricular tachycardia appears to follow a circadian rhythm, presenting a minimum peak between 4 and 6 a. m. and two maximal peaks in the morning and afternoon. In contrast, the likelihood for development of an episode of paroxysmal atrial fibrillation (PAF) is the same in wakefulness, slow sleep and REM sleep. Power spectral analysis of heart rate variability has established that PAF episodes are always preceded by a shift in the sympathovagal balance towards the sympathetic limb. The influence of sleep on ventricular arrhythmias (ventricular premature beats (VPB) and ventricular tachycardia (VT)) is more controversial. Most studies show that sleep exerts an inhibitory effect on ventricular arrhythmias with a possible circadian trend (the lowest incidence occurring in the early morning hours). Our polygraphic studies failed to disclose any effect of sleep on ventricular arrhythmias. Obstructive sleep apnea syndrome (OSAS) is one of the most common causes of cardiac arrhythmias during sleep. Of these, the most frequent is brady-tachyarrhythmia. First and second degree atrioventral blocks, severe bradycardia and sinus arrests lasting over 2.5 s. (but also more than 10 s.) are also common. Even though these arrhythmias are severe, it has yet to be established whether they are a direct cause of sudden death in OSAS patients.In conclusion, even though many types of arrhythmias may arise in sleep, there is no evidence that sleep is a determinant factor. Some arrhythmias with a minimal incidence in the early hours of the morning appear to be more affected by a circadian rhythm, which are at least partly sleep-dependent. The only arrhythmias truly linked to sleep are sinus arrests in REM sleep and arrhythmias linked to obstructive sleep apneas.Keywords A-V heart blocks -heart rate variability -obstructive sleep apnea -paroxysmal atrial fibrillation -paroxysmal supraventricular tachycardia -sinus bradycardiaventricular ectopic beats -sinus arrest.