REM sleep-related brady-arrhythmia syndrome.

Rapid eye movement (REM) sleep-related brady-arrhythmia syndrome is a cardiac rhythm disorder characterised by asystoles lasting several seconds during REM sleep in otherwise healthy individuals. In contrast to arrhythmias associated with obstructive sleep apnea, REM sleep-related sinus arrests and atrioventricular (AV) blocks are not associated with episodes of apnea or hypopnea. In literature, only few cases have been published, suggesting that the prevalence of this nighttime rhythm disorder is very rare. In this paper, we report two new cases of REM sleep-related sinus arrests and one case of REM sleep-related total AV block. To explore the underlying mechanism, an analysis of heart rate variability was performed. In a matched control population, we observed a significant lower low-to-high frequency (LF/HF) ratio in slow wave sleep as compared to REM sleep (2.04 +/- 1.2 vs 4.55 +/- 1.82, respectively [Mann-Whitney U test p < 0.01]), demonstrating a global increase in sympathetic activity during REM. When using the same technique in two of three patients with REM-related arrhythmias, the shift to an increased LF/HF ratio from slow wave sleep to REM sleep tended to be lower. This may reflect an increased vagal activity (HF component) during REM sleep in these subjects. We, therefore, hypothesise that, in our patients with REM sleep-related arrhythmias, the overall dominance of sympathetic activity during REM is present but to a lesser extent and temporarily switches into vagal dominance when the bursts of REMs occur. As it was still unclear whether these REM sleep-related asystoles needed to be paced, we compared our treatment and these of previously reported cases with the current American College of Cardiology/American Heart Association guidelines for implantation of cardiac pacemakers.