Objectives: Important adjustments in the autonomic nervous system occur during sleep. Bradycardia, due to increased vagal tone, and hypotension, caused by reduction of sympathetic activity, may occur during non rapid eye movement (REM) sleep (NREM). Increased sympathetic activity, causing increased heart rate, is conversely a feature of phasic REM sleep. During REM sleep, sinus arrests and atrioventricular (AV) blocks unrelated to apnea or hypopnea have been described. These arrhythmias are very rare and only a few cases have been reported in the literature.
Patients/methods: Following an ECG performed for other reasons, two patients with no history of sleep complaints nor symptoms of heart failure or heart attack were referred to our center for nocturnal brady-arrhythmias.
Results: 24h ECG Holter recorded several episodes of brady-arrhythmia with sinus arrest in the first patients and brady-arrhythmias with complete AV block in the second patient. In both patients, episodes of brady-arrhythmia were prevalent in the second part of the night. Nocturnal polysomnography (PSG) demonstrated that episodes occurred only during REM sleep, particularly during phasic events. Treatment with pacemaker was considered only for the patient with complete AV blocks.
Conclusions: These types of brady-arrhythmias are usually detected accidentally due to their lack of symptoms. It has been suggested that in some patients they may lead to sudden unexpected death. Thus, the identification of predisposing factors is mandatory in order to prevent potentially dangerous arrhythmic events.
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