Cardiac arrhythmias during normal sleep and in obstructive sleep apnea syndrome

Normal sleep is associated with a slowing in heart rate due to a relative shift from sympathetic to parasympathetic neural dominance. Bradyarrhythmias consisting of sinus bradycardia, sinus arrest and second degree (Mobitz type 1) heart block are not uncommon in young adults. With aging, bradyarrhythmias decrease in frequency while atrial arrhythmias and ventricular ectopy increases. Patients with obstructive sleep apnea (OSA) have been demonstrated to have bradyarrhythmias and increased ventricular ectopy in association with apneas when oxyhemoglobin desaturations become severe. Although retrospective studies have suggested that cardiovascular mortality may be increased in patients with OSA, this remains to be proven in prospective clinical studies. Sudden death during sleep secondary to apnea related brady or ventricular tachyarrhythmias may occur. However, this is likely to be a very rare event that remains to be documented in the literature.