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Abstract
Prolonged asystole provoked by acute arousal to noise in an otherwise healthy man is unusual. Guilleminault1 described a woman with recurrent presyncopal symptoms after waking to noise and one syncopal event, in whom 24-hour ECG showed nocturnal pauses of up to 9 seconds. Up to 15 seconds of symptomless sinus arrest can occur in healthy individuals during sleep and is assumed to be due to vagal overactivity.1,2 The longest pauses are seen in veteran athletes.' During sleep the parasympathetic system is largely responsible for modulation of heart rate. Acute arousal by noise and other emotional and environmental stimulators of sympathetic tone precipitate ventricular arrhythmias in the long QT syndrome.3 Our patient had sinus arrest with a normal QT interval. Mentally mediated vagotonic mechanisms such as fear of pain induce bradycardia and asystole in healthy people of all ages.4 Sudden auditory stimulation, possibly by provoking fear, induces bradycardia and apnoea in new born babies, birds, and some mammals.5 This response superimposed on naturally high vagal tone at night combined with minor abnormalities of autonomic control might cause asystole. It is useful to reproduce the provoking conditions in difficult or atypical cases of syncope.