Cardiac arrhythmias during wakefulness and sleep in 15 patients with 
sleep-induced obstructive apnea, and the effect of atropine and tracheostomy on 
these arrhythmias were studied by continuous overnight Holter 
electrocardiographic, respiratory and electroencephalographic recordings. Sleep 
was characterized by marked sinus arrhythmia in 14, extreme sinus bradycardia ( 
less than 30 beats/minute) in six, asystole of 2.5 to 6.3 seconds in five, 
second degree atrioventricular (A-V) block in two, and ventricular 
arrhythmias--complex premature ventricular beats in 10 and ventricular 
tachycardia in two. Arrhythmias during wakefulness were limited to premature 
ventricular beats in six. Atropine administration was partially and tracheostomy 
highly effective in preventing the majority of these arrhythmias during sleep. 
Marked sinus arrhythmia during sleep is characteristic of the syndrome of 
obstructive sleep apnea and is frequently accompanied by potentially 
life-threatening tachy- and bradyarrhythmias. Possible mechanism of production 
of these arrhythmias, the mode of action of tracheostomy and atropine, and the 
probable role of similar arrhythmias in the sudden infant death syndrome are 
discussed.