Healthy teens and adults performed four vagotonic maneuvers. A large series
of strabismus surgery patients had deliberately quantified tension on extr
aocular rectus muscles during general anesthesia. The mean bradycardia was
greatest for diving response (apneic facial exposure to cold) and Valsalva
maneuver and least for pressure on the globe and carotid sinus massage. Bra
dycardia occurred for every subject for the non-surgical maneuvers, however
extraocular muscle tension frequently caused no change in heart rate or ev
en tachycardia. The inter-subject variance in percent heart rare change was
greatest for surgical oculocardiac reflex. Of the rectus muscles, the infe
rior caused the most bradycardia while the lateral caused the least. The pe
rcent oculocardiac reflex was not age dependent. Occasional patients demons
trated profound bradycardia with strabismus surgery.
Of these maneuvers, diving response has theoretical advantage in treating p
aroxysmal atrial tachycardia.
The human cardiac vagal efferent was stimulated by several carefully contro
lled maneuvers resulting in wide inter-maneuver differences in bradycardia
magnitude. The greatest intra-maneuver variability occurred with surgical o
culocardiac reflex.