The human heart rate response profiles to five vagal maneuvers

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.