Swallowing syncope: complex mechanisms of the reflex.

A 69-year-old woman was admitted to our hospital for the examination of syncope. When she ate solid food, she had dizziness or loss of consciousness. The ambulatory ECG suggested sino-atrial block during swallowing with a maximum sinus pause of 6 seconds. An electrophysiologic study revealed pre-existing sinus node dysfunction, which was exaggerated by the balloon inflation in the esophagus. Atropine counteracted the slowing of the basal sinus rate induced by esophageal pressure, but it did not block the effect on the maximum sinus node recovery time. This observation suggested that the syncope was mediated partly by a non-vagal mechanism.