Hypersensitive Carotid Sinus Reflex

A patient with transient, intermittent, complete heart block had periods of asystole, accompanied by syncope, whenever his cardiac rhythm shifted spontaneously from regular sinus rhythm to complete auriculoventricular dissociation. Similar clinical and electrocardiographic findings were produced by carotid sinus pressure when there was regular sinus rhythm. During the periods of heart block carotid sinus stimulation produced no effects. Physiologic studies suggested that the site of sensitivity of the hyperactive carotid sinus reflex was located at the effector end of the reflex arc. The possibility of structural damage to the heart from repeated stimulation of a hyperactive carotid sinus reflex is considered.