BETA(2)-AGONIST INDUCED VENTRICULAR DYSRHYTHMIAS SECONDARY TO HYPEREXCITABLE CONDUCTION SYSTEM IN THE ABSENCE OF A LONG QT SYNDROME

Background: The use of inhaled beta(2)-agonists for bronchodilation in the treatment of lower airway obstruction is accepted worldwide. Thes e agents are used for symptomatic relief of lower airway obstruction a nd, as well, can be employed prophylactically in exercise-induced bron chospasm. Cardiac dysrhythmias, specifically the long QT syndrome, hav e been associated with cardiac events precipitated by sympathomimetics . There are reports of documented long QT syndrome in association with syncope in children; however, there are no reports of beta(2)-agonist -induced syncope in the absence of long QT syndrome. Objective: To det ermine predisposing cardiac factors resulting in syncope associated wi th inhaled beta(2)-agonist use. Method: Case report. The index case wa s evaluated for cardiac pathology through non-invasive techniques, car diac catheterization, and electrophysiologic studies. Electrophysiolog ic studies included provocative challenge with parenteral adrenergic a gents. Results: Non-invasive studies were unremarkable. There was no e vidence of prolonged QT syndrome or support for vasopressor syncope. E lectrophysiologic studies revealed reproducible polymorphic ventricula r tachycardia. This predisposition required a ventricular stimulation program of higher intensity while on mexilitine. Conclusions: This cas e of syncope associated with inhaled, short-acting beta(2)-agonist res ulted from a hyperexcitable conduction system rather than the presence of a long QT syndrome.