Advances in syncope: a combined approach utilizing head-up tilt testing and electrophysiologic evaluation

The electrophysiological evaluation of syncope of unknown origin yields a diagnosis in approximately 40% of patients. In the presence of structural heart disease ventricular tachycardia is the most common etiology accounting for 20% of cases. Over the past several years head-up tilt table testing with isoproterenol provocation has highlighted the syndrome of neurocardiogenic syncope. This syndrome accounts for an additional 30-40% of patients with syncope. There is compelling evidence that this syndrome involves the Bezold-Jarisch reflex with excessive stimulation of ventricular mechanoreceptors (C-fibers) located predominantly in the inferoposterior portion of the heart. Tilt table testing is now an established tool both for diagnosis of this syndrome and for guiding therapy with beta blockers, disopyramide, theophylline, or alpha-agonists. Tilt table testing combined with invasive electrophysiological testing significantly increases the diagnostic yield in the evaluation of syncope.