title: The evaluation of syncope with electrophysiologic studies.
abstract: An electrophysiologic study is appropriate in patients with syncope that remains unexplained after a complete clinical, neurologic, and non-invasive cardiovascular evaluation. However, not all abnormalities demonstrated by electrophysiologic testing can be assumed to be related to syncope. The findings that have a high and low probability of being clinically significant are summarized in Table 2. If patients with the carotid hypersensitivity syndrome are screened out before electrophysiologic testing, the most common clinically significant abnormality in patients with structural heart disease is inducible unimorphic ventricular tachycardia, which is found in approximately 30 per cent of patients. The overall yield of clinically significant findings in patients with unexplained syncope is 40 per cent. In contrast, the overall yield of clinically significant abnormalities in patients who do not have structural heart disease is extremely low, less than 10 per cent. Because the yield is low, an electrophysiologic study is not indicated in patients without structural heart disease unless the syncope is recurrent and problematic or there is a specific reason to suspect an arrhythmia as the cause of syncope. However, in patients who have structural heart disease, an electrophysiologic study is appropriate after even one episode of unexplained syncope, because of the importance of identifying those patients in whom a potentially lethal arrhythmia may be the cause of syncope.
mesh_terms: D004568:Electrodiagnosis; D004594:Electrophysiology; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D013575:Syncope / Q000175:diagnosis* / Q000503:physiopathology