THE ETIOLOGY OF SYNCOPE IN PATIENTS WITH NEGATIVE TILT-TABLE AND ELECTROPHYSIOLOGICAL TESTING

Background Patients with syncope of unknown etiology after negative no ninvasive and electrophysiological testing may suffer from recurrent d isability. Syncopal episodes are often too infrequent and unpredictabl e for detection by conventional ambulatory monitoring techniques. Meth ods and Results A long-term subcutaneous monitoring device was implant ed in patients with negative ambulatory monitoring, tilt table and ele ctrophysiological testing to establish cardiac rhythm during spontaneo us syncope. Sixteen patients. aged 57+/-19 years with a mean of 8.4+/- 4.4 previous episodes of syncope underwent device implantation. Fiftee n patients (94%) had recurrent syncope 4.4+/-4.2 months after implanta tion. The remaining patient has not had recurrent syncope and continue s to be followed. A diagnosis was obtained in every patient who had re current episode. Syncope was secondary to sinus arrest in 5, atriovent ricular block in 2, ventricular tachycardia in 1, supraventricular tac hycardia in 1, and nonarrhythmic in 6. Successful therapy was implemen ted in an 15 patients, without recurrence of syncope during 13.0+/-8.4 months of follow-up. Conclusions Unexplained syncope in patients with negative investigations has a broad spectrum of etiologies, the most common of which is bradycardia. An implantable long-term monitoring de vice is useful for establishing a diagnosis when symptoms are recurren t but too infrequent for conventional monitoring techniques.