The etiology of syncope in patients with negative tilt table and electrophysiological testing.

BACKGROUND: Patients with syncope of unknown etiology after negative noninvasive and electrophysiological testing may suffer from recurrent disability. Syncopal episodes are often too infrequent and unpredictable for detection by conventional ambulatory monitoring techniques.

METHODS AND RESULTS: A long-term subcutaneous monitoring device was implanted in patients with negative ambulatory monitoring, tilt table and electrophysiological testing to establish cardiac rhythm during spontaneous syncope. Sixteen patients aged 57 +/- 19 years with a mean of 8.4 +/- 4.4 previous episodes of syncope underwent device implantation. Fifteen patients (94%) had recurrent syncope 4.4 +/- 4.2 months after implantation. The remaining patient has not had recurrent syncope and continues to be followed. A diagnosis was obtained in every patient who had recurrent episode. Syncope was secondary to sinus arrest in 5, atrioventricular block in 2, ventricular tachycardia in 1, supraventricular tachycardia in 1, and nonarrhythmic in 6. Successful therapy was implemented in all 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 device is useful for establishing a diagnosis when symptoms are recurrent but too infrequent for conventional monitoring techniques.