[Usefulness of the implantable subcutaneous recorder in the diagnosis of recurrent syncope of unknown etiology in patients without structural heart disease and negative tilt test and electrophysiological study].

Background And Objectives: In up to 38% of the cases, the etiology of syncope difficult to determine. The main obstacle for diagnosis of the causes of syncope lies in the unpredictable frequency of episodes. Development of implantable loop recorders allows long term electrocardiographic monitoring. The aim of this study was to evaluate the usefulness of the implantable loop recorder for the diagnosis of recurrent syncope of unknown origin.

Patients And Methods: From May 1991 to April 1999, a cohort of 176 patients with recurrent syncope was prospectively assessed. Investigations, including Holter monitoring, Tilt Test and electrophysiological study, allowed the determination of the etiology in 161 patients. The remaining 15 patients, without structural cardiac disease were selected for continuous electrocardiographic monitoring using an implantable loop recorder.

Results: During follow up after implant, 15 +/- 2 months (X- +/- SEM), 9 patients showed recurrence of symptoms concordant with prior episodes (time: 105 +/- 30 days). In 7 cases records during symptoms were diagnostic (0.47; CI 95%: 0.21-0.73), in 3 cases a diagnosis with documented arrhythmia was achieved, and in 4 other cases a presumptive clinical diagnosis of non-arrhythmic cause was made. In 8 patients, 6 with no recurrences, diagnosis was not possible. There were no complications related to the use of the device.

Conclusions: The strategy of long term monitoring with the implantable loop recorder is safe and effective in patients with recurrent syncope of unknown etiology.