Recurrent syncope. Experience with an implantable loop recorder.

The cause of recurrent syncope is often difficult to determine when initial laboratory investigations are negative. Advances in implantable monitoring technology permit long-term monitoring of the electrocardiogram in patients with recurrent undiagnosed syncope. A pilot device implanted in the left pectoral region established the cardiac rhythm during syncope in all 20 of 24 patients who developed syncope during follow-up. The cause was arrhythmic in 10 and nonarrhythmic in 10. Therapy resulted in resolution of symptoms in 17 of 20 patients. The implantable loop recorder is a promising diagnostic tool for investigation of syncope.