Use of the implantable loop recorder in patients with unexplained syncope.

Syncope is a complex clinical syndrome with multiple etiologies that can be very difficult to diagnose. The major obstacles to diagnosis are the periodic and unpredictable nature of events and the high spontaneous remission rate. Conventional testing is often unproductive in patients when initial non-invasive testing is negative, particularly when a paroxysmal ar-rhythmia is suspected. Holter monitoring is often employed initially, with limited utility. Holter monitoring provides a rhythm profile, but rarely achieves the gold standard of a symptom rhythm correlation. The external loop re-corder extends the period of monitoring, enhancing the diagnostic yield to as high as 60% in patients with symptoms likely to recur during a month of device use. Finally, implantable loop recorders further extend the ability to monitor cardiac patients, enhancing the diagnostic yield to as high as 85% in difficult to diagnose syncope. Several recent studies suggest that prolonged monitoring with an implantable loop recorder has a role in patients with syncope and conduction disturbances, negative tilt testing, unexplained seizures and may be superior to conventional testing with tilt and electrophysiologic studies in select patients.