When is a Holter monitor or loop event recorder indicated in the workup of syncope?

Updated: Jan 13, 2017
  • Author: Rumm Morag, MD, FACEP; Chief Editor: Erik D Schraga, MD  more...
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This is an outpatient test. In the past, all patients with syncope were monitored for 24 hours in a hospital. Later, loop recorders and signal-averaged event recorders allowed for monitoring over longer time periods, which increased the yield of detecting an arrhythmia.

Studies showed that age-matched asymptomatic populations have an equivalent number of arrhythmic events recorded by ambulatory monitoring. Loop recorders have a higher diagnostic yield than Holter monitor evaluation with a marginal cost savings. [4]

In a prospective, randomized, controlled study, Sulke et al evaluated the first-line use of a remotely monitored implantable loop recorder (ILR) in the initial investigation of unexplained syncope, in comparison with conventional therapy and a dedicated Syncope Clinic (SC). [33] A total of 246 patients were randomly allocated to conventional management, SC alone, ILR alone, or SC + ILR, with a median follow-up of 20 months. ILRs offered rapid diagnosis, increased the likelihood of syncope being reported, showed a high rate of intermittent bradycardia that required pacing, and reduced recurrent syncope.

A study completed through an ECG outpatient registry in Vermont by Gibson and Heitzman, involving 1512 patients referred for syncope, showed that symptomatic arrhythmias were found in just 0.5% of patients. [5] In fact, patients had symptoms without arrhythmias more often than symptoms with arrhythmias, advancing the notion that the negative diagnostic yield of ambulatory monitoring is a higher than its positive yield.

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