event monitoring (event recording, loop recording)

Introduction

Similar to HOLTER, but is worn for longer periods of time. Diagnostic yield of event recording is generally greater than that of HOLTER monitoring.

Indications

• infrequent symptomatic brief arrhythmias
• recurrent syncope
• an implantable loop recorder is useful in identifying infrequent arrhythmias when previous 30-day monitoring is non diagnostic

Advantages

(not mentioned above)

• captures arrhythmia onset

Disadvantages

• ECG leads limit patient activity

Clinical significance

• definitive results (i.e. event with or without dysrhythmia is obtained about 30% of tests)

Procedure

• continuous electrocardiographic monitoring
• before or after symptoms, the patient may trigger the memory loop*
• when activated, the preceding 30-120 seconds of ECG activity are recorded; several minutes of post triggering may be recorded
• loop recording allows for weeks to months# of continuous surveillance
• devices are generally external
• implantable event recorders are placed subcutaneously under local anesthesia
  • capacity is 42 minutes
  • battery life is 3 years
• a small pocket-size recorder that is held to the chest when symptoms are present is also available (see Notes)

* The patient must trigger the device to capture the ECG tracing.

# Generally, devices are provided to patients for a 30 day period.

Interpretation

Results are limited by:

• frequency of syncopal episodes
• patient's failure to trigger recorder

Notes

• post-symptom event recorders, in contrast to looping recorders, begin rhythm recording after the device is triggered by the patient
  • small, pocket-sized recorders held to the chest when symptoms are present
  • not useful for evaluation of syncope since the patient awakens to activate the device when the symptoms have resolved
• it is the loop recording feature that allows event recording to capture event(s) within the two minutes prior to patient- initiated device activation
• mobile cardiac outpatient telemetry systems are used in some centers

More general terms

• ambulatory arrhythmia monitoring

More specific terms

• implanted ECG recorder; implantable loop monitor (LINQ)

Additional terms

• HOLTER