Traditional Holter monitors record on 2 or 3 ECG channels for 24 hours. Recorders are currently available in four types:
Continuous recorders, with every beat recorded and available for analysis.
Patient-activated recorders, which are especially useful when a patient can predict symptoms of the arrhythmias and activate the recorder.
Arrhythmia-activated recorders, in which the monitor turns on when a rhythm disturbance begins and off when it terminates (accuracy depends on the arrhythmia-detection algorithm)
Transmitters for on-line or stored transtelephonic sending of ECG signals during a detected arrhythmia or during symptoms (especially helpful with infrequent but predicted symptoms; not indicated for arrhythmias associated with syncope)
Event monitors, continuous or transmitted, have the disadvantage of requiring patient perception of the arrhythmias. Many patients may be unaware of significant or serious bradyarrhythmias or tachyarrhythmias but able to detect others.
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Therefore, significant arrhythmias may be missed and incorrect treatment strategies employed. Each system has advantages and disadvantages; selection must be tailored to the individual. With any system, however, patients must record in some fashion (e.g. diary) symptoms and activities during the monitored period.
What percentage of patients have symptoms during the monitoring? What percentage of such symptoms occur with a rhythm disturbance?
Approximately 25-50% of patients experience a complaint or symptom during a 24-hour recording. Of such symptoms, only 2-15% correlate with or are believed to be caused by arrhythmia.