CardiologyTier 2Topic

Holter monitoring

Principle

Ambulatory ECG recording (typically 24-48 hours, extendable) capturing rhythm over a period of normal activity - used to correlate symptoms with rhythm and detect paroxysmal arrhythmia missed on a single resting ECG

Diagnostic yield

Diagnostic yield depends heavily on symptom frequency - infrequent symptoms (e.g. monthly) are poorly captured by 24-48h monitoring, prompting longer-duration or event-triggered alternatives

Device choice

Device	Duration	Best for
Holter monitor	24-48h (up to 7 days some devices)	Frequent (daily) symptoms
Event/loop recorder (external)	Weeks	Less frequent symptoms, patient-triggered
Implantable loop recorder	Up to ~3 years	Infrequent, unexplained syncope

Symptom-rhythm correlation

Patient symptom diary correlated against the recorded rhythm is essential - a rhythm abnormality without symptoms, or symptoms without a rhythm abnormality, are both informative (the latter argues against an arrhythmic cause for that episode)

Acting on the result

Guides decisions on anticoagulation (detecting paroxysmal AF), pacemaker/ICD need (detecting significant bradyarrhythmia or non-sustained VT), and antiarrhythmic efficacy monitoring

Indications

Paroxysmal atrial fibrillation, unexplained syncope, palpitations workup, cryptogenic stroke (extended monitoring increasingly used to detect occult AF)

Limitations

A negative short-duration Holter in a patient with a strong clinical suspicion and infrequent symptoms should prompt escalation to longer-term monitoring rather than reassurance

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