Match the monitoring duration to the frequency of the symptoms
Expansion
| Device | Duration | Best for |
|---|---|---|
| 24 hour Holter | 1 day | Daily symptoms, rate control assessment |
| 48 to 72 hour, or 7 to 14 day patch | Days to 2 weeks | Symptoms several times a week |
| Event recorder, patient activated | Weeks | Sustained, predictable symptoms |
| External loop recorder | Weeks to a month | Brief symptoms, including syncope |
| Implantable loop recorder | Up to 3 years | Infrequent syncope, cryptogenic stroke |
The governing principle is symptom rhythm correlation. A monitor that records no arrhythmia during a period when the patient had no symptoms has answered nothing; a monitor that records a normal rhythm during a typical episode has excluded arrhythmia, which is equally valuable. Patients must therefore keep a symptom diary.
Indications
- Palpitations, to identify the underlying rhythm
- Syncope where an arrhythmic cause is suspected, particularly with structural heart disease, exertional syncope or an abnormal ECG
- Atrial fibrillation: detection after cryptogenic stroke, and assessment of rate control or burden
- Assessing pauses, heart block and pacemaker function
- Silent ischaemia and QT assessment in selected cases
What a normal recording does not exclude: an infrequent arrhythmia. Escalating the duration of monitoring is the answer, not repeating a 24 hour tape.
In cryptogenic stroke, prolonged monitoring markedly increases the detection of paroxysmal atrial fibrillation compared with a 24 hour tape, and the finding changes antithrombotic treatment from antiplatelet to anticoagulant, which is why it is pursued so persistently.