Role of extended external loop recorders for the diagnosis of unexplained syncope, pre-syncope, and sustained palpitations

The diagnosis of syncope and sustained palpitations of suspected arrhythmic origin remains a difficult task in clinical cardiology, often leading to multiple admittances to the emergency room and repetition of different diagnostic tests. The clinical presentation is often not univocal, as the history of pre-syncope, syncope, and sustained palpitations coexist in the same patient.

All the recent guidelines for the management of patients with syncope, palpitations, ventricular arrhythmias and sudden death, supraventricular arrhythmias, and atrial fibrillation recommend the use of prolonged electrocardiogram (ECG) monitoring techniques to allow a better correlation between the symptoms and the arrhythmias, and to detect asymptomatic significant rhythm disturbances.
In the diagnostic work-up of the syncope, external or implantable ECG recorders are specifically recommended in patients with a high pre-test probability of arrhythmic syncope.1,2 The choice of monitoring technique mainly depends on the predicted recurrence rate.

Routine standard 24 h Holter recorders have a low diagnostic yield as they are unlikely to capture the reoccurrence of syncope, unless in extremely frequent episodes, while it may contribute to identifying
ECG markers suggestive of arrhythmic origin. Implantable loop recorders (ILR) have a higher diagnostic yield for infrequent syncope; therefore, a more extensive early usage in the initial phase
of the diagnostic work-up may be recommended. However, ILR are expensive and mildly invasive, therefore unfit as first level diagnostic tools in general clinical practice.

The role of external loop recorders (ELRs) in the diagnostic workup of the syncope is more debated, as the available studies showed conflicting results, with diagnostic yield spanning from 10 to 50%, mainly due to the duration limited to about 1 month. Thus, current indications for ELR are limited to patients with a high
probability of recurrent events.2,4 However, technological advances such as auto-trigger capability and mobile cardiac outpatient telemetry are now showing promising results. In sustained palpitations, the indication for ELR is more clearly established, since several studiesshowed that50–75%of sustained
palpitations recurred within 1 month.5,18 However, most available ELR have technical limitations, due to relativelylow-memory capacity and lack of auto-trigger function.

The main goal of this studywas to evaluate the diagnostic yield of a new generation of ELR with high-memory capacity, extended backward and forward memory, and auto-trigger functions in consecutive
patients with syncopal and/or pre-syncope or palpitations.

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