A 57 year-old woman with a loop recorder in-situ for investigation of syncope presents to the emergency department with recurrent dizzy spells. Loop recorder tracings (1 & 2) are shown:

Image 1
Image 2

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The Answer:

When reviewing any loop recorder / device tracings it is important to establish a symptom-rhythm correlation – this patient did not have any symptoms at the time of the two traces. Trace 1 represents clear artefact with non-physiological signals seen at baseline, then accentuated later in the trace. The true QRS complexes can be seen marching through and can be mapped out. It is important to have a high index of suspicion for ‘spurious’ / artefactual / undersensing for all logged episodes when this degree of artefact is seen. In trace 2 (reported as a long pause), one can appreciate gradual QRS signal attenuation likely related to patient position / movement. In fact, if one zooms in closely, the QRS complexes never disappear but just become low amplitude before gradually increasingly in amplitude. Fortunately this patient did not receive a pacemaker or defibrillator on the basis of these traces!