Time Interval Between Arrhythmia Detection and Clinical Diagnosis in Patients With Implantable Loop Recorders ― A Single-Center Experience With Current In-Office Follow-up Strategy ―

Background: Implantable loop recorders (ILRs) are essential for diagnosing unexplained syncope and embolic stroke of undetermined source (ESUS). However, the timing of clinical diagnosis often depends on the follow-up model. This study aimed to quantify the “diagnostic gap” (i.e., the interval between arrhythmia onset and clinical recognition) in a conventional in-office follow-up setting in Japan. Methods and Results: We retrospectively analyzed 143 consecutive patients who underwent ILR implantation. Actionable arrhythmias were detected in 45 patients (31%). Except for 2 patients in whom arrhythmia events were detected during hospitalization, 43 patients were divided into 2 groups: an “unscheduled” group (n=8), who sought urgent care due to symptoms, and a “scheduled” group (n=35), whose arrhythmias were discovered during routine office visits. Although the median diagnostic gap in the unscheduled group was 0 days, the scheduled group experienced a median gap of 25 days (interquartile range: 4–75 days). Approximately 80% of clinical interventions were delayed until a scheduled appointment, despite the device having recorded the event much earlier. Conclusions: In a conventional in-office follow-up model, a significant diagnostic lag existed for the majority of ILR patients, particularly for those with asymptomatic events. To maximize the clinical benefit of ILR and ensure timely therapeutic intervention, our findings support the potential role of remote monitoring in reducing this gap.