Time-Dependent Diagnostic Yield and Therapeutic Impact of Implantable Loop Recorders, Brugada Syndrome as the...

The optimal duration of implantable loop recorder (ILR) monitoring remains uncertain and may differ according to the indication for implantation. We evaluated whether the time-dependent diagnostic yield and clinical relevance of ILR-detected arrhythmias differ among patients implanted for syncope, palpitations, cryptogenic stroke, or Brugada syndrome.

This study sought to define the time-dependent diagnostic yield of ILRs across clinical indications and to assess whether early and late diagnoses differed in their impact on clinical management.

We retrospectively analyzed 1734 consecutive patients undergoing ILR implantation at 5 Italian centers for unexplained syncope, palpitations, cryptogenic stroke, or Brugada syndrome. Diagnosis of interest was defined according to the implant indication: pauses for syncope, supraventricular tachycardia or atrial fibrillation for palpitations, atrial fibrillation for cryptogenic stroke, and ventricular tachycardia or pauses for Brugada syndrome. Median follow-up was 34 months. Maximally selected rank statistics identified 26 months as the global threshold separating early from late diagnoses, while indication-specific optimal diagnostic windows were 14 months for syncope, 13 months for palpitations, 16 months for cryptogenic stroke, and 55 months for Brugada syndrome. In syncope and palpitations, most actionable diagnoses occurred early, and diagnostic efficiency declined markedly after 26 months, with late findings often less clearly related to the index presentation. In cryptogenic stroke, atrial fibrillation detection was most frequent early but could still lead to changes in antithrombotic management later, supporting an individualized "gray-zone" approach to prolonged monitoring. By contrast, Brugada syndrome showed sustained diagnostic yield over extended follow-up, with late ventricular arrhythmias or pauses retaining major prognostic and therapeutic implications, including implantable cardioverter-defibrillator implantation and device-type selection.

The value of ILR monitoring is strongly time- and indication-dependent. Prolonged routine monitoring or reimplantation appears to have limited incremental value in syncope and palpitations when early follow-up is unrevealing, whereas extended surveillance may remain justified in Brugada syndrome and should be individualized after cryptogenic stroke. These observations support indication-driven ILR follow-up strategies rather than a uniform approach based on device longevity alone.