Diagnostic Value of Implantable Loop Recorders in Elderly Adults.

Abstract

Syncope is a common presentation in elderly adults and is a significant healthcare burden in terms of mortality, quality of life, and economic cost.1, 2 An implantable loop recorder (ILR), a small device implanted subcutaneously, allows for long-term rhythm monitoring. The device can be activated in response to symptoms, and newer-generation devices have algorithms for autodetection of arrhythmias, including atrial fibrillation (AF). ILRs are an established tool in the investigation of unexplained syncope.3, 4 ILRs have been shown to be effective in younger individuals, but there is a paucity of data on older adults, particularly those age 75 and older.5 This was a single-center observational study of individuals aged 75 and older with unexplained syncope who had an ILR inserted between April 2004 and February 2012. All participants underwent a comprehensive guideline-directed clinical assessment in a tertiary care syncope clinic before implantation.5 The objectives of this study were to determine the diagnostic yield and efficiency of an ILR in older adults with unexplained syncope. Fifty-seven individuals were included; 38 were female, and their mean age was 82 ± 5. The median number of lifetime syncopal events was 4, and median time from first episode was 12 months; 30% had ischemic heart disease. Median follow-up was 22 months. Three individuals elected to have the device explanted because of discomfort. Symptoms occurred during rhythm monitoring (symptom-rhythm correlation) in 32 participants. Time to diagnosis ranged from 1 to 41 months after implantation (median 10 months). Twenty-five were diagnosed with bradyarrhythmia or tachyarrhythmia, including two with complete heart block, one with second-degree heart block, nine with sinus or junctional bradycardia, and 13 with AF with rapid ventricular response (RVR) (Table 1). This observational study of ILR implantation in elderly adults for the investigation of unexplained syncope demonstrated a yield of 56% for achieving symptom-rhythm correlation and identified a large proportion of individuals (44%) with tachyarrhythmia or bradyarrhythmia. A higher than expected proportion of individuals with AF with RVR as the rhythm associated with a syncopal episode was found. With a median time to diagnosis of 10 months, this represents an efficient diagnostic strategy in this population. Two previous cohort studies have reported on ILR use in older adults with syncope. A diagnostic yield of 27% was reported in a cohort of 15 individuals with a mean age of 73.6 Another study reported a diagnostic yield of 56% in 78 individuals aged 65 and older,7 but the proportion of participants aged 75 and older was not reported. The high diagnostic yield in the current study's older cohort may be related to improvements in technology, longer follow-up, and greater clinical experience with the device over time.3 Nine individuals unexpectedly experienced AF with RVR documented as the rhythm associated with syncope. In all cases, these episodes occurred without conversion pauses. AF in the absence of pauses is not classically considered a common mechanism for syncope, although recent studies have shown a significant association between AF and syncope.8, 9 Onset of AF can be associated with high vagal tone.10 Diastolic dysfunction and antihypertensive medication use, which are common in elderly adults, could further exacerbate these vagal changes. The concept that a high proportion of elderly adults with unexplained syncope could have undiagnosed or subclinical AF has further implications because it could represent a stroke risk that could be modifiable with anticoagulation. This association between AF and unexplained syncope requires further exploration. This observational study is, to the best of the knowledge of the authors, the largest reported series of individuals aged 75 and older who were implanted with an ILR for diagnosis of unexplained syncope. Although its small size, single-center design, and different models of ILR (some of which had AF detection algorithms) limited this study, the study suggests that ILR implantation in selected individuals aged 75 and older is feasible and well tolerated and has a high diagnostic yield. There was a higher than previously reported incidence of AF with RVR as the rhythm associated with syncope. The use of long-term monitoring devices should be considered in elderly adults in whom, despite a detailed clinical evaluation, the cause of their syncope remains elusive. Conflict of Interest: The authors declare no competing interests. Author Contributions: McIntyre, Seifer: study concept and design, analysis and interpretation of data, preparation of manuscript. Liebrecht, Daba: acquisition of subjects and data. Sponsor's Role: None.