Diagnostic value of implantable loop recorders in unexplained syncope patients: A single-center experience

Background: The role of implantable loop recorders (ILRs) in the evaluation strategy for recurrent syncope in China is limited. This study aimed to clarify the clinical usefulness of ILRs in the diagnosis and management of patients with unexplained syncope. Subjects and Methods: This was an observational cohort study in unexplained syncope patients. This retrospective study enrolled 37 patients (24 men and 13 women; mean age: 59.5 ± 19.1 years) who were implanted with ILRs and diagnosed with unexplained syncope in the First Affiliated Hospital of Dalian Medical University between January 2013 and October 2018. All patients were followed up every 3–6 months after implantation to record the patients' conditions, electrocardiogram (ECG) data, and presence of syncope. Any patients with a history of postimplantation syncope were recommended for prompt medical attention. The study was approved by the Institutional Review Board of the First Affiliated Hospital of Dalian Medical University (approval No. 2017-046) on March 22, 2017. Results: In the 37 patients, 22 (59.46%) experienced syncope within 187.73 ± 177.12 days after loop recorder implantation, including 9 cases of sinus bradycardia or sinus arrest, 6 of third-degree (advanced) atrioventricular block, 1 of ventricular tachycardia, 2 of supraventricular tachycardia, and 4 of atrial fibrillation accompanied by long RR intervals (>5 seconds). In addition, there was one syncope-free atrial fibrillation case with long RR intervals. Among all the patients, 16 were implanted with permanent pacemakers, 1 received an implantable cardioverter-defibrillator, and 2 received catheter ablation. Based on the analysis of sex, age, underlying comorbid conditions, preimplantation syncope episodes, and ECG data, syncope could be predicted from the occurrence of long RR intervals (≥2 seconds) on Holter. Conclusions: The ILR was an effective tool to establish the cause of unexplained syncope in 59.46% of the study patients and to assist these patients in medical treatment. The occurrence of long RR intervals (≥2 seconds) on Holter was an important predictor for arrhythmic syncope.