Implantable loop recorders in patients with unexplained syncope: Clinical predictors of pacemaker implantation

Background: Implantable loop recorders (ILR) are a valuable tool for the investigation of unexplained syncopal episodes. The aim of this retrospective single center study was to identify predictive factors for pacemaker implantation in patients with unexplained syncope who underwent ILR insertion. Methods: One hundred six patients were retrospectively analyzed (mean age 59.1 years; 47.2% male) with unexplained syncope and negative conventional testing who underwent ILR implantation. The primary study endpoint was detection of symptomatic or asymptomatic bradycardia requiring pacemaker implantation. Results: The average follow-up period after ILR implantation was 20 +/- 15 months. Pacemaker implantation according to current guidelines was necessary in 22 (20.8%) patients, mean duration until index bradycardia was 81 +/- 88 (2- 350) days. Ten (45.5%) patients received a pacemaker due to sinus arrest, 7 (31.8%) patients due to third-degree atrioventricular block, 2 (9.1%) patients due to second-degree atrioventricular block and 1 (4.5%) patient due to atrial fibrillation with a slow ventricular rate. Three factors remained significant in multivariate analysis: obesity, which defined by a body mass index above 30 kg/m(2) (OR: 7.39, p = 0.014), a right bundle branch block (OR: 9.40, p = 0.023) and chronic renal failure as defined by a glomerular filtration rate of less than 60 mL/min (OR: 6.42, p = 0.035). Conclusions: Bradycardia is a frequent finding in patients undergoing ILR implantation due to unexplained syncope. Obesity, right bundle branch block and chronic renal failure are independent clinical predictors of pacemaker implantation.