Clinical Symptoms Associated with Asystolic or Bradycardic Responses on Implantable Loop Recorder Monitoring in Patients with Recurrent Syncope

Background: Implantable loop recorders (ILR) have been found to be useful in the diagnosis and management of syncope of unclear etiology. The clinical symptoms of abnormalities seen during ILR monitoring have not been adequately studied. Aim: The aim of this retrospective study was to determine the clinical symptoms which were the best predictors of asystolic or bradycardic responses during ILR monitoring. Methods: Patients with either asystole or bradycardia recorded during ILR monitoring were analyzed from our database. The clinical characteristics of these patients were compared to the patients with ILR's who did not have recorded bradycardic episodes. The episodes were characterized as being convulsive or nonconvulsive, brief (<5 minutes) or prolonged (> 5 minutes), and having had a prodrome or no prodrome. Results: Eleven patients (4 males and 7 females; age 39 ±11years) had asystole or bradycardia on ILR monitoring. Eleven patients (2 males and 9 females; age 46±23) had no bradycardiac events. Palpitations, convulsive syncope, prolonged episode, and prodrome were present in 37% vs. 74% (P = 0.125), 62% vs. 0% (P = 0.002), 87% vs. 0% (P=0), and 73% vs. 13% (P=0.009) patients, respectively, in the asystole/bradycardia and non-bradycardia groups. In the asystole/bradycardia group eight patients had bradycardia (HR < 20) for > 10 seconds and three patients had asystole >10 seconds. Conclusion: Convulsive syncope, prolonged loss of consciousness during syncopal episode, and absence of prodrome or aura are clinical predictors of asystole or bradycardia on ILR monitoring.