ADEnosine testing to determine the need for Pacing Therapy with the additional use of an Implantable Loop Recorder (ADEPT-ILR)

Abstract

Aim: To determine the efficacy of permanent pacing in preventing syncopal episodes in patients with unexplained syncope and a positive adenosine test via a randomised double-blind placebo-controlled crossover trial with an accompanying negative adenosine test implantable loop recorder arm. Methods: Individuals presenting to secondary care with unexplained syncope underwent adenosine testing as defined by the European Society of Cardiology. Those with a positive test had a permanent pacemaker implant and were randomised to pacemaker on or off for 6 months before crossing over to the alternative mode. Those with a negative adenosine test underwent a loop recorder implantation. The primary outcome was cumulative syncope burden as reported by monthly syncope diaries. Results: Fifty-two patients were included in the trial and had adenosine testing. There were 35 positive adenosine tests (67%) and 17 negative adenosine tests (33%). There was a mean of 0.4 fewer syncopal episodes per patient during the pacemaker on period compared to the pacemaker off period (1.2 vs. 1.6 episodes) with a higher relative risk of syncope in the pacemaker off period compared with the pacemaker on (RR 2.1, 95% CI 1.0 to 4.4, p=0.048). In the adenosine negative arm, one patient developed bradycardia requiring permanent pacing, giving a negative predictive value of the adenosine test for identifying a bradycardia pacing indication of 0.94 (95% CI 0.69 to 1.0). Conclusion: Permanent pacing reduces the syncope burden in patients with unexplained syncope and a positive adenosine test, whilst a high negative predictive value demonstrates the low likelihood of a missed opportunity for pacemaker implantation. Our study suggests that a positive adenosine test unmasks bradycardia pacing indications without the need for prolonged and invasive investigations, providing opportunity for early and effective intervention.