Abstract 13424: Prospective Trial of Adenosine on Atrioventricular Nodal Conduction in the Pediatric Transplanted Heart

Introduction: Supraventricular tachycardia (SVT) is common after heart transplant. Adenosine is the standard of care for SVT treatment in children and adults, but is relatively contraindicated post-transplant due to presumed risk of prolonged atrioventricular (AV) block in denervated hearts. This is the first trial of adenosine use in pediatric and young adult heart transplant patients. Hypothesis: Adenosine use after heart transplant does not cause prolonged asystole and is effective in blocking AV nodal conduction. Methods: This was a single center prospective clinical trial including healthy heart transplant recipients ages 6 months - 25 years presenting for routine cardiac catheterization from July 2015 to April 2016. After catheterization, a pacing catheter was placed in the right ventricle and adenosine was given according to a stepwise protocol (12.5mcg/kg, 25mcg/kg, 50mcg/kg, 100mcg/kg and 200mcg/kg, with maximum doses of 0.8mg, 1.5mg, 3mg, 6mg and 12mg for patients ≥ 60kg) until AV block was achieved. The primary outcome was clinically significant asystole ≥ 12 seconds following adenosine that required rescue ventricular pacing. The effects of patient characteristics on adenosine dose and total adenosine effect were tested. Results: Eighty patients completed adenosine testing. No patient (0%, 95% CI 0-3%) required rescue ventricular pacing. AV block was observed in 77 patients (96%, 95% CI 89-99%) at different doses (Figure 1). The median longest AV block was 1.9 seconds (IQR 1.4-3.2) and the mean total adenosine effect was 4.3 seconds (±2.0). No patient characteristics were significant predictors of adenosine dose and total adenosine effect. Results were similar when patients were stratified by weight ≥60kg. Conclusion: Adenosine is a safe medical therapy for the induction of AV block in pediatric and young adult heart transplant patients when using low initial doses (25mcg/kg; 1.5mg if ≥60kg) and gradually escalating therapy.