Abstract 4137564: Management of Atrial Flutter (AFL) Using Intrinsic Antitachycardia Pacing (iATP) Protocol

Background: The recently introduced iATP algorithm augments traditional ventricular antitachycardia pacing (ATP) with programmed stimulation (PS) resulting in greater efficacy terminating ventricular tachycardia than traditional ATP in avoiding ICD shocks. The use of iATP in the atrium may similarly enhance termination of atrial arrhythmias, avoiding prolonged arrhythmia burden or need for cardioversion. Objective: To compare efficacy of 3 atrial ATP protocols (PROT[GS1] ) in either converting AFL to sinus rhythm or accelerating AFL to atrial fibrillation (AF). Methods: Patients presenting in AFL for ablation were recruited. Patents underwent all three pacing protocols, twice, and in random order (6 times total). 1. PROT 1 – Ramp pacing at 91% of tachycardia cycle length (TCL) for 13 beats with 5 or 10ms decrement, avoiding pacing cycle length (CL) <160 ms. 2. PROT 2 – Ramp pacing at 81% of TCL for 13 beats again with 5 or 10ms decrement, avoiding CL <160 ms. 3. PROT 3 (iATP) – Drive train of 88% of TCL for 15 beats with singles, doubles, and triples down to atrial effective refractory period. If AFL terminated, it was re-induced with PS or burst pacing. Termination and CL acceleration to AF are defined as the positive effect. No effect is defined as the negative effect. CL acceleration and termination were treated similarly in the analysis because AF is clinically easier to manage than AFL. Results: Of the 21 patients enrolled, 17 completed the entire protocol. 4 patients (excluded from analysis) did not complete the protocol due to non-inducibility following AFL termination. The TCL of the AFL ranged from 190ms to 290ms. PROT 1 terminated AFL 6 out of 34 attempts (17.6%). PROT 2 terminated AFL 7 out of 34 attempts (20.5%). iATP terminated AFL 13 out of 34 attempts (38%). It also accelerated AFL more frequently than the other two protocols (PROT 1:1, 2:4, 3:8). Conclusion: Atrial iATP was significantly more effective in either terminating or accelerating AFL, compared to ramp pacing protocols.