Antitachycardia pacing success in implantable cardioverter-defibrillators by patient, device, and programming characteristics

BACKGROUND Antitachycardia pacing (ATP) is an established implantable cardioverter-defibrillator (ICD) therapy that terminates ventricular tachycardias (VTs) without painful ICD shocks. However, factors influencing ATP success are not well understood.OBJECTIVE The purpose of this study was to examine ATP success rates by patient, device, and programming characteristics.METHODS This retrospective analysis of the PainFree SmartShock Technology study included spontaneous ATP-treated monomorphic VT episodes. ATP success rates were calculated for various factors. Also, the relationship of ATP programming on shock burden and syncope were investigated.RESULTS Of the 2770 enrolled patients (2200 [79%] male; mean age 65 years), 1699 (61%) received an ICD and 1071 (39%) a car-diac resynchronization therapy - defibrillator. ATP had .80% rate of success for terminating VTs overall, with similar rates observed between ICD and cardiac resynchronization therapy - defibrillator devices (82.2% vs 80.3%, respectively; P = .81) as well as between primary and secondary prevention patients with ICDs (77.2% vs 83.9% respectively; P = .25). Arrhythmias with a median cycle length of >320 ms had a significantly higher ATP success rate (88.0%; 95% confidence interval 84.8%-90.6%). The cumulative percentage of ATP success increased from 71% at 1 ATP sequence delivered to 87% at >8 sequences delivered. Programming more ATP sequences was associated with lower shock burden (P = .0005). There was no evidence that more sequences were associated with higher rates of syncope (P = .16).CONCLUSION Delivering more ATP sequences resulted in a higher overall success of terminating VTs, while programming more ATP was associated with decreased shock burden and no evidence of increased syncope or acceleration. This suggests that more ATP se-quences should be programmed when possible, but confirmation in prospective studies will be necessary.