Atrial and ventricular anti-tachycardia pacing as a method of rhythm discrimination

Background: Inappropriate shock by implantable cardioverter defibrillators (ICD) remains a significant clinical problem. We evaluated a new algorithm for discriminating 1:1 SVT and VT, based on the response to atrial (A) and ventricular (V) anti-tachycardia pacing (ATP). Methods: 64 pts (age: 46 plusmn 16 yrs, 34 male, LVEF: 54 plusmn 11%) undergoing EP testing or SVT ablation underwent AATP and VATP through a customized external Marquis ICD once tachycardia was induced. The response to A or V ATP was classified as AT or non-AT according to predetermined criteria. Results: The V ATP algorithm correctly identified AT with a sensitivity of 70% (53%-82%) and specificity of 77% (61%-88%). The A ATP algorithm correctly identified AT with a sensitivity of 96% (84%-99%) and specificity of 91% (67%-98%). Conclusions: Analysis of cross chamber response patterns during and after ATP can successfully discriminate tachycardia mechanism and prevent inappropriate ICD shocks.