Postextrastimulus delay of ventricular tachycardia return cycle: Indicator of a good ablation site

Abstract

3 A 67-year-old man was referred for catheter ablation of ncessant ventricular tachycardia (VT). He had suffered a yocardial infarction 10 years earlier. VT had occurred 2 ears ago, prompting insertion of an implantable cardioerter-defibrillator (ICD). He began having palpitations folowed by shocks. ICD interrogation showed VT episodes cycle length (CL) 450 ms] terminated by a single shock ach after failed antitachycardia pacing attempts. Intraveous amiodarone was administered. Episodes became more requent and then became incessant but slower (CL 590 ms). T ablation was attempted after retrograde aortic access to he left ventricle. Based on the ECG morphology of VT, the nferobasal free wall was mapped. An electrogram in this egion showed early and late diastolic components (Abld, igure 1). Burst pacing at this site resulted in entrainment ith concealed fusion with a stimulus-to-QRS interval qual to the electrogram-to-QRS interval and a postpacing nterval equal to VT CL. Single extrastimuli were delivered rom this site to ascertain if termination would occur. At elatively long coupling intervals, resetting occurred with a timulated QRS identical to VT. At short coupling intervals, he extrastimulus (S) caused delay of the next VT complex again with identical QRS; asterisk in Figure 1). Intervals in he figure correspond to R-R intervals in the right ventriclar (RV) recording. Based on these findings, radiofre-