In Secondary Prevention ICD Patients, Does the Initial Presenting VT Cycle Length Predict Subsequent Cycle Length of VT Episodes?

Background: In secondary prevention patients, ICD detection zones are often tailored individually. We aim to determine whether patients initial presenting VT tachycardia cycle length (TCL) prior to ICD implant predicts subsequent VT TCL.Methods: All secondary prevention ICD patients on follow up with available records of appropriate ICD therapy for VT within a 3-year period were studied.Results: 249 VT events in 20 patients were analysed. Mean age 55.8 years, median 5-years follow up. All had sustained VT on 12-lead ECG prior to ICD implant. Mean presenting VT TCL was 313±46 (SD) ms. In majority, post implant VT TCL increased by 20–50 ms compared to at presentation (R=0.52, p=0.02). In the entire group, mean TCL of VTs post implant was 350±43 (SD) ms. Reasons for the increased TCL include medications, ischaemia, scar size changes and different VT circuits.Conclusion: In our population, VT cycle lengths post implant are on average longer, but remain correlated to presenting TCL. Detection cycle lengths 50 ms longer than the TCL of the presenting VT should be programmed if under-detection of subsequent VTs is to be minimised.