Ventricular tachycardia (VT) is a life-threatening heart rhythm disorder. Special pacemakers called implantable cardiac defibrillators (ICDs) help treat VT episodes, however they do not prevent the VT episodes from occurring. Catheter ablation for VT is a minimally-invasive and established procedure for preventing VT recurrence. This involves placing wires in the heart to find the diseased areas that are responsible for the VT episodes. The diseased areas are shown on computer-generated maps and are later removed via controlled tissue heating (ablation). A major challenge during the VT ablation procedure is locating the diseased area responsible for the VT episodes. Several methods have been described to locate the diseased heart area, however these methods are not always effective. In this study, we aim to improve the identification of the diseased heart areas responsible for the VT episodes using a novel method. Our research group have developed, tested and peer-reviewed this improved method of locating diseased areas by looking for signals called decrementing evoked potentials (DeEPs). Ablation will target DeEPs shown on the computer-generated maps. We will assess if VT can be triggered at the end of the procedure. Patients will be monitored over 12 months to see if ablation of DeEPs leads to a reduction in VT episodes. We aim to recruit 77 patients with established heart disease of any cause, who have suffered VT episodes with ICDs. Suitable patients will be identified and recruited from inpatient and outpatient settings. A quality-of-life questionnaire will be completed by patients before and after the ablation procedure. The procedure will be performed as routine standard of care, in the cardiac catheter laboratory across multiple recruiting cardiac centres in the UK providing well established VT ablation service. Overall, this study will contribute towards developing refined VT ablation techniques, aiming to improve patient outcomes.