CASTLE-VT is a randomized evaluation of prophylactic ablative treatment of arrhythmogenic ventricular scar in patients referred for HTx evaluation and diagnosed with ICM. Ablation will be performed with the use of a substrate-based approach in which the myocardial scar is mapped and ablated while the heart remains predominantly in sinus rhythm. The primary end point is the composite of all-cause mortality, worsening of HF requiring prioritized transplantation or LVAD implantation. The main secondary study end points are all-cause mortality, cardiovascular mortality, incidence of implantable cardioverter-defibrillator (ICD) therapy, hospitalizations, Quality of life, time to first ICD therapy, number of device-detected ventricular tachycardia/ventricular fibrillation episodes, LV function, and exercise tolerance. CASTLE-VT will randomize 160 patients with a follow up period of 2 years.

Inclusion Criteria:

1. Ischemic cardiomyopathy with left ventricular ejection fraction ≤ 35% (measured in the last 6 weeks prior to enrollment)
2. Eligible for heart transplantation due to end-stage heart failure
3. NYHA class ≥ III
4. Impaired functional capacity or inability to exercise
5. Indication for ICD therapy due to primary prevention
6. Implanted ICD or ICD implantation within 3 months after randomization
7. The patient is willing and able to comply with the protocol and has provided written informed consent
8. Age ≥ 18 years

Exclusion Criteria:

1. Previous catheter ablation for ventricular arrhythmias
2. Previous appropriate ICD-therapy for ventricular arrhythmias
3. Acute coronary syndrome, cardiac surgery, angioplasty, or cerebrovascular accident within 4 weeks prior to enrollment
4. Untreated hypothyroidism or hyperthyroidism
5. Woman currently pregnant, breastfeeding, or not using reliable contraceptive measures during fertility age
6. Mental or physical inability to participate in the study
7. Listed as "high urgent" for heart transplantation
8. Cardiac assist device implanted
9. Planned cardiovascular intervention
10. Life expectancy ≤ 12 month
11. Uncontrolled hypertension
12. Requirement for dialysis due to end-stage renal failure