 Patients with ventricular tachycardia VT undergo catheter ablation. During the ablation procedure, the heart is mapped to determine areas of heart muscle damage. The heart scarring areas are often the source of the VT. Delayed enhancement CT has recently been used to determine areas of scarring . This study is to determine if the areas of damaged heart muscle mapped with the delayed enhancement CT correlate with the same areas that are determined during the catheter ablation. 