 Catheter ablation of ventricular tachycardia VT is performed in patients who have recurrent VT despite the use of other therapies. Electroanatomic mapping of the left ventricular myocardium is performed as part of these procedures to define the arrhythmogenic substrate for subsequent ablation. We hypothesize that delayed enhancement multi-detector computed tomography MDCT will identify areas of myocardial scarring or fibrosis that correlate with findings of voltage mapping in patients with a prior myocardial infarction who are undergoing VT ablation. We will perform a pilot study involving 10 patients with coronary artery disease scheduled for VT ablation to determine the ability of delayed enhancement MDCT to identify arrhythmogenic substrates in these patients, when compared with electroanatomic mapping. All patients will undergo a standard of care 64-slice MDCT study, followed 5 minutes later by the research delayed enhancement acquisition. We will evaluate the relationship between hyperenhanced myocardium, as detected by delayed enhancement MDCT, and abnormal myocardium detected on voltage mapping, defined as areas of myocardium with 0.5 mV signal amplitude. Studies will be performed on the new Siemens 64-slice dual source CT scanner, which reduces radiation exposure from the scan by 33-50. This study will generate preliminary data which will be used for subsequent NIHAHA grant applications or industry sponsored trials. 