In patients with scar in the hearts after heart attacks, the risk for dangerous abnormal heart rhythms, including sudden death is high. This is because dead muscle fibers are replaced by scar tissue, creating a physiological condition promoting abnormal heart rhythms.These abnormal heart rhythms are called ventricular arrhythmias or ventricular tachycardias. In these patients, ablation procedures can be helpful, however the recurrence rate of arrhythmias after ablation remains unacceptably high. The primary reason for this high recurrence rate is nonspecific mapping methodologies for identifying the heart area responsible for these arrhythmias. Therefore, new methods for increasing the specificity of mapping have been the subject of significant research for many years, however implementation of these methods in clinical practice has been challenged by limited technologies. Recently, a new mapping technology named "parallel mapping" has been developed, received FDA approval and is routinely utilized at the Cleveland Clinic. However, the workflow of using parallel mapping, and the efficacy of ablation using this technology have not been evaluated.