Role of catheter mapping in the preoperative evaluation of ventricular tachycardia

Although surgery is an accepted mode of therapy for refractory ventricular tachycardia, routine aneurysmectomy has yielded unpredictable results. This is believed to have occurred because there was no documentation that the arrhythmia actually arose from resected aneurysmal tissue. Catheter endocardial mapping has been used to localize preoperatively the area of origin of the arrhythmia. This technique has established that the arrhythmias arise near the endocardium at the borders of the aneurysm or infarction, or both. These regions, particularly when they occur in the interventricular septum, are not resected by standard aneurysmectomy. Intraoperative endocardial and epicardial mapping have validated the accuracy of this technique. We believe that catheter mapping should be performed before surgery for the following reasons: (1) In some patients ventricular tachycardia is not inducible in the operating room (for example, automatic ventricular tachycardia can be mapped in the catheterization laboratory); (2) in some patients not all morphologic forms of tachycardia can be induced or mapped intraoperatively because of failure of inducibility, time constraints or degeneration of the arrhythmia to ventricular fibrillation; and (3) intraoperative endocardial mapping occasionally cannot be performed because of lack of technical skills, physical factors such as mural thrombosis, or the inability to induce ventricular tachycardia after aneurysmectomy. Other methods currently being evaluated to localize the origin of ventricular tachycardia that do not require induction of arrhythmia are analysis of ventricular electrograms during sinus rhythm and pacemapping.