CURRENT ROLE AND FUTURE PERSPECTIVES FOR RADIOFREQUENCY CATHETER ABLATION OF POSTMYOCARDIAL INFARCTION VENTRICULAR-TACHYCARDIA

The most common substrate for ventricular tachycardia (VT) is a postmy ocardial infarction (MI) scar. Radiofrequency catheter ablation (RFCA) in post-MI VT faces clinical, electrophysiologic, anatomic, and metho dologic difficulties not found in many other human tachycardias. The p athophysiologic understanding of post-MI VT is incomplete; this influe nces the process of selecting RFCA target sites, which is time consumi ng, demands catheter stability, and has low sensitivity and predictive value for VT interruption by RF current. Improving and simplifying th e methodology of RFCA in post-Mi VT is badly needed. We review the pat hophysiology of post-MI VT from the data reported on endocardial, epic ardial, and intramural ventricular mapping obtained either intraoperat ively or in a Langendorff perfused set-up in hearts from transplanted patients. From these studies we conclude that (1) some post-MI VT case s are not amenable to RFCA (reentry around the scar, VT having a subep icardial or deep intramural substrate, or a wide, extensive, subendoca rdial intrascar area of slow conduction); and (2) searching for the en docardial exit is advantageous for selecting the RFCA targets. We also comment on a new self-reference mapping catheter that allows the reco rding of high gain, noise-free, unfiltered and filtered unipolar signa ls as well as unipolar pacing. Among the unresolved issues in these pa tients is the meaning of fast nonclinical VT induced after successful RFCA of the clinical VT, which may explain why a substantial number of these patients still receive an implantable cardioverter defibrillato r.