Radiofrequency Catheter Ablation in Ventricular Tachycardias

Overview

Limitations of pharmacological therapy for ventricular tachycardias have led to developmentof nonpharmacological treatment methods. Among these, methods allowing removal or modifi-cation of an arrhythmogenic substrate or focus should be preferred. Besides surgical ablationprocedures, catheter techniques do exist that provide the means for detailed identification anddestruction of the critical region of the tissue. Routine use of these techniques enabled moreexact classification of ventricular tachycardias that is based on presumed mechanism of originand on their anatomical substrate. As a result of this process, several distinct forms ofventricular tachycardias that are amenable to catheter ablation have been identified. All theseare monomorphic tachycardias, i.e. arrhythmias originating from one focus or involvingcirculatory movement of the impulse around a well defined circuit. From the viewpoint ofcatheter ablation, ventricular tachycardias can be divided into either focal or nonfocal. Focaltachycardias arise from one point source that is amenable to a discrete application of radiofre-quency current. The mechanism of such arrhythmia may be either enhanced automaticity ortriggered activity and/or microreentry. A nonfocal tachycardia involves a larger area ofventricular muscle and the mechanism is almost always reentry. Most frequently, the impulsecirculates at the interface between healthy myocardium and a scar after myocardial i nfarction.Then, the critical zone of slow conduction needs to be identified the modification of which mayprevent arrhythmia from occurrence. In other cases (e.g. tachycardias after surgical correctionof congenital heart disease), a linear lesion crossing the path of impulse propagation betweentwo anatomical barriers is necessary to accomplish. An exemption in this respect is bundlebranch reentry that could be cured by technically simple ablation of a right bundle branch insinus rhythm. The aim of this paper is to review the role of catheter ablation in ventriculartachycardias.

Key words:
radiofrequency catheter ablation - ventricular tachycardia - treatment.