[Catheter ablation of supraventricular tachyarrhythmias: experimental findings]

In the majority of cases, atrial fibrillation seems to depend on multiple, simultaneously active reentrant circuits. Their pathlength is defined by local refractory periods and conduction velocities. Active circuits experience constant changes in number, location and dimension. Ablative interventions targeting individual circuits are, therefore, not likely to be successful. Current approaches aim at multiple, electrically isolated atrial segments providing insufficient space for the given minimal size of potential reentrant circuits. Pharmacologic interventions either result in conduction delay and subsequent conduction block, or in prolongation of local refractoriness increasing the size of existing circuits. Creation of isolated atrial segments by endocardial catheter ablation implies the feasibility of extended, contiguous transmural lesions. Mapping studies in healthy dogs demonstrated that contiguous anatomic lesions are very hard to achieve with conventional catheter techniques. Functional conduction blocks, however, may be obtained. Furthermore, application of radiofrequency energy induces prolongation of local refractoriness even at a distance from the actual anatomic lesion. Thus, in the interventional therapy of atrial fibrillation, functional effects of radiofrequency ablation might at least serve to facilitate the strenuous implementation of the isolation concept.