Purpose: analyze the utility of transcatheter ablation with high-frequency currents to create different experimental models of altered cardiac automatism and conduction.
Method: the results were obtained in six anesthetized dogs subjected to electrophysiological study after selectively applying transcatheter radiofrequency ablation to different zones of the specific cardiac conduction system. Ablation was carried out using conventional bipolar 7F catheter-electrodes. High-frequency currents (0.7 MHz) were emitted through the distal electrode, with variable intensity and duration according to the aim of the experiment. Anatomic (fluoroscopic) and electrophysiological criteria were used to position the electrode within the ablation zone.
Results: selective radiofrequency application to the atrioventricular junction zone affords complete A-V blocks with escape rhythms located in the A-V node or His-Purkinje system, together with different degrees of infra- and intra-hisian and intranodal blocks. The modification of intranodal refractoriness and conduction without interrupting atrial pulse transmission may manifest atypical patterns with truncated nodal conduction curves. The abolition of sinus function through ablation in the zone of the sulcus terminalis makes it possible to obtain supraventricular subsidiary rhythms. The obtaining of intranodal complete blocks with supra-Hisian escape rhythms demonstrates phenomena such as the modulation of subsidiary automatism by non-transmitted atrial pulses, analyzed by constructing phase-response curves.
Conclusion: transcatheter ablation using high-frequency currents is useful in demonstrating phenomena related to intranodal and His-Purkinje conduction, subsidiary pacemaker automatism or the modulation of automatism and conduction via non-transmitted pulses.