Abstract 19467: Direct Slow Pathway Capture: A New Electrophysiological Method of Catheter Ablation for Atrioventricular Nodal Reentrant Tachycardia

Background: Antegrade slow pathway (ASp) has been targeted during catheter ablation of slow-fast (S/F) and sometimes slow-slow (S/S) forms of atrioventricular nodal reentrant tachycardia (AVNRT). But radiofrequency (RF) energy applications have been performed without identifying the precise input sites to ASp. Objectives: The purpose of this study was to identify the precise input sites to ASp electrophysiologically by pacing method based on the direct slow pathway capture (DSPC). Methods: 5 S/F and 2 S/S AVNRT patients were studied. High-output (10 - 20V / 1ms) single extrastimuli (St) with various coupling intervals (CI) were delivered to the anatomical slow pathway region during tachycardia. Significant prolongation of return cycles (RC) following St during tachycardia indicated that pacing sites were DSPC positive. RF energy applications were performed at DSPC positive/negative sites and the effects of RF energy applications were compared. Results: DSPC was demonstrated in all patients. Combination of RC minus tachycardia cycle length (TCL) / TCLх100 > 24.75 or RC minus TCL / TCL minus CI >1.515 was diagnostic for DSPC with sensitivity 97.2%, specificity 80.4%, PPV 39.3%, NPV 94.2%. RF energy applications were successful at any sites of DSPC positive and resulted in ASp elimination in 4 of 6 patients, but were not successful at any sites of DSPC negative. The number of RF energy applications was 1.3±0.5. Conclusions: DSPC was an electrophysiological indicator of ASp and was useful not only for identifying the precise input sites to ASp but also for reducing the number of RF energy applications.