Tracking dynamic conduction recovery across the cavotricuspid isthmus

OBJECTIVES We sought to assess the dynamic temporal course of conduction recovery during and after radiofrequency (RF) catheter ablation of the cavotricuspid isthmus. BACKGROUND Although cavotricuspid isthmus block is accepted as the best end point of ablation for typical flutter, conduction recovery is thought to underlie many eventual recurrences. Its time course and frequency have not been determined. METHODS In a prospective group of 30 patients (26 men and 4 women, age 64 ± 12 years) undergoing ablation of typical flutter in the cavotricuspid isthmus, the morphology of the P wave during pacing from the low lateral right atrium after achievement of complete isthmus block was identified as a reference. Regression of this morphologic P wave change was confirmed to be associated with intracardiac evidence of the recovery of cavotricuspid isthmus conduction and was observed throughout the procedure both during ablation in sinus rhythm (n = 15, group B) and just after flutter termination (n = 15, group A). RESULTS Stable complete isthmus block was achieved in all patients; 29 had a terminal positivity of the paced P wave. Flutter termination resulted in stable block and terminal P wave positivity in three patients, transient terminal P wave positivity and transient block despite continuing RF at the same site in five patients and no block in the remaining seven patients. Conduction recovery identified by recovery of P wave changes was nearly as common (48%) during ablation in sinus rhythm. Multiple recoveries were noted in some patients, and 72% of all recoveries occurred within 1 min. Conduction recovery was only rarely associated with coagulum, impedance elevation or pops. CONCLUSIONS Conduction recovery in the cavotricuspid isthmus is common during and after ablation and can be accurately, dynamically and continuously observed by monitoring the recovery of the low lateral right atrial paced P wave change.