Tracking dynamic conduction recovery across the cavotricuspid isthmus

OBJECTIVES We sought to assess the dynamic temporal course of conduction re covery during and after radiofrequency (RF) catheter ablation of the cavotr icuspid isthmus. BACKGROUND Although cavotricuspid isthmus block is accepted as the best end point of ablation for typical flutter, conduction recovery is thought to u nderlie many eventual recurrences. Its time course and frequency have not b een 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 is thmus, the morphology of the P wave during pacing from the low lateral righ t atrium after achievement of complete isthmus block was identified as a re ference. Regression of this morphologic P wave change was confirmed to be a ssociated with intracardiac evidence of the recovery of cavotricuspid isthm us conduction and was observed throughout the procedure both during ablatio n 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 te rminal P wave positivity and transient block despite continuing RF at the s ame site in five patients and no block in the remaining seven patients. Con duction recovery identified by recovery of P wave changes was nearly as com mon (48%) during ablation in sinus rhythm. Multiple recoveries were noted i n some patients, and 72% of all recoveries occurred within 1 min. CONCLUSIONS Conduction recovery was only rarely associated with coagulum, i mpedance elevation or pops. Conduction recovery in the cavotricuspid isthmu s is common during and after ablation and can be accurately, dynamically an d continuously observed by monitoring the recovery of the low lateral right atrial paced P wave change. (C) 2000 by the American College of Cardiology .