SAFETY OF SLOW PATHWAY ABLATION IN PATIENTS WITH LONG PR INTERVAL - FURTHER EVIDENCE OF FAST AND SLOW PATHWAY INTERACTION

Whether the presence of abnormal PR before selective slow pathway abla tion for AV node reentrant tachycardia increased the risk of complete heart block remains controversial. We report our experience in seven p atients with prolonged PR intervals undergoing catheter ablation for A V reentry tachycardia. Their mean age was 66 +/- 12 years; four patien ts were female and three were male. RF ablation was performed using an anatomically guided stepwise approach. In six patients, common type A V node reentry was induced and uncommon type was observed in the remai ning patient. In all seven patients, successful selective slow pathway ablation was associated with no occurrence of complete heart block an d was followed by shortening of the AH interval in five patients. In a ll seven patients, successful ablation was achieved at anterior sites (M-1 in two patients and M-2 in five patients). Despite AH shortening after ablation, the 1:1 AV conduction M as prolonged after elimination of the slow pathway, excluding either sympathetic tone activation or parasympathetic denervation. In conclusion, selective slow pathway abl ation can be performed safely in the majority of patients with prolong ed PR interval before the procedure. Because successful ablation is ac hieved at anterior sites in most patients, careful selection and monit oring of catheter position is required.