Prolongation of activation-recovery interval over a preexcited region before and after catheter ablation in patients with Wolff-Parkinson-White syndrome

Introduction: Preexisting changes in repolarization properties play an impo rtant role in T wave abnormalities (cardiac memory) after ablation in patie nts with Wolff-Parkinson-White (WPW) syndrome. However, no report has provi ded direct evidence for prolongation of action potential duration (APD) ove r a preexcited region before and after ablation. Methods and Results: We studied 10 patients with ventricular preexcitation due to a left-sided accessory pathway (AP) (group M) and 12 patients with c oncealed left-sided AP (group C) to clarify prolongation of APD using activ ation-recovery intervals (ARIs) from epicardial and endocardial unipolar el ectrograms in patients with WPW syndrome. ARI was calculated from unipolar electrograms at the His bundle and the coronary sinus adjacent to the AP du ring atrial pacing (100 beats/min) before and 30 minutes after ablation. Be fore ablation, ARIs at the AP site were significantly longer in group M tha n in group C (255 +/- 21 msec vs 211 +/- 24 msec; P < 0.01), whereas ARIs a t the His bundle did not differ between the two groups (255 +/- 20 msec vs 245 +/- 27 msec; P = NS). After ablation, group M showed no significant cha nges in ARIs at the AP and His bundle (256 +/- 19 msec and 253 +/- 15 msec) compared with before ablation. Conclusion: We found by direct analysis of ARIs from the epicardium that AP D prolongation over the preexcited region was present before catheter ablat ion and persisted after catheter ablation. The gradual changes in repolariz ation properties, including APD prolongation after discontinuation of AP, m ay be one mechanism of cardiac memory after catheter ablation in patients w ith WPW syndrome.