Surface ECG and intracardiac electrograms from a patient with Wolff-Parkinson-White syndrome (WPW) and a right lateral accessory pathway are simultaneously recorded. The patient is initially being paced from the high right atrium (HRA) at a cycle length of 500 milliseconds to maximize preexcitation. The accessory pathway is localized to an area of the tricuspid annulus (Ta), and radiofrequency (RF) current is delivered via a deflectable tip ablation catheter. Preexcitation disappears (*) within 1.2 seconds.
