RADIOFREQUENCY CATHETER ABLATION OF CONCEALED ATRIOVENTRICULAR ACCESSORY PATHWAYS USING A SIMULTANEOUS PACING METHOD

The retrograde atrial potential at a successful ablation site is usual ly obscured by the wide and large ventricular potential during atriove ntricular reentrant tachycardia or ventricular pacing, which makes it difficult to determine the appropriate ablation site for a concealed a ccessory pathway. A pacing maneuver named the ''simultaneous pacing me thod'' is proposed herein to differentiate the retrograde atrial poten tial from the ventricular potential for a successful ablation of the c oncealed accessory pathway. Catheter ablation was performed in 12 pati ents with a single left free-wall concealed accessory pathway. The atr ial insertion site was determined by the simultaneous pacing method in six patients (group I) and by ventricular pacing in six patients (gro up II). In the simultaneous pacing method, electrograms recorded durin g ventricular pacing in the earliest retrograde atrial activation site are a fusion of the ventricular potential and the following retrograd e atrial potential. When atrial and ventricular pacings are performed simultaneously (simultaneous pacing), the end portion of the electrogr ams recorded at the same site is solely the ventricular component, bec ause atrial is activated earlier. The atrial potential can be confirme d during ventricular pacing in comparison with the electrograms during the ''simultaneous pacing.'' Radiofrequency catheter ablation was suc cessful in eliminating conduction through the accessory pathway in all 12 patients. The radiofrequency applications in group I were signific antly fewer than those in group II (1.7 +/- 1.0 in group I 5.3 +/- 3.2 in group II, P < 0.05). The total procedure time in group I was signi ficantly shorter than in group II (57.8 +/- 15.7 vs 106.7 +/- 41.6 min s in group II, respectively, P < 0.05). The fluoroscopy time in group I was significantly shorter than in group II (54.0 +/- 7.9 vs 81.3 +/- 26.3 mins, respectively P < 0.05). We were able to determine the atri al insertion site of accessory pathways by the simultaneous pacing met hod. The simultaneous pacing method was useful in eliminating conceale d left free-wall accessory pathways.