A previously healthy 17-year-old male presented with palpitations and documented recurrent episodes of narrow QRS complex reciprocating atrioventricular (AV) tachycardia. Twelve-lead electrocardiogram was consistent with pre-excitation from an anteroseptal pathway. Detailed three-dimensional Carto™ map through a 7-Fr open-irrigated ablation contact force catheter (Thermocool® SmartTouch™, D type, Biosense Webster) demonstrated earliest ventricular activation at close proximity with His bundle. Although good catheter stability was achieved, initial radiofrequency (RF) ablation (42°C, 30 W with 17 mL/min flow, contact force of 4 g, duration of 30 s) had no effect on accessory pathway (AP) conduction. Subsequently, a second RF pulse was applied with a contact force of 16 g (42°C, 30 W with 17 mL/min flow, duration of 120 s) and AP block occurred within <5 s of RF delivery.
Contact between the tip electrode of the ablation catheter and the myocardial tissue affects both the accuracy of maps and the efficacy of energy delivery. Catheter ablation based on precise electroanatomical mapping and contact force technology appears to be an effective and radical treatment modality even for patients with ‘high risk’ pathways close to the AV junction (5 mm distance from the His bundle).