Paroxysmal supraventricular tachycardia is treated with radiofrequency ablation recently. This procedure is performed by ablating slow pathway or accessory pathway using radiofrequency ablation catheter. Recently developed mirofidelity (MIFI) catheter has mini-electrodes that can record local eletrogram with higher resolution. We aimed to investigate the efficacy of MIFI catheter in the ablation of paroxysmal supraventricular tachycardia compared to conventional radiofrequency ablation catheter. Enrolled patients undergo conventional electrophysiologic study. Patients with sustained supraventricular tachycardia during the study are randomized to either study group or control group. Radiofrequency ablation is performed using MIFI catheter in the study group, and conventional catheter (Blazer II) in the control group. The study endpoints are recorded immediately after ablation and there is no additional follow up or management after procedure.

Inclusion Criteria:

• Patients who are scheduled to undergo radiofrequency ablation for paroxysmal supraventricular tachycardia or WPW syndrome with atrial fibrillation
• Give written informed consent for the study

Exclusion Criteria:

• Unable to induce supraventricular tachycardia during electrophysiologic study.
• Cognitive impairment to understand study procedure

IPD would be provided with an appropriate request from other investigators.