The purpose of this study is to compare the safety and effectiveness of cryoablation and radiofrequency ablation in the treatment of the commonest kind of supraventricular tachycardia, namely atrioventricular nodal reentrant tachycardia. The study hypothesis is that cryoablation is non-inferior to radiofrequency.

Inclusion Criteria:

• Patients who are referred for catheter ablation of supraventricular tachycardia and diagnosis of AVNRT is made by cardiac electrophysiology study

Exclusion Criteria:

1. Patients who aged less than 18 or over 80.
2. Patients who are pregnant.
3. Patients who cannot give informed consent.
4. Patients who are judged to have severe mental impairment and cannot report symptoms of palpitation during follow-up.
5. Patients who had previous AVNRT ablation before.
6. Patients who have comorbid congenital heart disease.