Background: To a large extent, the heart's functions are influenced by the autonomic nervous system involving hemodynamics, properties of cardiac conduction, heart rate (HR), as well as cardiac myocytes cell functions, and cardiac arrhythmogenesis. In the present study, heart rate variability (HRV) was evaluated in patients receiving radiofrequency catheter ablation for supraventricular tachycardias to determine if there was a correlation between the amount of radiofrequency current used and the HRV change. Patient and Methods: For this one-arm clinical trial, 60 patients with drug-resistant supraventricular tachycardias were recruited; they underwent radiofrequency ablation and were followed up for 6 months after the procedure. Results: Compared with pre-ablation data, at the follow-up evaluation after radiofrequency ablation, HRV were found to be shorter. Results from a 24-hour Holter monitor showed an increase in mean HR, whereas HRV parameters such as time domain indices (SDNN, rMSSD) and frequency domain index, which reflect the attenuation of parasympathetic tone, were reduced in the follow-up at 1 month and 6 months post-ablation. 30 patients, or 50%, had a high sinus rate 6 months after ablation. Compared to patients without AV nodal modification or postero-septal accessory pathway ablation, HRV changes were more pronounced in those with these procedures. Conclusion: Six months following radiofrequency ablation, cardiac autonomic dysfunction was still evident when measured by alterations in time domain and frequency domain HR variability measures. Perhaps one cause of parasympathetic denervation is its role in post-ablation sinus rate.