Objectives The present study evaluated the clinical benefits of a new therapeutic method of radiofrequency catheter ablation (RFCA) using an EnSite system for inappropriate sinus tachycardia (IST). Materials and Methods Six patients with debilitating IST underwent RFCA using EnSite. Using the betaadrenergic blocker and agonist, the heart rate was controlled between 70 to 150 bpm before and after the RFCA. The areas of the breakout sites (BOSs) were clearly distinguished between those from the normal Pwave zones during rates of less than 100 bpm and those from more upper rate sites during rates of more than 100 bpm using the EnSite system, in accordance with the appearance of tall P-waves (tall P-wave zone) in the IST patients. This was selected as the target for ablation. Results After the RFCA, the BOSs observed during heart rates of more than 100 bpm moved completely from the tall P-wave zone to the normal P-wave zone in the IST patients. The total number of heart beats and average heart beat on the 24-h Holter monitoring decreased statistically from that before the RFCA to that after, and no adverse heart rate responses was observed after the RFCA. Before the RFCA, the brain natriuretic peptide was elevated, New York Heart Association functional class was worse, and there was an impaired exercise tolerance observed with exercise electrocardiogram testing. The RFCA for the IST significantly improved those parameters. Conclusion This new therapeutic method for IST using EnSite is effective and produces clinical benefits.
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