Electrophysiological characteristics and radiofrequency ablation of focal atrial tachycardia originating from the superior vena cava.

The initiation of focal atrial tachycardia (AT) from the superior vena cava (SVC) remains unclear. In 3 patients (2 females, 1 male; aged 57, 66 and 50 years, respectively) with focal AT arising from different parts of the SVC, the AT occurred spontaneously, rather than being induced by electrical stimulation. The cycle length of the tachycardia was highly variable, ranging between 190 and 300 ms in patient 1, 180 and 320ms in patient 2, and 200 and 300ms in patient 3. The clinical or associated arrhythmias were atrial fibrillation (AF) (patients 1, 3) and atrial flutter (AFL) (patients 2, 3). A presumed SVC potential that was earlier than the activation of all the other mapping sites was recorded during AT at the lower anterior (15-mm above the atriocaval junction), the mid-anterior (25-mm above the atriocaval junction) and the lower posterior aspect of the SVC (17-mm above the atriocaval junction. Radiofrequency (RF) ablation targeting the SVC focus with the SVC potential promptly eliminated the focal AT in all 3 patients. The coexistent typical AFL was ablated, but the AF was not. The follow-up period was 6, 6, and 3 months, respectively, for each of the patients under no antiarrhythmic medication; there has not been a recurrence of symptomatic palpitation. In conclusion, focal electrical firing in the SVC can initiate AT and this type of focal AT is always associated with AFL or AF. RF ablation guided by the presumed SVC potential is safe and highly effective in eliminating the tachycardia.