Electrophysiologic characteristics of atrial tachycardia originating from the superior vena cava

Introduction  This study sought to investigate electrophysiological characteristics in patients with focal atrial tachycardia (AT) arising from the superior vena cava (SVC). Methods  This study included five patients undergoing radiofrequency ablation (RFA) with focal AT. Activation mapping was performed during tachycardia to identify an earliest activation in the SVC. Results  AT occurred spontaneously or was induced by isoproterenol infusion. The tachycardia demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave was highly positive in leads I, II, III, aVF in all patients, and isoelectric in lead aVL, lead V1 showed biphasic (positive then negative) component in four of five patients. Lead V2–V6 showed positive component in five patients and isoelectric in one patient. The earliest endocardial activity occurred at the SVC ahead of P-wave in all five patients. Mean tachycardia cycle length was 378 ± 18 ms and the earliest endocardial activation at the successful RFA site occurred 35.3 ± 8.4 ms before the onset of P-wave at 2 ± 1 cm above the SVC–right atrium junction, located at the anterior and lateral wall aspect of the SVC. RFA was acutely successful in all five patients, except one patient accompanied with sick sinus syndrome. Long-term success was achieved in five of five over a mean follow-up of 24 ± 5 months (range 12–36 months). Conclusions  The SVC is an uncommon site of origin for focal AT (1.7%). There were consistent P-wave morphology and endocardial activation associated with this type of AT. The SVC focal ablation is safe and effective. Long-term success was achieved with focal ablation in all patients.