Electrical Connections between Persistent Left Superior Vena Cava and Left Atrium during Catheter Ablation for Atrial Tachycardia

A 74-year-old man presented with palpitation and 12-lead ECG exhibited atrial premature contraction (APC) at general check-up. Holter ECG demonstrated narrow QRS tachycardia with a rate of 160/min and more than 31,000/day atrial premature beats. The P wave morphology of atrial premature beats showed negative in II, III, aVF and biphasic in V1. Venography was performed and disclosed persistent left superior vena cava (LSVC) draining into the right atrium via the markedly dilated coronary sinus (CS). Electrogram recordings from LSVC and CS were obtained with an electrode catheter via the left subclavian vein. At the level where a ventricular potential disappeared, the intra-LSVC potentials began to show a discrete second sharp potential after local left atrial signals. Double potentials were obtained within the LSVC from the lower left atrium (LA) to the higher LA. A proximal-to-distal activation sequence of the second components was observed. The interval between the 1st and 2nd component ranged from 8 to 22 msec between the proximal LSVC and distal LSVC. The double potentials resulted in fusion at the lower part of the LSVC, indicating the presence of an electrical connection between the LSVC and lower LA.