Atrial double potentials associated with the elimination of the electricalconnection between the coronary sinus (CS) and the left atrium in two cases of Wolff-Parkinson-White syndrome with a CS-connected accessory pathway

A curious retrograde conduction in connection with the coronary sinus (CS) musculature was observed in 2 patients. After the failed ablation procedure , the atrial electrogram during ventricular pacing presented double potenti als, the first component of which was sharp and with an activation sequence that was the same before ablation (CS distal to proximal). The second comp onent of the double potentials was dull and had a decremental property; its activation sequence was in reverse (proximal to distal). In both cases, th e first component disappeared after successful ablation. These findings sug gest that the first component was the CS electrogram conducted over the acc essory pathway and the second component was the left atrial electrogram con ducted through the inter-atrial septum. The separation of each electrogram is probably the result of a block between the accessory pathway connected t o the CS musculature and the left atrium. These are unusual cases of an acc essory pathway connected to the CS musculature, which separates the left at rial myocardium at the distal portion from the ostium.