Would a complete electrophysiological study allow us to make a correct diagnosis? Case report

BACKGROUND: Oblique course of some left accessory pathways is rare An incomplete electrophysiological study may confuse us between an oblique accessory pathway or the presence of two accessory pathways. The proximity of all atrial and ventricular electrograms, at each pole of the catheter, within the coronary sinus may be a novel finding. CASE PRESENTATION: A 68-year-old woman patient presented arrhythmias with hypotension requiring electrical cardioversion. Her electrocardiogram (ECG) was interpreted as atrial fibrillation by accessory pathway. We performed with the protocol of ablation stablished in our laboratory: two punctures on the right femoral vein with placement of introducers (8F and 7F) by Seldigner technique and one puncture on the left femoral vein (7F). The study was performed with BIOTRONIK technology (Multicath study catheter), a non-deflectable 7F quadripolar catheter with 2 mm tip electrode to record the His electrogram, a non-deflectable decapolar catheter with 5 pairs of coronary sinus (CS) electrodes. Accessory pathway mapping was performed in right and left cavities and within the CS. All electrograms into CS showed short AV from proximal to distal CS. Finally, ablation of two accessory pathway recordings was achieved at two distant epicardial points within the CS. CONCLUSIONS: Ablation at two distant sites, one on the ventricular side and the other on the mitral annulus, suggests the presence of an oblique accessory pathway and at the same time the differential diagnosis of the presence of two accessory pathways. In our point of view according the above, we consider this is a very rare case of oblique AP with epicardial trajectory. The sequence of electrograms (in this case) along the CS has not been seen before in the literature reviewed. It is important, regardless of the urgency, to follow diagnostic and therapeutic protocols in invasive electrophysiology.