br Discussion Wellens reported an association between access
Discussion Wellens  reported an association between accessory pathways characterized by anterograde decremental conduction and the description of nodoventricular connections by Mahaim . Consequently, these accessory pathways were erroneously referred to as “Mahaim pathways.” McClelland et al.  clarified that decremental conducting pathways responsible for antidromic tachycardia with LBBB and superior axis are atriofascicular accessory pathways that connect the right atrium with the right fascicle. McClelland et al.  reported that a high-frequency accessory potential can be detected at the tricuspid ring and can be mapped along the accessory pathway to the connection with the right fascicle. Currently, this potential still provides the best ablation target to eliminate these pathways. The present case integrates a traditional electrophysiological approach to the treatment of this unique accessory pathway with three-dimensional (3-D) mapping to perform a zero-fluoroscopy procedure. The anatomical location of the accessory pathway potential was clearly located through CARTO mapping. Several reports have shown the feasibility and safety of 3-D-system-guided procedures for reducing radiation exposure from electrophysiological procedure in young patients [4,5]. Radiation exposure bears particular importance in younger individuals because of their greater vulnerability to radiation effects and longer life expectancy . In our opinion, a zero-fluoroscopy 3-D guided approach should be considered in electrophysiological procedures in children and younger adults. To maintain safety and efficacy, intracavitary electrograms should be carefully interpreted and monitored during a non-fluoroscopic procedure than during a conventional fluoroscopic approach. This case represents a good Phos-tag of traditional electrophysiological study methods and a 3-D guided technique for catheter ablation of an accessory pathway.
Conflict of interest
Case report A 76-year-old woman presented to our department with sinus bradycardia-induced asthenia (38beats/min). There were multiple pauses up to 7s on telemetry monitoring with frequent episodes of paroxysmal atrial fibrillation. A sinus node dysfunction was made, and a single-chamber pacemaker was required. Her height was 150cm. A first attempt for temporary pacing via the right subclavian vein failed because of the abnormal path of the wire, which made PLSVC possible. The patient was given isoprenaline and scheduled for a left-sided permanent pacemaker implantation. A thoracic computed tomography (CT) scan was thus performed, showing clearly the PLSVC with a posterior target behind the left atrium, ending in a dilated coronary sinus (CS) with an absent right SVC (Fig. 1A–C). After an easy puncture of the left subclavian vein, a wire was introduced, toward the left downward pathway. We used a catheter to visualize the CS that was drained into the right atrium (Fig. 1D). A 58cm St Jude Medical active-fixation pacing lead (model 2088TC/58) was inserted through the left superior vena cava by using a steerable stylet. A wide loop of the lead was made in the right atrium, and the tip of the lead was directed toward the tricuspid valve using the curved stylet. After a few manipulations, the lead could be positioned in the RV apex (Fig. 1E). The lead parameters were satisfactory, with a pacing threshold of 0.7V at a 0.5-ms pulse width, a pacing impedance of 564Ω, and R-wave amplitude of 10.2mV. The device was connected to the lead and implanted in the left pectoral region. The total fluoroscopy time for the procedure was 14min. The pacing thresholds were good, and no complication occurred intra- and post-procedurally. The patient was doing well 1 year post-pacemaker implantation. Transthoracic echocardiography (TTE) ruled out any associated complications.
Discussion PLSVC with an absent right superior vena cava is a rare anatomic variation (0.07–0.13%) . It represents the most common variation of the thoracic venous system, typically asymptomatic and discovered incidentally during device implantation.