Background and purpose:
Transseptal puncture (TSP) is the main access route during left-sided ablations. We have hypothesized that using of three anatomical orientation lines may help in the identification of optimal TSP site on the 3D map.

Methods:
100 consecutive patients who underwent ablation for left-sided arrhythmia were included. The images from preprocedural multislice-detector computer tomography were merged with a 3D-electroanatomical map allowing for more accurate spatial orientation during the procedure. Transseptal puncture was conducted under fluoroscopy. We draw three imaginary lines connecting the anterior and posterior margins of superior vena cava (SVC) and inferior vena cava (IVC) as well as coronary sinus (CS) ostia on the 3D-EAM (Fig 1). The position of the actual site of TSP was then projected onto these lines and measurements were compared to reveal a trend.

Results:
The TSP site was always at the safe distance (in average 8 ±5mm) from the anterior line (between anterior margin of SVC and coronary sinus ostia) and was comparable with the data’s described earlier. No periprocedural cardiac tamponade and no mislead TSP into the aortic root occurred. The novel orientation lines between SVC and IVC demonstrated stable association with the TSP site. The distance from TSP to IVC line was 15 ±6mm in average and it was at the mark of 56 ±1% on the IVC line. The distance of TSP to SVC line composed 12 ±7mm in average and it was at the mark of 31 ±1% on the SVC line.

Conclusion:
The novel SVC and IVC lines together with the anterior line are a helpful additional tool for identification of an optimal TSP site. This finding can increase the safety of the procedure and decrease the need of fluoroscopy.   

Keywords:
transseptal puncture, zero fluoroscopy ablation, fossa ovalis, electroanatomical map.

Figure 1.

Left: anatomical specimen showing the structures of interatrial septum from the left atrial side. Dotted lines describes the SVC and IVC lines; the yellow arrowheads along the Waterstones groove.

Middle: 3D-electroanatomical map of the right atrium (grey) and the integrated CT scan of the left atrium in blue.

Right: schematically illustration of additional anatomical measurements: Anterior, SVC and IVC lines, distances from the TSP to the lines as well as level of the TSP according to the line (measured in percentage): anterior line level, SVC level and IVC level. FO -fossa ovalis; Ao – ascending aorta;  IVC – inferior vena cava; SVC- superior vena cava; CS – coronary sinus, TSP-transseptal puncture.