Radio-frequency needle technique
In difficult cases with initially unsuccessful TSP due to stiff or thickened IAS the RF needle technique was utilized. The main advantage of this technique is that significant mechanical force is not needed for successful and safe TSP (10). In short, after the long sheath / dilator / transseptal needle assembly was positioned at the optimal location on the IAS (panel D, Figure 1), the transseptal needle was pushed against the oval fossa. During consistent pressure of the needle and under uninterrupted ICE guidance the RF energy was applied to the shaft of the metal needle with the ablation catheter. Due to the expected rise of the impedance the high impedance cutoff on the RF generator was set to the maximum value. The RF energy of 20W was generally applied for 5 -10 seconds until the tip of the needle was visualized in the LA cavity (panel E, Figure 1). The subsequent steps of TSP were as previously described in Figure 1.