The short sheaths in the right groin are exchanged for a long transseptal sheath. You will see a transeptal sheath with a needle inside guided all the way up in to the superior vena cava. From this point the entire transseptal apparatus (sheath, needle, and wire) is moved as one piece slowly down towards the interatrial septum. This is done under the guidance of x-ray. The doctor will determine if the puncture site is appropriate or not using intracardiac echo. You can see the septum change shape as the transseptal apparatus tries to cross it (this is called tenting). A clear image of this tenting helps in avoiding puncturing the heart . You will see a squirt of radio-opaque dye injected into the left upper chamber to confirm the entry of the sheath into the chamber. Once the transseptal sheath crosses into the left upper chamber it is flushed with saline solution containing heparin, and an additional dose of heparin is given through the IV to prevent clotting. Next, a circular mapping catheter is placed in the left upper chamber through the sheath. You can see it parked inside the left upper pulmonary vein. The location of the catheter can be confirmed by the intracardiac echo. You can also see a second transseptal sheath with the needle in the superior vena cava. The second puncture is done very similar to the first, using x-ray, intracardiac echo, and heart pressure readings to successfully gain access to the left upper chamber. Then the ablation catheter is passed through this sheath for further mapping and ablation.
