LV lead placement
In the Inner-Cath group, a 7Fr Inner-Cath with 90 degree-angled tip was advanced to the CS trunk using a 5Fr EP-catheter (EP star, Japan Lifeline, JAPAN) or 3.5-inch guide wire through a 7 Fr short sheath placed in the left or right subclavian vein (Figure 1). A 5Fr EP catheter or 3.5-inch guide wire was inserted into the CS as deeply as possible to strengthen backup force for an Inner-Cath insertion into the CS without additional use of an Outer-Cath. Then a CS venogram was performed by injecting contrast medium through the Inner-Cath or a catheter with a balloon on its tip for occlusive venography if necessary. In cases where the Inner-Cath was directly cannulated into a CS tributary, selective venography through the Inner-Cath was possible (Figure 1). A 0.014-inch guide wire inserted within an LV lead was initially advanced to the target CS tributary under fluoroscopy. Then, an LV lead was advanced to the target vein along with the guide-wire alone. After confirming the LV lead had been steered into appropriate position, the Inner-Cath and 7Fr sheath were peeled off for removal. In cases of difficult CS cannulation with an Inner-Cath alone or difficult LV lead placement in a target vein, an Outer-Cath was additionally used. In the Outer-Cath group, a 9Fr or 10Fr Outer-Cath with different angles was advanced to the CS trunk through 9Fr or 10Fr sheaths placed in the subclavian vein using conventional methods. A CS venogram was performed using a balloon catheter and the LV lead was advanced to the target CS tributary. In cases of difficult CS cannulation with an Outer-Cath or difficult LV lead placement in the target CS tributary, an Inner-Cath was additionally used.