Disclosed herein are extension members for use with a standard guide catheter, which extension members provide backup support against forces that would otherwise tend to dislodge the guide catheter from the branch artery during interventional cardiology devices. During use, the extension member may be deeply seated in a branch artery that branches off from a main artery when extended through the lumen of the guide catheter and beyond the distal end of the guide catheter. An expandable balloon disposed adjacent the distal tip of the extension member provides additional stabilization and backup support. Also disclosed are methods of using the extension members.