The size of the radial artery, and the tortuous route to the coronary ostea from the radial approach, limit catheter selection for the transradial interventionalist with potential adverse consequences for backup support. This is most evident in the setting of coronary calcification and tortuosity, leading to difficulties with equipment delivery. For these reasons, it is especially important that the transradialist interventionalist is familiar with the wide range of techniques to improve backup support and overcome vessel resistance.
Backup support can be defined as the resistive force of a guide catheter within the aortic root against which stents and other equipment are advanced into the coronary artery. Greater forces will be required when delivering bulky equipment and in the setting of coronary calcification and tortuosity due to increased friction. Techniques to achieve equipment delivery in this setting include vessel straightening using buddy wires or support wires, vessel preparation using rotational atherectomy or high pressure dilatation, and methods to increase backup support such as deep intubation, anchor balloon techniques, or the use of guide catheter extensions. Vessel straightening using buddy and support wires increases the coaxial alignment of the equipment with the guide catheter and improves forward force transmission as well as reducing axial forces that may displace the guide catheter. Balloon dilation and rotablation respectively displace and ablate plaque, thus reducing obstruction. Backup support can be influenced greatly by guide catheter shape, stiffness, positioning within the aortic root, and intubation depth. Deep intubation may be achieved either with the guide catheter itself, or by using a guide catheter extension. Anchor balloon techniques involve locking the guide in position by using an inflated balloon in a distal branch.