Percutaneous coronary intervention depends on the guiding catheter holding its position. The catheter is seated in the coronary ostium, and everything that treats the lesion travels through it. When a balloon or stent is pushed forward, the reaction force pushes the catheter backward, and if it disengages, the operator loses the working platform. Resisting that is called backup support, and it is the main reason curve shapes differ.
Curve selection follows the target vessel and the access route. Judkins shapes are familiar and work well in straightforward anatomy. Extra backup curves such as EBU and XB brace against the opposite aortic wall, which gives more support for crossing hard lesions in the left coronary system. Amplatz curves suit awkward take-offs and the right coronary. Internal mammary and multipurpose shapes cover grafts and unusual origins. Having twelve families available matters because a case that will not cross with one shape often crosses easily with another.
French size follows the equipment rather than the vessel. 6F is the working standard and accommodates most single-stent work through radial access. Bifurcation techniques placing two stents, parallel wire approaches in chronic total occlusions, and larger rotational atherectomy burrs all need the wider lumen that 7F or 8F provides. Side holes are a separate decision. They preserve flow past an engaged catheter, which helps in ostial disease and long procedures. They also divert contrast and dampen the pressure trace, so they are used selectively.
Medigear.uk supplies the instructions for use with every INT Medical Guiding Catheter order.