Successful transradial intervention by switching from 6 French to 5 French guiding catheter.

We report a case of percutaneous coronary intervention (PCI) where a 6 French (Fr) guiding catheter could not be advanced through extremely tortuous subclavian and brachiocephalic arteries with a right transradial approach. Downsizing from a 6 Fr to 5 Fr guiding catheter was effective to reach to the coronary cusp, and we successfully performed transradial PCI without access-site crossover. When a catheter cannot be advanced in a tortuous vessel during transradial intervention, downsizing the catheter is an option to reduce resistance and enable successful PCI without access-site crossover.