Guide extension, unmissable tool in the armamentarium of modern interventional cardiology. A comprehensive review.

Due to the aging population undergoing percutaneous coronary intervention (PCI), interventional cardiologists are confronted daily with treatment of lesions with complex anatomy. Despite improvements in stent devices and PCI techniques, these lesions remain a challenge in terms of procedural success. Guide-extensions (GE) are coaxial "mother and child" catheters employed to facilitate device delivery but they can be used in many different complex scenarios. A comprehensive review of the possible applications of GE and of the GuideLiner™ (GL), the most widely used GE device, is missing. We therefore aim to provide a comprehensive review of all the potential applications of the GL and other GE devices, describe its limitations as well as tips and tricks for successful usage of this GE catheter.