A guide extension catheter assembly including a guide extension catheter and a support device. The guide extension catheter includes a shaft and a tubular member. The support device includes a push member and a shuttle member. The guide extension catheter assembly is configured to selectively provide a delivery state in which at least a portion of the shuttle member is disposed within the lumen, a leading end of the shuttle member is distal a distal end of the tubular member, and the shuttle member is directly, physically connected to the tubular member. In the delivery state, a longitudinal distal force applied to the push member is transferred to the tubular member as a longitudinal distal force via the shuttle member. The guide extension catheter assemblies of the present disclosure can promote a two stage guide extension catheter deployment.
