An introducer assembly includes a distal sheath and a proximal sheath. A splitting element is located at a proximal end of the distal sheath and is arranged to split the distal sheath in a distal direction, so as to deploy first a branch element of a medical device and thereafter the distal end of the medical device. The proximal sheath can then be retracted to release the proximal end of the medical device. Deployment of the medical device from the branch element first enables accurate positioning of the branch element prior to deployment of the main body portion of the medical device.