Catheter shaft construction for tavr delivery systems

A method of flushing a liquid into a compartment of a delivery device for implanting a medical device in a patient, the method comprising:

• providing the delivery device having a catheter assembly and an operating handle, the operating handle having a housing and a carriage movable relative to the housing, the catheter assembly including an inner shaft around which a compartment for the medical device is defined, an outer shaft surrounding at least a portion of the inner shaft, a distal sheath fixedly connected to the outer shaft, the distal sheath being movable between a fully closed condition covering the compartment and an open condition uncovering the compartment, and a spline tube surrounding at least a portion of the inner shaft, at least a portion of the spline tube being disposed in the lumen of the outer shaft, the spline tube and the outer shaft together defining one or more channels providing liquid communication between the operating handle and the compartment;
• mounting the medical device in the compartment;
• sliding the distal sheath to cover the compartment and the medical device;
• and
• flushing the liquid from the operating handle to the compartment through the one or more channels,
• wherein the spline tube has first portions having a first maximum thickness in a radial direction of the inner shaft and second portions having a second maximum thickness in the radial direction, the second maximum thickness being greater than the first maximum thickness, and the one or more channels are each at least partially bounded by the inner surface of the outer shaft, one of the first portions, and two adjacent ones of the second portions.