Hydraulically actuated handle assembly for medical device deployment system

A method of deploying a medical device within a body lumen using a medical device deployment system, wherein the medical device deployment system includes:

• an inner shaft having an elongate body, a proximal end, a distal end, and a medical device support region at the distal end of the elongate body;
• a retractable sheath having an elongate tubular body defining a lumen extending from an open proximal end to an open distal end, wherein the inner shaft is telescopically received within the retractable sheath;
• the medical device being positioned over the inner shaft at the medical device support region;
• and a handle assembly including a hollow handle body defining a movement axis and having an open distal end receiving the inner shaft and the retractable sheath therethrough, a hollow washer positioned within the hollow handle body and movable along the movement axis, wherein the open proximal end of the retractable sheath is attached to the hollow washer and the inner shaft is received through an opening defined by the hollow washer, an expandable fluid chamber within the hollow handle body between the open distal end of the hollow handle body and the hollow washer, and a deployment port through the hollow handle body in fluid communication with the expandable fluid chamber, the method comprising steps of:
• advancing a distal portion of the medical device deployment system toward a deployment site within the body lumen with the medical device deployment system in a pre-deployment configuration in which the hollow washer has an initial position within the hollow handle body, the expandable fluid chamber has an initial volume, and the retractable sheath restricts radial expansion of the medical device;
• increasing the initial volume of the expandable fluid chamber toward an expanded volume by introducing fluid into the expandable fluid chamber through the deployment port;
• proximally retracting the retractable sheath by moving the hollow washer toward a retracted position proximally spaced from the initial position responsive to the increasing step;
• and
• radially expanding the medical device responsive to the proximally retracting step.