A delivery device for a collapsible prosthetic heart valve, the delivery device comprising: an operating handle having a housing and a carriage selectively fixed or movable relative to the housing; and a catheter assembly, including: an inner shaft around which a compartment is defined, the inner shaft being operatively connected to the housing, the compartment being adapted to receive the valve in an assembled condition; an outer shaft surrounding at least a portion of the inner shaft, the outer shaft being fixedly connected to the carriage and movable relative to the inner shaft and the housing, the outer shaft having a compressed length and an extended length greater than the compressed length along an axis of elongation of the outer shaft; and a distal sheath fixedly connected to the outer shaft, the distal sheath being movable between a closed condition covering the compartment and an open condition uncovering the compartment for deployment of the valve; characterized in that the catheter assembly includes a mechanism configured to apply a distal force to the outer shaft while the carriage is fixed relative to the housing to stretch the outer shaft from the compressed length to the extended length. an operating handle having a housing and a carriage selectively fixed or movable relative to the housing; and a catheter assembly, including: an inner shaft around which a compartment is defined, the inner shaft being operatively connected to the housing, the compartment being adapted to receive the valve in an assembled condition; an outer shaft surrounding at least a portion of the inner shaft, the outer shaft being fixedly connected to the carriage and movable relative to the inner shaft and the housing, the outer shaft having a compressed length and an extended length greater than the compressed length along an axis of elongation of the outer shaft; and a distal sheath fixedly connected to the outer shaft, the distal sheath being movable between a closed condition covering the compartment and an open condition uncovering the compartment for deployment of the valve; characterized in that the catheter assembly includes a mechanism configured to apply a distal force to the outer shaft while the carriage is fixed relative to the housing to stretch the outer shaft from the compressed length to the extended length. an inner shaft around which a compartment is defined, the inner shaft being operatively connected to the housing, the compartment being adapted to receive the valve in an assembled condition; an outer shaft surrounding at least a portion of the inner shaft, the outer shaft being fixedly connected to the carriage and movable relative to the inner shaft and the housing, the outer shaft having a compressed length and an extended length greater than the compressed length along an axis of elongation of the outer shaft; and a distal sheath fixedly connected to the outer shaft, the distal sheath being movable between a closed condition covering the compartment and an open condition uncovering the compartment for deployment of the valve; characterized in that the catheter assembly includes a mechanism configured to apply a distal force to the outer shaft while the carriage is fixed relative to the housing to stretch the outer shaft from the compressed length to the extended length.