An assembly for tethering a medical device to a delivery catheter includes a tether, a collet, and a spring-biased holding element that is coupled to a distal end of the tether and that extends around the collet, being moveable between first and second positions. At the first position, corresponding to the spring bias thereof, the holding element prevents fingers of the collet, which are configured to grip a proximal end of the device, from opening； at the second position, the collet fingers are allowed and/or caused to open. The assembly is coupled to a tubular member of the catheter, and, when the tethering assembly abuts a distal end of the catheter tubular member, a pull force applied to a proximal end the tether, which extends out from a proximal opening of the catheter, moves the holding element from the first position to the second position.
