Troubleshooting in PM Leadless: How to manage an indissoluble knot

: A 77-year-old patient, with permanent atrial fibrillation, underwent successful Micra transcatheter pacing system (MTPS) implantation. Once begun the pull-back of the tether, an increasing resistance was felt by the operator until complete blockage. A challenging recapture of MTPS into the delivery system was performed. The retrieved MTPS showed an indissoluble knot close to the docking button that blocked the running of the tether, and a long clot inside the delivery system. The new design of internal handle components of MTPS recently updated seems to favor clot formation. We suggest a reconsideration of the standard recommendations about delivery system flushing and design of the inner flushing tube system.