A delivery system for implanting a biostimulation device comprising a stylet extending along an axis from knob end to a threaded end configured to engage an internally threaded nut of the biostimulation device and a catheter tube configured to axially contain the stylet. The catheter tube comprises a feature that engages a corresponding feature on the biostimulation device whereby the stylet can be rotated relative to the catheter tube for disengagement of the stylet threaded end from the biostimulation device threaded end.