Tissue anchors and assemblies are described for securing a suture thread in a tissue approximation procedure. The suture thread is provided with a plurality of protrusions arranged along a length of the suture thread. The tissue anchor includes an anchor body having an elongate shape, a passageway for the suture thread through the anchor body. A pawl is adjacent to an outlet of the passageway and configured to engage with the plurality of protrusions so as to prevent movement of the suture thread in a first direction from the outlet inwards into the anchor body. The pawl includes a pawl body pivotally coupled to the anchor body and the anchor body comprises a seat for the pawl body, such that a force exerted by one of the plurality of protrusions on the pawl body in the first direction pivots the pawl body to abut on the seat.