A method of treating a heart of a patient is provided. The method includes implanting a first tissue anchor in cardiac tissue of the patient and a second tissue anchor in the patient, such that the first and the second tissue anchors are coupled together by one or more tethers. Thereafter, after allowing at least 24 hours for tissue growth on the first tissue anchor to strengthen anchoring of the first tissue anchor in the cardiac tissue, tension is applied between the first and the second tissue anchors using at least a longitudinal portion of the one or more tethers. Other embodiments are also described.