A sheath is transluminally introduced a sheath into an atrium of a heart of a subject. A guide member is advanced out of the sheath and to a chorda tendinea of the heart, the guide member having a proximal portion that includes a longitudinal element, and a distal portion that includes a helical chord-engaging element. The chord-engaging element is wrapped around the chorda tendinea. While the chord-engaging element remains wrapped around the chorda tendinea, (i) the chord-engaging element is slid over the chorda tendinea toward a papillary muscle that is coupled to the chorda tendinea； and (ii) subsequently, a tool is moved out of the sheath and toward the papillary muscle by sliding the tool along the longitudinal element. Other embodiments are also described.
