Apparatus is provided for puncturing a fossa ovalis of a heart, the apparatus including a catheter shaped to define a catheter lumen, and a puncturing element slidably disposed within the catheter lumen. The puncturing element is configured to be deployed from a distal portion of the catheter and to puncture the fossa ovalis. The apparatus is shaped to define one or more orifices configured to facilitate positioning of the puncturing element by directing a flow from the apparatus of one or more streams of a contrast agent at an angle of at least 10 degrees with respect to a distally-pointing vector that is parallel to a longitudinal axis of the catheter at the one or more orifices. Other embodiments are also described.
