Cardiac catheterization is carried out by constructing a left atrial model of a heart of a living subject, selecting a global catheter that is dimensioned to conform to the left atrial model, representing the catheter in the left atrial model; extending the length axis of the catheter in the left atrial model to form an intersection with the foramen ovale, and reporting the intersection as a recommended site of transseptal puncture for insertion of the catheter therethrough.