1. A method, comprising the steps of: introducing a catheter into a coronary sinus of a heart of a living subject; while the catheter is in the coronary sinus acquiring a first set of frames at first and second primary angles, the first set of frames comprising 2-dimensional images of the catheter using an imaging device; thereafter acquiring a second set of frames at first and second primary angles, the second set of frames comprising 2-dimensional images of the catheter using the imaging device; establishing respective 2-dimensional models of the catheter in frames of the first set and the second set, the 2-dimensional models comprising respective tracked 2-dimensional paths of the catheter; synchronizing the first set with the second set by identifying a first pair of frames from the first set and the second set taken at the first primary angle and a second pair of frames from the first set and the second set taken at the second primary angle that are in respective phases of a cardiorespiratory cycle; constructing first and second 3-dimensional models of the catheter from the synchronized frames using the respective 2-dimensional models; geometrically transforming the first and second 3-dimensional models to minimize a distance function there between; and displaying the transformed 3-dimensional models; wherein the subject has a sagittal plane and wherein the steps of acquiring the first set and acquiring the second set each comprise acquiring frames at a first primary angle and at a second primary angle with the sagittal plane; and wherein the difference between first and second primary angles varies by up to 120°.