Cardiac catheterization is carried out by importing image data of a heart of a living subject into an image-processing computer system, representing the image data as a first model of the heart and the coronary sinus in a first coordinate space, and introducing a probe into the coronary sinus. Thereafter fluoroscopic image data of the probe are used to prepare a second model of the coronary sinus in a second coordinate space, and the first model is transformed into the second coordinate space by placing the coronary sinus of the second model in registration with the coronary sinus of the first model.
