A method of cannulating the coronary sinus or accessing a side branch of the coronary sinus of a patients heart using a guide catheter. The guide catheter has a proximal portion and a distal portion formed into a preformed shape configured such that the distal portion of the shaft is supported on a wall of the superior vena cava during insertion of the distal portion into the coronary sinus. The preformed shape includes a first arc, a second arc, a third arc, a fourth arc, and a generally straight terminal portion. The preformed shape is generally a J-shape, having a terminal portion generally parallel to the proximal portion, a generally closed arc or a generally open arc.
