A method of accessing lateral branch veins of the coronary sinus with a pacing lead and guide catheter assembly. The guide catheter has an open lumen extending therethrough and a distal end provided with a pre-formed guide curve, while the pacing lead has a distal end provided with a first curve and a second curve extending proximally from the first curve. The guide catheter is inserted into an access vessel of the heart and advanced along the access vessel to the coronary sinus. The pacing lead is inserted into the guide catheter lumen and advanced distally through the guide catheter lumen. The pacing lead is rotated by advancing the second curve of the pacing lead through the guide curve to align the first curve with a pre-determined plane. The first curve of the pacing lead into one of the lateral branch veins of the coronary sinus.