An improved balloon catheter has a catheter body with an expandable member, such as a balloon, mounted to the exterior surface thereof. Preferably, means for preventing sticking of the expandable balloon to the exterior surface of the catheter body are provided. In one aspect, the catheter has an expandable member, preferably a balloon, positioned substantially equidistant from the proximal and distal ends of the catheter body. The retention catheter is positioned externally of the heart and partially surrounds the heart so that the balloon is positioned immediately adjacent the coronary sinus and when inflated, the balloon bears against the coronary sinus and at least one of the inferior vena cava and diaphragm thereby preventing inadvertent movement or removal of the RCSP catheter from the coronary sinus.