Disclose herein is a method of measuring pressures in a coronary sinus. In one embodiment, the method includes: introducing a distal portion of a lead or tool into the coronary sinus, wherein the distal portion includes first and second pressure sensors and at least one selectably expandable member; expanding the at least one expandable member such that the first and second sensors are isolated from each other within the coronary sinus; and taking pressure measurements with the first and second sensors when isolated from each other.