A medical electrical lead configured for use in stimulating the left side of the heart (i.e., the left ventricle). In one embodiment, the lead includes an elongate lead body including an inner surface. An inflatable member is disposed on the outer surface of the body between its proximal and distal ends, the inflatable member being adapted when inflated to impart a radial force on and frictionally engage a surface of the coronary sinus or coronary vein for fixation of the distal end of the lead therein. The lead further includes a conductive member extending from the proximal end toward the distal end, and an inner insulating layer positioned between the conductive member and the inner surface of the body. Separation between the inner insulating layer and the inner surface of the body defines an inflation lumen in fluid communication with the inflatable member.
