An integrated bipolar implantable medical electrical lead, which may be employed by a cardiac defibrillator, has a single low voltage electrode and a single high voltage electrode and employs a relatively robust and fail-safe configuration of three conductors. Each of the three conductors extends within an individual lumen of a tri-lumen insulative body of the lead. First and second conductors of the three connect, in parallel, the low voltage electrode to a first contact of a connector terminal assembly of the lead, and a third conductor of the three connects the high voltage electrode to a second and a third contact of the connector terminal assembly. A configuration of the third conductor differs from that of the first and second conductors in order to make the third conductor more susceptible to fracture, relative to the first and second conductors, after many years of chronic implant under extreme loading conditions.