According to one embodiment, the present invention includes an elongate implantable medical lead having a distal portion that is relatively flexible, a proximal portion that is relatively stiff, and a transition portion which has a variable transition stiffness. The transition stiffness varies over the length of the transition portion that generally decreases in a distal direction. The relatively stiff proximal portion of the lead gives the lead steerability while the gradual change in stiffness in the transition portion reduces the likelihood that the lead will prolapse when it is guided into a branch vein. The distal stiffness is less than the proximal stiffness giving the lead a safe end that is unlikely to puncture vascular walls and is able to maneuver around various tortuosities when the lead is implanted into a patient.