Lead conductor lumen with cross-sectional shape to minimize effects of compressive forces

An implantable endocardial lead extending between proximal and distal ends for use with a cardiac stimulation device comprising:

• an elongated lead body of flexible resilient material having a longitudinally extending lumen defined by a plurality of longitudinally extending side wall surfaces, adjacent pairs of the side wall surfaces lying in angularly disposed planes and intersecting at an energy absorbing corner ridge;
• and
• at least two electrical conductors located loosely within and extending longitudinally along the lumen between proximal and distal ends, the diameter of each of the conductors being greater than the spacing between adjacent corner ridges;
• whereby forces imposed laterally on the lead body by the conductors engaging the side wall surfaces of the lumen upon bending of the lead body are absorbed without damaging the lead body by reason of engagement of the conductors with a corner ridge thereby causing the corner ridge thereby engaged to recede toward a condition of being coplanar with its subtended pair of side wall surfaces.